An understanding of the changes in water holding capacity of rehydrated shiitake mushroom (Lentinula edodes) from cell wall, cell membrane and protein

Textural formation of instant controlled pressure drop-dried peach chips: Investigation of the electrical, thermal, and textural properties of predried peach slices with osmotic dehydration pretreatment

In this study, the effect of osmotic dehydration (OD) pretreatment with various sugar (erythritol, glucose, and trehalose) on the quality of hot-air-predried peach slices was investigated, particularly focusing on electrical properties, texture, thermal stability, and cell wall strength. Furthermore, the correlation between the properties of predried peach slices and the texture of the instant controlled pressure drop (DIC) dried peach chips was explored. OD pretreatments improved the stability and integrity of the cell wall and cell membrane of pre-dried peach slices, which inhibited the excessive expansion of samples during DIC drying. Especially, peach chips with trehalose-OD exhibited the highest crispiness (1.05 mm), the highest hardness (101.34 N) was obtained in erythritol-OD samples. Overall, the type of osmotic agents affected the texture of DIC peach chips with OD pretreatments. It should be noted that trehalose is a promising osmotic agent for controlling and regulating the quality of DIC peach chips.

Effects of combined drying techniques and cellulase hydrolysis on the nutritional value and sensory properties of shiitake mushrooms (Lentinus edodes)

Dried shiitake mushrooms offer rich nutritional value and unique sensory properties, prompting further investigation. The effects of different drying techniques (hot air drying (HAD), infrared hot air drying (IRHAD), pulsed vacuum drying (PVD), vacuum freeze drying (VFD), and natural drying (ND)) combined with enzymatic hydrolysis on the release of flavor compounds and nutrients from shiitake mushrooms were explored. The combination of HAD with cellulase hydrolysis yielded notably high levels of umami amino acids (5.4723 ± 0.1501 mg/g) and 5'-nucleotides (4.0536 ± 0.0062 mg/g), and superior volatile flavors. Combined with cellulase hydrolysis, IRHAD achieved the highest level of total sugars (6.57 ± 0.34 mg/mL), VFD resulted in the greatest soluble protein content (153.21 ± 0.23 μg/mL), PVD yielded the highest total phenolics content (93.20 ± 0.41 μg GAE/mL), and ND produced the maximum reducing sugar content (5.79 ± 0.13 mg/mL). This study addresses crucial gap in the post-drying processing of shiitake mushrooms, offering valuable insights for further product development of shiitake mushrooms.

Innovative hybrid strategy for quality improvement of Goji tea: ultrasonic-ethyl oleate pretreatment combined with heat pump drying

BACKGROUND

Goji berries, renowned for their nutritional benefits, are traditionally dried to extend shelf life and preserve quality. However, conventional drying methods often result in uneven drying, color loss and reduced rehydration capacity. This study investigates an innovative hybrid strategy combining ultrasonic-ethyl oleate (US+AEEO) pretreatment with heat pump drying (HPD) to enhance the drying process of Goji berries.

RESULTS

Fresh Goji berries underwent US+AEEO pretreatment, which significantly disrupted the waxy layer, enhancing drying efficiency and water infiltration during rehydration. Compared to freeze drying (FD), HPD combined with US+AEEO pretreatment resulted in higher retention of total polyphenol content (TPC) and total flavonoid content (TFC) in the Goji soaking soup. Specifically, the HPD-US+AEEO samples exhibited the highest TPC and TFC levels, significantly outperforming FD samples. Additionally, the DPPH and ABTS antioxidant assays demonstrated higher scavenging activities in HPD-US+AEEO samples. The rehydration kinetics revealed that HPD samples had a superior rehydration rate and final moisture content compared to FD samples. Low-field nuclear magnetic resonance and magnetic resonance imaging analyses confirmed enhanced water distribution and higher mobility in HPD-US+AEEO samples. Scanning electron microscopy indicated a more porous structure in US+AEEO-treated samples, facilitating better water absorption and functional component retention.

CONCLUSION

The combination of US+AEEO pretreatment with HPD significantly improves the drying process of Goji berries, enhancing nutrient retention, color preservation and rehydration properties. This innovative drying method offers a promising solution for producing high-quality dried Goji berries, benefiting both the food industry and health-conscious consumers. © 2024 Society of Chemical Industry.

Effects of different cooking methods on proximate composition, digestion characteristics, and antioxidant activity of Lentinus edodes

Lentinus edodes (SM) are highly appreciated by the food industry together with consumers for nutrition and flavour. It is hypothesized the results of our study can indicate to the suitable cooking method for maximal nutrient retention, this study investigated the effects of six cooking methods on the proximate composition, digestive properties, and antioxidant activities of SM in vitro simulated digestion. The results revealed that the ash and protein contents of cooked samples were reduced excluding steaming and roasting, and likewise minerals during deep-frying and boiling (e.g., Mg from 1080.07 to 629.03 mg/kg, deep-frying). A conspicuous rise in fat and energy was found in deep-frying and stir-frying. Steaming retained more reducing sugar (3.80 mg/mL). Roasting improved bioaccessibility of most amino acids (e.g., 82.61%, Asp). Using oil as a medium was associated with higher antioxidant activities using water. Steaming and roasting were better for preserving the nutrient composition of cooked Lentinus edodes.

Synergistic mechanism of steam blanching and freezing conditions on the texture of frozen yellow peaches based on macroscopic and microscopic properties

Freezing and blanching are essential processing steps in the production of frozen yellow peaches, inevitably leading to texture softening of the fruit. In this study, the synergistic mechanism of stem blanching, freezing conditions (-20°C, -40°C, -80°C, and liquid nitrogen [-173°C]), and sample sizes (cubes, slices, and half peaches) on macroscopic properties of texture, cellular structure, and ice crystal size distribution of frozen yellow peaches were measured. Blanching enhanced the heat and mass transfer rates in the subsequent freezing process. For nonblanched samples, cell membrane integrity was lost at any freezing rate, causing a significant reduction in textural quality. Slow freezing further exacerbated the texture softening, while the ultra-rapid freezing caused structural rupture. For blanched samples, the half peaches softened the most. The water holding capacity and fracture stress were not significantly affected by changes in freezing rate, although the ice crystal size distribution was more susceptible to the freezing rate. Peach cubes that had undergone blanching and rapid freezing (-80°C) experienced 4% less drip loss than nonblanched samples. However, blanching softened yellow peaches more than any freezing conditions. The implementation of uniform and shorter duration blanching, along with rapid freezing, has been proven to be more effective in preserving the texture of frozen yellow peaches. Optimization of the blanching process may be more important than increasing the freezing rate to improve the textural quality of frozen yellow peaches.

Vacuum-steam pulsed blanching: An emerging method to enhance texture softening, drying behavior and physicochemical properties of Cornus officinalis

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.

Dehydration-rehydration vegetables: Evaluation and future challenges

In this review, the rehydration kinetics model, the quality factors affecting of vegetables during rehydration process, the future challenges and development direction of rehydration process were comprehensively analyzed. Based on the fitting equation for the change in moisture content during rehydration, a suitable rehydration model can be selected to describe the rehydration process of vegetables. Optimal pre-treatment, drying and rehydration methods were selected by considering quality, energy consumption and environmental aspects, and new technologies were developed to improve the quality characteristics of rehydrated vegetables. It is necessary to classify vegetables according to their shape and type to establish the criteria of rehydration processing through mathematical modeling. Industrial production from pre-treatment to product packaging will be precisely adjusted through process parameters. Furthermore, improvements the quality of rehydrated vegetables can be considered in terms of the structural and compositional aspects of the cell wall and cell membrane.

Structural Characteristics and Multiple Bioactivities of Volvariella volvacea Polysaccharide Extracts: The Role of Extractive Solvents

The chemical structures and functional properties of plant-based polysaccharides are critically influenced by extractive solvents, but their roles are not clear. In this study, the structural characteristics and multiple bioactivities of Volvariella volvacea polysaccharides (VVPs) subjected to water (VVP-W), alkalis (sodium hydroxide, VVP-A), and acids (citric acid, VVP-C) as extractive solvents are investigated systematically. Of the above three polysaccharides, VVP-W exhibited the highest molecular weights, apparent viscosity, and viscoelastic properties. Functional analyses revealed that VVP-C had an excellent water-holding capacity, foaming properties, and emulsifying capacity, while VVP-A exhibited a promising oil-holding capacity. Moreover, VVP-C displayed strong inhibitory effects on α-amylase and α-glucosidase, which could be attributed to its content of total phenolics, proteins, and molecular weights. These findings have important implications for selecting the appropriate extraction techniques to obtain functional polysaccharides with targeted bioactive properties as food additives.

Review of postharvest processing of edible wild-grown mushrooms

Edible wild-grown mushrooms, plentiful in resources, have excellent organoleptic properties, flavor, nutrition, and bioactive substances. However, fresh mushrooms, which have high water and enzymatic activity, are not protected by cuticles and are easily attacked by microorganisms. And wild-grown mushroom harvesting is seasonal the harvest of edible wild-grown mushrooms is subject to seasonality, so their market availability is challenging. Many processing methods have been used for postharvest mushroom processing, including sun drying, freezing, packaging, electron beam radiation, edible coating, ozone, and cooking, whose effects on the parameters and composition of the mushrooms are not entirely positive. This paper reviews the effect of processing methods on the quality of wild and some cultivated edible mushrooms. Drying and cooking, as thermal processes, reduce hardness, texture, and color browning, with the parallel that drying reduces the content of proteins, polysaccharides, and phenolics while cooking increases the chemical composition. Freezing, which allows mushrooms to retain better hardness, color, and higher chemical content, is a better processing method. Water washing and ozone help maintain color by inhibiting enzymatic browning. Edible coating facilitates the maintenance of hardness and total sugar content. Electrolytic water (EW) maintains total phenol levels and soluble protein content. Pulsed electric field and ultrasound (US) inhibit microbial growth. Frying maintains carbohydrates, lipids, phenolics, and proteins. And the mushrooms processed by these methods are safe. They are the focus of future research that combines different methods or develops new processing methods, molecular mechanisms of chemical composition changes, and exploring the application areas of wild mushrooms.

The role of fructose at a range of concentration on the texture and microstructure of freeze-dried pectin-cellulose matrix cryogel

Freeze-dried (FD) fruit and vegetable materials with a large amount of sugar are unstable. With the aim to understand the structure formation of FD products, the effects of fructose content on the texture and microstructure of FD matrix were investigated by using pectin-cellulose cryogel model. Cryogels containing fructose of 0-40% were produced using freeze-drying at three different primary drying temperatures of -40, -20, and 20°C. The resultant cryogels were characterized by texture profile analyzer, scanning electron microscope, and μCT. Results indicated that at drying temperature of -40°C, increasing fructose concentration promoted the hardness of the cryogels, and cryogels of 16% fructose obtained maximum hardness. Excessive fructose (≥20%) weakened the described hardness, while exhibiting stronger springiness and resilience. The microstructure showed that dense pores and increased wall thickness due to fructose aggregation were critical factors responsible for increased hardness. The porous structure as well as relatively large pore size were necessary for crispness, in addition, rigid pore wall with certain strength were also required. At the drying temperature of 20°C, large hetero-cavities dominated the microstructure of cryogels with 30% and 40% fructose, caused by melting inside during FD process. In this situation, lower Tm (-15.48 and -20.37°C) were responsible for cryogels' melting In conclusion, if possible, regulating fructose content and state may enable the precision texture design of FD fruit and vegetable foods.

Metabolomic analysis provides insights into the mechanism of color and taste changes in Dictyophora indusiata fruiting bodies under different drying processes

In this study, we systematically assessed how the morphology and texture of edible fruiting bodies of D. indusiata (EFD) varied under three drying techniques: vacuum freeze drying (FD), vacuum drying (VD), and hot air drying (HD). It was discovered that freeze-dried EFD samples (FD-EFD) had an intact microstructure, and thus, a good appearance, textural characteristics, and rehydration properties. Quantitative metabolomic analysis revealed 801 metabolites, where 236 211 metabolites were significantly different in abundance in the comparison of hot-air dried EFD samples (HD-EFD) versus FD-EFD and vacuum-dried EFD samples (VD-EFD) versus FD-EFD, respectively. VD and HD significantly affected the abundance of taste-related compounds and resulted in the improvement of EFD's umami. The acidity of EFD is provided by organic acids produced through the tricarboxylic acid cycle. The browning of HD-EFD was caused by Maillard reactions, oxidative degradation of ascorbic acid, and endogenous enzymatic browning process dominated by the phenylalanine metabolic pathway. The metabolomic analysis provides new insights into changes in EFD by different drying processes.

Hot Air Drying of Seabuckthorn (Hippophae rhamnoides L.) Berries: Effects of Different Pretreatment Methods on Drying Characteristics and Quality Attributes

Seabuckthorn berries are difficult to dry because the outermost surface is covered with a dense wax layer, which prevents moisture transfer during the drying process. In this study, uses of ultrasonic-assisted alkali (UA), pricking holes in the skin (PH) and their combination (UA + PH) as pretreatment methods prior to hot air drying and their effects on drying characteristics and quality attributes of seabuckthorn berries were investigated. Selected properties include color, microstructure, rehydration capacity, as well as total flavonoids, phenolics and ascorbic acid contents. Finally, the coefficient of variation method was used for comprehensive evaluation. The results showed that all pretreatment methods increased the drying rate; the combination of ultrasonic-assisted alkali (time, 15 min) and pricking holes (number, 6) (UA15 + PH6) had the highest drying rate that compared with the control group, the drying time was shortened by 33.05%; scanning electron microscopy images revealed that the pretreatment of UA could dissolve the wax layer of seabuckthorn berries, helped to form micropores, which promoted the process of water migration. All the pretreatments reduced the color difference and increased the lightness. The PH3 samples had the highest value of vitamin C content (54.71 mg/100 g), the UA5 and PH1 samples had the highest value of total flavonoid content (11.41 mg/g) and total phenolic content (14.20 mg/g), respectively. Compared to other pretreatment groups, UA15 + PH6 achieved the highest quality comprehensive score (1.013). Results indicate that UA15 + PH6 treatment is the most appropriate pretreatment method for improving the drying characteristics and quality attributes of seabuckthorn berries.

Investigation on the rehydration mechanism of freeze-dried and hot-air dried shiitake mushrooms from pores and cell wall fibrous material

Shiitake mushrooms are unique in their porous structure, which could be affected by various chemical/physical changes during freeze-drying process. In this work, rehydration characteristics of freeze-dried products which were pre-frozen at -20 ℃, -40 ℃, -80 ℃, and -196 ℃ (by liquid nitrogen) were explored from aspects of pores and cell wall fibrous material. Although the appearance and rehydration rate of freeze-dried samples was better than hot-air dried samples with drying temperature ranging from 30 ℃ to 90 ℃, the final rehydration ratio was still less than hot-air dried samples dried at low temperature (30 ℃ and 40 ℃) due to the more serious structural damage by freeze-drying. Hydration capacity of the cell wall fiber was increased by freeze-drying, which might be ascribed to the loosen structure of cell wall instead of composition changes. Thus, hot-air drying at low temperature is still recommend and freeze-drying should be further optimized.

Effect of shiitake mushrooms polysaccharide and chitosan coating on softening and browning of shiitake mushrooms (Lentinus edodes) during postharvest storage

We investigated the browning and softening of fresh Lentinula edodes (LE) coated with polysaccharides (LEP) isolated from LE stalks and stored at 4 °C for 15 days. The results showed that compared to the chitosan-coated and uncoated LE, the LEP-treated mushrooms showed significant improvements in several qualities during storage, such as reduced weight loss, retention of hardness and springiness, improved soluble protein content, and reduced browning, malondialdehyde content, and electrolyte leakage rate. The best results were obtained with 1.5 % LEP. LEP improved the activities of peroxidase, catalase, superoxide dismutase, ascorbate peroxidase, and phenylalanine ammonialyase and significantly reduced the accumulation of hydrogen peroxide during storage compared to the control samples. In addition, the LEP treatment maintained the high antioxidant activity of LE during storage. Notably, LEP inhibited browning-related enzymes (polyphenol oxidase and tyrosinase) to reduce browning. It also maintained high levels of cellulase, chitinase, and β-1,3 glucanase to improve softening during storage. These findings suggest the potential of LEP to improve the post-harvest quality of mushrooms, allowing a storage period of up to 15 days (extending the shelf life by six days) and indirectly suggesting that the polysaccharide component of LEP can act as a self-defense additive to protect against spoilage during storage.

The Effect of Hot-air Dried Lentinula edodes on the Quality and Organoleptic Properties of Rolled-dumplings

The effect of hot-air dried Lentinula edodes pileus (DLE) on the quality and organoleptic properties of rolled-dumplings was evaluated. DLE was prepared by drying at 60°C for 24 h and added (Non, 7%, and 9%) to rolled-dumplings. The proximate composition, pH, color (CIE L*, a*, b*), and cooking yield were analyzed. Texture profile analysis, electronic-nose (e-nose), electronic-tongue (e-tongue), and organoleptic evaluation were also conducted. The cooking yield of dumplings with 9% DLE was significantly lower than that of the congeners without DLE, whereas 7% DLE did not lead to significant differences compared without DLE. With increasing DLE addition, the pH and lightness of the dumplings decreased significantly, whereas the redness tended to increase. The texture profile was significantly higher for the dumplings with DLE compared to those without DLE. E-nose analysis confirmed that DLE addition led to the positive odors (methanethiol: meaty, sulfurous; 3-methylbutanal: malty, toasted) and the negative odors (trimethylamine: ammoniacal; acetic acid: acidic, sour). E-tongue analysis showed that DLE addition decreased the intensity of the sourness and increased the intensity of the saltiness and umami of rolled-dumplings. DLE addition improved the overall organoleptic properties, but 9% DLE can be recognized as a foreign substance in organoleptic acceptance. Consequently, DLE has the potential to serve as a flavor and odor enhancer for rolled-dumplings, and the addition of DLE can positively improve consumer acceptance by improving the quality and organoleptic properties.

Effect on purine releasement of Lentinus edodes by different food processing techniques

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Freeze-drying could notably decrease the purine release from lentinus edodes.

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Roast-drying reduced guanine and adenine levels in lentinus edodes.

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Roast-drying raised the level of strong uricogenic purine hypoxanthine in lentinus edodes.

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The total purine content was higher than that of raw LE after moist heating.

Lentinus edodes (LE) is very popular in the world and also considered as high purine food. However, few focuses on purine types and its change during food processing. Here, we first compared 3 drying techniques, including roast-drying, freeze-drying, sun-drying on purine contents of LE by using acidolysis and HPLC. It showed that adenine decreased significantly after roast-drying (120 °C), which may be caused by thermal damage of DNA. Total purine decreased significantly after freeze-drying, while roast-dried and sun-dried LE remained unchanged. The effect of moist heat (boiling) on LE purine were also evaluated. Total purine increased due to xanthine increasement (331.72 ± 50.07%). And purine contents transferred into boiled liquid was higher than that in boiled solid. Compared with sun-dry and roast-dry processing, freeze-drying could notably affect the purine release from LE and decrease purine contents. Therefore, freeze-drying is recommended for process techniques for hyperuricemia and gouts populations.