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

Molecular mechanism of quality changes in solid endosperm of tender coconut during room temperature storage based on transcriptome and metabolome

Tender coconut (TC) is popular around the world. Postharvest storage of TC leads to a decline in its appearance quality and flavor in both liquid endosperm (LE) and solid endosperm (SE). While LE is the most consumed part and remains in a liquid state, SE is the only cellular tissue directly connected to LE and may be the main contributor to flavor deterioration during storage. This study focused on investigating SE changes during TC storage at 25 °C using computed tomographic technology, transcriptome and metabolome analyses. The results showed increased thickness and density, elevated protein and fat contents, and decreased reducing and soluble sugars in SE of TC during storage. Integrated transcriptome and metabolome analysis revealed that these changes were mainly associated with the gene transcription levels involved in amino acid, carbohydrate and lipid metabolisms, along with specific metabolites. These findings offer valuable insights for controlling TC quality during storage.

Investigating the Respiratory and Energy Metabolism Mechanisms behind ε-Poly-L-lysine Chitosan Coating's Improved Preservation Effectiveness on Tremella fuciformis

Freshly harvested Tremella fuciformis contains high water content with an unprotected outer surface and exhibits high respiration rates, which renders it prone to moisture and nutrient loss, leading to decay during storage. Our research utilized ε-poly-L-lysine (ε-PL) and chitosan as a composite coating preservative on fresh T. fuciformis. The findings revealed that the ε-PL + chitosan composite coating preservative effectively delayed the development of diseases and reduced weight loss during storage compared to the control group. Furthermore, this treatment significantly decreased the respiration rate of T. fuciformis and the activity of respiratory metabolism-related enzymes, such as alternative oxidase (AOX), cytochrome c oxidase (CCO), succinic dehydrogenase (SDH), 6-phosphogluconate dehydrogenase, and glucose-6-phosphate dehydrogenase (6-PGDH and G-6-PDH). Additionally, the composite coating preservative also delayed the depletion of ATP and ADP and maintained higher levels of the energy charge while preserving low levels of AMP. It also sustained heightened activities of Mg2+-ATPase, Ca2+-ATPase, and H+-ATPase enzymes. These results demonstrate that utilizing the ε-PL + chitosan composite coating preservative can serve as a sufficiently safe and efficient method for prolonging the shelf life of post-harvest fresh T. fuciformis.

Transcriptome analysis provides insight into gamma irradiation delaying quality deterioration of postharvest Lentinula edodes during cold storage

To better determine how gamma irradiation (GI) improves abiotic stress resistance, a transcriptome analysis of postharvest L. edodes in response to 1.0 kGy GI was conducted, and further the underlying mechanism of GI in delaying quality deterioration over 20 d of cold storage was explored. The results suggested that GI was involved in multiple metabolic processes in irradiated postharvest L. edodes. In comparison with the control group, the GI group contained 430 differentially expressed genes, including 151 upregulated genes and 279 downregulated genes, which unveiled characteristic expression profiles and pathways. The genes involved in the pentose phosphate pathway were mainly upregulated and the expression level of the gene encoding deoxy-D-gluconate 3-dehydrogenase was 9.151-fold higher. In contrast, the genes related to other energy metabolism pathways were downregulated. Concurrently, GI inhibited the expression of genes associated with delta 9-fatty acid desaturase, ribosomes, and HSP20; thus, GI helped postpone the degradation of lipid components, suppress transcriptional metabolism and regulate the stress response. Additionally, the metabolic behavior of DNA repair induced by GI intensified by noticeable upregulation. These regulatory effects could play a potential and nonnegligible role in delaying the deterioration of L. edodes quality. The results provide new information on the regulatory mechanism of postharvest L. edodes when subjected to 1.0 kGy GI during cold storage.

Whole-transcriptome RNA sequencing reveals changes in amino acid metabolism induced in harvested broccoli by red LED irradiation

Whole-transcriptomic profiling combined with amino acid analysis were conducted in order to gain a better understanding of global changes in amino acid metabolism induced in broccoli by red LED irradiation. The results showed that the contents of almost all 16 amino acids in postharvest broccoli were maintained under red LED illumination. The red LED irradiation enhanced the anabolism of amino acid, including the biosynthesis of aromatic amino acids by upregulating the genes' expression in the shikimate pathway, as well as by upregulating the genes' expression which encoding biosynthetic enzymes in the branched-chain amino acid biosynthesis pathway. Red LED irradiation induced the expression of genes encoding aspartate aminotransferase, which plays a role in Asp synthesis, aspartate kinase, which functions in aspartate metabolism, and a cytoplasmic aspartate aminotransferase that converts 2-Oxoglutarate into Glu. Genes encoding imidazole glycerol-phosphate synthase and histidinol-phosphatase, which function in the His biosynthesis pathway, were also upregulated. According to our results, red LED irradiation delays broccoli's yellowing and senescence by regulating amino acid metabolism. These results enhance our understanding of the role of amino acid metabolism in the senescence of broccoli and the mechanism of red LED irradiation to alter amino acid metabolism in harvested broccoli.

Emerging technologies for preservation and quality evaluation of postharvest edible mushrooms: A review

Edible mushrooms are the highly demanded foods of which production and consumption have been steadily increasing globally. Owing to the quality loss and short shelf-life in harvested mushrooms, it is necessary for the implementation of effective preservation and intelligent evaluation technologies to alleviate this issue. The aim of this review was to analyze the development and innovation thematic lines, topics, and trends by bibliometric analysis and review of the literature methods. The challenges faced in researching these topics were proposed and the mechanisms of quality loss in mushrooms during storage were updated. This review summarized the effects of chemical processing (antioxidants, ozone, and coatings), physical treatments (non-thermal plasma, packaging and latent thermal storage) and other emerging application on the quality of fresh mushrooms while discussing the efficiency in extending the shelf-life. It also discussed the emerging evaluation techniques based on the various chemometric methods and computer vision system in monitoring the freshness and predicting the shelf-life of mushrooms which have been developed. Preservation technology optimization and dynamic quality evaluation are vital for achieving mushroom quality control. This review can provide a comprehensive research reference for reducing mushroom quality loss and extending shelf-life, along with optimizing efficiency of storage and transportation operations.

Characterization of an active film prepared with Lentinus edodes (shiitake) polysaccharide and its effect on post-harvest quality and storage of shiitake

The aim of this study was to prepare a film based on shiitake (Lentinus edodes) stalk polysaccharides (LEP) for mushroom preservation. The effects of different LEP concentrations on physical, mechanical, antioxidant, and antimicrobial properties of the prepared film were evaluated. Using scanning electron microscopy, it was revealed that the addition of 1.5 % LEP resulted in homogeneous distribution in the prepared film, as well as greatly improved its antimicrobial properties. Moreover, LEP film resulted in superior mushroom preservation by regulating enzyme activities related to mushroom browning and softening, thereby decaying these processes. In addition, the prepared film maintained mushroom quality by reducing the accumulation of H₂O₂ and activating the regulatory system against oxidative stress. Collectively, the findings of the present study highlight the potential benefits of LEP films as a strategy to improve mushroom quality and prevent post-harvest spoilage, hence constituting a novel prospect for the development of shiitake by-products.

l-Cysteine Treatment Delayed the Quality Deterioration of Fresh-Cut Button Mushrooms by Regulating Oxygen Metabolism, Inhibiting Water Loss, and Stimulating Endogenous H2S Production

Although fresh-cut button mushrooms are popular with consumers, quality deterioration presents a significant shelf-life challenge. In this study, fresh-cut button mushrooms were treated with 0.25 g/L l-cysteine (l-Cys) and evaluated in terms of quality, physiology, and transcriptome sequencing. The results indicated that l-Cys application significantly delayed the browning degree of fresh-cut button mushrooms and reduced weight loss. l-Cys treatment reduced the malondialdehyde content, lipoxygenase activity, and reducing sugar levels while enhancing the soluble protein and total phenolic content. Furthermore, l-Cys treatment reduced the O₂^- generation rate and H₂O₂ accumulation while enhancing the catalase activity. Moreover, l-Cys improved the superoxide dismutase, glutathione reductase, and phenylalanine ammonia-lyase activities while reducing those of polyphenol oxidase and peroxidase. Additionally, l-Cys treatment increased endogenous H₂S production and AbCBS enzyme activity while decreasing AbCSE enzyme activity. Notably, additional treatment with 1 mM propargylglycine significantly reduced the effect of l-Cys. Moreover, transcriptome sequencing analysis indicated that the differentially expressed genes in the l-Cys group were primarily related to the reactive oxygen species metabolism, oxidoreductase process, membrane integrality, and sulfur metabolism. These findings suggested that l-Cys treatment delayed the aging and extended the shelf life of fresh-cut button mushrooms by regulating the active oxygen species metabolism and water loss and stimulating endogenous H₂S production.

Fucoidan treatment alleviates chilling injury in cucumber by regulating ROS homeostasis and energy metabolism

INTRODUCTION

Chilling injury is a major hindrance to cucumber fruit quality during cold storage.

METHODS AND RESULTS

In this study, we evaluated the effects of fucoidan on fruit quality, reactive oxygen species homeostasis, and energy metabolism in cucumbers during cold storage. The results showed that, compared with the control cucumber fruit, fucoidan-treated cucumber fruit exhibited a lower chilling injury index and less weight loss, as well as reduced electrolyte leakage and malondialdehyde content. The most pronounced effects were observed following treatment with fucoidan at 15 g/L, which resulted in increased 1,1-diphenyl-2-picrylhydrazyl and hydroxyl radical scavenging rates and reduced superoxide anion production rate and hydrogen peroxide content. The expression and activity levels of peroxidase, catalase, and superoxide dismutase were enhanced by fucoidan treatment. Further, fucoidan treatment maintained high levels of ascorbic acid and glutathione, and high ratios of ascorbic acid/dehydroascorbate and glutathione/oxidized glutathione. Moreover, fucoidan treatment increased the activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase and their gene expression. Fucoidan treatment significantly delayed the decrease in ATP and ADP, while preventing an increase in AMP content. Finally, fucoidan treatment delayed the decrease of energy charge and the activities and gene expression of H⁺-ATPase, Ca²⁺-ATPase, cytochrome c oxidase, and succinate dehydrogenase in cucumber fruits.

CONCLUSION

Altogether, our findings indicate that fucoidan can effectively enhance antioxidant capacity and maintain energy metabolism, thereby improving cucumber cold resistance during cold storage.

Ultrasonic treatment decreases Lyophyllum decastes fruiting body browning and affects energy metabolism

Lyophyllum decastes is a common mushroom that is prone to browning during prolonged storage. In this study, the effects of ultrasonic treatment on metabolic gene expression, enzyme activity, and metabolic compounds related to L. decastes browning were investigated. Treatment of the fruiting body at 35 kHz and 300 W for 10 min reduced the browning index of L. decastes by 21.0 % and increased the L* value by 11.1 %. Ultrasonic treatment of the fruiting body resulted in higher levels of total phenols, flavonoids, and 9 kinds of amino acid with catalase (CAT) and peroxidase (POD) activities maintained at high levels. Higher cytochrome c oxidase (CCO), succinate dehydrogenase (SDH), phosphofructokinase (PFK), and pyruvate kinase (PK) activities may be ascribed to increased antioxidant capacity. Moreover, ultrasonication retained higher adenosine triphosphate (ATP) concentrations with an increased energy charge, while there were lower levels of adenosine diphosphate (ADP) and reduced and oxidized nicotinamide adenine dinucleotide (NADH and NAD⁺), respectively. Meanwhile, lower lignin contents were observed, along with retarded polyphenol oxidase (PPO) and lipoxygenase (LOX) activities. Lower PPO activity reduced the fruiting body enzymatic browning rate through decreased expression of LdPpo1, LdPpo2, and LdPpo3 during storage at 4 °C for 16 days. This activity may be used to determine the effectiveness of ultrasonication.

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.

Comparison of the Nutritional and Taste Characteristics of 5 Edible Fungus Powders Based on the Composition of Hydrolyzed Amino Acids and Free Amino Acids

The nutritional characteristics and taste of some edible fungus powders were scientifically evaluated and compared. Five common edible fungus powders were used as test materials (Agrocybe chaxinggu edible fungus powder, Pleurotus citrinopileatus edible fungus powder, Flammulina velutipes edible fungus powder, Lentinus edodes edible fungus powder, and Hericium erinaceus edible fungus powder). The hydrolyzed amino acid and free amino acid content were measured by an automatic amino acid analyzer, and the ratios of hydrolyzed amino acid and free amino acid components and the taste characteristics of these eatables were systematically compared. The results showed that the total amount of hydrolyzed amino acids contained in the 5 edible fungus powders was between 2.583 and 14.656 g/100 g. The total amount of free amino acids contained in the 5 edible fungus powders was between 0.550 and 2.612 g/100 g. Comparative analysis of the mass fractions and composition of amino acids indicated that Pleurotus citrinopileatus edible fungus powder best met the ideal protein standard. The taste characteristics of protein were evaluated by calculating the taste active value (TAV) of taste-producing free amino acids. The most significant TAV values of the 5 edible fungus powders appeared in glutamic acid, and this amino acid is an umami amino acid. Principal component analysis (PCA) suggested that four principal components could reflect all the information on the free amino acids with a total cumulative variance contribution rate of 100%, and three principal components could reflect most of the information on the hydrolyzed amino acids with a total cumulative variance contribution rate of 99.143%, which could represent the main trends of free amino acids and hydrolyzed acids in edible fungus powder. The comprehensive evaluation model was established, and the comprehensive score indicated that Agrocybe chaxinggu edible fungus powder had the best comprehensive amino acid quality.

Exogenous γ-aminobutyric acid maintains fruit quality of apples through regulation of ethylene anabolism and polyamine metabolism

In this study, 'Golden Delicious' apples were dipped with γ-aminobutyric acid (GABA) solution to investigate the changes of quality parameters, ethylene anabolism, polyamine metabolism and GABA shunt. Results showed that GABA distinctly suppressed respiratory rate, reduced titratable acidity, maintained higher soluble solid content and pericarp firmness of apples. Compared to the control, GABA also repressed the activities and gene expressions of polyamine oxidase (PAO) and diamine oxidase (DAO), enhanced MdMT, MdMS, MdSAMS, MdSAMDC, MdSPDS, MdODC, MdADC, and MdACL5 expressions, and accelerated the accumulation of putrescine, spermidine, and spermine in the exocarp of apples. Moreover, GABA decreased ethylene release, MdACS and MdACO gene expressions in the exocarp. In addition, exogenous GABA activated MdGAD, MdGDH, MdGS expressions and inhibited MdGABA-T and MdSSADH expressions in the GABA shunt, therefore increased endogenous GABA, pyruvic acid and glutamate contents in the exocarp. These findings suggest that exogenous GABA regulates ethylene anabolism, polyamine metabolism and GABA shunt to maintain fruit quality of 'Golden Delicious' apples.

Effects of ultrasound and gamma irradiation on quality maintenance of fresh Lentinula edodes during cold storage

Microbial infection, senescence and water losses result in serious quality deterioration of postharvest mushrooms. The aim of this study was to investigate the impact of ultrasound treatment (US), gamma irradiation treatment (GI) and their combination on quality maintenance of fresh Lentinula edodes during storage. The results showed that US + GI was the most effective approach to maintaining the quality of mushrooms. US + GI reduced natural microflora present on L. edodes, such as total number of colonies, molds, yeasts, Pseudomonas and Enterobacteriaceae. Furthermore, US + GI stimulated phenylalanine ammonia lyase, maintained the highest level of total phenolic content (733.63 mg GAE/kg on Day 4), and postponed the occurrence of reduced ascorbic acid (33.7% retention relative to the control), which contributed to strengthening the antioxidant capacity. Additionally, US + GI retarded water mobility and loss. In brief, the US + GI in this study is an effective hurdle technology for preserving the quality of fresh L. edodes during storage.

Relationship between flavor and energy status in shiitake mushroom (Lentinula edodes) harvested at different developmental stages

To understand the relationship between flavor and energy, the flavor, energy, and enzyme activity related to energy metabolism in shiitake mushrooms harvested at different developmental stages were investigated. The results indicated that the adenosine triphosphate level increased significantly in developing mushrooms and was strongly correlated with the fresh weight. The levels of equivalent umami concentration (EUC), total aroma compounds, energy charge, adenosine triphosphatase, cytochrome c oxidase, and succinic dehydrogenase varied with maturity. In addition, a strong correlation was observed between aroma compounds, EUC, and energy status (p < 0.05). Our results suggest that the unique flavor of developing shiitake mushroom is closely related to energy. The findings may provide a new strategy to improve the flavor of mushrooms by regulating their energy levels. PRACTICAL APPLICATION: The unique flavor of shiitake mushroom, which has a significant impact on consumer preferences, is one of its key characteristics. This research paper provides a theoretical foundation for determining the optimal harvest period for shiitake mushrooms with high quality and a new strategy to improve the flavor of mushrooms by regulating their energy levels.

Biosynthetic Mechanism of Key Volatile Biomarkers of Harvested Lentinula edodes Triggered by Spore Release

In this study, headspace solid-phase microextraction-gas chromatography-mass spectrometry, multivariate analyses, and transcriptomics were used to explore the biosynthesis of key volatiles and the formation of spores in Lentinula (L.) edodes. Among the 50 volatiles identified, 1-octen-3-ol, phenethyl alcohol, and several esters were considered key aromas because of their higher odor activity values. Eleven volatiles were screened as biomarkers by orthogonal partial least squares discriminant analysis, and hierarchical cluster analysis showed that these biomarkers could represent all volatiles to distinguish the spore release stage. The activities of lipoxygenase (LOX), hydroperoxide lyase, alcohol dehydrogenase, and alcohol acyltransferase were higher in L. edodes with spore release. Moreover, linolenic acid and phenylalanine metabolism were involved in aroma biosynthesis. One LOX-related gene and five aryl alcohol dehydrogenase-related genes could regulate the biosynthesis of 1-octen-3-ol, phenethyl alcohol, and phenylacetaldehyde. In addition, several key genes were involved in meiosis to regulate sporulation.