Study On Modification To Improve The Solubility Of Peanut Protein At Acidic Condition And Product Development

Acidic beverages account for 60%~70% of the soft drink products,and are popular with consumers.However,because of their single ingredients and lack of protein,they cannot meet the needs of consumers today for balanced nutrition.Peanut protein is a high-quality protein resource,which has a large output and high nutritional value,but under acidic conditions,it will flocculate and precipitate,and its solubility is reduced,which limits its application in acid beverages.Therefore,our study explored the solubilization effects of different modification methods on peanut protein under acidic conditions,and characterized the physicochemical and functional properties of peanut protein during the modification process.Finally,the modified peanut protein was used in acidic beverages,which broadened its application in food,and had reference significance for the modification of plant proteins and their application in acidic food system.(1)Using low temperature defatted peanut protein powder as raw material,the effects of different single and composite modification methods on the nitrogen solubility index of peanut protein at pH 4.0 were evaluated,and the effects of different methods on the solubility of the protein under acidic conditions were evaluated.Among the single physical modification methods,the high-pressure homogenization and spray-cooking treatments were the best.The two single chemical modification methods were not effective and would not be used subsequently.Among the four protease,neutral protease was the best.Based on the single modification methods,the composite modification methods were researched.Responsive section experiments revealed the best parameters for high-pressure homogeneous-neutral proteolysis to increase the nitrogen solubility index of peanut protein under acidic conditions.Combined with the jet cooking method,it was found that the high-pressure homogeneous-neutral protease hydrolysis-jet cooking combined modification had the best effect.The optimal process obtained by response surface analysis is: homogeneous pressure 79.74 MPa,ratio of material to liquid 7.23%,enzymatic hydrolysis time 48.20 min,and enzyme addition amount 1.034%.The NSI of modified peanut protein at pH 4.0 increased from 4.04% to 39.07%.(2)The structural and functional characteristics of peanut protein during the High-pressure homogenization-enzymatic hydrolysis-hydrothermal cooking combined modification process was determined.The TSI value of the peanut protein acidic solution decreased from 10.9 to 1.5 after the composite modification treatment,and the stability was significantly improved.SDS-PAGE results showed that the composite modification method would cause dissociation of insoluble protein aggregates and increasement of soluble aggregates.Meanwhile,the particle size of peanut protein would gradually decrease during these three treatments,and the final particle size can be decreased to 21.74 ± 0.17 ?m.During the composite modification process,the surface hydrophobicity of peanut protein decreased,the exposure of hydrophilic groups increased,and the protein hydration was more sufficient.Zeta potential of the modified peanut protein changed significantly,and it was still negatively charged near the original isoelectric point.And the electrostatic repulsion between protein molecules prevented the aggregation of peanut protein,thereby improving the solubility and solution stability.(3)Acid-regulated centrifugal supernatant of high pressure homogenization-enzymatic hydrolysis-hydrothermal cooking modified protein was spray-dried as raw materials for product development.The research results show that when the amount of acid soluble protein added is ?3%,the protein content in the juice sample is 0.83(g/100g),which meets the standards of compound protein beverages and other protein beverages and peanut milk beverages.By comparing the stability of beverages with different protein additions,it was found that the juice stability of 3% and 4% protein additions was better,TSI was 1.95 and 2.23,respectively.There is no significant difference in the stability of the juice added with 3% sample compared with the juice without protein.Finally,the sensory evaluation was carried out from four aspects: color,acidity,taste,and morphology.It was found that the sensory evaluation result of 4% protein content was the best.In summary,4% modified protein added fruit juice is the best.