Four peptides with ACE inhibitory activity from the edible fungus Flammulina velutipes were prepared by proteolysis to develop high-activity functional peptides. Their secondary structures were analyzed by Fourier transform infrared (FTIR) spectroscopy and Circular dichroism (CD). The effects of pH, temperature, metal ions and gastrointestinal digestion on their ACE inhibitory activities were determined. Their antihypertensive effects were evaluated by an H₂O₂-induced oxidative stress injury, human umbilical vein endothelial cells (HUVECs) model. All four peptides had relatively stable secondary structures. The peptides with sequences FDGY and FHPGY had similar peak shapes but the FHPGY had the highest random coil content. The FAGGP peptide had a relatively flat peak shape and a high random coil content. The WADP peptide had the highest β-sheet content, the lowest random coil content, and the most stable secondary structure. The four peptides showed good resistance to pH and temperature changes, the presence of metal ions and gastrointestinal digestion. FHPGY had good ACE inhibitory activity in all tested pH and temperature ranges. Metal ions had the least effect on the ACE inhibitory activity of FHPGY. After gastrointestinal digestion, the ACE inhibitory activity of FHPGY was above 95%. At concentrations up to 3 mM, the four F. velutipes-derived ACE inhibitory peptides had no significant negative effect on HUVECs viability, while increasing intracellular NO and SOD levels and reducing ET-1 and MDA production. The four peptides all had strong antihypertensive effects. FHPGY increased the secretion of NO and reduced the ET-1 secretion of by 97.69% and 109.59%, respectively, of that of the positive control captopril, and appeared to have the potential to be developed into an effective ACE inhibitory peptide for medicinal use.

This study was carried out in order to explore the effect of second inoculation time on the volatile flavor components of fermented dry-cured meat. Fermented dry-cured meat samples were prepared by sequential inoculation of Staphylococcus xylosus MT, a dominant strain in traditional Longxi bacon, followed by a 1:1 mixture of Lactobacillus plantarum ZR and Leuconostoc mesenteroides CM, also dominant strains in traditional Longxi bacon. The second inoculation was performed on day 6 (F-6), 10 (F-10) or 14 (F-14) of fermentation. Besides, naturally fermented meat was prepared as a control. The volatile flavor components of fermented dry-cured meat were analyzed using solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) combined with relative odor activity value (ROAV) and principal component analysis (PCA). The results showed that 38, 51, 57, and 43 volatile flavor compounds were detected in the control, F-6, F-10 and F-14 samples, respectively. The number and amount of volatile flavor components in the inoculated groups were higher than those in the control group. The largest number of volatile flavor components were found in the F-10 group, and those with ROAV values greater than 0.1 accounted for a high proportion of the total. Nonanal, benzaldehyde, (E,E)-2,4-decadienal, ethyl caproate, ethyl octanoate and 1-octene-3-ol were the key flavor compounds in the inoculated groups. Meanwhile, the sensory evaluation results indicated that F-10 had the best flavor and the highest score. The findings revealed that sequentially inoculated fermentations could significantly increase the number and amount of volatile flavor substances in fermented dry-cured meat (P < 0.05), and that F-10 treatment was more favorable for the formation of the flavor, which provides a theoretical reference for the production of fermented dry-cured meat by inoculated fermentation.

To extend the shelf life of Agaricus bisporus, the optimal concentration and soaking time for hydrogen-rich water (HRW) treatment were selected through sensory evaluation as well as assessments of browning index, mass loss rate, and hardness. To investigate the effect of HRW combined with polyethylene (PE) nano (NA)-film packaging (HRW + NA) on the postharvest preservation of A. bisporus and to analyze the underlying mechanism, using HRW soaking combined with PE film packaging as the control, changes in the sensory quality, reactive oxygen species (ROS) metabolism, and antioxidant enzyme activity of HRW + NA treated mushrooms were dynamically monitored during low-temperature storage at (4 ± 1) ℃. The results showed that the selected HRW treatment conditions were soaking mushrooms in 50% HRW for 15 min. HRW + NA treated mushroom maintained better overall sensory quality with a fuller appearance, maintained better brightness value (L*), and showed a slower increase in ROS levels from days 9 to 15 of storage. Throughout the 15-day storage period, the activities of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) remained higher in the HRW + NA treatment group. In summary, the combination of HRW soaking with NA-film packaging delayed the decline in the quality of A. bisporus during postharvest storage, extending the low-temperature shelf life by 5–6 days compared with conventional commercial PE film packaging.