Research On Improving Utilization Of Apricot Seed Coats By Biotransformation

Apricot seed coat(ASC)is rich in active phenolic substances,which has a large yield,but the utilization of high value is very low,resulting in a waste of resources.The utilization rate and added value of ASC can be improved effectively by biotransformation.In this study,the ASC was used as the substrate,and Monascus and Lactobacillus were inoculated for solid-state fermentation to improve the nutritional composition,phenolic substances and biological activity of ASC.HPLC was used to quantitatively analyze the composition and content changes of phenolic substances during fermentation.At the same time,deep eutectic solvent(DESs)was used to extract phenolic compounds from ASC.The composition and contents of phenolic substances in ASC were analyzed and compared by HPLC,so as to further improve the release and transformation efficiency of polyphenols in ASC.The major conclusions are as follows:1.Through solid state fermentation of ASC by Monascus,it was found that Monascus could use ASC for biotransformation,which could increase the total phenol content(TPC)(22.86 mg/g)and the soluble protein content.The alcohol-soluble protein content(ASPC)was 4.48 mg/g,and the water-soluble protein content(WSPC)was 5.21 mg/g,but the antioxidant capacity of ASC was decreased by 97.80%.The WSPC,the reducing sugar,the TPC and the antioxidant capacity of ASC were decreased by 97.8%,71.36%,55.1%and 23.09%,respectively,and the ASPC was increased by 6 times when rice wine lees were properly added to assist fermentation.The content of reducing sugar,TPC and antioxidant capacity of apricot of coats decreased by 75.36%,91.2%and 99.01%,respectively,but the content of alcohol-soluble protein and water-soluble protein increased by 7.21 times and 1.64 times,respectively.High temperature sterilization could promote the release of polyphenols and increase the TPC by 23.49%.However,after Monascus fermentation,the TPC and the antioxidant capacity decreased by 14.87%and 57.55%.It was found that there was only a very small amount of polyphenol oxidase in the fermented ASC,so it was speculated that the decrease of total phenol content and antioxidant capacity might be related to the activity of hydrolase produced by Monascus.2.Through the fermentation of Lactobacillus plantarum,Lactobacillus pentosus and mixed Lactobacillus,it was found that the fermentation effect of single Lactobacillus was better than that of mixed Lactobacillus.The ASPC,the TPC and the titratable acidity were increased by 10.69,0.34 and 0.95 times by Lactobacillus pentosus fermentation,while the ASPC,the TPC and the titratable acidity were increased by 9.17,0.33 and 0.66 times by 30℃ mixed Lactobacillus fermentation.Fermentation by L.pentosus also promoted the conversion and release of phenolic substances,and the TPC increased by 40.15%.Single Lactobacillus fermentation was more likely to promote the increase of phenolic substances than mixed Lactobacillus fermentation.After single fermentation,the contents of protocatechuic acid,3,4-dihydroxyphenylacetic acid and epicatechin in almonds seed were increased by 5.29 times,0.79 times and 0.93 times,respectively,and the contents of gallic acid and chlorogenic acid were decreased by 80.96%and 68.75%,respectively.3.DESs was used to extract phenolic substances from ASC fermented by Lactobacillus.The extracting effects of DESs on TPC was significantly worse than that of traditional organic solvent extraction,and the TPC was reduced by more than 60%.But the antioxidant capacity of DESs extract was stronger and the DPPH radical scavenging ability was increased by 3 about times.Different DESs has different specificity in the extraction of phenolic substances,and new phenolic substances may be generated.After fermentation by Lactobacillus,phenolic substances in ASC are easier to be extracted by DESs.DESsl and DESs2 showed that contents of 12 phenolic substances in ASC after fermentation were increased to different degrees.The contents of gallic acid,protocatechuic acid and quercetin were significantly improved by DESsl,and the contents of gallic acid,protocatechuic acid,Syringate and quercetin were increased by 14.28 times,3375.14 times,16.5 times and 934 times,respectively,compared with the traditional solvent extraction of unfermented ASC.DESs2 significantly improved the extraction effect of gallinic acid and protocatechuic acid.Compared with traditional solvent extraction,the contents of unfermented almond seed coating were increased by 9.89 times and 1660.57 times,respectively.It can be seen that DESs2 is more specific in the extraction of protocatechuic acid,and DESsl is more specific in the extraction of protocatechuic acid.In this paper,Monascus and Lactobacillus were used to release and transform phenolic substances in almond seed coating.At the same time,the extraction method of DESs was adopted,and the phenolic substances after fermentation treatment were identified and the antioxidant capacity was evaluated,which provided theoretical basis and technical support for the multi-level and high value-added utilization of ASC in the future.