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The effects of ultrasound (US) pretreatment on drying kinetics and quality attributes including phenols and ascorbic acid content, color parameters (L*, a*, b*, ∆E, BI, and H°), and rehydration kinetics of kiwifruit slices were investigated. Microstructure observations of raw and US pretreated samples were also performed. Results revealed that US pretreatment reduced drying time of kiwifruit slices by 16.67–25.00% compared with the untreated samples. Weibull distribution model could precisely fit the drying behavior of samples under different treatments (R2 > 0.99). US pretreatment had a positive effect on phenolic compounds preservation but had a negative influence on ascorbic acid and solid retention. The highest loss of ascorbic acid was 40.69% after US pretreatment and 87.71% after drying compared to the content of fresh ones. Color change of kiwifruit slices was mainly caused by drying. Page model adequately predicted the rehydration characteristics of dried samples under all conditions. Microstructure observations explained why US pretreatment increased the moisture diffusion ratio and reduced the rehydration time. The findings in current work indicate that although US pretreatment can enhance drying process, it is not an ideal method for kiwifruit slices due to high loss of water-soluble nutrients. Effects of ultrasound pretreatment on the drying characteristics, ascorbic acid, phenol compounds and microstructure of kiwifruit slices. Graphical Abstract [ABSTRACT FROM AUTHOR]

Vacuum steam pulsed blanching (VSPB) was employed as a novel blanching technology on Cornus officinalis to soften the tissue for subsequent coring and dehydration. The current work aims to explore its effect on mass transfer behavior, PPO inactivation, drying characteristics, physicochemical properties, antioxidant capacity, and microstructure of C. officinalis. Results showed that VSPB increased water loss, decreased solid gain, and increased weight reduction with increased blanching cycles. Besides, VSPB significantly changed physical properties and extensively reduced drying time which was attributed to the cell wall components dissolving and cell turgor pressure decreasing, also verified by observing microstructure alteration. PPO was completely denatured after blanching in 6 cycles, but phenolic compounds were still diffused or degraded. Notably, the content of flavonoids and antioxidant capacity significantly increased compared to fresh samples probably due to increased extractability caused by the disrupting cell structure. Besides, the carotenoids and ascorbic acid could be well preserved. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of cold atmospheric pressure plasma pretreatment (CP) on the drying kinetics, physicochemical properties, content of chlorophylls (alpha and beta), lycopene, phenolic compounds and antioxidant capacity of hot air impingement dried (HAID) okra pods. CP treatment significantly increased moisture diffusivity from 3.04 x 10−9 to 5.07 x 10−9 m2/s and decreased the HAID time by 38%, i.e., from 235 to 145 min. CP resulted in a reduction of alpha chlorophyll and lycopene contents, whereas the combination of CP and HAID allowed both chlorophylls to be preserved. The HPLC-MS/MS analysis revealed that CP-treated samples showed lower content of phenolic compounds, while combination of CP for 15 s and HAID provided excellent preservation of these compounds. The results show that the combination of the advanced CP treatment and HAID method was useful to obtain optimal results for both drying kinetics and the quality of okra pods. [ABSTRACT FROM AUTHOR]

This work investigated the influences of dielectric barrier discharge (DBD) plasma on the drying characteristics, color, and phenolic acid content of lotus pollen. The microstructure was also evaluated to reveal the mechanism of the changes in the quality of lotus pollen. Results showed that the drying time of lotus pollen was reduced from 28 to 4 h when the drying voltage increased from 0 kV to 40 kV. Further, the DBD plasma-dried sample exhibited better color. Compared with the fresh sample, the vanillic acid content in natural open sun drying decreased by 22.7%, while the vanillic acid content of DBD plasma-dried sample increased by 47.9%. Interestingly, ferulic acid was converted into vanillic acid during DBD plasma drying. Total energy consumption was three to four orders of magnitude higher than net energy consumption. The microstructure observation elucidated the mechanisms of moisture migration and change of phenolic acid during DBD plasma drying. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of postharvest ripening (0–6 days, D0–6) on cell wall pectin profile, infrared-assisted hot air-drying characteristics, and sugar content. Results showed that during postharvest ripening progress, the content of water-soluble pectin (WSP) and chelate-soluble pectin (CSP) increased while the content of Na 2 CO 3 -soluble pectin (NSP) and hemicellulose (HC) decreased. In addition, the average molecular weight of WSP increased while the average molecular weight of NSP decreased. Secondly, the drying time of plums with different postharvest ripening periods was in the order: D3 < D4 < D2 < D1 < D0 < D5 < D6. Furthermore, the sugar content of dried plums was mainly influenced by drying time, with three stages of sugar changes observed, tied to moisture content: (1) Sucrose hydrolyzes (50–85%); (2) Fructose and glucose degrade (15–50%); (3) Sorbitol degrades (15–42%). These findings indicate that the transformation of cell wall pectin profile during the postharvest ripening process alters drying behavior and regulates the sugar content of dried plums. Galacturonic acid (PubChem CID: 439215); Acetone (PubChem CID: 180); Distilled water (PubChem CID: 962); Trans-1,2-Diaminocyclohexane-N, N, N, N′-tetraacetic acid (PubChem CID: 2723845); Na 2 CO 3 (PubChem CID: 10340); Glucose (PubChem CID: 5793); fructose (PubChem CID: 2723872) sucrose (PubChem CID: 5988) sorbitol (PubChem CID: 5780) and Sodium borohydride (PubChem CID: 4311764). [Display omitted] • Postharvest ripening affects plum's drying characteristics and dried plum's sugar content. • Postharvest ripening process alters cell wall polysaccharide content. • Molecular weight of pectin and microstructure were used to explore quality changes. • Postharvest ripening process affects the water distribution status of plums. • Plum drying has three sugar change stages tied to moisture content. [ABSTRACT FROM AUTHOR]

As a measure to enhance drying kinetics, efficiency, and quality of the whole American ginseng root, step-down relative humidity (RH) convective hot air drying strategy was experimentally investigated. The effects of drying temperature (45, 50, 55, and 60 °C), RH (20, 30, and 40%), step-down RH, and continuous dehumidification, on hot air drying characteristics and quality attributes were examined. Results showed that the effective moisture diffusion coefficient varied from 1.155 × 10−10 to 2.885 × 10−10 m2/s while the activation energy was found to be 51.14 kJ/mol. Quality evaluation revealed that drying temperature, RH, and step-down RH had significant effect on color change. Additionally, the energy consumption was related to the drying time. The total ginsenosides content decreased with increasing drying temperature and decreasing RH. Microstructure comparison showed that a gel layer was formed on the sample surface when dried at temperature of 60 °C, which impeded internal moisture diffusion. Based on evaluation of the drying time and quality, air temperature of 55 °C and RH of 40% holding 5 h and then dropping it to 20% were proposed as the best drying conditions for whole root. [ABSTRACT FROM AUTHOR]

Effects of vacuum pressure duration (t-VPD of 5, 10, 15, and 20 min), ambient pressure duration (t-APD of 3, 5, 7, and 9 min), drying temperature (60, 65, 70, and 75°C), and slice thickness (3, 5, 7, and 9 mm) on drying kinetics, rehydration ratio (RR), water holding capacity (WHC), and microstructure of Chinese ginger were investigated using a pulsed vacuum dryer. Various parameters affecting drying rate significantly of ginger slices except t-APD, and the shortest drying time of 300 min was obtained when the t-VPD, drying temperature, and slice thickness were 10 min, 70°C, and 3 mm, respectively. Weibull model fitted the experimental results better (R2 > 0.99) than first-order model. RR was increased with increasing of t-VPD while it was decreased with increasing of temperature, and a decreased trend of WHC was observed with increasing temperature or t-VPD. Microstructure observation indicated that increased t-VPD resulted in larger tunnel structure, and high temperature caused the formation of rigid structure, which well explained the changes of RR and WHC of dried ginger. The findings in current work contribute to good understanding of the pulsed vacuum drying behavior and quality of ginger. [ABSTRACT FROM AUTHOR]

Abstract Chili pepper is difficult to dry as the outermost surface is covered with an epicuticular wax layer, which hinders moisture transfer. Chemical dipping pretreatments and thermal blanching methods are often employed to enhance its drying process. However, chemical pretreatments hold the issues of chemical additives residue and thermal blanching methods tend to result in a high loss of bioactive compounds. Cold plasma is an ionized gas that contains different electrons, ions, and reactive neutral species. In current work, the feasibility of cold plasma as a non-thermal pretreatment technology for chili pepper drying is explored. The effects of different cold plasma pretreatment time (15, 30, 45, 60 s) on hot air drying kinetics and quality attributes of chili pepper, such as colour, red pigment retention, antioxidant activity, and microstructure were investigated. Results indicate that cold plasma can enhance the drying rate and the exposure time of 30 s achieves the optimum result. Microstructure observations show the existence of micro-holes, which explain how plasma treatment can enhance the drying kinetics. Quality attributes showed that the colour parameters had no significant changes under various treatment times. The retention of red pigment content was improved by plasma treatment of 30 s, whereas longer exposure times had a negative effect. The antioxidant activity of samples increased with the increase of cold plasma exposure time. Results indicate that cold plasma is a promising pretreatment technology for chili peppers as it enhances drying kinetics and quality attributes of chili pepper. Highlights • Cold plasma effectively enhances drying process of chili peppers. • Pigment extraction was improved for cold plasma exposure time up to 30 s. • Micro-holes generated in surface of pretreated chili pepper. • Colour profile had no significant changes under various treatment times. • Antioxidant activity increased with increase of cold plasma exposure time. [ABSTRACT FROM AUTHOR]

Results of an experimental study are presented and discussed for pulsed vacuum drying (PVD), infrared-assisted hot air-drying (IR-HAD), and hot air-drying (HAD) on drying kinetics, physicochemical properties (surface color, nonenzyme browning index, red pigments, rehydration ratio, water holding capacity, and ascorbic acid), antioxidant capacity (ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity), and microstructure of red pepper. As expected, the drying time decreased with an increase in drying air temperature, IR-HAD needed the shortest drying time, followed by HAD and PVD. The effective moisture diffusivity (Deff) of red pepper under PVD, HAD, and IR-HAD was computed to be in the range 1.33-5.83 × 10−10, 1.38-6.87 × 10−10, and 1.75-8.97 × 10−10 m2/s, respectively. PVD provided superior physicochemical properties of dried red pepper compared to samples dried by HAD and IR-HAD. In detail, PVD yielded higher rehydration ratio, water holding capacity, red pigment and ascorbic acid content, brighter color, lower nonenzyme browning index, and comparable antioxidant capacity compared to samples dried by HAD and IR-HAD at the same drying temperature. Furthermore, PVD promoted the formation of a more porous structure, while HAD and IR-HAD yielded less porous structure. The current findings indicate that PVD drying has the potential to produce high-quality dried red pepper on commercial scale. [ABSTRACT FROM AUTHOR]

The effect of drying temperature (60, 65, 70, and 75 °C) on drying characteristics, shrinkage, rehydration kinetics, microstructure and color profiles of lemon slices were investigated using a far-infrared radiation heating assisted pulsed vacuum dryer. Results showed that the drying time of lemon slices was reduced from 10.5 to 5.5 h when the drying temperature was increased from 60 to 75 °C. Weibull model could precisely describe the drying of samples under different drying temperatures ( R 2  > 0.99). Moisture effective diffusivity ( D eff ), which was determined by taking shrinkage effect into consideration, varied with moisture content. At the initial drying stages, the volume shrinkage of samples followed a linear relationship with decreasing moisture content as the volume shrinkage is approximately equal to the volume of evaporated water. Microstructure observation illustrated that the “skeleton” was fixed when moisture content decreased to approximate 60% w.b. Page model could well model the rehydration kinetics ( R 2  > 0.98). In terms of color evaluation, temperature of 75 °C significantly caused color deterioration and it recorded the highest color change ( ΔE ) of 14.23, Browning Index ( BI ) of 27.14 and lowest Hue Angle ( H 0 ) of 79.46. The findings indicate that FIR-pulsed vacuum drying is a promising alternative method for lemon slices as it can enhance drying process as well as preserve the quality attributes of lemon slices. [ABSTRACT FROM AUTHOR]

The drying kinetics and mathematical modeling of hot-air drying of yam slices were investigated under two-stage relative humidity (RH) control strategy with 60 °C and 1.5 m/s as its constant drying temperature and air velocity, respectively. Results indicate high RH in the initial stage results in high sample's temperature that enhances water diffusion in the falling rate drying period. Within the scope of current work, change in RH in the later drying period has insignificant influence on sample's temperature rise while low RH can accelerate the drying rate. Compared to drying at constant 20 % RH at the same drying air temperature, the drying strategy of using 40 % RH over the first 15 min and then lowing to 20 % RH for the remainder time yields a shorter drying time. Weibull model adequately described the moisture content variation with time for all experiments with the scale parameter ranging from 105.02 to 122.38 min and the values of shape parameters from 0.988 to 1.183. The effective moisture diffusivity determined from the Weibull model varied from 2.032 to 2.610×10−8 m2/s. The rehydration ratio increased as the overall drying time was reduced. Microstructure examination shows that higher RH in the initial drying stage can lead to a more porous microstructure which enhances drying, while fast drying rate in the initial drying period generates a crust layer which hinders drying. [ABSTRACT FROM AUTHOR]

Kiwifruit undergoes rapid quality changes after harvest, which has an important influence on quality grading and processing. The effects of postharvest ripening on water status, distribution, drying characteristics, and the effects of ripening and drying on volatile profiles, phytochemical contents, antioxidant capacity, and microstructure of kiwifruit were investigated. During postharvest storage, the water binding ability decreased, the water distribution, migration path, and the microstructure changed, which led to the shortening of drying time first and then prolongation. Ripeness affected kiwifruit's volatile composition, phytochemical composition and antioxidant capacity, and the drying process after storage reduced the differences of nutrients and volatile components caused by different postharvest ripeness. The findings in current work provide practical implications for the quality classification and effective drying of kiwifruit during post-harvest ripening. • Postharvest ripening affected physicochemical properties and drying characteristics. • Changes in water binding state and microstructure led to differences in drying rate. • Ripeness of kiwifruit affected the heat transfer during drying process. • Both postharvest ripening and drying significantly affected the volatile profiles. • Storage and drying progress affected phytochemical and antioxidant activity. [ABSTRACT FROM AUTHOR]

The effects of drying temperature (50, 60, and 70°C) and absolute humidity (65, 90, 115, 140 g/kg at the initial stage) on drying kinetics and color attributes of apricot halves under process-based drying temperature and humidity integration control (PDTHIC) were investigated. Results indicated that appropriate PDTHIC could reduce the drying time by 18.75% compared to the control group. The absolute humidity parameter should be controlled well rather than continuously dehumidify for traditional practices. The moisture effective diffusivity (Deff) at 70°C presented drastic fluctuations with increasing absolute humidity parameters, calculated using the Weibull distribution model. The activation energy (Ea) of samples treated by continuous dehumidification and PDTHIC were 31.40 and 74.18 kJ/mol, respectively. The variation trend of color parameters was different from the conventional hot air drying probably due to the dehydration mechanism. Observation of the microstructure of the dried samples indicated that the PDTHIC process can enhance the drying rate of apricot through generating a larger pore network compared to continuous dehumidification at the same temperature. The findings of the current work clearly indicated that process-based drying temperature and humidity integration control enhances the drying kinetics of apricot halves, leading to a promising technology for energy savings. [ABSTRACT FROM AUTHOR]

Peeling is an essential operation for tomato processing. A new peeling method, high-humidity hot air impingement blanching (HHAIB) heating technology, was developed as an alternative to the conventional lye and hot-water peeling to eliminate the use of chemicals and the discharge of wastewater. The current work explored the feasibility of HHAIB for tomato peeling. The effects of heating temperature (100–120 °C), relative humidity (20%–40%) and heating time (0–180 s) on the peeling performance were investigated. The optimum treatment was found to be 110 °C heating temperature in combination with 40% of relative humidity and 75 s treatment time, which resulted in lower peeling loss, firmness loss and color deterioration compared with other HHAIB conditions that achieved 100% peelability. The comparative study of optimized HHAIB peeling with conventional lye and hot-water peeling showed that HHAIB peeled tomato obtained lower peeling loss and firmness loss, and higher preservation of phytochemicals, antioxidant capacity and color. In addition, compared with fresh tomatoes, HHAIB processing increased the antioxidant activity, lycopene, and total phenolic content in peeled tomatoes by 16.01%, 10.46%, 12.80%, respectively. The laser scanning confocal microscopy image of fresh tomato skin surface and the scanning electron microscope images of peels and flesh showed that HHAIB caused cracking of the epidermis and melting of the cuticular membrane while reduced the serious damage of flesh. Peeling is a necessary step in tomato processing, which impacts subsequent processing efficiency and product quality. At present, the most common used peeling methods in the industry are hot water or/and alkali peeling, but it induces the loss of water-soluble nutrients, chemical residues and waste liquid treatment. Therefore, the industry urgently needs an alternative peeling technology. The current work shows that HHAIB is a very promising peeling technology as it not only has an excellent peeling performance, but also enhances the preservation of phytochemicals, antioxidant capacity and quality attributes compared to conventional lye and hot-water peeling. • A new peeling technology, HHAIB technology was developed. • Optimum peeling conditions were 110 °C, 40% relative humidity and 75 s. • HHAIB improved the peeling performance and quality of peeled tomatoes. • LSCM and SEM observation reveal the microstructure changes and clarify the peeling mechanism. • HHAIB is a promising method for tomato peeling processing. [ABSTRACT FROM AUTHOR]

A new drying technology, far-infrared radiation heating assisted pulsed vacuum drying (FIR-PVD) was applied to process blueberries. Influences of drying temperature, vacuum pressure duration (VPD), and ambient pressure duration (APD) on drying characteristics and quality attributes of blueberries were investigated under FIR-PVD. Results showed that drying temperature, APD, and VPD had significant influence on drying time and quality attributes of dried blueberries expect for color and cohesiveness. Compared to hot air dried blueberries, FIR-PVD seriously damaged the cellular walls of blueberries during drying at 65 °C. The highest total phenolics (TP) and total monomeric anthocyanins (TMA) contents of dried blueberries were obtained at 65 °C with pulsed ratio of 15 min: 4 min and 15 min: 2 min, respectively. The FIR-PVD products obtained lower color difference, better mechanical properties and rehydration performance and maintained higher antioxidant capacity by shortening drying time, reducing exposure to oxygen, and modifying the microstructure compared to hot air drying. Blueberry is a popular function fruit around the world. With high moisture content and tender tissue, fresh blueberry is very susceptible to microbial infection even under low temperature storage conditions. Drying is a good alternative to extend the shelf life and increase the availability of fresh blueberries. However, the existence of waxy hydrophobic layer covered the surface of blueberries inhibits moisture diffusion during drying. Chemical dipping and thermal blanching pretreatments were usually used to reduce the influence of skin hydrophobicity and promote moisture diffusion. Nevertheless, the chemical additive residue leads to food safety risk and it's a big challenge to deal with the corrosive waste chemical solutions, while thermal blanching resulted a high loss of bioactive compounds. FIR-PVD is a recent developed emerging drying technology to process berries with waxy layer beyond pretreatments. Results indicated that FIR-PVD is a very promising technology for processing blueberries with the improvement of drying efficiency and quality attributes. [Display omitted] • FIR-PVD promoted drying process and preserved blueberry quality. • FIR-PVD seriously damaged the cellular walls of blueberries. • FIR-PVD samples maintained higher antioxidant capacity. • More porous microstructures were observed in FIR-PVD products. • FIR-PVD products showed better mechanical properties and rehydration performance. [ABSTRACT FROM AUTHOR]

In current work, pulsed vacuum drying was employed to dry the bananas and the effect of ripeness on drying kinetics and physicochemical properties was explored and related mechanism was understood through the analysis of sugar and the microstructural changes. Results showed that, with the increase in the ripeness of banana, the drying time decreased from 6.0 to 5.0 h, the rehydration ratio increased from 1.76 ± 0.09 to 2.98 ± 0.11. Fourier transform infrared spectroscopic analysis illustrated ripening and pulsed vacuum drying hardly affects the chemical composition of starch molecules. Regardless of fresh or dried samples, the reducing sugar and total sugar content both increased with increase in ripeness. Compared to the dried ripeness III samples, total color difference of samples with ripeness I and II decreased by 25.03% and 25.49%, respectively. As ripeness increased, the total phenolics and DPPH assay of fresh samples decreased, whereas in pulsed vacuum dried samples it significantly increased. The overall findings indicate that the decrease of starch and the increase of sugar with the increase in ripeness have a significant impact on the pulsed vacuum drying kinetics, microstructure and physicochemical properties of the banana samples. • With increasing ripeness, drying decreased, RR and △ E increased. • With increasing ripeness, starch particles decreased and the micropores expanded. • The PVD process increased the TP content and antioxidant activity of bananas. • Transformation between starch and sugars during ripeness changed drying behavior. [ABSTRACT FROM AUTHOR]

Exploring new blanching technology can help to deal with the challenge of better preservation of fruits and vegetables in food industry. In current work, vacuum-steam pulsed blanching (VSPB) was employed to ginger and its effect on peroxidase (POD) inactivation, drying behavior, texture profiles, microstructure, ultrastructure, phytochemicals (6, 8, 10-gingerols and 6-shagaol) and antioxidant capacity were investigated. Results showed that VSPB inactivated POD completely within 4 cycles. The starch granules gelatinized, the plasma membrane ruptured, the cell wall degraded and fractured gradually during the VSPB process under the action of thermal effect and pressure fluctuation, these changes further led to texture softening and shortening of drying time. Compared to the untreated ginger, VSPB reduced the drying time by 4.41%–22.79%. In the case of dried quality, it was found that the 6, 8, 10-gingerols, total phenolics and antioxidant capacity of dried products under three cycles blanching treatment were higher by 20.2%, 53.0%, 22.4%, 28.6%, 14.0% (DPPH), and 13.4% (FRAP) compared to that of the unblanched dried ginger. The findings in current work indicate VSPB is a promising technique for ginger as it enhances drying process and improve the dried quality through efficiently inactivating the enzymes, altering the texture, microstructure and ultrastructure. [Display omitted] • A new blanching technology, vacuum-steam pulsed blanching technology was developed. • VSPB enhanced ginger drying, phytochemical contents, antioxidant capacity. • Ultrastructural and microstructure observations clarified the mechanism of quality enhancement. • The effects of thermal and pressure fluctuation on ginger quality were considered. • The pressure and Temp of the steam and the core Temp of ginger were monitored. [ABSTRACT FROM AUTHOR]

As a new type of blanching technology, vacuum-steam pulsed blanching (VSPB) has higher blanching efficiency and quality, but the mechanism of this technology on texture softening and drying enhancement is still unclear. In this study, the mechanism was revealed from texture, pectin, nanostructure, cell ultrastructure, calcium, and water state. Results revealed that VSPB treatment reduced the hardness and chewiness, increased water-soluble pectin, decreased sodium‑carbonate-soluble and chelate-soluble pectin concentration, and resulted in depolymerization and degradation of pectin nanostructure. However, transmission electron microscopy showed that blanching damaged the cell wall structure and the integrity of the middle layer. Scanning electron microscope - Energy dispersive X-ray spectroscopy measurement observations indicated that lipid droplets containing calcium ions were formed under the action of VSPB. In addition, low field nuclear magnetic resonance showed that the redistribution of moisture in carrot was facilitated by VSPB. The findings reveal the mechanism of texture softening and drying rate enhancement driven by blanching. Thermal blanching is an essential thermal treatment for many fruits and vegetables processing. Hot water blanching and steam blanching are the two most frequently employed blanching methods due to simple to establish and easy to operate. However, hot water and steam blanching holds several disadvantages, e.g., hot water blanching requires a huge amount of water and generates an excessive amount of wastewater, particularly loss of water-soluble nutrients during blanching due to leaching and diffusion, while for steam blanching, the existence of air and water vapor among the piled materials leads to low blanching efficiency and un-uniform heating. VSPB is an innovative steam blanching method. In the VBSP process, the air and water vapor are expelled by the vacuum pump to facilitate steam deep penetration in the materials, particularly the piled materials, so as to improve blanching efficiency and uniformity. Previous study indicated VSPB could soften texture and reduce the drying time of carrot, but the mechanism was not clear. The current work reveal that VSPB softens texture and enhances drying rate of carrot via micro-, ultra-structure modification, pectin polysaccharides degradation and changes of water state. The findings have important implications for understanding and controlling the blanching triggered texture formation and drying enhancement. • A new blanching technology, vacuum-steam pulsed blanching technology was developed. • SEM, TEM, AFM, EDX and LF-NMR were used for quality analysis during VSPB of carrot. • Micro, ultra, nanostructure and ion changes clarify the mechanism of tissue softening. • Tissue softening and moisture variation clarify the reason of accelerated drying rate. • Pectin content and structure affect texture, microstructure, water state, calcium ion. [ABSTRACT FROM AUTHOR]

Kiwifruit undergoes rapid softening and quality changes after harvest, which has an important impact on consumer appeal, shelf life and market value. Effects of postharvest ripeness on physicochemical properties, microstructure, cell wall fraction (pectin, hemicellulose and cellulose) contents and nanostructure, and pectin molecular weight were investigated. As the postharvest time increased from 0 to 6 days, the contents of total soluble solid and water-soluble pectin increased by 77.4% and 113.0%, respectively; while the content of starch, water insoluble pectin, and hemicellulose decreased by 89.9%, 46.5%, and 33.5%, respectively. Disappearance of starch granules and the increase of intercellular space were observed using SEM. AFM analysis showed that both hemicellulose and pectin depolymerized gradually during storage. Measurements of the molecular weight confirmed the occurrence of depolymerization and degradation of pectin, while the cellulose content, nanostructure, and diameter of individual microfibrils did not change significantly. The findings in current work revealed the quality evolution and related mechanism of kiwifruit during storage. [Display omitted] • Post-ripening process affected physicochemical properties and texture. • Cell wall structure destruction and starch hydrolysis led to the softening. • Nanostructure of pectin, hemicellulose and cellulose were characterized by AFM. • The micromorphology of hemicellulose changed and its molecules and nodes height decreased. • Molecular weight of pectin and microstructure were used to explore quality changes. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the effectiveness of different blanching methods, the dynamic effects of vacuum-steam pulsed blanching (VSPB), steam blanching (SB), and hot water blanching (HWB) on enzymes activity, color, betalains content (BC), total phenolics content (TPC), texture, and microstructure of red beetroot were investigated. With the extension of blanching time (30–180 s), the texture, enzyme activity, and color of red beetroots during blanching process changed significantly. It was found that VSPB took 60 s to completely inactive peroxidase and polyphenol oxidase enzymes compared to 120 s and 90 s for HWB and SB, respectively. In addition, VSPB retained more betalains (118.13 g/kg) and total phenolics (6.44 mg/g) in red beetroots compared to HWB (82.32 g/kg and 4.97 mg/g) and SB (112.96 g/kg and 5.54 mg/g) after 60 s of blanching. In terms of hardness, after 180 s of blanching, the hardness decreased from 22.50 to 11.68, 14.59, and 11.86 N for HWB, SB, and VSPB, respectively. Additionally, microstructure observation showed that VSPB mitigates cell damages compared to other blanching methods. The current work indicated that VSPB is a promising blanching technology for beetroot as it can extensively shorten the blanching time and reduce nutrition loss compared to HWB and SB. • Vacuum-steam pulsed blanching （VSPB） is developed for red beetroot blanching. • VSPB inactivated the peroxidase and polyphenol oxidase of red beetroot in 60 s. • VSPB effectively retained the texture, pigment and total phenolics. • Cell wall structure of red beetroot were severely altered under blanching. [ABSTRACT FROM AUTHOR]

• New blanching method, vacuum-steam pulsed blanching, was employed to carrot. • Compared with HB, the VSPB treatment had higher blanching efficiency and quality. • VSPB enhanced carrot drying, phytochemical contents, antioxidant capacity and colour. • Ultrastructural and microstructure observations clarified the mechanism of quality enhancement. • Chlorogenic acid in blanched carrot increased more than 220 times compared to fresh samples. An emerging blanching technology, namely vacuum-steam pulsed blanching (VSPB) was employed to blanch the carrots and its effects on blanching efficiency, microstructure and ultrastructure, drying kinetics, colour, texture, phytochemicals (phenolics and β-carotene) and antioxidant capacity of carrot slices were explored and compared with the traditional hot water blanching. Results showed that both blanching treatments enhanced the drying velocity and shortened the drying time by 25.9% compared with untreated samples. VSPB yielded higher blanching efficiency, better colour (more red and yellow), greater antioxidant capacity and higher preservation of phytochemicals compared with hot water blanched samples. Especially, compared to hot water blanched carrots, the p-hydroxybenzoic acid, ferulic acid, and caffeic acid content of VSPB samples increased of 106.6%, 42.0%, and 19.0%, respectively. Interestingly, the chlorogenic acid content in the blanched carrot increased more than 220 times compared to fresh samples. Ultrastructure and microstructure observation clarify the mechanism of quality enhancement of VSPB. [ABSTRACT FROM AUTHOR]

Pulsed pressure (each cycle: 301 kPa pressure time of 10 min and atmospheric pressure relaxation time of 10 min), constant high pressure (301 kPa), and constant atmospheric pressure (101 kPa) pickling were carried out for 48 h to evaluate their quality formation efficiency of "Laba" garlic processing. The kinetics of acetic acid transfer, color parameters (L ⁎, a ⁎, b ⁎) and thiosulfinates content, as well as the hardness change of garlic were investigated. Additionally, the surface microstructure and ultrastructure of raw and pickled garlics were observed using confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM), respectively. Results indicated that the pulsed pressure pickling effectively enhanced acetic acid transfer (from 0.32% to 0.65%), degradation of thiosulfinates (from 5.18 mg/mL to 1.72 mg/mL), changes in color (L ⁎: from 81.53 to 38.61, a ⁎: from −1.66 to −19.75, b ⁎: from 21.03 to 2.23), and hardness (from 19,249.87 g to 12,116.40 g) of garlic cloves in 48 h. Garlic cloves turned green initially at the bottom stem node plateau and the top part and then the changes gradually spread to the hollow middle section. Compared with the intact fresh garlic cells, the cell membranes and cell walls of the pickled garlic were severely altered under pulsed pressure pickling process, while the typical plasmolysis was observed under atmospheric pressure. The findings indicate that the pulsed pressure pickling can extensively shorten the processing time due to effective mass transfer of acetic acid and at the same time enhances the final products quality. "Laba" garlic is a popular Chinese pickling snacks due to its desired green color and acid taste as well as its health promoting functions. At present, natural pickling under constant atmospheric pressure is still the main method of producing "Laba" garlic. However, the low mass transfer and poor quality change during the pickling process hinder the industrial production of "Laba" garlic pickles. The findings in this study reveal that the pulsed pressure pickling of "Laba" garlic can be a promising pickling method compared to the commonly used pickling methods due to its high processing efficiency. This study also provides insightful information for developing industrial "Laba" garlic pickling process. • Pulsed pressure pickling enhances acetic acid mass transfer and quality formation of "Laba" garlic. • Color turns green initially at the bottom and top part and then spreads to the hollow middle section. • Cell membranes and cell walls of garlic were severely altered under pulsed pressure pickling process. • Pulsed pressure pickling is a promising method for "Laba" garlic processing. [ABSTRACT FROM AUTHOR]