Preparation,Physicochemical Properties,and Hypoglycemic Activity Of Camellia Seed Cake Peptides

Camellia seed cake is a by-product of oil extraction from Camellia oleifera.Its rich protein content extends it broad application prospect in the field of peptide product development.The preparation,physicochemical properties and hypoglycemic activity,of camellia seed cake peptides were studied in this paper,which not only provide the reference for the application of camellia seed cake in functional food but also provide hint for the valorization of food byproducts.The main research contents and achievements of this paper are presented as follows:1.Quality analysis of different camellia seed cake.The protein content,oil content,water content and ash content of 7 kinds of camellia seed cake were compared.The results showed that the camellia seed cake of variety 2 was more suitable for protein extraction,its protein content was 28.81%±1.14%,oil content was 4.67%±0.16%,water content was 8.67%±0.33%,and ash content was 4.66%±0.13%.2.Isolation and identification of hypoglycemic peptides from camellia seed cake.The inhibitory activities ofα-glucosidase of different proteases hydrolysates were compared.It was found that the inhibitory activities of alcalase hydrolysates were the highest.The hydrolysate of alcalase was fractionated based on the molecular weight of peptide.The results showed that the component with molecular weight less than 3 k Da had the bestα-glucosidase inhibitory activity.Three peptides,SPGYYDGR,GLTSLDRYK,and GHSLESIK were identified by mass spectrometry after purification with High-performance liquid chromatography.Molecular docking models showed that these peptides could inhibitα-glucosidase activity mainly through hydrogen bond,salt bridge and hydrophobicity,and the target amino acid may be the Asp⁵⁴²ofα-glucosidase.3.Determination of physicochemical properties of camellia seed cake peptides.It was found that the solubility of camellia seed cake polypeptide was the lowest near the isoelectric point,and increased far away from the isoelectric point.The oil holding capacity and water holding capacity of camellia seed cake peptides decreased with the decrease of molecular weight.The oil holding capacity and water holding capacity of the molecular weight components with more than 10k Da were 1.70±0.12 m L/g and 2.65±0.14 m L/g,respectively.The foaming and emulsifying properties of camellia seed cake peptides were the lowest at p H=4.0,and increased with the rise in p H.The thermal analysis showed that the lower molecular weight of camellia seed cake peptide was more suitable for thermodynamic processing.4.Effects of in vitro digestion on antioxidant activity andα-glucosidase inhibitory activity of camellia seed cake peptides.After in vitro digestion,the antioxidant activity andα-glucosidase inhibitory activity of camellia seed cake were enhanced by more than4%.Fluorescence spectrum analysis showed that the peptides with higher molecular weight were more easily hydrolyzed by digestion,and the hydrophobicity of the digested peptides was enhanced.