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Limitations of microwave processing due to inhomogeneities of power input and energy absorption have been widely described. Over- and underheated product areas influence reproducibility, product quality, and possibly safety. Although a broad range of methods is available for temperature measurement and evaluation of time/temperature effects, none of them is sufficiently able to detect temperature differences and thermally induced effects within the product caused by inhomogeneous heating. The purpose of this review is to critically assess different methods of temperature measurement for their suitability for different microwave applications, namely metallic temperature sensors, thermal imaging, pyrometer measurement, fiber optic sensors, microwave radiometry, magnetic resonance imaging, liquid crystal thermography, thermal paper, and biological and chemical time-temperature indicators. These methods are evaluated according to their advantages and limitations, method characteristics, and potential interference with the electric field. Special attention is given to spatial resolution, accuracy, handling, and purpose of measurement, that is, development work or online production control. Differences of methods and examples of practical application and failure in microwave-assisted food processing are discussed with a special focus on microwave pasteurization and microwave-assisted drying. Based on this assessment, it is suggested that infrared cameras for measuring temperature distribution at the product surface and partially inside the product in combination with a chemical time/temperature indicator (e.g., Maillard reaction, generating heat-induced color variations, depending on local energy absorption) appear to be the most appropriate system for future practical application in microwave food process control, microwave system development, and product design. Reliable detection of inhomogeneous heating is a prerequisite to counteracte inhomogeneity by a targeted adjustment of process and product parameters in microwave applications.

In this study, the influence of iota carrageenan (IC) addition at different steps to the protein blends based on pea protein isolate (PPI) and wheat gluten (WG) as well as hydration mixing time and temperature of IC on the quality attributes of plant-based meat alternatives was studied. In more detail, IC was added before (B, in water with mixing times of 15 or 30 min and temperatures of 25 or 75 °C) or after (A, in powder form) the addition of PPI to the mixture with or without calcium chloride (Ca) in the formulation. The results showed that the addition of IC after PPI, especially combination with Ca resulted in the products with the most visible fibers, which can be considered as a quality improvement. IC addition to the formulations with or without Ca also increased the browning index, water holding capacity, tensile stress, and air bubble numbers compared to the PPI.WG formulation. However, no considerable difference in these parameters was found regarding the addition order of IC (before or after the addition of PPI). As the addition of IC after PPI hydration needs less energy for mixing, and, thus, less time for preparation, this order of addition can be recommended for improving the quality of plant-based meat alternatives containing IC. Therefore, hydration of IC in water, especially at high temperatures, is not necessary for the production of plant-based meat alternatives produced in the high-temperature shear cell (HTSC).

Currently, studies are underway to use pea protein isolate (PPI) for the production of meat analogues because it is considered as a more sustainable alternative to soy. The potential of PPI has been demonstrated in extrusion and PPI in combination with wheat gluten has been studied in the shear cell. To enlarge the possibilities to make meat analogues with a broader range of properties, the effects of L-cysteine (CYS) and L-ascorbic acid (AA) on PPI and wheat gluten (WG) blends were examined at different concentrations (0, 100, 500, 1000 and 2000 ppm). The results showed that both CYS and AA altered the properties of the products formed by the high-temperature shear cell (HTSC). Both additives altered the fibrousness and the mechanical properties of the products obtained after processing. Especially CYS revealed an increase in tensile stress, tensile strain and Young's modulus as its concentration increased. However, products containing CYS depicted a relatively stable anisotropic index of 1, which corresponded to a densely packed matrix that was observed by microstructural analysis. A small elevated anisotropic index (>1) of products containing AA at concentrations of 500–2000 ppm could be attributed to the formation of pores parallel to the shear flow direction in these samples visualized by a confocal laser scanning microscope (CLSM) and the scanning electron microscope (SEM). In the products containing 2000 ppm of AA and 2000 ppm CYS, small and large fibers were formed, respectively. Therefore, this research pointed out the potential application of CYS and AA to alter and control the textural attributes of products. This application could aid in improving the consumer acceptance of meat analogues and, thus, contribute to being able to feed the increasing population of the world.

Pea protein isolate (PPI) and mung bean protein isolate (MBPI) are rising alternatives for soy protein isolate in producing meat analogues. Transforming these isolates into full products is challenging due to their differences in functional properties compared with soy. Here, we report on the use of transglutaminase to improve the mechanical and rheological properties of dense MBPI and PPI dispersions. Gels from PPI and MBPI (40 wt% dry matter) were produced with 0, 0.1, 0.3, 0.5, and 0.7 wt% transglutaminase and incubation temperatures of 30, 40, 50, and 60 °C. Their mechanical and rheological properties were determined by tensile and closed cavity rheometer tests. The degree of crosslinking was determined by the OPA assay. Transglutaminase significantly increased fracture stress and strain of PPI gels, and to a lesser extent those of MBPI gels. The degree of free amino confirmed that this increase in PPI was due to formation of additional crosslinks. Amplitude sweeps identified that the rheological properties of PPI gels and MBPI gels were affected by the addition of transglutaminase, but in an opposite manner. Stress relaxation experiments showed that transglutaminase increased the elasticity of PPI gels and formed mainly small aggregates in MBPI gels. This work showed that the fibrous structure diminished when >0.1 wt% transglutaminase was added to PPI/MBPI - wheat gluten blends. To conclude, transglutaminase can be used to create intermolecular crosslinks in PPI gels, creating a full network, while mostly intramolecular crosslinks are formed in MBPI gels, leading to a cluster structure.

The texture, appearance and juiciness of meat analogues should resemble meat as much as possible to enhance their adoption by consumers. The effects of the addition of different hydrocolloids (xanthan (X), iota-carrageenan (CA), sodium alginate (SA), guar gum (GG), carboxymethyl cellulose (CMC), low acyl gellan gum (GZ), low methylated pectin (P), and locust bean gum (LBG)) at three concentrations (1%, 2% and 3%) were assessed on blends containing pea protein isolate and wheat gluten that were processed using shear cell technology. The addition of X, CMC and GG resulted in a more strongly flow-oriented structure and the formation of fibers compared to materials without any hydrocolloids. However, the water holding capacity, except with X, hardly increased. X also increased the anisotropy index of samples, but it did not improve the tensile stress of products. The addition of GZ resulted in a much larger tensile stress, especially at higher concentrations. Overall, these findings show the great potential of X and GZ hydrocolloids to improve the textural attributes of meat analogues, which will be an important step to make the transition of meat towards meat analogues more pleasant.

Meat analogues, mimicking the textural and sensorial properties of meat, could help consumers transition from animal-based foods to plant-based ones. However, improving the quality attributes of meat analogues, especially their textural properties is crucial to convincing more consumers to include these products in their diet. Here the effect of L-cysteine at a concentration of 0.2% in pea protein isolates (PPI) and wheat gluten (WG) blends was investigated according to the processing temperature (100, 110, 120, 130, 140, and 150 °C) in the high-temperature shear cell (HTSC). The macrostructure of fibers, as well as mechanical, microstructural, and quality attributes of products, were investigated to characterize the influence of L-cysteine on the PPI-WG blends processed at different temperatures. The results of this study showed that L-cysteine had different effects at different processing temperatures. It weakened the product structure and prevented fiber formation at processing temperatures of 100 and 110 °C. This effect was also observed at 140 and 150 °C but to a lesser extent. Conversely, at processing temperatures of 120 and 130 °C, the structure of the products with L-cysteine was stronger than those without L-cysteine, and they presented thicker fibers in visual pictures as well as the pictures obtained by scanning electron microscopy. It is concluded that L-cysteine can improve the textural properties of the meat analogues under precise processing temperatures. Thus, the potential of L-cysteine for improving the textural and quality attributes of meat analogues represents an important step towards the acceptance of a prevailing plant-based diet.

The present study adopted electrohydrodynamic (EHD) and ultrasonic (US) pretreatments to enhance the extraction of phenolic compounds from Melissa officinalis. The effects of pretreatment time (EHD: 0–20 min and US: 0–60 min) and diffusion conditions (including ethanol/water ratios of 0.4, 0.8 and 1.2 (w/w), time of 30, 45, 60 min, and the temperature of 30, 50 and 70 °C) on the total phenolic content (TPC) and antioxidant activity of the extracts were investigated using Folin-Ciocalteu and DPPH assay, respectively. The results showed that EHD and US pretreatments could enhance the process of the extraction of phenolic compounds and also improve the extracts’ antioxidant activity. The highest extraction occurred at EHD time of 10 and 20 min, ethanol/water ratio of 1.2 and diffusion temperature of 70 °C. The Fourier transform infrared (FTIR) spectra also revealed that the structure of the extracted compounds was not altered as a result of EHD pretreatment. No changes, however, occurred in the functional groups of the extracts by increasing the EHD duration, diffusion temperature, and ethanol/water ratio.

One of the parameters that has the most influence in the uniformity of microwave heat processing is frequency. Unlike the traditional magnetron microwave system, it is possible to control and set up the frequency with the newly developed solid-state microwave system. The aim of this study was an investigation of the effect of fixed frequencies and frequency sweep loops (in the range of 2400–2500 MHz) on the uniformity of heat processing in circular gellan gel model samples containing Maillard reactive agents in a solid-state microwave system. Therefore, the purpose was to compare the solid-state system at fixed frequencies in which the megaton generator also works. While the magneton generator runs at random frequencies within a certain range, solid-state systems are capable of conducting heat processing at fixed frequencies. This novel characteristic will be evaluated through the implementation of different trials at various fixed frequencies. Additionally, the effect of changing frequencies is evaluated through frequency sweep loops, where the frequency of the solid-state system is changed in a pre-determined pattern. The results obtained from the time-temperature indicator of the Maillard reaction and the temperature indicator of infrared thermography showed that the heat processing of samples with the frequency sweep loops, even without turntable rotation, can be more uniform in comparison to those with fixed frequencies and turntable rotation. Moreover, the frequency sweep loops not only improved the uniformity of temperature distribution of the heated sample, but also increased the average temperature of processed samples and, thus, microwave heating absorption.

In a previous paper, we established a test routine and found in cuboid gellan test samples containing Maillard reactive agents that the solid-state system yields a more uniform heating profile. This was attributed to a more uniform microwave energy distribution profile in the solid-state oven cavity. In this work, we aim at determining the heating profile in various test sample shapes exposed to classical magnetron and innovative solid-state microwave systems. Therefore, we assessed the uniformity of heat processing between both solid-state and magnetron microwave generators using other test sample shapes of spherical and cylindrical forms and compare the results with the test samples with cuboid shape. The comparison confirms that the solid-state microwave system also results in more uniform heating of the cylindrical test samples like in the cuboid test sample, while the spherically-shaped test sample this was not the case. The explanation most likely is that the focus of microwave energy in the center of the spherical sample is more dominating such that the external microwave energy distribution is less decisive for a uniform heating profile. In other words, the possibility of distinguishing the differences between the solid-state and magnetron microwave generators and comparing the uniformity of their thermal processing requires a certain sample shape. Spherical samples are less suitable, because of the focusing of energy towards the sample center and difference between the systems can be determined much less sensitively compared to other shapes. These results contribute to understand microwave heating systems better and provide guidance in product development in terms of shapes most suitable to achieve heating profiles with reduced issues related to hot/cold spots in the product.

Nowadays, there is great attention to extract natural colorants and food additives from the by-products of food processing industries. In this research, the β-carotene extraction from carrot pomace was investigated using electrohydrodynamic (EHD) pretreatment and ultrasonic process as an innovative extraction technique. To achieve this purpose, the statistical method of Complete Randomized Design (CRD) was used to estimate the effects of EHD time (at six levels of 2.5, 5, 10, 15, 20 and 25 min) and EHD voltage (at five levels of 0, 14, 16, 18, 20 and 22 kV) on the dependent factors of β-carotene content, antioxidant activity, total phenolic content, and extraction yield of the carrot pomace extracts. The ultrasonic extraction was performed at similar procedure with a temperature of 30 °C, power of 500 W, frequency of 20 kHz, and time of 80 min. It was found that the highest values of β-carotene concentration (415.28 ± 0.56 mg/L; P ≤ 0.01), antioxidant activity (90.42 ± 0.48%; P ≤ 0.001), total phenolic content (151.48 ± 76 mg/L; P ≤ 0.001), and extraction yield (9.15 ± 0.25%; P > 0.05) were achieved at EHD time of 20 min. Moreover, the highest recovery of the β-carotene concentration (433.42 ± 1.86 mg/L; P ≤ 0.001), antioxidant activity (92.35 ± 0.52%; P ≤ 0.001), total phenolic content (155.42 ± 7.73 mg/L; P ≤ 0.001), and extraction yield (9.70 ± 0.10%; P ≤ 0.01) of the extracts were obtained at EHD voltage of 20 kV. Fourier transform infrared (FT-IR) spectroscopy displayed no degradation of functional groups of the carrot pomace extracts during the EHD pretreatment. Therefore, the application of EHD pretreatment method leads to higher levels of β-carotene content, antioxidant activity, total phenolic content, and extraction yield from the carrot pomace extracts.

Date seed oil is a good source of natural antioxidants due to the presence of phenols, tocopherols, and sterols. The present research is the first study on the extraction of date seed oil by combining the ultrasound-assisted aqueous enzymatic extraction method and the cooking pretreatment. In this study, the effects of two independent variables namely the sample to solvent ratio (at six levels of 1: 2, 1: 3, 1: 4, 1: 6, 1: 8 and 1:10) and the cooking time (at four levels of 0, 20, 40 and 60) were investigated on dependent variables namely the extraction yield, total phenolic compound, peroxide value, and acid value of date seed oil. The results indicated that optimum conditions for extraction of date seed oil were sample to solvent ratio of 1: 2 and the cooking time of 40 min. Furthermore, the Scanning Electron Microscopy images of date seed powder after selective treatments indicated the destruction and fragmentation of residual pulp structures by increasing the cooking time. In general, results of the present study indicated that it was important to select the appropriate sample to solvent ratio and implement the pretreatment of cooking to extract oil with high yield and quality. Combination of the ultrasound-assisted aqueous enzymatic extraction method and the cooking pretreatment can be proposed as a new extraction method in the oil industry. This new extraction method can improve the oil extraction efficiency and the quality of extracted oil.

Every year, huge amounts of fruit and vegetable by-products in the food processing factories are produced. These by-products have great potential to be used for different targets especially the extraction of value-added ingredients. The target of this study is to review the challenges of extraction of value-added ingredients from fruit and vegetable by-products on the industrial scale and to describe current trends in solving these problems. In addition, some strategies such as multi-component extraction as well as application of fermentation before or after the extraction process, and production of biofuel, organic fertilizers, animal feeds, etc. on final residues after extraction of value-added ingredients are discussed in this review paper. In fact, simultaneous extraction of different value-added ingredients from fruit and vegetable by-products can increase the extraction efficiency and reduce the cost of value-added ingredients as well as the final volume of these by-products. After extraction of value-added ingredients, the residues can be used to produce biofuels, or they can be used to produce organic fertilizers, animal feeds, etc. Therefore, the application of several appropriate strategies to treat the fruit and vegetable by-products can increase their application, protect the environment, and improve the food economy.

Dry fractionation of mung bean, yellow pea, and cowpea was performed to investigate the compositions and functional properties of the obtained fractions. Dry fractionation consisted of milling and subsequent air classification using three air classifier wheel speeds. Water holding capacity, gelation, and rheological properties of all fractions were studied. Separation between protein and starch granules was successfully performed by air classifying, as visualized with SEM images. Protein contents in fine fractions ranged from 42% to 58% (w/w), which was dependent on classifier wheel speed and material source. The correlation between water holding capacity and protein content was dependent on material source. Gelation of fine fractions occurred at lower concentrations than flours and coarse fractions. Fine fractions of all materials formed gels with higher elastic modulus (G') than the flour and coarse fractions, while the flour and coarse fractions formed more solid-like gels (lower tan δ). Industrial relevance: The need for functional plant protein ingredients for food applications is growing continuously. It is thus important to study sustainable methods for plant protein extraction. Dry fractionation is often considered an efficient alternative to the conventional wet fractionation process, that preserves the native functionality of the proteins in addition. For the application of ingredients produced from dry fractionation in food products, it is important to understand their functional properties. Therefore, the functional properties of dry fractionated ingredients produced from three different legumes are evaluated in this manuscript.

Orange pomace, a byproduct of orange juice production, is an important source of phenolic compounds. In this study, the effect of Electrohydrodynamic time (at four levels of 2, 10, 20 and 30 min) and EHD voltage (at four levels of 0, 14, 18 and 22 kV) on the total phenolic compounds (TPC), antioxidant activity (AA), and extraction efficiency (EE) of the extracts from orange pomace powder (OPP) was investigated using Electrohydrodynamic (EHD) process. The results showed that the optimal EHD treatment had the extraction time of 10 min and the voltage level of 18 kV. Under this condition, the TPC, AA, and EE of the extracts were 617.76 ± 6.15 mg/L, 91.97 ± 0.43%, and 64.00 ± 0.00%, respectively. Scanning Electron Microscopy (SEM) pictures illustrated considerable interspaces and pores in the remaining OPP after EHD extraction treatments, compared to the control treatment without EHD process. Moreover, Fourier Transform Infrared (FTIR) spectroscopy of the extracts did not show any destruction of the functional groups of the extracts during EHD process. Therefore, EHD treatment could be an effective method for extraction of natural compounds such as phenolic compounds.

In the present investigation, the ultrasound-assisted convective drying process for zucchini slices was studied. In this regard, the effects of convective air velocity (in three levels of 1, 2, and 3 m/s) and ultrasonic pretreatment time (in three levels of 0, 15, and 30 min) on drying kinetic, drying time, and qualitative characteristics of the dried product were investigated. Moreover, the effects of these independent variables on functional groups of dried zucchini slices were also studied using Fourier Transform Infrared spectroscopy (FTIR), and those on the microscopic structure of dried zucchini slices were investigated using Scanning Electron Microscopy (SEM). Based on the results obtained in this study, the ultrasonic pretreatment for 30 min and convective air velocity of 2 m/s are recommended for drying zucchini slices with optimal product quality and short drying time. Compared to untreated samples, less wrinkled tissues and more microscopic channels were observed in pretreated samples especially at 30 min sonication time. In terms of functional groups, there was no difference in the FTIR spectra at different levels of ultrasonic pretreatment time and convective air velocity.

In this research, extraction of phenolic compounds from orange processing waste was investigated by combination of ultrasound and enzymatic processes using ethanol as the solvent. In order to achieve the maximum total phenolic content and extraction yield, and the minimum hue angle of the extract, optimal conditions of ultrasonic enzymatic treatment using ethanol as the solvent (UET-ES) were determined. The obtained optimal conditions are as follows: the pectinase enzyme concentration of 0.5%, the ultrasonic time of 120 min, and the pH of 4 using response surface methodology. The extract of optimal UET-ES compared to the extracts of ultrasonic enzymatic treatment using water solvent and maceration treatment using ethanol solvent (MT-ES) had an improved antimicrobial effect against two foodborne pathogens of Staphylococcus aureus and Escherichia coli. The results of Fourier transform infrared spectroscopy showed similar spectra of the extracts obtained through either the optimal UET-ES or MT-ES. Thus, degradation or alteration in functional groups of the extracts obtained through either of the two methods has not occurred.

The tomato processing wastes are rich in lycopene pigment, which can be consumed as a natural food colorant and bioactive ingredient. The present study investigates the appropriateness of ultrasound pretreatment and enzymatic treatment with cellulase and pectinase enzymes to extract lycopene pigment from tomato processing wastes using response surface methodology (RSM). To achieve this goal, a central composite design consisting of four independent variables including cellulase concentration (0–10%), pectinase concentration (0–5%), ultrasonic time (0–60 min) and pH (3.5–5.5) was used to examine the influences of these process variables on the lycopene extraction. The second order model of lycopene extraction obtained from RSM analysis had the p value less than 0.001 and represented a coefficient of determination (R2) of 93.82%. Thus, a satisfactorily agreement between experimental and predicted values for lycopene content obtained by the second order model was observed. In addition, the Fourier Transform Infrared spectroscopy results did not show any destruction of functional groups of the investigated extracts containing lycopene pigment. Scanning electronic microscopy images from the remaining tomato processing wastes after treatment with more lycopene content extraction demonstrated more porous structure. These results implied that ultrasound-assisted enzymatic extraction was an efficient extracting method.

In the present study, the extraction of β-carotene from carrot processing waste was studied using the combination of ultrasonic pretreatment and shaking incubation process. In this regard, the effects of ultrasonic time (in three levels of 0, 40, 80 min) and shaking incubation time (in three levels of 30, 75 and 120 min) as well as the mutual effects of these two variables on dependent responses of β-carotene content, antioxidant activity, and color parameters of L*, a* and b* of the extracts containing β-carotene pigment were investigated. The results of this study showed that the increase of ultrasonic time from 0 to 80 min caused the significant increase of β-carotene (P ≤ 0.001), antioxidant activity (P ≤ 0.01), a* color parameter (P ≤ 0.01), and b* color parameter (P ≤ 0.001) of the extracts. Furthermore, the increase of shaking incubation time from 30 to 120 min led to the significant increase of β-carotene content of extracts (P ≤ 0.001). Fourier Transform Infrared spectroscopy did not show any destruction of functional groups of the extracts. In addition, scanning electron microscopy images indicated more porous structure of solid residues in condition of the increase of ultrasonic and shaking incubation times.

Understanding the rheological properties of fluid foods, especially their viscosities, plays an important role in determining the quality control and design of equipment for food industry plants. Hence, in this research, the time-independent rheological behavior of peach syrup was determined using a Brookfield viscometer, and the effects of concentrations at 35, 40, 45, and 50 °Brix, and temperatures at 15, 25, 35, 45, 55, and 65 °C were investigated in a range of 1.4-49.78 s−1 shear rate. To investigate the rheological effect of these parameters, the shear stress and apparent viscosity parameters were plotted at different shear rates. To describe the time-independent behavior of peach syrups, Power law, Bingham, Casson, and Herschel–Bulkley models were used; among these models, the Power law model with an R2 of 0.9980, the root mean square error (RMSE) of 3.2717, and the Chi square (χ2) of 20.2782 was determined as the best one for the description of shear stress-shear rate diagrams. Furthermore, the dependence of consistency coefficient obtained from the Power law model on temperature parameter was investigated using the Arrhenius model, and the dependence of consistency coefficient on concentration parameter was determined using the Power and exponential models. Overall, the results showed that peach syrup had a non-Newtonian pseudo-plastic behavior. The investigations also showed that an increase in the concentration of peach syrup led to enhancing the apparent viscosity of the samples, while an increase in the temperature and shear rate reduced the apparent viscosity.

For the first time, a carboxymethyl cellulose (CMC) coating pretreatment was used in an electrohydrodynamic (EHD) system to produce convectively dried banana slices with improved quality and nutritional attributes. To this end, the impacts of the sample to CMC solution ratio (S:CSR) parameter at two levels of 1:1 and 1:2 and the EHD voltage parameter at four levels of 0, 16, 18, and 20 kV were investigated. The results showed that an increase in the EHD voltage from 0 to 20 kV significantly increased the water absorption capacity (WAC) (117.86%) and the total phenolic content (TPC) (20.83%) of the dried banana slices and significantly reduced their total energy consumption (SETₒₜₐₗ) (30.03%), the drying time (27.9%), the shrinkage (74.52%), the shear stress (SS) (76.48%), and the total color difference (ΔE) (78.74%). Moreover, an increase in the S:CSR from 1:1 to 1:2 significantly reduced the shrinkage (20.62%), the SS (21.93%), and ΔE (33.02%) of the dried banana slices and significantly increased their WAC (24.40%) and TPC (16.88%). PRACTICAL APPLICATIONS: According to the results obtained in this study, carboxymethyl cellulose coating pretreatment in an EHD system can be introduced as an innovative and practical pretreatment technique for production of convectively dried products. This approach improves both the quality indexes and nutritional attributes while increasing the performance of the convective drying process.

In this research, extraction of β‐carotene pigment from orange processing waste was investigated by combining ultrasonic and enzymatic processes using ethanol solvent. In order to optimize the extraction conditions, the effect of pectinase enzyme concentration [0–5% (w/w)], ultrasonic time (10–120 min), and pH of solution (3.5–6) on dependent variables of β‐carotene content, antioxidant activity, color parameters of L*, a*, and b*, and browning index (BI) of extracts was investigated using response surface methodology. Optimal condition of ultrasonic‐assisted enzymatic extraction treatment using ethanol solvent was estimated as pectinase concentration of 0.40% (w/w), ultrasonic time of 115.55 min, and pH of 5.11 to achieve the highest amounts of β‐carotene content, antioxidant activity, color parameters of L*, a*, and b*, and the lowest amount of BI parameter. The results of scanning electron microscopy images showed that using ultrasound waves and the pectinase enzyme, in particular in the case of using ethanol solvent, disrupted the sample tissue. The results of Fourier transform infrared spectroscopy showed that the functional groups of the extracts were not degraded during the ultrasonic and enzymatic processes. PRACTICAL APPLICATIONS: The increasing awareness and demand of consumers for enriched functional foods with bioactive compounds such as β‐carotene pigment is promising. It has resulted in an improved interest in extracting β‐carotene pigment from food processing waste sources. In addition, it has led to application of novel extraction methods such as ultrasonic‐assisted enzymatic extraction. The results of this study showed that optimal treatment of ultrasonic‐enzymatic treatment using ethanol solvent compared to maceration treatment using ethanol solvent resulted in a higher β‐carotene content.

The major challenge of heat processing of foods using the traditional microwave (MW) systems containing magnetron power source is the inhomogeneity of the heating. The aim of this study was to compare a novel solid-state MW system with the traditional magnetron MW system for heat processing of the gellan gel cuboids containing Maillard reaction substrates as model food sample. To evaluate both systems, samples were processed in different positions of turntable in both MW cavities with and without turntable rotation in different levels of absorbed MW power. To investigate the MW heating uniformity, optic fiber temperature sensors were used to determine temperature and were compared with the Maillard reaction induced brown color creation inside the samples. The results show more uniform and homogenous color changes and heating patterns of samples processed in the solid-state MW system compared to those in the magnetron MW system.

Drying is one of the oldest methods of food preservation. However, this method requires careful promotion and maintenance of the quality of the dried products. In this paper, Carboxymethyl cellulose (CMC) coating and sonication pretreatments were employed as a new approach to improve the efficiency of convective drying and produce dried banana slices with acceptable quality in a short period. To achieve these goals, the effects of ultrasonic power (at three levels of 0, 500, and 1000 W) and sample to CMC coating solution ratio (with three levels of 1:2, 1:3, and 1:4), as well as the mutual effect of these two independent variables, were evaluated. The results showed that increasing the ultrasonic power from 0 to 1000 W decreased the drying time (P ≤ 0.001), energy consumptions of the convective drier (P ≤ 0.001), total energy consumption (P ≤ 0.001), shrinkage (P ≤ 0.001), apparent density (P ≤ 0.001), shear stress (P ≤ 0.001), and the total color change (P ≤ 0.001); it also increased energy consumptions of the ultrasonic system (P ≤ 0.001), porosity (P ≤ 0.001), and TPC (P ≤ 0.001) of the dried banana slices significantly. Moreover, changing the sample to coating solution ratio from 1:2 to 1:4 reduced the shrinkage (P ≤ 0.001), apparent density (P ≤ 0.001), shear stress (P ≤ 0.001), and total color change (P ≤ 0.01); this also led to remarkable increase in the porosity (P ≤ 0.001) and TPC (P ≤ 0.05) of the dried samples. With respect to the cross-sectional scanning electron microscopy (SEM) images of the dried banana slices, it was found that the CMC coating pretreatment in an ultrasonic system, especially with an ultrasonic power of 1000 W and a sample to coating solution ratio of 1:4, enhanced the porosity of the dried banana slices. Overall, the combined application of ultrasonication and Carboxymethyl cellulose coating pretreatments could be considered as an effective approach to improve the quality of the dried products through convective drying.

In this paper, drying of button mushroom (Agaricus bisporus) slices with an innovative drying technique of hot air combined with Electrohydrodynamic (EHD) drying process was investigated at three electrode gaps (5, 6, and 7 cm) and voltage levels (17, 19, and 21 kV). The effects of different hot air combined with EHD drying treatments on the temperature of the mushroom slices, drying time, final color and protein denaturation features including enthalpy (ΔH), onset temperature (To), peak transition temperature (Tp), conclusion temperature (Tc), and temperature range (Tc–To) of endothermic peaks were systematically evaluated. In addition, water state changes in DSC cooling thermograms of dried mushroom slices were investigated. The results obtained by differential scanning calorimetry showed that the ΔH values in the DSC traces of the EHD-dried mushroom slices were reduced with a decrease in the electrode gap and an increase in the voltage. Specifically, among voltages of 21, 17, and 19 kV, a voltage of 21 kV resulted in the lowest ΔH and Tc–To values and the highest Tp and To values. This result indicated that voltage had a significant effect on these responses. Similarly, the DSC results showed a considerable effect of high electric field intensity on ΔH, Tc–To and Tp responses related to protein denaturation in comparison to low electric field intensity.

In this study, hot air combined with an electrohydrodynamic (EHD) drying system was designed and examined for drying button mushroom (Agaricus bisporus) slices. The effects of three levels of voltage (17, 19 and 21 kV) and electrode gap (5, 6 and 7 cm) on solid and bulk density, porosity, shear strength, water absorption capacity (WAC) and total color difference (ΔE) of dried mushroom slices in comparison to oven dried mushroom slices were investigated. ANOVA showed that the hot air combined with EHD drying method had significant effects on bulk density and shear strength (p ≤ 0.01) reduction as well as on porosity (p ≤ 0.001) and WAC increase (p ≤ 0.01), but this system had no significant effects (p ≥ 0.05) on the solid density and ΔE parameters in comparison to the oven drying system. In addition, results indicated that increasing the voltage or decreasing the electrode gap resulted in some advantages such as bulk density and shear strength reduction or porosity and WAC increase that introduced this combined drying method as an improved method for drying mushroom slices.

Researches about mathematical modeling of electrohydrodynamic (EHD) drying are rare. In this study, hot air combined with electrohydrodynamic (EHD) drying behavior of thin layer mushroom slices was evaluated in a laboratory scale dryer at voltages of 17, 19, and 21 kV and electrode gaps of 5, 6, and 7 cm. The drying curves were fitted to ten different mathematical models (Newton, Page, Modified Page, Henderson and Pabis, Logarithmic, Two-term exponential, Midilli and Kucuk, Wang and Singh, Weibull and Parabolic models) and a proposed new empirical model to select a suitable drying equation for drying mushroom slices in a hot air combined with EHD dryer. Coefficients of the models were determined by non-linear regression analysis and the models were compared based on their coefficient of determination ( R 2 ), sum of square errors (SSE) and root mean square error (RMSE) between experimental and predicted moisture ratios. According to the results, the proposed model that contains only three parameters provided the best fit with the experimental data. It was closely followed by the Midilli and Kucuk model that contains four parameters. Therefore, the proposed model can present comfortable usage and excellent predictions for the moisture content changes of mushroom slices in the hot air combined with EHD drying system.

In this study, hot air combined with EHD drying is examined as an improved method for drying mushroom slices. The effects of three levels of voltage (17, 19, and 21 kV) and electrode gap (5, 6, and 7 cm) on the drying kinetics, time, effective water diffusion coefficient, and energy consumption of the EHD, pure hot air (provided within a chamber), and hot air combined with EHD drying systems were investigated. ANOVA showed that there were significant differences between EHD treatments and control (pure hot-air-drying treatment) for all of the investigated responses. Voltage and electrode gap factors had significant effects on all investigated responses. The results confirmed that the combination of EHD and hot air can significantly reduce the drying period, resulting in a greater effective water diffusion coefficient and drying rate and reduced energy consumption. As such, this technique offers a promising solution to the considerable energy consumption of the drying industry.

This paper deals with the key issue of the coating technology applied to button mushroom (Agaricus bisporus) slices prior to convective drying. Response surface methodology (RSM) was used to predict the effects and to optimize the concentrations of carboxymethyl cellulose (CMC) (0–3% w/w) and CaCl2 (0–2% w/w) on the quality of dried mushroom slices. The final product was evaluated in terms of responses such as water absorption capacity (WAC), dry matter holding capacity (DHC), rehydration ability (RA), scavenging effect (SE) assay, shear stress (SS) and color (L0 – L and ΔE). The results showed that WAC, RA, SE and SS increased and L0-L and ΔE decreased with CMC concentration increase. Based on response surface and desirability functions, the optimum product qualities in terms of RA (0.50), SE (78.51%), L0-L (20.86), ΔE (27.73) and SS (307.01 N/cm2) responses were obtained at 3% CMC concentration. Practical Applications Fresh mushrooms are very perishable and usage of the best postharvest techniques to enhance the shelf life and to maintain their quality plays a crucial role for commercialization. Materials with high moisture content such as mushrooms do not have a stable structure necessary during conventional dehydration; therefore, a special process must be developed to provide a crispy dried product. Using carboxymethyl cellulose (CMC) as a coating agent provided dried mushroom slices with better quality attributes, including more rehydration ability, brighter color and higher nutritional value (more antioxidant properties).

In this study, ultrasound‐assisted enzymatic technique was investigated using n‐hexane solvent for walnut oil extraction. To achieve this goal, ultrasonic pre‐treatment time (0–70 min) and enzymatic extracting conditions; namely, cellulase concentration (0–2 %) and incubation time (60–240 min) were optimized using response surface methodology. The optimal ultrasonic‐enzymatic extraction treatment using n‐hexane solvent was 47.37 min ultrasonic time, 2.00 % cellulase concentration and 110.91 min incubation time. This treatment resulted in significantly more EY (p≤0.001), TPC (p≤0.001) and IV (p≤0.01) and low level of PV (p≤0.01) of extracted walnut oil, compared to stirring incubation extraction using n‐hexane solvent, ultrasound‐assisted aqueous enzymatic extraction, and aqueous stirring incubation extraction treatments. Gas chromatography–mass spectroscopy showed higher content of unsaturated fatty acids of extracted oil; and scanning electron microscopy showed more pores and interspaces of walnut powder residues of optimal ultrasonic‐enzymatic extraction using n‐hexane solvent than those of stirring incubation treatment using n‐hexane solvent. PRACTICAL APPLICATIONS: The ultrasonic‐enzymatic technique using n‐hexane solvent can improve the extraction yield, total phenolic content and iodine value of extracted walnut oil. The extracted walnut oil had more poly‐unsaturated fatty acids (linolenic acid and linoleic acid) than that obtained by stirring incubation method using n‐hexane solvent. Thus, the results illustrated that this method was a promising extraction method for more extraction yield of walnut oil with high quality.

Electrohydrodynamic (EHD) drying is an innovative drying method. For this investigation, a combined convective-EHD drying system with two variables of voltage (at four levels of 0, 20, 25 and 30 kV) and velocity (at two levels of 0.4 and 2.2 m/s) on drying kinetics, remaining moisture content, porosity, shrinkage, rehydration ratio, shear strength, color, and microstructure of mushroom slices was envisaged. The eight drying treatments (30 kV–0.4 m/s, 25 kV–0.4 m/s, 20 kV–0.4 m/s, 0 kV–0.4 m/s, 30 kV–2.2 m/s, 25 kV–2.2 m/s, 20 kV–2.2 m/s and, 0 kV–2.2 m/s) were carried out at 45 °C for a period of 5 h. ANOVA showed that these eight drying treatments had a significant effect with p ≤ 0.01 on porosity and with p ≤ 0.001 on moisture content, shrinkage, rehydration ratio, and shear strength, but no significant difference was observed in the color of the dried mushroom slices. The advantages of the mushroom slices dried at a higher voltage or air flow velocity included a higher drying rate, porosity and rehydration ratio and a lower remaining moisture content. However, the higher voltage or air velocity caused the development of a wrinkled and broken structure, leading into more shrinkage and shear strength.

Electrohydrodynamic (EHD) is a promising process for reducing the energy consumption of convective drying processes. In this study, a combined convective-EHD drying system was designed, constructed, and examined as an economical drying system for drying mushroom slices. The effects of two levels of velocities (0.4 and 2.2 m/s) and four levels of voltages (0, 20, 25, and 30 kV) on drying kinetics, drying rate, final moisture content, and specific energy consumption of EHD system (SECEHD), convective system (SECtunnel), and combined convective-EHD system (SECtotal) were studied. The results confirmed that by applying electric field at 0.4 m/s air velocity, the enhancement in the drying rate increased with the applied voltage. The combination of 30 kV voltage with the air velocity of 0.4 m/s could significantly increase the drying rate and simultaneously reduce the specific energy consumption of the combined convective-EHD system. However, a cross-flow with the high velocity of 2.2 m/s diminished corona wind effect. Results showed that increasing velocity alongside decreasing voltage reduced the SECEHD, but SECtunnel and SECtotal declined as velocity diminished. In fact, 30 kV-0.4 m/s treatment resulted in statistically similar averaged drying rate and final moisture content to 0 kV-2.2 m/s, 20 kV-2.2 m/s, 25 kV-2.2 m/s, and 30 kV-2.2 m/s treatments, but it represented considerably less SECtotal value in comparison to them. As such, the appropriate combination of electric field intensity with air velocity such as 30 kV-0.4 m/s treatment is a promising solution for reducing the substantial energy consumption of industries using convective drying technique.