| As the secondary origin and main production area of kidney beans,China has a wide range of cultivation areas,and many new varieties have appeared during the long time cultivation and breeding process.There is a lack of systematic studies on the nutritional quality and functional structure of different varieties of kidney bean proteins in different regions and the differences in bioavailability of different kidney bean proteins after human digestion.In this study,we selected25 varieties of kidney beans from the main planting provinces in China,analyzed the nutritional composition and amino acid nutritional value of different varieties of kidney beans,used principal component analysis and cluster analysis to comprehensively evaluate the quality of kidney beans,and systematically characterized the origin properties of physicochemical properties and functional properties of isolated proteins of kidney bean varieties,and deeply explored the spatial conformation of different varieties of kidney bean proteins and the digestive properties of in vitro simulated digestion products.The relationship between the spatial conformation of different varieties of kidney bean proteins and the digestive properties of in vitro simulated digestive products was explored in depth,and the results of the study were as follows:1.Based on 25 types of kidney beans grown in major provinces in China,their nutritional composition was determined.The nutritional value of kidney bean protein was systematically analyzed using indicators such as essential amino acid index(EAAI)and amino acid ratio coefficient score(SRC).The quality of 25 types of kidney beans was comprehensively evaluated based on principal component analysis and cluster analysis.The results showed that the protein content of 25 kidney beans ranged from 18.96 to 31.50 g/100g;The total amino acid content ranges from 59.73 to 77.73 g/100 g.Except for GZ-LSKPI and HLJ-JRKPI,other varieties have EAAI>94 and SRC between 68.82 and 77.49,with significant differences among varieties.The limiting amino acid is sulfur-containing amino acid.Two principal components were extracted through principal component analysis,with a cumulative variance contribution rate of 89.847%.The five kidney bean varieties with the highest comprehensive evaluation quality ranking were YN-BSKPI,NMG-WKPI,NMG-PSKPI,HLJ-ZHKPI,and HLJ-BSKPI.Cluster analysis divided25 types of kidney beans into 4 categories,with the first category having the highest nutritional value,namely YN-BSKPI,NMG-RKPI,NMG-PSKPI,and NMG-WKPI.The results were consistent with the comprehensive evaluation.2.A comparative analysis was conducted on the physicochemical and functional properties of 25 types of kidney bean proteins grown in major provinces of China.The results showed that the solubility of kidney bean protein isolate showed a trend of first decreasing and then increasing with increasing p H;The water and oil holding capacity of NMG-WKPI,NMG-PSKKKPI,and YN-BKPI are all high;HLJ-BSKPI,SD-TNKPI,HLJ-RKKPI,NMG-RKKPI,HB-JZY3 KPI,and XJ-XY6 KPI have good foaming performance;The emulsifying properties of SD-LLKPI,HB-BYKPI,and XJ-XY6 KPI are higher than those of other kidney bean varieties;Most kidney bean proteins form gel at 10 g/100 m L.Principal component analysis(PCA)showed that the first five principal components accounted for 76.4%of the total variance,and all kidney bean proteins were reflected in two clusters and six outlier.The first cluster was mainly located on the upper left panel of PC1,and the emulsifying,surface hydrophobicity,and water holding properties of NMG-PSKKPI,HLJ-YKPI,NMG-LSKPI,NMG-WKPI,YN-PSKPI,YN-LSKPI,and GZ-BWKPI were similar or similar;The second cluster is mainly located in the lower right panel,with SX-BSKPI,SD-TNKPI,HLJ-JRKPI,SX-SWKPI,GZ-RPRI,HB-BYKPI,SX-RPRI,SD-LLSKPI,GZ-LSKPI,and HLJ-ZHKPI having similar or similar emulsion stability,Zeta potential,and foaming stability.3.The protein structure and digestive characteristics of gastrointestinal simulated digestion products of 25 species of kidney beans from the main planting provinces in China were determined.The correlation analysis of structure and digestive characteristics was also carried out.A comprehensive evaluation of the structural and digestive properties of kidney beans was also performed based on the principal component analysis.The results showed that different varieties of kidney bean proteins showed seven subunit bands,and the subunit molecular weights were mainly concentrated in the range of 17～95 KDa.The secondary structures were mainlyβ-folded.The hydrolysis and digestibility of the digested products showed an overall increasing trend in the simulated digestion stages of gastric start,gastric end and intestinal end,and the particle size showed an increase followed by a decrease.The hydrolysis degree and digestibility increased by 65.53%～68.41% and 19.19%～68.91%,and the particle size distribution decreased by 18.17%～43.40% in the end of the intestine compared with the end of the stomach.Correlation analysis showed a significant negative correlation between β-folding and end-gastric and end-intestinal hydrolysis(-0.901,-0.537).Irregular curl and β-turn angle showed a significant positive correlation with gastric end hydrolysis degree(0.399,0.695).Surface hydrophobicity was significantly negatively correlated with gastric end and intestinal end hydrolysis degrees(-0.778,-0.403).It showed that the content of β-folded,irregularly curled,and β-turned structures in kidney bean protein had a significant effect on the hydrolysis degree of digestive enzymatic digestion of kidney bean protein.The principal component analysis showed that the cumulative variance contribution of the first four principal components was 72.738%.The kidney bean varieties with a combined score greater than zero were,in descending order,GZ-BWKPI,YN-PSKPI,NMG-LSKPI,NMG-RKKPI,HLJ-ZHKPI,YN-WKPI,NMG-WKPI,SX-BSKPI,HB-BYKPI,SD-TNKPI,GZ-LSKPI,and SX-RKPI.These strains exhibited higher digestive and absorption qualities. |
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