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The macromolecules in the food system such as starch, protein and lipid are essential components and major sources of calories in the human diet. Thermal treatment is one of the most widely used processing methods for foods. Traditional thermal treatment methods could induce undesirable degradation of food quality attributes, especially for heat-sensitive food materials. Therefore, novel thermal technologies have been developed as alternative methods for food processing. This review focuses on the effects of novel thermal processing technologies, including microwave heating, radio frequency heating, ohmic heating and infrared heating on improving the modification of structures and functionalities of macromolecules including starch, protein and lipid in food systems. The principles and mechanisms of these novel technologies are introduced as well as challenges and future trends in developing and applying these technologies in the food industry are also discussed in the current review. For starch, novel thermal processing technologies induce the morphological and crystalline structure of starch granules and affect swelling, water holding capacity, oil holding capacity, solubility and digestibility of starch. For protein, they cause the structure changes via the creation of free radicals and alter the primary, secondary, tertiary and quaternary structures of protein, thereby affecting the functional characteristics such as solubility, digestibility, swelling, foaming, emulsification, water holding capacity, and oil holding capacity. For lipids, novel thermal processing technologies affect the functional properties of lipids such as oxidation stability. Therefore, novel thermal processing technologies are effective in the modification of the structures and functionalities of starches, proteins and lipids for expanding their potential applications. • Effects of processing on starch, protein and lipid macromolecules are discussed. • Structural changes in macromolecules depend on processing severity. • Functional properties of macromolecules are altered significantly by processing. [ABSTRACT FROM AUTHOR]

• Bilayer passive cooler comprised aerogel and hydrogel for daytime passive cooling. • Aerogel achieved daytime radiative cooling and thermal insulation. • Aerogel was hydrophobic and exhibited self-cleaning function. • Hydrogel achieved daytime evaporative cooling and nighttime moisture capture. • Evaporative cooling efficiency was regulated by aerogel thicknesses. The combination of daytime radiative and evaporative cooling has been considered a promising complementary technology for lessening greenhouse gas emissions and global energy consumption. However, this cooling strategy is impaired by environmental heat; its evaporative cooling capacity and cooling time are uncontrollable, and water consumption is significant. Inspired by the cactus's ability to cope with arid and hot environments, the bilayer passive cooler (BPC) consisting of aerogel with particle coating and hydrogel with hygroscopic agent was developed to overcome these challenges. The aerogel with particle coating possessed high solar reflectance (∼0.95), strong infrared radiation (∼0.94), low thermal conductivity (∼42 mW m−1 K−1), and great hydrophobicity (CA = 138°) to perform daytime radiative cooling, thermal insulation, and self-cleaning function. The hydrogel with hygroscopic agent achieved the nighttime moisture capture. The evaporative cooling capacity and cooling time could be regulated by the aerogel and hydrogel thicknesses. The field test showed that the BPC achieved a temperature drop of ∼ 8℃ compared to the ambient temperature of ∼ 30℃ and a cooling power of ∼ 222 W m−2 under the sunlight. Thus, the present study should open a new daytime passive cooling technology pathway. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual-bioinspired photothermal eutectogels are prepared for passive anti-freezing. • Natural deep eutectic solvent can remarkably increase nanofiller loading capacity. • Molecular dynamics simulation proves uniform dispersion of hCNTs in the system. • Uniform hCNTs distribution abates stress concentration and load transfer failure. • Eutectogels show desirable performance in anti-frosting, anti-icing, and deicing. Icing and frosting always cause troubles in present-day human activities, appealing for effective anti-freezing strategies to break through the bottleneck. Inspired by "predominant metabolites in the body fluid of cold-tolerant animals" and "poikilotherms that increase body temperature by absorbing solar energy", natural deep eutectic solvents (NADES) and carbon nanotubes (CNTs) were incorporated within calcium alginate (CA) backbone to fabricate dual-bioinspired and ultra-flexible photothermal eutectogels (CNTs/NADES@CA). Normal CNTs (nCNTs) and hydroxylated CNTs (hCNTs) were used to investigate the effects of hydrogen-bonding networks of NADES on the dispersal/aggregation behaviours of nCNTs/hCNTs. Molecular dynamics (MD) simulation proved that hCNTs could form intense hydrogen-bonding interactions with NADES and disperse more uniformly, ultimately contributing to better mechanical properties. Spectral characteristics covering solar absorption and infrared emissivity showed that higher nanofiller loading could cause increased infrared emissivity, leading to more thermal energy loss during photothermal conversion. Besides, moisture absorption–desorption tests further confirmed the excellent function reproducibility and sustainability of the materials. One of the hCNTs-based eutectogels (4%-hCNTs) behaving the best in photothermal conversion was selected for anti-freezing tests concerning anti-frosting, anti-icing, and deicing capacities, announcing that the CNTs/NADES@CA could be highly efficient for passive anti-freezing. This study proposed a highly efficient nanofiller dispersion strategy enabled by NADES to fabricate ultra-flexible photothermal eutectogel by a physically simple method, and it is hoped that this work could open up new avenues for bioinspired materials and attract more concerns for the proposed dual-bioinspired anti-freezing strategy. [ABSTRACT FROM AUTHOR]

Constant power microwave heating (CPMH) based on solid-state generators, a new microwave heating system, shows better repeatability than traditional microwave heating (TMH) powered by magnetron when performing experiments, while its detailed heating patterns and field distribution are still not fully understood. In this study, numerical simulations for model juice (about 1–5 mL) heated by CPMH and TMH systems were carried out to compare the heating performance. The simulation was performed through coupling electromagnetic, thermal and fluid fields, using a laminar flow model to simulate the flow behaviour of the model juice during the heating operation. Both surface temperature distributions and inner point temperatures were investigated for model validation, and the simulated data agreed well with the experimental ones, indicating that the modelling was rational and correct. Results showed that CPMH gave higher heating efficiency and better temperature uniformity, which was verified by determining both inner point temperature and surface temperature distribution. Besides, influences of sample volume and microwave input power on the heating performance of the CPMH system were studied, suggesting that greater sample volume could cause worse temperature uniformity, although a faster temperature increase was observed. When fixing total microwave input energy to 3 kJ, different input powers were found to achieve similar final average volumetric temperatures (50.46 °C–51.22 °C) but significantly different heating uniformity (final coefficient of temperature variance: 0.065–0.115), indicating that smaller microwave input power could contribute to better heating uniformity. It is hoped that this study could provide references to further understand the heating effects of CPMH systems, leading to better design and upgrade for microwave heating systems. • Model juice heated by constant power microwave heating (CPMH) system was simulated. • Heating performance of traditional microwave heating (TMH) system was compared. • CPMH showed higher heating efficiency and better temperature uniformity than TMH. • Central zone of the model juice gained more microwave energy for heating. • For CPMH, greater power made heating faster but decreased temperature evenness. [ABSTRACT FROM AUTHOR]

Polyphenols and enzymes usually suffer from degradation during transportation due to the lack of a cold chain system in developing countries and regions. In this study, anthocyanin and trypsin were selected as examples of polyphenols and enzymes and investigated for minimizing their degradation during ambient transportation using hydrogel packaging with combined evaporative and daytime radiative cooling functions. A polyacrylamide/polyvinyl alcohol contained with nanoparticles (NPs@PAAm/PVA) hydrogel packaging was thus developed. The NPs@PAAm/PVA packaging exhibited desirable swelling behaviour, high solar reflectance, and strong atmospheric emissivity to synergistically achieve evaporative and daytime radiative cooling. The indoor experiments indicated that the vial with NPs@PAAm/PVA packaging realised sub-ambient temperatures under different working temperatures and humidities, and the field tests indicated that the vial with NPs@PAAm/PVA packaging could effectively preserve the anthocyanin and trypsin without degradation caused by strong sunlight and high temperature. Consequently, the NPs@PAAm/PVA packaging with evaporative and daytime radiative cooling effects has promising prospects for anthocyanin and trypsin transportation in an energy-saving and sustainable manner. [ABSTRACT FROM AUTHOR]

The detection of food quality and safety is important in the whole food supply chain. In recent years, fluorescent detection technology has been extensively applied in food analysis. In particular, nanomaterial-based "on-off-on" fluorescent sensors have received much attention because of their high sensitivity, wide detection range, strong anti-interference ability, and flexible design. Nevertheless, there is no review focusing on the "on-off-on" fluorescent sensors for food analysis. In the current review, several common nanomaterials are introduced, including quantum dots (QDs), carbon dots (CDs), graphene quantum dots (GQDs), and metal nanoclusters (MNCs). Main detection strategies of "on-off-on" fluorescent sensors are elaborated, involving redox reaction, competitive reaction, DNA hybridization reaction and enzymatic reaction. In addition, recent applications of "on-off-on" fluorescent sensors for trace level detection of nutrients, food additives, drug residues, pesticide residues, foodborne pathogenic bacterias, mycotoxins, and heavy metal ions are also summarized. Finally, advantages, challenges and future prospects for developing the "on-off-on" fluorescent sensors are presented. The "on-off-on" fluorescent sensors exhibit a wide detection range, strong anti-interference ability, and excellent linear responses to various analytes. However, current detection applications are still at the laboratory stage, commercial and industrial applications are rarely reported. Future research should focus on developing high-throughput detection techniques, and portable or visual fluorescent sensors, including kits and filter papers based sensors. Apps on smartphones should also be developed in future work. • We present principles and applications "on-off-on" fluorescent sensors. • We discuss four detection strategies for the fluorescent sensors. • The sensors have strong anti-interference ability and wide detection range. • The sensors can detect nutrients and harmful substances in foods. • Future research can focus on high-throughput, portable, and visual detection. [ABSTRACT FROM AUTHOR]

Inspired by the natural plant cuticles, a novel strategy was proposed for the fabrication of biomimetic plant cuticles from pullulan-graphene oxide (PU-GO) and beeswax-stearic acid (BW-SA), which could serve as hydrophilic polysaccharides and hydrophobic waxes, respectively. PU-GO and PU-GO/BW-SA in different GO concentrations (0, 10, 30 and 50 μg/mL) were prepared, and their structural characteristics and basic properties were investigated. Results showed that PU-GO/BW-SA possessed a hydrophilic layer and a hydrophobic structure similar to the structure of natural plant cuticles. The incorporation of GO enhanced the barrier properties of the films and PU-GO/BW-SA showed a higher contact angle, lower tensile strength and higher barrier properties compared with PU-GO. In addition, PU-GO/BW-SA in 10 μg/mL GO concentration (PU-GO 10 /BW-SA) possessed the lowest WVP (7.2 × 10−7 g/(m h Pa)) and a contact angle (93.78°) similar to natural plant cuticles. Applications in Citrus Limon Rosso further proved the potential of PU-GO 10 /BW-SA as a biomimetic plant cuticle in fruit preservation. • Pullulan-graphene oxide and beeswax-stearic acid (PU-GO/BW-SA) films are made. • Biomimetic plant cuticles are fabricated from PU-GO/BW-SA. • The structure of PU-GO/BW-SA is similar to natural plant cuticles. • PU-GO/BW-SA perform water loss prevention property. • PU-GO 10 /BW-SA exhibits well in citrus fruit preservation. [ABSTRACT FROM AUTHOR]

• Composite hydrogel was developed for sustainable daytime passive cooling. • Mechanical properties of hydrogel were improved by highly entangled structure. • Hydrogel achieved coupling effects of daytime radiative and evaporative cooling. • Hydrogel realized atmospheric water harvesting at night for next evaporation. • Relationship of daytime passive cooling with night time rehydration was revealed. Daytime passive cooling technology supported by coupling effects of daytime radiative cooling and evaporative cooling has drawn significant attention for alleviating the burdens of energy consumption and greenhouse gas emissions. Incorporating a hygroscopic agent allows the daytime radiative/evaporative cooler to replenish water itself at night, thus ensuring evaporative cooling during the daytime. However, the mechanism of the relationship between daytime passive cooling and nighttime rehydration is not fully understood. Besides, the design of circulating daytime radiative/evaporative coolers is segmented at present, and the poor mechanical properties of hydrogel restrict the practical application. Hence, a tough and elastic hydrogel with a highly entangled structure was prepared by dense polyacrylamide chains, exhibiting the 18-fold tensile stress and 9-fold compressive stress of the control group. Integrating zirconium dioxide (ZrO 2) particles as a spectral regulator, the composite hydrogel possessed solar reflectance of 0.90 and mid-infrared emission of 0.88, realising daytime radiative cooling. After swelling in lithium bromide (LiBr) solution, the composite hydrogel achieved a cycle of daytime evaporative cooling and nighttime rehydration. Besides, the effects of LiBr concentrations on the evaporation and hygroscopicity of the composite hydrogel were investigated. Furthermore, two indoor experiments and one outdoor field test were performed, and the findings suggested that the design of strong hygroscopicity and effective evaporation was a contradiction, and it is crucial to narrow the gap between evaporation and rehydration instead of only pursuing the best cooling performance to achieve sustainable daytime passive cooling. Thus, it is hoped that this study could broaden the field of sustainable daytime passive cooling technologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly sensitive, specific, and low-cost detection strategy was developed. • G4-DNAzyme added Cas12a system achieved a simultaneous output of three signals. • G4-DNAzyme-based sensor realized smartphone-assisted portable detection of AFB1. • The sensor correctly identified negatives and positives from peanut samples. Aflatoxin B1 (AFB1) contamination severely threatens human and animal health, it is thus critical to construct a strategy for its rapid, accurate, and visual detection. Herein, a multimodal biosensor was proposed based on CRISPR/Cas12a cleaved G-quadruplex (G4) for AFB1 detection. Briefly, specific binding of AFB1 to the aptamer occupied the binding site of the complementary DNA (cDNA), and cDNA then activated Cas12a to cleave G4 into fragments. Meanwhile, the intact G4-DNAzyme could catalyze 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to form colourimetric/SERS/fluorescent signal-enhanced TMBox, and the yellow solution produced by TMBox under acidic conditions could be integrated with a smartphone application for visual detection. The colourimetric/SERS/fluorescent biosensor yielded detection limits of 0.85, 0.79, and 1.65 pg·mL−1, respectively, and was applied for detecting AFB1 in peanut, maize, and badam samples. The method is suitable for visual detection in naturally contaminated peanut samples and has prospective applications in the food industry. [ABSTRACT FROM AUTHOR]

Food safety is directly relevant to human health and has drawn the intense attention of the public. Surface-enhanced Raman scattering (SERS), as a rapid and facile technology, has been widely employed for food safety detection. SERS substrates, as an important part of this technology, greatly influence SERS performance. Currently, porous materials (PSM) nanohybridized with metal nanoparticles (MNPs) (PSM/MNPs) for serving SERS substrates have attracted great interest due to their excellent merits in the improvement of SERS sensitivity, specificity and stability, posing a great potential for rapid and in-situ detection for food contaminants in complex food matrixes. In this review, the types and synthesis methods of PSM available for the fabrication of SERS substrates, which include porous carbon (PC), porous silicon/silica (PS/PSiO 2), metal-organic frameworks (MOFs), high polymer, semiconductor, cellulose and other porous materials are introduced and their nanohybridization methods with MNPs are discussed. In addition, recent applications of PSM/MNPs for enhancing SERS detection in food safety areas such as pesticide and veterinary drug residues, illegal additives, foodborne bacteria, mycotoxin, spoilage markers and heavy metals are also presented, and future challenges and potential solutions are finally detailed in the current review. Compared to non-porous materials, porous materials with high porosity and large surface specific area prevent MNPs from aggregation and increase the adsorption of the target analyte, leading to the improvement in stability and sensitivity of SERS substrates. Moreover, adjustable pore sizes in these substrates enable the selective absorption of specific molecules, blocking interference of big molecules. On the other hand, multiple scattering from the porous structure enhances SERS intensity, leading to high sensitivity for analytes. Recent applications in detecting various food hazards show the promising prospect of PSM/MNPs for sustainable, environmentally friendly and large-scale detection for ensuring food safety. • Porous materials can be nanohybridized with metal nanoparticles as SERS substrates. • Different synthesis methods of various porous SERS substrates are summarized. • Porous SERS substrates will promote the detection of food contaminants. • Developing porous SERS substrates remains a challenge. [ABSTRACT FROM AUTHOR]

Tea is one of the most popular beverages around the world for its health benefit. The availability of rapid and reliable techniques for evaluating tea quality and safety is important for the tea industry. However, tea components and pesticide residues detection, sensory analysis, grading, and pricing are carried out by laborious, time-consuming, and destructive methods. Therefore, vibrational spectroscopy has emerged as an increasingly popular technology in tea quality and safety evaluation owing to its simple, nondestructive and rapid detection procedures. The current review compares the employment of different vibrational spectroscopic techniques including near-infrared (NIR), mid-infrared (MIR), Raman, Terahertz (THz) spectroscopies and hyperspectral imaging (HSI) in tandem with regression and classification models in the quantitative and qualitative analyses of tea quality and safety. Furthermore, band assignments of tea components based on these spectroscopies are summarized. NIR spectroscopy dominates the applications of vibrational spectroscopy in the evaluation of tea quality, while only one study is related to THz spectroscopy. Raman technology is mainly applied to detect pesticide residues. HSI providing both spectral and spatial information has a potential in the optimization of the tea production process. Additionally, regression models find widespread use in the quantitative analysis of tea, such as phenolics, flavonoids, pigments, sensory evaluation, and pesticide residues, while classification models are useful for discriminating geographical origins, varieties, and fermentation degrees. The online detection of tea quality and safety by vibrational spectroscopy on the industrial scale is still an important and challenging task for future studies. • NIR spectroscopy is the most used spectroscopy in tea quality evaluation. • Raman technology is mainly applied for detecting pesticide residues in tea. • Quantitative investigation is more extensive than qualitative evaluation of tea. [ABSTRACT FROM AUTHOR]

A sparse coefficients wavelength selection and regression (SCWR) method is proposed in the present study. SCWR can rapidly and simultaneously operate regression and select wavelengths on NIR datasets with multiple response variables without any random procedure and cross-validation in the model. The method expresses a normal spectral calibration as a form of least absolute shrinkage and selection operator (LASSO), then the problem is reformulated into the alternative direction multiplier method (ADMM) form. Sparse coefficients wavelength selection (SCWS) method is developed by planting a positive-negative counteract strategy into SCWR, it can select a specified number of wavelengths. A specified number SCWR (NSCWR) is also suggested in order to perform regression using a specified number of wavelengths. SCWR methods have been tested on three NIR datasets (potato, corn, and soil), and these methods have better performance and use fewer feature wavelengths than existing simultaneous regression and wavelength selection methods on predicting almost all attributes in these datasets. Results indicate that SCWR-based methods could select wavelengths with more useful information. For the determination of hyperparameters in SCWR, manual adjustment of hyperparameters is available on sparsity control because the regression performance of SCWR is robustness and insensitive when hyperparameters are in proper ranges. Image 1 • SCWR can simultaneously perform wavelengths selection and regression. • Extension methods NSCWR and SCWS were proposed. • SCWR-based selection was rapid without random process and cross-validation. • SCWR-based methods obtained better performance than most of chemometrics. [ABSTRACT FROM AUTHOR]

Hyperspectral imaging (HSI) is a promising technique to evaluate food quality in a rapid and non-destructive way. Several types of HSI sensors are now commercially available. The aim of the current study was to compare one single shot and two line-scanning based HSI sensors in different spectral regions by using two wavelength dispersive devices – a prism-grating-prism monochromator and a mosaic wavelength dispersion unit. The research sample was cured pork meat, which is a popular meat product due to its flavor and long shelf life. Three main chemical compositions of cured pork meat – moisture, protein and fat content – were evaluated. The spectral properties of the three sensors were employed to establish partial least squares regression (PLSR) predictive models by applying different optimal wavelengths selection strategies. The results showed that optimal wavelength selection was more important than the selection of the wavelength dispersion device. • Three hyperspectral imaging (HSI) systems were compared. • Prediction models for compositions of dry and wet cured pork were established. • Nine wavelengths were sufficient for predicting chemical compositions. • Slight differences between the two wavelengths dispersion systems were observed. • Optimal wavelength selection was a key step in improving models of HSI. [ABSTRACT FROM AUTHOR]

Cereals are globally consumed as staple food, providing essential nutrients to the consumers. The emerging problems associated with cereals are mycotoxin outbreaks and adulteration in both the cereals and their products. Both classical and emerging techniques are extensively exploited to tackle such problems. However classical methods still face more limitations as compared to emerging nondestructive methods. High-performance liquid chromatography, gas chromatography and enzyme-linked immunosorbent assays, are classical methods employed for assessing the quality and safety parameters of cereal foods, with limitations of offline, time consuming and destructiveness. On the other hand, emerging nondestructive methodologies like hyperspectral imaging, fluorescence spectroscopy, near infrared spectroscopy and Fourier transform infrared spectroscopy have been introduced as promising techniques for the assessment of fungal contamination, quality discrimination and adulteration detection in cereals and cereal products. This review highlights the most recent applications of enlisted classical and emerging approaches, their working principles and advances in determining various safety and quality attributes of cereals and their products. Besides, challenges and future trends, their advantages and limitations are also elucidated. Classical methods have been exploited for safety and quality measurement of cereal foods with relatively low efficiency, as compared to emerging nondestructive techniques. Classical methods suffer from disadvantages of destructiveness, thus they cannot be used for on-line monitoring, detection and evaluation. Emerging approaches are reliable with accurate, fast and non-invasive nature of investigations for the authentication of safety and quality attributes of cereal grains and their products during storage and processing. These innovative technologies can overcome the complexity, troubles, destructibility and slowness associated with classical analytical tools. • Cereal and their products are important staple foods with essential nutrients. • Fungal Infections reduce nutritional value and production of grains. • Both conventional and novel methods are applied for quality monitoring of grains. • Working principles, limitations and strengths of both methods are presented. [ABSTRACT FROM AUTHOR]

Fresh fruit are important for a healthy diet, however, their shelf-life can be shortened because of ethylene, a key phytohormone associated with the ripening process. Therefore, detecting ethylene concentration on trace level and regulating its activity by safe and effective approaches are of paramount importance in extending postharvest shelf-life and controlling maturity of fruit. In this review, ethylene detection technologies as well as ethylene regulating strategies are discussed, aiming to develop more innovative and effective approaches. Effects of ethylene on quality and shelf-life of fruit are presented. Ethylene detection and monitoring technologies available such as gas chromatography, electrochemical, optical, chemical methods, especially novel methods such as those based on colorimetric, luminescence, metal-organic frameworks, organic field effect transistors and surface enhanced Raman spectroscopy are described. In addition, shelf-life extending technologies for ethylene control, removal or inhibition such as suppressing ethylene synthesis, scavenging or oxidizing or adsorbing ethylene, and blocking ethylene receptor are summarized. Finally, future perspectives on developing strategies that can simultaneously satisfy the requirements of sensitivity, rapidness and on-line for wide utilization in ethylene monitoring of fresh products are also given. It is expected that miniature and sensitive ethylene detection techniques combined with feasible ethylene control methods should be an effective solution for fruit quality maintenance and shelf-life extension. However, each type of sensors and ethylene control strategies currently available has their own advantages and limitations. Therefore, attempts should be made to exploit more effective ethylene detection and controlling technologies. • Ethylene concentration affects postharvest shelf-life and maturity of fruit. • Detecting and regulating C 2 H 4 is important in fruit postharvest management. • Commercially available C 2 H 4 detection methods have specific application fields. • Nanotechnology should be employed to achieve in-situ and rapid C 2 H 4 detection. • Dynamic controlled atmospheres can be refined to avoid CO 2 and low O 2 injury. [ABSTRACT FROM AUTHOR]

Button mushroom (Agaricus bisporus) is widely used on the world market. Browning of mushroom surface is the most intuitive factor affecting consumer purchase. Developments of browning during postharvest are related to the flush number, mechanical damage, polyphenol oxidase, phenolic compounds, pathogens and postharvest environment. Many techniques such as cooling, modified atmosphere packaging (MAP) and coating are developed to control button mushroom browning. In this review, the main factors involved in mushroom browning including mushroom tyrosinase, postharvest factors and pathogen are discussed, and some detection methods for mushroom surface color are introduced. Furthermore, different methods for controlling browning including MAP, polyphenol oxidase (PPO) inhibitors, edible coating, irradiation, cooling and other emerging techniques are reviewed and compared. Internal factors of button mushroom browning include subtracts, enzyme and mushroom cellular integrity, which are affected by postharvest factors such as mechanical damage, temperature, relative humidity, and atmosphere gas. Imaging or computer vision and hyperspectral imaging are emerging methods for the detection of mushroom color and can be used to analyze each pixel of the entire surface of mushrooms. In order to control mushroom browning, preservation methods including MAP, coating, PPO inhibitors and irradiation are extensively studied. In addition, thermally buffered package, commercial film materials and gas composition of MAP, natural coating and PPO inhibitor materials should be investigated in future. • Button mushroom browning is affected by postharvest factors. • Modified atmosphere packaging is often used among all the control methods. • Tendency of inhibitory rate for L* during storage varies with control methods. • Computer vision is a rapid and reliable method for detecting mushroom color. [ABSTRACT FROM AUTHOR]

• A dual-mode freshness indicator based on DPA-Au/CuNCs was fabricated. • Simultaneous monitoring of ammonia and temperature was achieved for the first time. • Applications for in-situ and visual monitoring the seafood freshness. Seafood is highly perishable and monitoring its freshness this thus an important issue. For the first time, the current study developed a dual-mode freshness indicator based on d -penicillamine capped bimetallic gold/copper nanoclusters (DPA-Au/CuNCs) as a response probe for simultaneous monitoring of ammonia and temperatures to assess seafood freshness. Results indicated that the prepared DPA-Au/CuNCs have good sensitivity toward ammonia, with a limit of detection of 0.14 ppm. The indicator as a gas sensor for ammonia vapour detection exhibited highly recognizable fluorescence colour changes and the variations from white to yellow were observed with increasing storage temperature under natural light. For confirming its practical applications, the indicator was used to simultaneously monitor ammonia and temperatures during the storage of shrimp and fish, showing good potential for practical applications in evaluating seafood freshness for the food industry. [ABSTRACT FROM AUTHOR]

• Discovery of oxidase-like activity and degradable property of γ-MnOOH nanowires. • Understanding of the degradation-activity correlation of γ-MnOOH nanozymes. • Designing a colorimetric platform for POC detection of OPs and AChE activity. • Low LODs, high selectivity, anti-interfere capacity, and workable in real samples. • This portable detection platform possessing great ecological sustainability. Despite the tremendous achievements of existing sensing techniques, sensitive and portable sensing of organophosphorus pesticides (OPs) in a non-polluting manner remains a challenging issue. This work proposed a facile colorimetric paper sensor using γ-MnOOH nanowires (NWs) as a degradable nanozyme and 3,3′,5,5′-tetramethylbenzidine (TMB) as a chromogenic indicator for rapid and sensitive screening of OPs and acetylcholinesterase (AChE) activity. The sensing mechanism was based on the easy disintegration of the oxidase-like γ-MnOOH NWs into invalid Mn2+ ions by the selective reaction with thiocholine (TCh) produced by AChE and acetylthiocholine iodide (ATCh), triggering a remarkable activity loss of MnOOH nanozymes towards TMB oxidation. The concentration of OPs, as an AChE inhibitor, was measured by the changes in absorbance at 652 nm or blue color of oxTMB products. Such detection platform in solution state achieved relatively low limits of detection (LODs) for AChE activity (0.007 mU mL−1), and for two typical OPs, i.e., omethoate (0.35 ng mL−1) and dichlorvos (0.14 ng mL−1), respectively. Further, the portable assembly of such AChE-nanozyme tandem reaction on test paper performed well, reaching LODs of 0.1 mU mL−1 for AChE, 10 ng mL−1 for omethoate, and 3 ng mL−1 for dichlorvos, respectively. Meanwhile, this sensing system showed great selectivity and anti-interfering capacity in both solution and solid states, and worked well in real serum and vegetable samples. The abovementioned results, along with evidence of its good ecological sustainability, demonstrated the superiority of this well-performing platform for application in the food, environmental, and medical fields. [ABSTRACT FROM AUTHOR]

Cheese is produced around the world in a wide range of flavours, varieties, textures, and shapes, which can be used as a final product in human diet, and as an important ingredient in various foods. With consumer's continuing demand for quality cheese as well as increasing challenge from production facing the industry, nondestructive techniques are increasingly used to evaluate cheese quality. Considering the rapid development of novel nondestructive techniques, relevant literatures in the past 15 years (2004–2018) are reviewed in this paper. The main quality attributes of cheese and the importance of evaluating these attributes are discussed. The principles, developments and applications of computer vision (CV), computed tomography (CT), X-ray system, magnetic resonance imaging (MRI), fluorescence spectroscopy, near-infrared (NIR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, hyperspectral imaging (HSI), Raman imaging, ultrasonic and acoustic sensing and other nondestructive techniques are discussed in this review. Among all nondestructive techniques used for cheese quality evaluation, fluorescence spectroscopy is the most used method for classification, NIR spectroscopy is mainly used for predicting chemical components, FTIR spectroscopy shows the greatest scope of applications, while CV, X-ray and MRI are only used for monitoring eye growth. HSI and Raman imaging begins to attract research interest, and synchronous fluorescence spectroscopy gradually replaces front-face fluorescence spectroscopy, whereas CV is no longer applied to cheese evaluation and literatures about NIR spectroscopy also becomes less in recent years. It is hoped that this review should provide information on current research gaps and set some directions for future studies. • Nondestructive techniques for cheese quality evaluation are reviewed. • Cheese attributes and their importance are presented. • Applicability and the pros and cons of nondestructive techniques are discussed. • Future research directions are suggested. [ABSTRACT FROM AUTHOR]

Abstract An ultrasensitive method for the kanamycin (KANA) detection in milk sample using surface-enhanced Raman spectroscopy-based aptasensor was employed in the current study. Double strand DNA binding bimetallic gold@silver nanoparticles were developed as a sensing platform. Probe DNAs were first embedded on the surface of gold nanoparticles by the end-modified thiol, and after silver shell encapsulating, KANA aptamer DNAs with the Raman reporter Cy3 were then hybridized with probe DNAs by complementary base pairing. Results showed that with increase in the KANA concentration, the Raman intensity of Cy3 decreased. Besides achieving selectivity, an ultralow detection limit of 0.90 pg/mL, a broad linear relationship ranging from 10 μg/mL to 100 ng/mL in aqueous reagent and satisfactory recoveries of 90.4–112% in liquid whole milk were obtained. The result of actual sample proved that this aptasensor was promising in trace determination of KANA residue. Graphical abstract fx1 Highlights • Au@Ag NPs-ds DNA was synthesized and characterized. • Kanamycin concentrations could be monitored by the Raman intensity of Cyanine-3. • The aptamer-sensor showed high selectivity and sensitivity for kanamycin detection. • This method was successfully applied to determine kanamycin in milk. • This method was superior in detection limits compared with existing methods. [ABSTRACT FROM AUTHOR]

Abstract Plasmonic core-shell nanomaterials have attracted great attention and offered wide applications in surface-enhanced Raman spectroscopy (SERS) due to their unique localized surface plasmon resonance (LSPR) characteristics. In this study, the SERS performance of Ag coated Au nanoparticles aggregates (Au@AgNAs) substrate was explored. The fabrication of Au@AgNAs involved using spherical Au nanocrystals of 32 nm in diameter as the seeds, and ascorbic acid was used as the reductant. The thickness of the Ag shell deposited onto the Au surface was finely tuned from 3 to 13 nm by changing the amount of AgNO 3 precursor. Results in this study suggested that the LSPR of the Au core was rapidly attenuated with increasing Ag shell thickness, while the LSPR bands for Ag shell blue-shifted from 390 to 420 nm. Au@AgNAs with the Ag shell thickness of 8.5 nm exhibited excellent SERS activity, which could realize detecting R6G at an ultralow concentration of 1 × 10−12 M. Besides, the prepared Au@AgNAs showed well homogeneity and reproducibility, and the limit of detection of thiram was calculated as 1.09 × 10−9 M, indicating that the Au@AgNAs substrate could be potentially used for high-performance SERS sensing applications. Graphical abstract fx1 Highlights • SERS performance of Au@Ag nanoparticles aggregates (Au@AgNAs) was evaluated. • Conjunction of Au@Ag nanoparticles can generate a large amount of SERS hot spots. • The Au@AgNAs substrate showed excellent SERS sensitivity and reproducibility. • The detection of limit of thiram was down to 1.09 × 10−9 M using Au@AgNAs. [ABSTRACT FROM AUTHOR]

Abstract Secondary structure of proteins is closely related to the overall quality of meat. The sequence of the changes in chemical bonds caused by secondary structure modification and rapid detection method of secondary structure fractions was investigated by near-infrared hyperspectral imaging combined with generalized (G2D-CS) and heterospectral (H2D-CS) two-dimensional correlation analysis in this study. Synchronous and asynchronous spectral results from G2D-CS analysis indicated that, as α-helix fraction decreasing, the spectral intensity of N H stretching changed before that of the C H and O H, and the spectral fluctuation of O H stretching occurred after the carbonyl related C H band and before those aliphatic and aromatic C H band. Feature wavebands identified by H2D-CS analysis obtained good results with R2 CV of 0.836 in predicting α-helix fractions. The results of this study are useful for interpreting the secondary structure modification process of proteins during frozen storage and monitoring the secondary structure fraction in a rapid way. Highlights • NIR HSI was employed by the first time to monitor α-helix fraction of actomyosin. • G2D-CS was used for understanding the process of secondary structure modification. • H2D-CS was applied for identifying α-helix related NIR wavebands. • PLSR model built by the selected wavebands showed good results. [ABSTRACT FROM AUTHOR]

Abstract Protein is an important nutrient for people diet, and protein content is one of the most vital properties in quality assessment of pork meat. The potential of line-scanning based hyperspectral imaging (HSI) has been proved to be able to assess the protein content of meat, however quality of images obtained from line-scanning HSI is affected by sample transformation conditions. A novel single shot (snapshot) HSI sensor was employed to evaluate the protein content of numerous processed pork meat by using back propagation - neural network (BP-NN) and partial least squares regression (PLSR) predictive models. The results of BP-NN were better than that of PLSR. The best spectral profile was selected from reflectance, absorbance, and Kubelka–Munk (K–M) spectra by comparing the performances of their BP-NN models. The BP-NN model combined with absorbance spectra showed the best performance for evaluating the protein content of various processed pork meats with determination coefficient of cross-validation set (R2 CV) = 0.8318, and root mean square error of cross-validation set (RMSECV) = 8.38 mg/g, respectively. Results indicated the feasibility of determining the protein content of pork meats by means of single shot HSI. Highlights • The single shot hyperspectral imaging (HSI) could capture an image in 1/150 s. • Protein content of pork decreased after wet salting – dehydrating. • Absorbance spectra provided better accuracy. • BP-NN model was used to predict protein contents of pork by snapshot HSI. • Protein contents distribution of processed pork were showed by snapshot HSI. [ABSTRACT FROM AUTHOR]

Abstract The residual of pesticides in fruit and vegetables is one of the major food safety concerns for consumers. There is a demand for easy and rapid analytical methods to sense pesticide residues in foods. In this study, a core-shell Au@Ag nanoparticles aggregates (Au@AgNAs) based surface-enhanced Raman scattering (SERS) method was developed to detect trace amount of difenoconazole. Results suggested that by targeting the characteristic peaks at 700 and 808 cm−1, the logarithmic SERS signal intensities and logarithmic difenoconazole concentrations in the range from 5 × 10−7 to 2.5 × 10−5 M showed linear relationship with the coefficient of determination (R 2 ) of 0.990 and 0.985, and limit of detection (LOD) values of 5.01 × 10−8 and 2.8 × 10−8 M, respectively. The Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method was used to extract difenoconazole in grapes for SERS measurements. The LOD of difenoconazole in grapes using this developed method was as low as 48 μg/kg, which was significantly lower than the maximum residue limit (MRL) values prescribed by European Union and China. This study demonstrated that the Au@AgNAs-based SERS method can be used as a simple, rapid and sensitive approach for sensing trace contaminants in food. Graphical abstract fx1 Highlights • SERS is an alternative method for rapidly detecting trace contaminants. • Au@Ag nanowire aggregates was used as SERS substrate for detecting pesticide. • The developed SERS method can detect as low as 48 μg/kg difenoconazole in grapes. • The entire analysis can be achieved within 25 min. [ABSTRACT FROM AUTHOR]

Highlights • A multispectral model was built for DHA and EPA prediction. • A novel PN-GA algorithm was used to select the key variables. • MLR models showed better results for DHA and EPA in two fish fillets. • The dynamic changes of DHA and EPA were visualized. Abstract A multispectral model for the detection of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) changes in grass carp and salmon fillet was developed using physarum network and genetic algorithm (PN-GA) method for the first time. Partial least-squares regression (PLSR), multiple linear regressions (MLR), and principal component regression (PCR) algorithms were used to predict the DHA and EPA using optimal wavelengths selected by PN-GA. The MLR models showed the best DHA prediction results for both grass carp and salmon fillets, and also showed good prediction for EPA in grass carp fillet but poor prediction in salmon fillet. The MLR models were then applied for visualizing the spatial distribution of DHA and EPA changes in two fish fillets. The current results demonstrated that a developed multispectral imaging system could be feasibly constructed for DHA and EPA measurement in fish species with the optimal wavelengths selected by PN-GA method. [ABSTRACT FROM AUTHOR]

• A high-sensitivity, stable and uniform Au@Ag NRs-CMC SERS chip was fabricated. • CMC hydrogel was used for Au@Ag NRs stabilization, homodisperse and protection. • Negatively-charged CMC hydrogel and Au@Ag NRs repel each other to form NRs arrays. • Au@Ag NRs-CMC chip has high SERS activity, reproducibility and long-term stability. • Au@Ag NRs-CMC chip achieves sensitive detection of pesticide residue in fruits. Cellulose material holds considerable promise for effective surface-enhanced Raman scattering (SERS) substrate construction due to its extensive availability, chemically modifying capacity, ease of manufacture, high flexibility and low optical activity. A large-area, high-sensitivity, stable and uniform Au@Ag nanorods (NRs)-CMC substrate was successfully developed via electrostatic repulsion by using negatively-charged core–shell Au@Ag NRs as SERS active plasmonic nanomaterial, combined with negatively-charged carboxymethylcellulose (CMC) hydrogel for nanoparticles stabilization, homodisperse and protection. The obtained Au@Ag NRs-CMC substrate showed excellent sensitivity for the detection of thiram residues in fruits containing low and abundant pigment interferents, such as apples and blueberries, with detection limits of 58 and 78 ppb, respectively. Additionally, it retained more than 80% SERS performance after storage for 9 months under ambient conditions, demonstrating its great potential in facilitating the commercialization of cellulose-based SERS technology for cost-effective detection of food contaminants with advantages of facile preparation procedure, uniformity, reproducibility and long-term stability. [ABSTRACT FROM AUTHOR]

Hyperspectral imaging (HSI) technology fusing spectroscopic technology and imaging technology has been proposed to achieve rapid and non-destructive inspection of food quality. In order to make full use of the hyperspectral data containing rich information, it is needed to develop effective and efficient data analysis methods to mine new information from hyperspectral data. The feature construction (FC) method, as a method of extracting information to construct new features, is applied to construct more representative and informative features from hyperspectral data for the detection of food quality. The review focuses on the construction methods of different dimensional features including zero-dimensional (0-D) features, one-dimensional (1-D) features, two-dimensional (2-D) features and three-dimensional (3-D) features in detail and presents their principles and implementation steps. In the review, applications of the HSI technology combined with different dimensional FC methods for the quality inspection of food are also discussed, and challenges and future work of the HSI technology combined with FC methods are presented. The current review is expected to provide some guidance to researchers on different dimensional FC methods, which should further encourage more applications of the HSI technology in food quality inspection. Despite the challenges in combining FC methods with hyperspectral technology, the encapsulation of FC methods in miniaturised hyperspectral instruments is an inevitable trend for future development. • Principles and implementation of different dimensional FC methods are discussed. • HSI technology combined with FC methods in food quality inspection is presented. • Challenges and future work of HSI technology combined with FC methods are offered. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) spectra contain abundant data, heterospectral two-dimensional correlation (H2D-CS) analysis offers a good way to interpret these data. For the first time, H2D-CS was used to correlate the NIR hyperspectral imaging (HSI) data with mid-infrared spectra and to identify feature-related wavebands for developing models for monitoring the oxidative damage of pork myofibrils during frozen storage. The HSI images were acquired at frozen state without thawing and the oxidative damage of myofibrils was assessed by carbonyl content. Results showed that the simplified PLSR model based on H2D-CS identified feature wavebands obtained determination coefficient in prediction (R 2 P ) of 0.896 and root mean square error in prediction (RMSEP) of 0.177 nmol/mg protein, which was better than the partial least square regression (PLSR) model based on full wavebands (R 2 P  = 0.856, RMSEP = 0.209 nmol/mg protein). Therefore, H2D-CS was effective in selecting feature-related wavebands of NIR HSI. [ABSTRACT FROM AUTHOR]

Background The irrational usage of chemical substances including pesticides and drugs in agricultural and food production is a significant food safety issue due to its residues. Therefore, the detection of harmful residues in foods is an indispensable step for guaranteeing the consumer's health. Conventional methods, such as HPLC, GC-MS and LC-MS are accurate enough, but they fail to meet the requirements of the modern industry for rapid and on-line detection. Novel reliable techniques should thus be developed as alternatives. Scope and approach In this review, fundamentals of surface-enhanced Raman spectroscopy (SERS) is introduced. Recent advances in its usage for detecting harmful chemical residues in agricultural products including pesticides, antibiotics and β 2 -adrenergic agonists are discussed by two typical ways of detection improvement, and the advantages of SERS are addressed. Finally, future trends to routine use of SERS applications in harmful residues are presented. Key findings and conclusions SERS is a promising detection technique for the detection of common harmful chemical residues with merits of simple sampling, rapid data collection and non-destructiveness. Despite rapid developments in the technology, there is much studies should be done before SERS could be used as a daily tool for the industry. [ABSTRACT FROM AUTHOR]

Background Frozen dough technology could effectively extend the shelf life of bread to ensure the freshness, which is widely used and gradually replace the traditional bread production. However, during the production and storage of frozen dough, a series of problems could take place, such as inhibition of yeast activity, damage of the structure of the dough, leading to the deterioration of dough quality. Scope and approach This review summarizes the factors that affect the final quality of frozen dough, including yeast activity, dough structure and dough properties. Some effective methods for improving freeze tolerance of yeast, dough structure and dough properties are discussed, including addition of various additives, use of genetic engineering technique, optimization of freezing and storage conditions, and employment of novel freezing technology. Key findings and conclusions The addition of additives can not only improve the freeze tolerance of yeast but also maintain the rheological and thermophysical properties of dough. Through the modification of gene, freeze tolerance and fermentation ability of yeast can be improved. Optimizing freezing and storage conditions ensures the activity of yeast as well as dough network structure so that freezing damage due to ice crystals can be minimized. In addition, novel freezing technology such as ultrasound-assisted freezing can simultaneously accelerate the freezing process as well as generate fine and uniform ice crystals, thus protecting dough network structure. [ABSTRACT FROM AUTHOR]

The study investigated the possibility of using hyperspectral imaging (HSI) in the spectral range of 1000–2200 nm to characterize myofibrils cold structural deformation degrees of frozen pork samples. The HSI images of pork samples frozen under different freezing rates were acquired in the frozen state without thawing. The myofibrils cold structural deformation degrees were evaluated by surface hydrophobicity (S 0 ANS) and Ca 2+ -ATPase activity. Spectral angle mapping (SAM) algorithm was used for the first time to extract the spectral information for regression. Compared with the optimized partial least square regression (PLSR) models based on selected wavebands by successive projections algorithm (SPA), the optimized PLSR models developed based on the spectral angles calculated by the SAM algorithm achieved comparable or even better performance with R 2 P of 0.896 for S 0 ANS and 0.879 for Ca 2+ -ATPase activity, respectively. The implications of the frozen meat spectrum were also analyzed in the current study. [ABSTRACT FROM AUTHOR]

In this work, a rapid and accurate surface-enhanced Raman spectroscopy (SERS) based on silver nanodots (AgNDs) array substrate method was used to detect Alternaria alternata ( A. alternata ) in both sterile water and pear juice (an example of complex food matrix). The substrate fabrication conditions were firstly optimized to obtain the maximal SERS enhancement. SERS and Raman mapping methods were then used to scan the A. alternata adsorbed on the surface of the substrate, and the intrinsic and distinct SERS signals of A. alternata were used as the basis for detection. It was found that using A. alternata in sterile water as a model sample, the method was able to detect the A. alternata with a limit of detection (LOD) as low as 1.0 × 10 3 cfu/mL. Moreover, the newly developed method could also realize rapid detection of A. alternata in pear juice, and the lowest detectable A. alternata concentration was less than 1.0 × 10 4 cfu/mL. In addition, the A. alternata concentration range from 1.0 × 10 4 cfu/mL to 1.0 × 10 6 cfu/mL could be detected by SERS mapping. This study provides a convenient method for the detection of low-level A. alternata in complex food matrix, and further information and guidance for the design of a SERS-based detection. [ABSTRACT FROM AUTHOR]

Background Cold plasma (CP) is an emerging technology, which has attracted the attention of scientists globally. It was originally developed for ameliorating the printing and adhesion properties of polymers plus a variety of usage domains in electronics. In the last decade, its applications were extended into the food industry as a powerful tool for non-thermal processing, with diverse forms for utilization. Scope and approach This review presents an overview of recent studies on the application of cold plasma in the food industry. Specific areas discussed include microbial decontamination of food products, packaging material processing, functionality modification of food materials and dissipation of agrochemical residues. The application of CP has also been expanded into areas, such as hydrogenation of edible oils, mitigation of food allergy, inactivation of anti-nutritional factors, tailoring of seed germination performance and effluent management. In addition, the paper provides a summary of plasma chemistry and sources, factors influencing plasma efficiency and strategies for augmentation. Furthermore, key areas for future research are highlighted and salient drawbacks are discussed. Key findings and conclusions The recent studies conducted on the interaction of reactive species with food contact surfaces establish plasma processing as an eco-friendly technique with minimal changes to food products, making it a befitting alternative to traditional techniques. Active researches focused on up-scaling for commercial applications are urgently required. [ABSTRACT FROM AUTHOR]

Background Advanced food processing technologies such as microwave heating have experienced increased popularity, as alternatives to conventional processing methods for diverse applications in the food industry. A new dimension, is the concept of microwave-assisted food processing techniques, which utilize the advantages of microwave energy to overcome the shortcomings of conventional and some emerging food processing methods. Scope and approach This paper reviews some microwave-assisted (MA) food processing technologies, such as MA-ultrasonication, MA-ohmic heating, MA-electron irradiation, MA-freezing, MA-osmotic dehydration, MA-infrared heating, and microwave-vacuum processing (MA-VC). In particular, their effects in terms of enhancing product quality and process efficiency, including principles and mechanisms are discussed. Promising food applications includes drying, extraction, baking, roasting, pasteurization/sterilization, tempering. Future strategies to further widen their applications are highlighted and salient drawbacks are also taken into consideration. Key findings and conclusions In general, the resultant benefits of microwave assistance to conventional or emerging food processing technologies include high thermal efficiency, shorter processing time, reduced operational cost and improved product quality. It is hoped that this paper will increase positive ratings for microwave assisted food processing technologies and promote their adoption by the food industry. However, it is important that appropriate simulation models for process optimization be developed alongside. [ABSTRACT FROM AUTHOR]

Background Proteins are essential nutrients required in various body functions and normal human life. However, in the food industry, the application of proteins especially those of plant origin have been limited due to their poor functionality. Although nowadays, diverse modification techniques are usually employed to improve their performance in food products, it is also important that effective methods for monitoring the resultant conformational changes induced during protein modification are developed. Scope and approach In this review, the relationship between protein conformation and functionality is briefly discussed. Thereafter, the underlying principles behind five selected spectroscopic techniques i.e. Fourier transform infrared, Raman, circular dichroism, fluorescence, and ultraviolet spectroscopies are introduced and their recent applications for monitoring conformational changes that occur during physical, chemical or enzymatic modification of proteins are addressed. In addition, the advantages and limitations of each spectroscopic technique are comparatively discussed and perspectives on the current situation alongside future trends are highlighted. Key findings and conclusions Spectroscopic techniques present an attractive panacea for evaluation of conformational changes during protein modification. Although certain challenges especially with complex food materials require urgent attention thus, more robust spectroscopic solutions should be exploited in the future. [ABSTRACT FROM AUTHOR]

Background The safety and quality of agri-food products is a critical public concern over the years. In order to guarantee human heath, it is essential to develop a rapid and non-destructive tool for assuring high-quality agri-food products in the market. Terahertz (THz) spectroscopic imaging is an emerging non-destructive technique. THz wave with the frequency range between the infrared and the microwave can penetrate many commonly used nonpolar dielectric materials and indicate vibrational modes of many biomolecules, which make it an extremely attractive tool for agri-food products inspection. Scope and approach This current paper presents the THz sources and fundamentals of THz spectroscopic imaging technique and discusses chemometric methods applied in THz spectra for qualitative and quantitative analysis. In addition, recent advances in its applications for the safety and quality control of agri-food products over the years 2012–2017 are reviewed. Finally, some perspectives on the current situation and future trends of using THz technique are addressed. Key findings and conclusions It is expected that THz technique combined with chemometric methods has great potential for agri-food products evaluation, and continuous wave THz imaging performs better for identifying low-density foreign bodies embedded in foodstuffs as compared to X-ray imaging. Additionally, THz technique shows the ability to detect packaged agri-food products. The future development of cost-effective and portable THz spectrometer with high sensitivity will make this technique in practical applications. [ABSTRACT FROM AUTHOR]

Background Microwave-assisted extraction (MAE) have gained enormous popularity as a preferred method for the recovery of various active compounds from food materials. They proffer benefits such as the reduction of extraction time, environmental friendliness, low cost and enable automation or on-line coupling to other analytical procedures. Recently, newer add-ons or technological modifications have been incorporated into MAE systems, in an effort to continuously improve extraction efficiency and ensure a greener implementation. Scope and approach The core pathways of such meliorations include integrating microwave extraction with other technologies, e.g., ultrasound assisted extraction (UAE), negative pressure cavitation (NPC), enzyme assisted extraction (EAE), hydrodiffusion extraction (HDE), and supercritical fluid extraction (SFE) or replacement of extraction medium with suitable alternatives including ionic liquids, deep eutectic solvents, non-ionic surfactants, etc. This review confers their underlying principles and mechanisms, equipment and apparatuses, practicalities, as well as resultant benefits such as increased yield, intensification of mass transfer and reduction of energy consumption, in a manner not achievable by MAE alone or previous intermediary modifications. Key findings and conclusions It is hoped that this paper reinforces the need to initiate more studies focused on process validation and optimization of such emerging MAE systems, in furtherance of their scale-up, sustainability and robust adoption by the food industry. [ABSTRACT FROM AUTHOR]

Background Microwave processing techniques have been extensively used in the food industry due to its significant reduction in cooking time and energy consumption. Microwave processing technologies such as microwave drying, heating and sterilizing play a significant role in food quality and safety control. However, few reviews have been published in recent years summarizing the latest developments in the application of microwave technology in the food industry. Scope and approach This review focuses on recent applications of microwave processing technologies including microwave drying, heating, and sterilizing in fruit (banana, apple, olive, sour cherries, pomegranate arils, blueberries, kiwifruit, aronia, strawberry, and grape tomato), vegetables (potato, bamboo shoot, purslane leaves, onion, green bean, pumpkin, eggplant, edamame, sea tangle, garlic, kale, red cabbage, tomato, cassava, lentils, chickpea, broccoli, Brussels sprouts, cauliflower, jalapeño peppers, and coriander foliage), and meat products (sardine fish, restructured silver carp slices, sea cucumber, beef semitendinosus muscle, bovine supraspinatus muscle, camel longissimus dorsi muscle, foal meat, bovine gluteus medium muscle, chicken steak, mature cows semimembranosus and semitendinosus muscles, kavurma (a ready-to-eat meat product), salmon, cod, drumettes, and beef slices), changes in product quality as affected with microwave processing are discussed in details, and future directions of research are presented. Key findings and conclusions Microwave drying has the advantages of low energy consumption and high efficiency as compared to conventional drying, while producing more porous structure of foods. Microwave drying usually combines with other conventional drying to enhance the quality of a food product. Compared with the traditional method, microwave heating or cooking can generally retain higher levels of bioactive components, antioxidant activity and attractive color of vegetables, while microwave cooking with water can cause a serious drop in nutrients due to leaching and thermal liability. Microwave sterilization has the capacity to completely inactivate microorganisms and effectively destroy enzyme activity, and less effect on antioxidant activity, texture and color of food products compared with conventional pasteurization. [ABSTRACT FROM AUTHOR]

Effects of protein denaturation caused by high pressure freezing, involving Pressure-Factors (pressure, time) and Freezing-Factors (temperature, phase transition, recrystallization, ice crystal types), are complicated. In the current study, the conformation and functional changes of natural actomyosin (NAM) under pressure assisted freezing (PAF, 100,150,300,400,500 MPa P −20 °C/25 min ), pressure shift freezing (PSF, 200 MPa P −20 °C/25 min ), and immersion freezing ( 0.1MPa P −20 °C/5 min ) after pressure was released to 0.1 MPa, as compared to normal immersion freezing process (IF, 0.1 MPa P −20 °C/30 min ). Results indicated that PSF ( 200 MPa P −20 °C/30 min ) could reduce the denaturation of frozen NAM and a pressure of 300 MPa was the critical point to induce such a denaturation. During the periods of B → D in PSF or B → C → D in PAF, the generation and growth of ice crystals played an important role on changing the secondary and tertiary structure of the treated NAM. [ABSTRACT FROM AUTHOR]

The potential of chemical imaging for rapid measurement of dry matter concentration (DMC) and starch concentration (SC) in both potato and sweet potato tubers was investigated. The time series images of tuber samples were acquired, then the resulting reflectance spectra (R S ) were corrected and transformed into absorbance spectra (A S ), and exponent spectra (E S ). Full wavelength regression models including multiple linear regression (MLR), partial least squares regression (PLSR) and locally weighted partial least squares regression (LWPLSR) were established based on spectral profiles with measured DMC and SC values. The best calibration model for measuring DMC and SC was LWPLSR based on E S and R S where the coefficients of determination in cross-validation ( R 2 CV ) were 0.987 and 0.985, and the root mean squared errors in cross-validation (RMSECV) were 0.015 and 0.014, respectively. After, six groups of eight feature wavelengths were chosen from R S , A S and E S based on wavelength selection methods including β-coefficient (βC) of PLSR and the first derivative and mean centering iteration algorithm (FMCIA), and were successively used to build simplified models. The acquired FMCIA-R S -LWPLSR and βC-R S -LWPLSR models showed better accuracy than other simplified models, with R 2 P of 0.985 and RMSEP of 0.016 for DMC prediction, and R 2 P of 0.983 and RMSEP of 0.015 for SC prediction, respectively. Besides, the optimal models for MLR and PLSR were obtained using FMCIA on the basis of the E S . After further reducing the number of feature wavelengths, only six wavelengths (1028, 1068, 1135, 1208, 1262 and 1460 nm) were selected and utilized to develop the simplest FMCIA-Es-MLR model for determining DMC and FMCIA-Es-PLSR model for detecting SC, yielding a reasonable level of accuracy with R 2 P of 0.962 and 0.963 as well as RMSEP of 0.025 and 0.023, respectively. Furthermore, the time series variations of DMC and SC on tuber samples were visualized based on an equation to apply the simplest models to the spectral images. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent tag based on dual-emissive hydrophobic carbon dots (H-CDs) with well volatile base nitrogens (VBNs)-response was fabricated, offering the in-situ, real-time, and visual evaluation of seafood freshness. The presented H-CDs aggregates exhibited a sensitive response to VBNs, with a limit of detection of 7 μM and 137 ppb for spermine and ammonia hydroxide, respectively. Subsequently, a ratiometric tag was successfully fabricated by depositing dual-emissive CDs on cotton paper. Upon the treatment with ammonia vapour, the presented tag exhibited highly recognizable colour variations from red to blue under UV light. In addition, the cytotoxicity was explored by CCK8 assay, and the results proved the nontoxicity of the presented H-CDs. To our knowledge, this is the first ratiometric tag based on dual-emissive CDs with aggregation-induced emission properties for recognition of VBNs and seafood freshness in a real-time and visual manner. [Display omitted] • A dual-emissive hydrophobic CDs was synthesized as VBNs-response indicator. • A ratiometric fluorescent tag was prepared for rapid visualization of VBNs. • The designed tag can realize bimodal real-time monitoring of VBNs. • Successful in-situ recognition of seafood food freshness was achieved. [ABSTRACT FROM AUTHOR]

• Effects of isochoric freezing on quality attributes of chicken meat were studied. • Samples frozen in pure water and 1.5% NaCl solution were significantly affected. • Samples frozen in 2.5% NaCl solution at −4 and −8 °C had no significant change. • Pressure negative effect was minimized with increasing NaCl concentration. This study investigated the potential of isochoric freezing for chicken breast meat for the first time. Chicken breast samples were immersed in isochoric NaCl solutions with various concentrations of 0 (pure water, PW), 1.5 and 2.5 % at −4 and −8 °C, respectively, and effects of process parameters such as temperature, pressure, and solution concentration on quality characteristics of the sample including colour, water holding capacity, weight loss, texture, microstructure, and water mobility were evaluated. Results showed that increasing NaCl concentrations depressed freezing temperature and pressure and samples treated in PW and 1.5 % NaCl solution at −4 and −8 °C exhibited a significant decrease (P < 0.05) in the quality characteristics, while those treated in 2.5 % solution at −4 and −8 °C showed no significant difference compared with the control. These results indicated the potential for enhancing the quality of meats preserved in isochoric systems. [ABSTRACT FROM AUTHOR]

• Nanocomposite hydrogel was developed for daytime passive cooling. • Mechanical, swelling, and hygroscopic properties of hydrogel were analyzed. • Combined effects of radiation and evaporation were achieved. • Radiative and evaporative cooling powers were determined. • Hydrogel showed effective building cooling and ice-food preservation during daytime. Both radiative and evaporative cooling as passive cooling technologies can reduce dependence on active cooling technologies. However, most reported studies investigated radiative and evaporative cooling separately, and significant challenges still remain in achieving highly efficient combined radiative and evaporative cooling. Hence, a polyacrylamide/polyvinyl alcohol hydrogel with nanoparticles (NPs/NADES@PAAm/PVA) was fabricated by natural deep eutectic solvent for highly efficient daytime passive cooling. The NPs/NADES@PAAm/PVA with a solar reflectance of ∼0.95 and an atmospheric emissivity of ∼0.92 could realize daytime radiative cooling. Besides, the NPs/NADES@PAAm/PVA possessed robust mechanical strength, excellent flexibility, and great rehydration. After water absorption, both swollen NPs/NADES@PAAm/PVA and hygroscopic NPs/NADES@PAAm/PVA could simultaneously achieve radiative and evaporative cooling. Outdoor experiments demonstrated that the NPs/NADES@PAAm/PVA, swollen NPs/NADES@PAAm/PVA, and hygroscopic NPs/NADES@PAAm/PVA obtained an average temperature drop (Δ T) of ∼2.9, ∼6.2, and ∼3.6 °C under the sunlight, respectively, compared with the ambient temperature of ∼35.0 °C, indicating that the NPs/NADES@PAAm/PVA could achieve a sub-ambient temperature while the swollen and hygroscopic NPs/NADES@PAAm/PVA possessed better cooling performances due to the combined cooling effects. Another outdoor experiment proved that the NPs/NADES@PAAm/PVA had great application potential in building cooling and iced food preservation under sunlight, further promoting passive cooling technology. [ABSTRACT FROM AUTHOR]

The growing concerns about microbial food safety and environmental contamination call for sustainable food active packaging materials and practices with high performance. This contribution proposed a biocatalytic spraying coating for fruit preservation using carboxymethyl cellulose nanofibers grafting enzyme-like metal-organic frameworks (CNF@Ce-MOF) with banana and mango as model fruits. The well-characterized biohybrid nanofibers were verified to simultaneously mimic good oxidase-like and apyrase-like activities, enabling effective enzyme-like sterilization against three typical foodborne pathogens, i.e. Escherichia coli O157: H7, Staphylococcus aureus , and methicillin-resistant Staphylococcus aureus , reaching killing rates as high as 90.46%. The biocidal •O 2 − generation and adenosine triphosphate depletion were the possible mechanisms causing the nonspecific bacteria death. Such antibacterial performance, as well as additional protective properties of CNF@Ce-MOF, facilitated the quality preservation during the 12-day storage of bananas and mangos by spray coating with the biomimetic CNF@Ce-MOF. It is expected that this work walks out the first step of nanozyme toward active packaging engineering for the fields of food, agriculture, and biomedicine. [Display omitted] • Biopolymeric nanozyme was created by biomineralizing in situ MOF on nanocellulose. • Dual enzyme biomimicry by CNF@MOF produced.•O 2 − species and depleted ATP • CNF@MOF possessed bacteriostatic activities, UV resistance and biocompatibility. • Pioneering research was conducted by introducing nanozyme into active packaging. • CNF@MOF coating improved quality and extended shelf life of banana and mango. [ABSTRACT FROM AUTHOR]

Aflatoxin B1 (AFB1) is a highly toxic mycotoxin that can contaminate foods. Hence, a surface-enhanced Raman scattering (SERS) and fluorescence dual signal-on biosensor was developed for AFB1 detection. Specifically, aminated mesoporous silica nanoparticles (MSNs) were used as nanocontainers to load the Rhodamine 6G (R6G) with fluorescence and Raman effects, aptamers and polydopamine (PDA) were sequentially assembled on the surface of the MSNs as dual-gated molecules, and MXenes and Au nanorods were used as SERS substrates. After adding AFB1 under acidic conditions, the degradation of PDA and specific bringing of the aptamer with AFB1 resulted in the release of R6G. Results showed that AFB1 could be quantified by Raman and fluorescence spectroscopic with detection limits of 0.133 pg mL−1 and 0.214 pg mL−1, respectively. Moreover, the biosensor could be applied to the detection of AFB1 in real peanut, maize and badam samples, providing a possible alternative solution for the detection of other analytes. [Display omitted] • Mesoporous silica biosensors with dual-gating molecules were constructed. • MXenes and Au nanorods substrates for SERS signal amplification were synthesized. • AFB1 could be quantified by integrating Raman and fluorescence techniques. • The results of the ELISA method verified the accuracy of the sensing platform. • A highly sensitive, label-free, and low-cost detection strategy is achieved. [ABSTRACT FROM AUTHOR]

Food aflatoxin B1 (AFB1) contamination greatly threatens human health and its sensitive determination is imperative. In this study, a surface-enhanced Raman scattering (SERS) and fluorescence dual-signal aptasensor was constructed for sensitive AFB1 detection in peanuts, walnuts, and almonds samples. Fluorescent dye cy5 was used as fluorophore and Raman reporter, while polyethyleneimine modified Ag coating magnetic nanoparticles (MNP@Ag-PEI) were utilized to absorb the cy5 modified aptamer (apt-cy5). Results indicated that linear ranges of 0.001–1000 ng/mL and 0.2–20,000 ng/mL with detection limits of 0.45 pg/mL and 0.135 ng/mL for the SERS and fluorescence methods were obtained, respectively, and AFB1 detection in the nut samples using the aptasensor achieved satisfactory recoveries of 95.2%–108.6% for SERS and 94.7%–109.7% for fluorescence. Compared with other mono signal detection, the established aptasensor facilely fused the merits of the two signals and improved the detection accuracy and flexibility. [Display omitted] • MNP@Ag-PEI microspheres were developed as SERS substrates for AFB1 detection. • Fluorescent dye cy5 was used as Raman and fluorophore (FL) reporters. • The preferential apt-cy5 and AFB1 binding caused changes in SERS and FL signals. • The dual-signal aptasensor possessed unique detection sensitivity and flexibility. [ABSTRACT FROM AUTHOR]

Two pesticides in terms of chlorpyrifos and imidacloprid contaminating edible jujube fruits were determined using hyperspectral imaging (900–1700 nm) and gas chromatograph-mass spectrometry (GC–MS). Hyperspectral images of jujube samples contaminated by pesticides at different concentrations were collected. Their spectral data extracted in reflectance (R S ), absorbance (A S ), exponent (E S ) and Kubelka–Munck (K-M S ), were respectively used to develop partial least squares discriminant analysis (PLSDA) and locally weighted partial least square regression (LWPLSR) models. Based on these spectral parameters, corresponding models defined as A S -PLSDA and E S -PLSDA acquired optimal results, with correlation coefficients of cross-validation ( R CV ) of more than 0.900 for recognition of chlorpyrifos concentrations and R CV of over 0.713 for identification of concentrations of the imidacloprid. The E S -LWPLSR model obtained the best R CV of 0.864 for quantitative determination of chlorpyrifos residuals, and the best R CV of 0.885 for determination of imidacloprid residuals. The feature wavelengths were selected based on the automatic weighted least squares and gap segment derivative (AWLS-GSD) coupled with regression coefficient (RC) method. The better performance was obtained by the resulting simplified E S -AWLS-GSD-RC-LWPLSR model established using only eight characteristic wavelengths, with R CV of 0.757, RMSECV of 3.75 × 10 −3 for chlorpyrifos residuals, and R CV of 0.898, RMSECV of 0.311 × 10 −3 for imidacloprid residuals. To summarize, hyperspectral imaging technology shows a great potential to predict pesticide residuals of jujube fruit. [ABSTRACT FROM AUTHOR]

Background Thermal processing has been widely employed in the food industry for food safety assurance. However, thermal processing may cause some undesirable changes or form by-products that negatively affect the nutritional value, flavor, color and texture of the final product. With increasing awareness of food and health, consumers prefer more naturally and minimally processed foods. Therefore, investigation of nonthermal processing technologies is important and necessary not only for its minimal impact on food but also for its extension of product shelf-life by inhibiting or inactivating microorganisms. Scope and approach This review presents a general perspective of nonthermal inactivation technologies based on electromagnetic fields, including pulsed electric fields, high voltage arc discharge, pulsed light, ionizing radiation, microwave and cold plasma. The inactivation mechanisms, characteristics and research progress, as well as the limitations of these technologies, are also discussed. Key findings and conclusions Compared to thermal treatments, nonthermal inactivation technologies have shown significant advantages with great potential. Hybrid technologies based on these methods should play a significant role in enhancing inactivation efficiency. In addition, combination of these methods with thermal treatment can lower the treatment temperature and achieve high reductions of microorganisms in foods. Despite various degrees of success in these technologies, their widespread applications in the food industry are yet to flourish. Further studies are still needed to understand these processes to provide a platform by which their limitations can be overcome. [ABSTRACT FROM AUTHOR]

When considering food security and huge market interest, a high-efficiency method to ensure the authenticity of the food product is necessary. For this goal, spectral imaging was explored for quantitative detection of Irish organic wheat flour (OWF) adulterated with common wheat flour (WF), cassava flour (CaF) and corn flour (CoF). Hyperspectral images (900–1700 nm) of OWF samples with a series of adulteration percentages were collected. The acquired spectra were pre-processed by second derivative (2nd Der) and standard normal variate (SNV) before modelling. Then partial least squares regression (PLSR) and principal component regression (PCR) were employed for quantitative analysis of adulteration proportion of CoF, CaF and WF in OWF. To develop more effective simplified models, three groups of feature wavelengths were selected from the loading plots of principal component analysis (PCA), and first-derivative and mean centering iteration algorithm (FMCIA). The models developed using FMCIA were better than PCA. After, the corresponding feature wavelengths were further reduced based on model regression coefficients (RC). The optimal result of admixture detection was emerged by the RC-FMCIA-PLSR model, with a determination coefficient of prediction ( R 2 P ) of 0.973 and a root mean square error of prediction (RMSEP) of 0.036 for OWF adulterated with CoF, R 2 P of 0.986 and RMSEP of 0.026 for OWF adulterated with CaF, and R 2 P of 0.971 and RMSEP of 0.038 for OWF adulterated with WF. Visualization maps were generated by calculating the spectral response of each pixel on flour samples. This result indicates that spectral imaging integrated with multivariate analysis has the potential to authenticate the admixtures in specific wheat flour in the range of 3–75% (w/w). [ABSTRACT FROM AUTHOR]

The feasibility of hyperspectral imaging (HSI) (400–1000 nm) for tracing the chemical spoilage extent of the raw meat used for two kinds of processed meats was investigated. Calibration models established separately for salted and cooked meats using full wavebands showed good results with the determination coefficient in prediction (R 2 P ) of 0.887 and 0.832, respectively. For simplifying the calibration models, two variable selection methods were used and compared. The results showed that genetic algorithm-partial least squares (GA-PLS) with as much continuous wavebands selected as possible always had better performance. The potential of HSI to develop one multispectral system for simultaneously tracing the chemical spoilage extent of the two kinds of processed meats was also studied. Good result with an R 2 P of 0.854 was obtained using GA-PLS as the dimension reduction method, which was thus used to visualize total volatile base nitrogen (TVB-N) contents corresponding to each pixel of the image. [ABSTRACT FROM AUTHOR]