Toughening and its association with the postharvest quality of king oyster mushroom ( Pleurotus eryngii ) stored at low temperature

Promoted metabolic remolding by overexpression of AspAT9 ameliorates cadmium toxicity in Arabidopsis

Cadmium (Cd) is a toxic heavy metal that poses a serious threat to crop safety and human health. Aspartate aminotransferase (AspAT) is a prime enzyme engaged in amino acid metabolism, contributing essential metabolic substances for plant growth and acclimatization to various stresses. In this study, we identified a novel AspAT9 gene with high responsiveness to Cd stress from poplar 'Nanlin895' and subsequently transformed it into Arabidopsis. The resulting transgenic AspAT9-1 plants (designated A9) and wild-type (WT) Arabidopsis were subjected to Cd treatment (T) or maintained under control conditions (CK). Phenotypic assessments showed that A9 plants displayed greater resistance to Cd stress compared to WT, as evidenced by their stay-green trait and higher biomass. Subsequent metabolism measurement revealed that A9 plants accumulated more Cd in their roots than WT. Meanwhile, the content of various proteinogenic amino acids, Cd-chelating compounds, such as lignin and phytochelatins (PCs), along with antioxidants like glutathione (GSH) and chlorophyll in A9-T exceeded WT-T. Further RNA-seq analysis uncovered significant transcriptional changes in genes implicated in aspartate-glutamate metabolism, antioxidant systems, phenylpropanoid biosynthesis, transporters, and photosynthesis activities. Our findings demonstrate the beneficial effect of overexpressing AspAT9 on Cd phytoextraction, highlights its potential as a valuable genetic resource for phytoremediation applications.

Synergistic antibacterial effect of 405 nm blue light-emitting diodes (LEDs) and gelatin film for inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium on stainless steel and fresh fruit peel

A combined antibacterial effect of 405 nm blue LEDs (BL) and gelatin film (G) was investigated on stainless steel (SUS) and fresh fruit peel for the inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium. On the SUS, the sum of the individual treatments of G for 20 min and BL at 20 J/cm2 was <1 log reduction (log CFU/cm2). In comparison, combination treatment of G and BL (G + BL) at 20 J/cm2 exhibited 2.37 and 3.09 log reduction on E. coli O157:H7 and S. Typhimurium. The G + BL treatment only increased a propidium iodide (PI) uptake, indicating that cell membrane damage occurred. In the G + BL treatment, reactive oxygen species (ROS) scavenging assay confirmed that ROS involved in the bactericidal mechanism. On orange peel, the G + BL treatment at 40 J/cm2 resulted in a 3.05 and 3.17 log reduction on E. coli O157:H7 and S. Typhimurium. In contrast, the individual treatment of G for 40 min led to reductions of 0.63 log CFU/cm2 for E. coli O157:H7 and 0.50 log CFU/cm2 for S. Typhimurium, while the BL treatment at 40 J/cm2 achieved reductions of 0.78 and 0.69 log CFU/cm2, respectively. A synergistic bactericidal effect was similarly observed in the combined treatment groups for both apple and grapefruit peels. In a color and texture analysis, G did not affect hardness, toughness, and visual color of fruit.

Modified atmosphere packaging maintains stem quality of Chinese flowering cabbage by restraining postharvest lignification and ROS accumulation

In this study, the impact of modified atmosphere packaging (MAP) on quality, lignin biosynthesis, reactive oxygen species (ROS) metabolism, and microstructures of stem in Chinese flowering cabbages was investigated. Compared with control, MAP treatment retained higher content of protein, total soluble solid, and vitamin C, while lower weight loss rate, carbon dioxide (CO2) production rate, electrolyte leakage, firmness and hollowing of stems. Lignin content in MAP-treated stems was 1.23-fold higher than that of control stems on the twelfth day. Moreover, MAP treatment inhibited the increasing in cell wall thickness by inhibiting activities of lignin biosynthesis-related enzymes. In addition, MAP suppressed ROS contents, while enhanced levels of ascorbic acid and reduced glutathione through promoting activities of antioxidant enzymes. The above results suggest that maintaining stems quality of Chinese flowering cabbages through MAP treatment is related to prevent lignin accumulation around the vascular tissue and enhance antioxidant capacity.

Identification of the Key Gene DfCCoAOMT1 through Comparative Analysis of Lignification in Dendrocalamus farinosus XK4 and ZPX Bamboo Shoots during Cold Storage

Dendrocalamus farinosus bamboo shoots, a species with rich nutritional value, are important in Southwest China. Lignin is an important factor affecting the postharvest flavor quality of bamboo shoots; however, the underlying mechanism of lignin deposition in D. farinosus bamboo shoots during cold storage is still not fully understood. In this study, the mutant D. farinosus XK4 with low lignin content at 3.11% and the cultivated variety ZPX at 4.47% were used as experimental materials. The lignin content of D. farinosus XK4 and ZPX, as well as the gene expression differences between them, were compared and analyzed during cold storage using transcriptomic and physiological methods. Our analysis revealed several key genes and found that D. farinosus CCoAOMT1 plays a key role in the regulatory network of bamboo shoots during cold storage. Tobacco heterologous transformation experiments demonstrated that overexpression of DfCCoAOMT1 significantly increases lignin content. This study provides a novel foundation for future research aimed at improving the postharvest quality and flavor of D. farinosus bamboo shoots through targeted genetic manipulation during cold storage.

Novel Post-Harvest Preservation Techniques for Edible Fungi: A Review

Edible fungi are well known for their rich nutrition and unique flavor. However, their post-harvest shelf-life is relatively short, and effective post-harvest preservation techniques are crucial for maintaining their quality. In recent years, many new technologies have been used for the preservation of edible fungi. These technologies include cold plasma treatment, electrostatic field treatment, active packaging, edible coatings, antimicrobial photodynamic therapy, and genetic editing, among others. This paper reviews the new methods for post-harvest preservation of mainstream edible fungi. By comprehensively evaluating the relative advantages and limitations of these new technologies, their potential and challenges in practical applications are inferred. The paper also proposes directions and suggestions for the future development of edible fungi preservation, aiming to provide reference and guidance for improving the quality of edible fungi products and extending their shelf-life.

Low molecular weight chitosan from Pleurotus ostreatus waste and its prebiotic potential

The booming mushroom industry envisages economic merits, and massive unutilized waste production (∼ 20 %) creates an opportunity for valorization. Chitosan, a bioactive polysaccharide, has drawn immense attention for its invaluable therapeutic potential. Thus, the present study was conducted to extract chitosan from mushroom waste (MCH) for its prebiotic potential. The structural characterization of MCH was carried out using NMR, FTIR, and XRD. The CP/MAS-13CNMR spectrum of MCH appeared at δ 57.67 (C2), 61.19 (C6), 75.39 (C3/C5), 83.53 (C4), 105.13 (C1), 23.69 (CH3), and 174.19 (C = O) ppm. The FTIR showed characteristic peaks at 3361 cm-1, 1582 cm-1, and 1262 cm-1 attributed to -NH stretching, amide II, and amide III bands of MCH. XRD interpretation of MCH exhibited a single strong reflection at 2θ =20.19, which may correspond to the "form-II" polymorph. The extracted MCH (∼ 47 kDa) exhibited varying degrees of deacetylation from 79 to 84 %. The prebiotic activity score of 0.73 to 0.82 was observed for MCH (1 %) when supplemented with probiotic strains (Lactobacillus casei, L. helveticus, L. plantarum, and L. rhamnosus). MCH enhanced the growth of Lactobacillus strains and SCFA's levels, particularly in L. rhamnosus. The MCH also inhibited the growth of pathogenic strains (MIC of 0.125 and 0.25 mg/mL against E. coli and S. aureus, respectively) and enhanced the adhesion efficiency of probiotics (3 to 8 % at 1 % MCH supplementation). L. rhamnosus efficiency was higher against pathogens in the presence of MCH, as indicated by anti-adhesion assays. These findings suggested that extracted polysaccharides from mushroom waste can be used as a prebiotic for ameliorating intestinal dysbiosis.

The combination of high oxygen and nanocomposite packaging alleviated quality deterioration by promoting antioxidant capacity and phenylpropane metabolism in Volvariella volvacea

Volvariella volvacea is a highly perishable mushroom that severely affects its postharvest commercial value. This study aimed to investigate the impact of high oxygen (O2) levels combined with nanocomposite packaging on the shelf-life quality of V. volvacea. Results showed that treatment with high concentrations of O2 (80% and 100% O2) and nanocomposite packaging effectively delayed the quality deterioration of V. volvacea, resulting in better postharvest appearance, higher firmness, lower weight loss, malondialdehyde (MDA) content, and leakage of membrane electrolytes. Further analysis revealed the combination treatments ameliorated oxidative stress by inducing antioxidant enzymes and the glutathione-ascorbate (GSH-AsA) cycle at both enzymatic and transcriptional levels, thereby activating the antioxidant system. Additionally, the treatments enhanced activities of key enzymes in phenylpropane metabolism, leading to a reduction in the decrease of total phenolics and flavonoids. This work provides new insights into the development of postharvest technologies to prolong the storage life of V. volvacea.

Effect of Combined Chitosan and Hyperbranched Poly-L-Lysine Based Coating on Prolonging the Shelf Life of Oyster Mushroom (Pleurotus ostreatus)

To extend the shelf life of oyster mushroom (Pleurotus ostreatus), the effects of chitosan (CS) and hyperbranched poly-L-lysine (HBPL) combined treatment on quality characteristics, nutritional quality, storage characteristics, and enzyme activity of oyster mushroom during postharvest storage at 4 °C were investigated. The results showed that CS-HBPL combined treatment could significantly reduce rot degree and weight loss and significantly inhibit the browning of oyster mushroom. At the same time, the loss of reducing sugar, vitamin C, soluble protein, and total phenolic was significantly reduced. Compared with the control, CS-HBPL combined treatment could also significantly inhibit an increase in malondialdehyde (MDA) and significantly decrease the relative electrolyte leakage of oyster mushroom. In addition, the activities of catalase (CAT), superoxide dismutase (SOD), phenylalnine ammonialyase (PAL), and peroxidase (POD) were significantly improved, and the activity of polyphenol oxidase (PPO) was significantly inhibited in oyster mushroom. In conclusion, CS-HBPL combined treatment had a good protective effect on the membrane permeability damage of oyster mushroom and could effectively delay the oxidation of phenolic substances and browning of oyster mushroom. Therefore, CS-HBPL combined treatment can be used as a potential strategy to extend the storage time of oyster mushroom.

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.

Recent advances in quality preservation of postharvest golden needle mushroom (Flammulina velutiper)

The golden needle mushroom (Flammulina velutiper) is one of the most productive mushrooms in the world. However, F. velutiper experiences continuous quality degradation in terms of changes in color and textural characteristics, loss of moisture, nutrition and flavor, and increased microbial populations due to its high respiratory activity during the postharvest phase. Postharvest preservation techniques, including physical, chemical and biological methods, play a vital role in maintaining postharvest quality and extending the shelf life of mushrooms. Therefore, in this study, the decay process of F. velutiper and the factors affecting its quality were comprehensively reviewed. Additionally, the preservation methods (e.g., low-temperature storage, packaging, plasma treatment, antimicrobial cleaning and 1-methylcyclopropene treatment) for F. velutiper used for the last 5 years were compared to provide an outlook on future research directions. Overall, this review aims to provide a reference for developing novel, green and safe preservation techniques for F. velutiper. © 2023 Society of Chemical Industry.

Advances in Postharvest Storage and Preservation Strategies for Pleurotus eryngii

The king oyster mushroom (Pleurotus eryngii) is a delicious edible mushroom that is highly prized for its unique flavor and excellent medicinal properties. Its enzymes, phenolic compounds and reactive oxygen species are the keys to its browning and aging and result in its loss of nutrition and flavor. However, there is a lack of reviews on the preservation of Pl. eryngii to summarize and compare different storage and preservation methods. This paper reviews postharvest preservation techniques, including physical and chemical methods, to better understand the mechanisms of browning and the storage effects of different preservation methods, extend the storage life of mushrooms and present future perspectives on technical aspects in the storage and preservation of Pl. eryngii. This will provide important research directions for the processing and product development of this mushroom.

Cauliflower-shaped Pleurotus ostreatus cultivated in an atmosphere with high environmental carbon dioxide concentration

Commercial aspects, physiological properties, and nutritional characteristics of Pleurotus ostreatus grown under various environmental carbon dioxide concentration ([CO2]e) conditions were assessed. As [CO2]e increased, the activity of antioxidant enzymes (catalase, peroxidase, and superoxide dismutase) in fruiting body increased, activities of succinate dehydrogenase and cytochrome c oxidase were inhibited, and malondialdehyde and adenosine triphosphate (ATP) syntheses were reduced, leading to incomplete development of pilei and stipes, or even absence of pilei. Under high [CO2]e (≥1.00%), fruiting body of P. ostreatus was morphologically altered to assume cauliflower shape. This cultivation condition resulted in high total contents of crude protein, crude fiber, and amino acids, increased levels of umami- and sweet-tasting amino acids, and reduced levels of bitter-tasting amino acids, thus enhancing the flavor of the product. In conclusion, a novel "cauliflower-shaped" mushroom (P. ostreatus) was successfully cultivated at high (≥1.00%) environmental CO2 concentration. The product has a delicious taste and high nutritional value, is relatively easy to transport and store, and has excellent potential for commercial development.

The Effect of Hot-Air Dried Lentinula edodes on the Quality and Oranoleptic 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.

Biodegradable phase change materials with high latent heat: Preparation and application on Lentinus edodes storage

In order to develop biodegradable phase change materials (PCMs) with high latent heat for cold chain logistics, superabsorbent resin (SAR) was prepared based on starch graft copolymerization. FTIR and DSC demonstrated that acrylic acid was successfully grafted onto starches and optimum latent heat of PCM was 330.4 J/g with 10% (w/w) starch. The water retention of PCM with 10% (w/w) starch was 0.49 after heating at 50 °C for 200 h, which was 4.9 folds higher than that of non-starch PCM. Biodegradation rate of PCM was 60.12% within 75-day burial, which was 6 folds higher than that of non-starch PCM. Moreover, significant reduction in browning index, odor, decay, relative conductivity and malondialdehyde (MDA) content was observed in Lentinus edodes treated by biodegradable PCM. These results indicated that the application of biodegradable PCM could extend the shelf life of fresh L. edodes stored at 25 °C.

A novel phase change coolant promoted quality attributes and glutamate accumulation in postharvest shiitake mushrooms involved in energy metabolism

Cold chain transportation is an important link in postharvest logistics of agricultural products. In current study, we developed a novel water-based phase change coolant (PCC), which showed longer effectiveness in maintaining low temperature condition compared with ice, and applied in preserving the postharvest mushrooms. The results showed that the novel PCC effectively inhibited water loss, as well as maintained quality attributes including firmness, color, phenolics, flavonoids, and thus prolonged the shelf-life of mushrooms. Low temperature condition created by the novel PCC treatment maintained high level of energy charge by activating the activities of SDH, CCO, H⁺-ATPase and Ca²⁺-ATPase, resulting in the delay of postharvest senescence. In addition, sufficient energy supply decreased the consumption of glutamate as carbon skeleton by inhibiting GDH activity, improved glutamate accumulation, and therefore maintained sensory properties as a result. Thus, the novel PCC might be an excellent substitute for ice in cold chain transportation of mushrooms.

Melatonin retards senescence via regulation of the electron leakage of postharvest white mushroom (Agaricus bisporus)

Currently, melatonin (N-acetyl-5-methoxytrytamine) is recognized as a potential scavenger of free radicals. In this study, the effect of exogenous melatonin at various concentrations (0.05, 0.1, and 0.2 mM) on the texture, sensory qualities, and electron leakage in white mushrooms was evaluated at 3 ± 1 °C. It was observed that mushrooms treated with 0.1 mM melatonin were of good quality and their electron leakage was dramatically dampened. The results showed that 0.1 mM melatonin retained a higher adenosine triphosphate level and also prevented the release of cytochrome c into the cytoplasm. More significantly, it prominently inhibited electron leakage by increasing the activities of complexes I and III by the upregulation of AbNdufB9 and AbRIP1. It also regulated respiratory states in mushrooms; delayed the decline of respiratory state 3; enhanced respiratory state 4; boosted the oxidative phosphorylation and efficiency of mitochondria; and ultimately retarded the senescence of the white mushrooms.

Chemical composition and deterioration mechanism of Pleurotus tuoliensis during postharvest storage

Pleurotus tuoliensis is a popular edible and medical mushroom, but it is highly perishable during postharvest storage. The quality parameters, chemical composition, malondialdehyde (MDA) concentration, and activity of metabolic enzymes were studied during 12 days of storage at 4 °C and 6 days of storage at 25 °C. Degradation was well described by changes in quality parameters, losses in nutritional value, increased metabolic enzyme activity, the accumulation of MDA concentrations, and the increase of total phenolic (TP) content. The phenylalanine ammonia lyase (PAL) significantly positively correlated with TP, which suggested an underlying mechanism of browning that the increased PAL activity stimulates the biosynthesis of phenols through the phenylalanine pathway. These results suggest that increased activity of laccase, lipoxygenase, PAL, TP and MDA accumulation, together with polysaccharide degradation, are the main factors involved in the deterioration of P. tuoliensis during storage.

Functional principal component analysis for near-infrared spectral data: a case study on Tricholoma matsutakeis

Tricholoma matsutakeis (TM) is the most expensive edible fungi in China. Given its price and exclusivity, some dishonest merchants will sell adulterated TM by combining it with cheaper fungi in an attempt to earn more profits. This fraudulent behavior has broken food laws and violated consumer trust. Therefore, there is an urgent need to develop a rapid, accurate, and nondestructive tool to discriminate TM from other edible fungi. In this work, a novel detection algorithm combined with near-infrared spectroscopy (NIR) and functional principal component analysis (FPCA) is proposed. Firstly, the raw NIR data were pretreated by locally weighted scatterplot smoothing (LOWESS) and multiplication scatter correction (MSC). Then, FPCA was used to extract valuable information from the preprocessed NIR data. Then, a classifier was designed by using the least-squares support-vector machine (LS-SVM) to distinguish categories of edible fungi. Furthermore, the one-versus-one (OVO) strategy was included and the binary LS-SVM was extended to a multi-class classifier. The 166 samples of four varieties of fungi were used to validate the proposed method. The results show that the proposed method has great capability in near infrared spectra classification, and the average accurate of FPCA-LSSVM is 97.3% which is greater than that of PCA-LSSVM (93.5%).

Low-temperature storage after harvest retards the deterioration in the sensory quality, health-promoting compounds, and antioxidant capacity of baby mustard

Baby mustard is a perishable vegetable, and thus its distribution and sale as fresh produce face several challenges. However, little effort has been made to identify optimal techniques for postharvest storage of baby mustard. Here, we evaluated the sensory quality, health-promoting compounds, and antioxidant capacity of baby mustard during postharvest storage for 6 days at low temperature (4 °C, LT) and ambient temperature (20 °C). The results showed that visual quality scores, weight, firmness, the contents of most glucosinolates, and the ferric reducing antioxidant power value decreased in the lateral buds of baby mustard during both treatments; however, LT treatment delayed declines in these characteristics. In addition, the contents of glucose, fructose, total soluble sugars, ascorbic acid, and flavonoids, as well as the level of 2,2-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid), decreased considerably throughout the storage period, sucrose content increased throughout the storage period, and the contents of proanthocyanidin and total phenolics first increased and then decreased at 20 °C; however, their contents remained stable throughout the storage period under the LT treatment. These findings indicate that LT provides a promising approach for maintaining the sensory and nutritional quality of baby mustard.

Low temperature retards the deterioration in sensory quality, main health-promoting compounds and antioxidant capacity in post-harvest baby mustard.

Effect of ultrasound treatment on microbial inhibition and quality maintenance of green asparagus during cold storage

The study focused on inhibiting microorganism and improving preservation of green asparagus (Asparagus officinalis L.) during cold storage. Green asparagus is treated with ultrasound (US), acetic acid and gibberellin acid (AG) separately as well as combination (US + AG) and then stored at 4 °C for 20 days. Microorganism, physicochemical qualities and sensory characteristics were monitored at regular intervals. Results showed that the US treatment significantly (p < 0.05) reduced the total number of colonies, mold and yeast merely in the 12th and 16th day of storage, while the US + AG treatment not only achieved an effective decontamination (up to 2 log reduction) of green asparagus throughout the storage, but also retained the physicochemical characteristics to a higher level in comparison to other treatments. The US + AG treatment exhibited lower weight loss, higher levels of total soluble solid (TSS), ascorbic acid, chlorophyll content and total phenolic content (TPC), as well as kept better sensory attributes. Moreover, the US + AG treatment significantly inhibited the activities of phenylalanine ammonia lyase (PAL) and peroxidase (POD) (p < 0.05), suppressing the biosynthesis of lignin. These results suggested that the US + AG treatment could be a potential strategy to preserve quality of green asparagus during cold storage.

Application of vibrational spectroscopy for classification, authentication and quality analysis of mushroom: A concise review

Chemical compositions of mushrooms are greatly dependent on the geographical region, and also the different parts of the same mushroom have different chemical constitutions. Several chemical methods are employed for quality control of mushrooms. However, these methods are destructive, require skilled personnel and are time consuming. To overcome these limitations researchers are aiming for vibrational spectroscopic techniques. This review is focused on various studies related to the application of vibrational spectroscopy for classification, authentication and quality analysis of mushrooms. It was concluded that vibrational spectroscopy could be efficiently employed for assessing the quality, authenticity and geographical origin of the mushrooms. Fourier-transform infrared (FTIR) and near infrared (NIR) spectroscopy were the most explored, whereas, Raman spectroscopy is the least explored technique in this field. Compact and cost-effective spectrometers based on the selective wavelengths have to be designed and installed at commercial and industrial level for rapid quality control of mushrooms.

Umami taste and its association with energy status in harvested Pleurotus geesteranus stored at different temperatures

Pleurotus geesteranus has recently been gaining popularity due to its strong umami taste. In the present study, umami taste, energy level, and energy metabolism-related enzymes activity in harvested P. geesteranus, stored at 20, 10, 5, and 0 °C, were investigated to evaluate the relationship between umami taste and energy status. Results showed that the mushroom at 5 °C exhibited significantly higher (p < 0.05) equivalent umami concentration (EUC), higher content of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and higher activity of succinic dehydrogenase (SDH) and cytochrome c oxidase (CCO) in late storage. AMP, associating umami taste with energy, presented a significantly positive correlation with EUC and umami determined by electronic tongue at 5 °C. Furthermore, there were better correlations between umami taste and energy status of mushroom at 5 °C. The results suggest that higher energy status of post-harvest P. geesteranus contributes to better umami taste.

Hydrogen-rich water increases postharvest quality by enhancing antioxidant capacity in Hypsizygus marmoreus

In the present study, we aimed to assess the effect of hydrogen-rich water (HRW) on the physicochemical characteristics and antioxidant capacity of Hypsizygus marmoreus during 12 days of postharvest storage at 4 °C. Different concentrations of HRW (25, 50 and 100%) were tested, and our data showed that 25% HRW treatment had the most significant effect on preservation of nutrients in H. marmoreus compared with the control group. In addition, 25% HRW treatment significantly reduced the relative electrolyte leakage rate and malonaldehyde (MDA) content (P < 0.05) and increased anti-superoxide-radical (O₂^-) activity compared with the control group. The activities of antioxidants, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) were activated by 25% HRW treatment, and the expression levels of these genes were also induced. These results suggested that HRW treatment could delay rot incidence in mushrooms during storage by regulating antioxidant defense ability. This study supplies a new and simple method to maintain the quality and extend the shelf life of mushrooms.

Effect of Protocatechuic Acid-Grafted-Chitosan Coating on the Postharvest Quality of Pleurotus eryngii

Protocatechuic acid-grafted-chitosan (PA-g-CS) solution with antioxidant activity was developed as a novel edible coating material for Pleurotus eryngii postharvest storage. The effect of PA-g-CS coating on the postharvest quality of P. eryngii was investigated by determination of various physicochemical parameters and enzyme activities. Results showed that the antioxidant capacity and viscosity of PA-g-CS solutions were closely related to the grafting degree and were much higher than that of chitosan (CS) solution. At the end of 15 days of storage, serious mushroom browning was observed in the control and CS coating groups. By contrast, PA-g-CS coating groups with medium and high grafting degrees maintained better physical appearance. Among all of the treatment groups, P. eryngii in PA-g-CS III coating group exhibited the highest firmness and the lowest weight loss, browning degree, respiration rate, malondialdehyde content, electrolyte leakage rate, superoxide anion production rate, and hydrogen peroxide content. Moreover, P. eryngii in PA-g-CS III coating group maintained relatively higher antioxidant enzyme activities but lower polyphenol oxidase activity than other treatment groups. Therefore, PA-g-CS III is a promising preservation agent for P. eryngii.