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The effects of different cooking methods (steaming, boiling, air frying, and oven baking) and cooking times (0, 5, 10, 15, and 20 min) on the bioactive components (total phenol, total flavonoid, crude polysaccharides, and eritadenine), color, texture, microstructure, and volatiles in shiitake mushrooms were investigated in this study. Steaming, boiling, and air frying for 5-20 min could decrease the contents of all the four bioactive components in the shiitake mushroom. However, oven baking for 5 min and 10 min showed the highest contents of total phenolics and total flavonoids, respectively. Moreover, the lowest losses of crude polysaccharides and eritadenine were observed for oven baking for 5 min and 15 min, respectively. The lightness of shiitake mushrooms was decreased by all treatments; however, steaming could keep a higher brightness compared with other methods. The microstructure was damaged by all cooking methods, especially air frying for 20 min. Meanwhile, steaming for 20 min decreased the hardness mostly, and there was no significant difference with air frying for 20 min. All cooking treatments decreased the complexity of the flavors and the relative contents of volatile compounds; the lowest contents were found when boiling for 5 min. From these results it can be seen that the physical, histological, and chemical features in shiitake mushroom were influenced by cooking methods and times. In addition, our results provide valuable information for the cooking and processing of shiitake mushrooms and other fungi.

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The carbon source, an essential factor for submerged culture, affects fungal polysaccharides production, structures, and activities. This study investigated the impact of carbon sources, including glucose, fructose, sucrose, and mannose, on mycelial biomass and the production, structural characterization, and bioactivities of intracellular polysaccharides (IPS) produced by submerged culture of Auricularia auricula-judae. Results showed that mycelial biomass and IPS production varied with different carbon sources, where using glucose as the carbon source produced the highest mycelial biomass (17.22 ± 0.29 g/L) and IPS (1.62 ± 0.04 g/L). Additionally, carbon sources were found to affect the molecular weight (Mw) distributions, monosaccharide compositions, structural characterization, and activities of IPSs. IPS produced with glucose as the carbon source exhibited the best in vitro antioxidant activities and had the strongest protection against alloxan-damaged islet cells. Correlation analysis revealed that Mw correlated positively with mycelial biomass (r = 0.97) and IPS yield (r = 1.00), while IPS antioxidant activities correlated positively with Mw and negatively with mannose content; the protective activity of IPS was positively related to its reducing power. These findings indicate a critical structure-function relationship for IPS and lay the foundation for utilizing liquid-fermented A. aruicula-judae mycelia and the IPS in functional food production.

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In this study, melanin from wild Auricularia auricula (WAA) was isolated using an ultra-high pressure (UHP)-assisted extraction method, and the physicochemical properties and antioxidant activity of WAA melanin were investigated. Under the optimized extraction conditions of a solid/liquid ratio of 1:30, a UHP of 450 MPa, a 22-min pressure holding time, a 1-mol/L NaOH concentration, and acid precipitation for 8 h, the WAA melanin extraction yield was 7.9 ± 0.16%. Moreover, the results showed that the surface of WAA melanin lacked structural order. Most melanin showed an average diameter of 1000 nm. WAA melanin had strong absorption at a wavelength of 210 nm and displayed typical characteristic absorption peaks. Moreover, WAA melanin contained 48.51% C, 6.88% H, 5.26% N, 0.45% S, and 38.90% O and may be a 3,4-dihydroxyphenylalanine melanin. An analysis of physicochemical properties showed that WAA melanin had good stability toward heat, light, and low concentrations of reducing agents and oxidizing agents. Furthermore, WAA melanin presented certain free radical scavenging activity. This study demonstrates that wild A. auricula melanin may have potential applications in the cosmetic or food industries as a natural antioxidant.

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To obtain activated fractions, the ethanol extract (EE) of Hericium erinaceus was fractionated to get petroleum ether fraction (PEF), chloroform fraction (CF), ethyl acetate fraction (EAF) and n-butanol fraction (NF). Total phenol content (TPC) and total flavonoid content (TFC) in the fractions were determined, and the phenolic compounds were characterized and quantitated using liquid chromatography-electrospray ionization-mass spectrometry. Meanwhile, in vitro antioxidant and antihyperglycemic activities of extracts were evaluated respectively based on their 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging abilities as well as α-amylase and α-glucosidase inhibitory abilities. Finally, the inhibition modes of extracts on α-amylase and α-glucosidase were detected by kinetic assay. The results showed that TPC, TFC, and the content of phenolic compounds in the extracts were different. EAF contained the highest contents of both TPC and TFC and exhibited strongest inhibitory effects on α-amylase and α-glucosidase, with half maximal inhibitory concentration (IC50) values of 0.47 ± 0.02 and 0.63 ± 0.01 mg/mL, respectively. However, CF showed the highest scavenging abilities on DPPH and ABTS radicals, with IC50 values of 2.30 ± 0.12 and 1.72 ± 0.06 mg/mL, respectively. Correlation analysis showed that the high antihyperglycemic ability of EAF may be related to ferulic acid, whereas cinnamic acid may be responsible for the high antioxidant ability of CF. Furthermore, all fractions were found to exert inhibition on α-amylase and α-glucosidase in mixed-type and competitive manners, respectively. Overall, these results suggest that H. erinaceus has a potential effect on antihyperglycemic and antioxidant activity.

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To improve the production of mycelial biomass and intracellular polysaccharide (IPS), the culture medium composition and culture condition were respectively optimized by response surface methodology and one-factor-at-a-time methodology. The impact of fermentation process on the transcription of genes involved in IPS synthesis was evaluated using quantitative reverse transcription PCR (qRT-PCR). The yield of biomass and IPS were increased by 150% and 177% under the optimized fermentation process, respectively. Moreover, the optimization of fermentation process significantly increased the transcription of genes involved in IPS synthesis, especially pgm-1, ugp, and pgi. This is the first exploration of gene transcription profile for IPS synthesis of Auricularia auricula-judae under submerged fermentation. These results could provide a potential tool for fermentation process optimization and transcriptional regulation of IPS biosynthesis in A. auricula-judae.

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