Effects Of Drying Methods On The Nutrients And Volatile Components Of Stropharia Rugosoannulata,and The Extraction And Function Studies Of Polysaccharides

Objective:To investigate the effects of drying methods on the nutrients and volatile components of Stropharia rugosoannulata（S.rugosoannulata）,a series of nutrients and volatile components were comparably analyzed in different drying samples,which could provide technical support for the storage of S.rugosoannulata.Additionally,the optimal drying method for the mushrooms will be chosen,then extracting S.rugosoannulata polysaccharides（SRP）and optimizing the conditions.Furthermore,the compositions and antioxidant activity of SRP and its influences on gut microbiota were studied,so as to provide theoretical basis for the extraction and utilization of SRP.Methods:1.Effects of drying methods on nutrients and volatile components:S.rugosoannulata was dried with hot air drying（HAD）,vacuum freeze drying（VFD）and natural air drying（NAD）.Then,the contents of general nutrients,bioactive components and volatile components were detected.Moreover,the sensory evaluation was conducted.And,the differences of each index in three groups were comparably analyzed.2.Extraction and condition optimization of SRP:S.rugosoannulata was dried with VFD,then SRP was extracted with ultrasonic assisted enzymatic method.Response surface method was used to optimize the extraction conditions of SRP,and the optimal extraction conditions were obtained to improve the extraction rate of SRP.3.SRP compositions and antioxidant activity and its effects on gut microbiota:（1）The compositions and antioxidant activity of SRP:Total sugar,reducing sugar contents and DPPH,ABTS⁺,OH^-radical scavenging rates of SRP were determined.（2）The vitro digestive properties of SRP:SRP was hydrolyzed by?-amylase,pepsin and pancreatic enzymes.Then,the contents of total sugar and reducing sugar in SRP were determined.（3）Changes of SRP and its effects on gut microbiota in vitro fermentation:Fresh fecal samples from four healthy volunteers were mixed with saline solution,and 10 mg/m L SRP（SRP group）and insulin（INL group）were used to ferment gut microbiota,while distilled water was used as negative control（Control group）.Samples were collected after 0,6,12,and 24 h of fermentation.Then,p H,total sugars,reducing sugars,and short chain fatty acids（SCFAs）were detected,and gut microbiota was analyzed by 16S r DNA high throughput sequencing.Results:1.Effects of drying methods on nutrients and volatile components:（1）S.rugosoannulata is the dietary source of protein,amino acid,vitamin D₂ and polysaccharides.（2）VFD treatment was the optimal method for preserving nutrients.（3）HAD-treated mushroom had the highest vitamin D₂ content and antioxidant activity.（4）The content of volatile compounds was the highest in NAD group.2.Optimization of SRP extraction conditions:（1）The results showed that cellulase,papain,liquid-solid ratio,time,p H and ultrasonic power were the key factors for the extraction of SRP（P（27）0.05）.（2）The optimal extraction conditions for SRP were as follows,cellulase:2%,papain:3%,liquid-solid ratio:30 m L/g,time:40min,p H:9,ultrasonic power:300 W.（3）The maximum extraction rate of SRP was6.64 g/100g.3.SRP compositions and antioxidant activity and its effects on gut microbiota:（1）The compositions and antioxidant activity of SRP:The contents of total sugar,reducing sugar were high,and the content of protein was low.The radical savenging rate was OH^->ABTS⁺>DPPH.（2）In vitro digestion process,there was no significant changes of the total sugar and reducing sugar contents in SRP,indicating that SRP was not degraded by digestive enzymes.（3）Changes of SRP and its effects on gut microbiota in vitro fermentation:（1）The contents of total sugar and reducing sugar in SRP decreased continuously during the fermentation process（P（27）0.05）,and reached lowest level at 24 h.（2）With the progress of fermentation,the p H value of each group decreased gradually,while the contents of SCFAs increased gradually.The p H of SRP group was lower than that of Control group（P（27）0.05）during the fermentation process.The contents of SCFAs in SRP group were higher than those in INL and control groups（P（27）0.05）,which suggested that SRP could significantly increase the contents of SCFAs.（3）Compared with the control group,SRP and inulin decreased the alpha diversity and changed the beta diversity of gut microbiota.At the phylum level,SRP increased the relative abundance of Actinobacteria and Firmicutes.At the family level,the relative abundances of Selenomonadaceae,Lachnospiraceae and Prevotellaceae in SRP group were higher than other two groups（P（27）0.05）.At the genus level,SRP could decrease the relative abundance of Escherichia＿Shigella and increase the relative abundance of Megamonas,Prevotella＿9 and Phascolarctobacterium.LEf Se analysis showed that the dominant species in SRP group were Negativicutes,Megamonas,Veillonellales and Selenomonadaceae.Conclusions:Different drying methods exhibit diverse impacts on the nutrients and volatile components of S.rugosoannulata.Vacuum freeze drying is the optimum method for maintaining nutrients,while natural air drying is more favorable for preserving volatile components.Furthermore,the employment of SRP exhibits potential to improve the relative abundance of beneficial bacteria,reduce the relative abundance of harmful bacteria,and stimulate the production of SCFAs.This is indicative of its promising capacity to promote intestinal health.