Bioactivities Of Different Forms Of Polyphenols From Leaf Of Rhus Chinensis Mill And Its Application In Chilled Pork Preservation

Rhus chinensis Mill is a perennial plant belonging to the genus Rhus and the family Anacardiaceae.It is well known as the host plant of the Chinese medicine gallnut.As a multifunctional economic tree species in China,Rhus chinensis Mill can be used as medicine for roots,leaves,flowers and fruits,and can also provide raw materials for pharmaceutical and industrial dyes.Leaves are rich in functional active ingredients,mainly containing polyphenols known as "seventh nutrient".Plant polyphenols have the effects of scavenging free radicals,delaying the aging of the body,preventing cardiovascular diseases,and preventing cancer.They have important application values in the fields of food,cosmetics,agricultural production,and medicine.In this project,physiologically mature leaves of Rhus Chinensis Mill in Taiyuan,Shanxi Province were used as test materials.This research focuses on the different forms of the polyphenols of Rhus Chinensis Mill leaves: optimization of extraction conditions,study of bioactivities,and preliminary application in the preservation of fresh pork.The research procedures start with optimizing the technological conditions for total soluble polyphenols;Second step is to use different extraction methods to obtain four different types of polyphenols and conduct systemic analysis and comparison of the antioxidant and bacteriostatic activities of different forms of polyphenols;And the last step is to compare different forms of polyphenols for chilled pork.The research can lay the foundation for the development of new bio-based food preservatives and the further comprehensive utilization of Rhus Chinensis Mill resources.The results shown that:1.Optimization of extraction conditions of total soluble polyphenolsTaking the leaves of Rhus chinensis Mill as the research object,screening ethanol as the extraction solvent,solvent volume fraction,material-liquid ratio,extraction time,and extraction temperature wereconsidered as the investigation factors,and its influence on the extraction amount of polyphenols was studied.The response was designed on the basis of single factor experiments The best extraction process to determine the total soluble polyphenols was: 60% ethanol volume fraction,30 minutes of sonication time,and liquid-to-material ratio of 1:40(g/m L).The extraction amount of polyphenols under these conditions was 67.36 mg/g,which is close to the theoretical prediction.2.Study of the antioxidant and bacteriostatic activities of different forms of polyphenolsThe total soluble polyphenols,soluble esterified polyphenols,acid-hydrolyzed bound polyphenols,and alkali-hydrolyzed bound polyphenols were extracted according to the solvent method,acid hydrolysis method,and alkaline hydrolysis method.Four different types of polyphenols were investigated.Scavenging effects of DPPH,ABTS,FRAP,OH free radicals,and bacteriostatic effects on Escherichia coli,Staphylococcus aureus,Bacillus subtilis and Salmonella.The results show that the antioxidant capacity and the increase in the mass concentration of different polyphenols are significantly higher.Positive correlation,among which esterified polyphenols and total soluble polyphenols have the strongest antioxidant capacity;bacteriostatic zone tests showed that in addition to acid-hydrolyzed bound polyphenols,the remaining polyphenols had varying degrees of bacteriostatic activity.3.Application of polyphenols of Rhus chinensis Mill leaves in chilled pork preservationTwo kinds of best polyphenols were selected,and was used as preservation object for preservation.The total number of sample colonies,volatile basic nitrogen(TVB-N value),and p H were measured at intervals of3 days.The results showed that the fresh-keeping liquid treatment group could effectively delay the spoilage and deterioration and extend the shelf life of 3-5 days,indicating that the Rhus chinensis Mill polyphenols had a good fresh-keeping effect.