Formation Mechanism,Structure,Properties And Application Of Arachin-Basil Seed Gum Composite Gels

Defatted peanut meal is a by-product of peanut oil extraction and is rich in protein.However,it is often used as animal feed,resulting in a waste of protein resources with good quality.Peanut protein is rich in essential amino acids and has high nutritional value,but the poor gelation property has restricted its application in food industry.In this dissertation,the arachin was isolated from defatted peanut crude protein powder by ammonium sulfate precipitation method,basil seed gum was extracted from swollen basil seeds using scraping technology and alcohol precipitation method.A small amount(0.05%-1%)of basil seed gum(BSG)was added into arachin solution(12%)to form heat-induced protein-polysaccharide composite gels.The effects of BSG on arachin gel properties and the interaction forces in the composite gels were investigated.Additionally,the p H value and concentrations of Ca Cl₂ or Na Cl in the arachin-basil seed gum composite solution were adjusted to explore these conditions on the structural,physicochemical properties of the composite gels.The possible mechanism was clarified by analyzing the changes of protein structure and interaction forces between arachin and BSG.Then,under the optimal p H condition,appropriate concentrations of Na Cl or/and TGase were added into the arachin-basil seed gum composite system to evaluate the improvement effect of Na Cl,TGase and their addition order on the structure and gelation properties of the composite gels.Finally,the composite gels were used to encapsulate vitamin D₃(VD₃)and the stability of VD₃ was detected.The gastrointestinal digestion was simulated to study the release of VD₃ and the digestion of arachin in the composite gels.Firstly,the effects of BSG on the structural and physicochemical properties of arachin gel were studied.The results showed that the BSG improved the gel formability and microstructure.With the concentration of basil seed gum increasing,the gel strength,water holding capacity,storage modulus(G')and loss modulus(G")of arachin gel increased.The results of interaction forces showed that electrostatic interaction,hydrophobic interaction,hydrogen bond and disulfide bond played important roles in stabilizing and maintaining the structure of the composite gels.Secondly,the heat-induced composite gels were formed by changing p H and the amounts of Ca Cl₂ or Na Cl added in arachin-basil seed gum composite system.The effects of p H,salt ion type and concentration on the composite gels were studied.It is obvious that the G',G",gel strength,water holding capacity of the composite gels increased by a low concentration of salt ions and the freeze-thaw stability was improved.The electrostatic interaction,hydrophobic interaction,hydrogen bond and disulfide bond in the composite gel system were enhanced when a proper concentration of salt ions(10m M)was added and it promoted the transformation of protein secondary structure from?-helix to?-sheet,resulting in a more compact microstructure of the composite gel.It showed that the effect of Na Cl was superior to that of Ca Cl₂.High concentration of salt ions tended to destroy the structure of the composite gel.In addition,the effects of TGase as well as the addition order of Na Cl and TG on the structural and physicochemical properties of arachin-basil seed gum composite gels were explored.TGase enhanced the cross-linking between arachin molecules and improved the gel properties.What's more,the effect of TGase was better than that of Na Cl.The heat-induced composite gel formed by adding Na Cl and subsequent cross-linking by TGase exhibited a higher gel strength,G',water holding capacity,freeze-thaw stability and the most compact microstructure.The addition of Na Cl facilitated the subsequent cross-linking of TGase among the protein molecules.The addition order of Na Cl and TGase also had an effect on the appearance color of the composite gel.Finally,the application of arachin-basil seed gum composite gels used for encapsulating VD₃was studied.The composite gel formed by adding Na Cl and subsequent cross-linking of TGase had the best protective effect on VD₃ and improved the stability of VD₃ against temperature,UV light and storage time.The results of in vitro simulated gastrointestinal digestion showed that VD₃ could be released more in the small intestine after encapsulating by the composite gels.SDS-PAGE results showed that the main bands of arachin still existed after digestion in the stomach,while only small molecular weight bands existed after digestion in the intestine,indicating that basil seed gum had a protective effect on arachin in the simulated gastric fluid.Protein-polysaccharide composite gels were suitable for the delivery of active ingredients.In summray,this dissertation showed that the formability and stability of arachin gel was improved by adding basil seed gum.The properties of arachin-basil seed gum composite gel can be regulated by changing p H and adding salt ions in the composite system.The structure of the composite gel can be improved by an appropriate amount of Na⁺and TG enzyme.These results may provide some theoretical basis for widening the application of arachin and basil seed gum in the food manufacture.