Effects Of Biomimetic Digestion In Vitro On Antigenicity And Structural Properties Peanut Proteins

Peanut is one of the eight major allergens in the world listed by the Food and Agriculture Organization of the United Nations(FAO).Peanut allergy is related to the digestion and absorption of the gastrointestinal tract.Its polypeptide interacts with the corresponding immune cells in the human body,which in turn triggers the immune response of the body.At present,there are many studies on peanut antigen epitopes and sensitization process.However,there are few studies on allergenic protein content,protein antigenicity and allergenicity of different peanut varieties.In this study,30 peanut varieties were collected and used as research objects.The allergenic proteins were extracted,the antigenicity and structure of peanut allergenic proteins were analyzed and tested,and static and dynamic digestion in vitro was carried out to analyze the changes of antigenicity of peanut protein in different peanut varieties and the structural characteristics of peanut protein in different varieties after digestion.The results were as follows:(1)Screening of peanut varieties and study on structural characteristics of peanuts proteinThe antigenicity of the proteins from 30 peanut varieties was detected,the antigenicity of different varieties in the same producing origins and different producing origins of the same variety was analyzed.The structural characteristics of the five peanut samples were analyzed to explore the relationship between peanut protein antigenicity and structural characteristics.The results of antigenicity showed that Henan-Nanyang Luhua 8 was the highest,and the antigenicity of Shandong-Jinan Silihong was the lowest.Among the peanut varieties in Henan area,Henan-Nanyang Luhua 8 had higher antigenicity,and Henan-Nanyang Tianfu 3had lower antigenicity.Among the varieties of Huayu series,Hebei-Tangshan Huayu 23 had higher antigenicity,and Shandong-Heze Huayu 16 had lower antigenicity.The relationship between protein structural characteristics and antigenicity was analyzed for the selected five peanut varieties.The results showed that there was a significant negative correlation between and β-sheet,α-helix and protein particle size in the secondary structure and a significant positive correlation between antigenicity and β-turn in the secondary structure.In addition,there was a positive correlation between antigenicity and random coil in secondary structure and disulfide bond,but they did not reach a significant level.There was a negative correlation between hydrophobicity and free sulfhydryl groups,but they also did not reach a significant level.(2)Effect of in vitro dynamic digestion on Ig G binding ability and structure of peanut proteinIn order to better observe the changes of antigenicity of peanut protein after in vitro digestion,and the sample of Henan-Nanyang Luhua 8 was selected.The single factor test and quadratic regression orthogonal test were used to optimize the static digestion conditions in vitro.The results of single factor test showed that the Ig G binding ability reached the lowest when the digestion temperature was 37.2 °C.When the digestion time was more than 100 min,there was no significant difference in Ig G binding ability.When the digestion p H value was 2,the Ig G binding ability was the lowest.There was no significant difference in Ig G binding ability when the digestive protease activity exceeded 4 500 U/m L.The optimal digestion conditions were obtained by quadratic regression orthogonal experiment: the digestion temperature was 37.2 °C,the digestion time was 120 min,the p H value was 1.4,the protease activity was 5 900 U/m L,and the Ig G binding capacity of peanut protein decreased to 27.45%.(3)Effect of in vitro dynamic digestion on Ig G binding ability and structure of peanut proteinIn order to simulate the digestion process of peanut protein in human body more realistically,the samples of Henan-Nanyang Luhua 8 and Shandong-Jinan Silihong were selected for in vitro simulated dynamic digestion.The antigenicity of peanut protein before and after digestion was determined by ELISA,and its structure was further analyzed..The results showed that the antigenicity of peanut protein of the two varieties decreased significantly after digestion.The structure of peanut protein digestion products,the results showed that the digestion caused the secondary and tertiary structures of the two varieties of peanut protein were destroyed,so that the amino acid side chains,tryptophan residues and other chromophoric amino acids were exposed to the polar environment,and the degree of exposure of protein hydrophobic groups increased,resulting in reduced antigenicity.In addition,it was observed on the morphology that the sample changed from a regular smooth sheet structure to an irregular small sheet after digestion,the structure became disordered and irregular,and the protein pores became larger,which led to a decrease in antigenicity.