Effect Of Cereal Glutenin And Gliadin Ratios On The Quality Of High Moisture Textured Vegetable Protein

Gluten plays a significant role in the quality of textured vegetable protein and refining the role of the two protein fractions of gluten in extrusion,glutenin(Glu)and gliadin(Gli),may serve as a guide for product development and quality improvement efforts.In addition,Zein has the potential to form a viscoelastic network and was combined with high nutritional value rice protein(RP)for extrusion to produce gluten-free high moisture textured vegetable protein,to find the optimal ratio and to add TG enzymes to improve the product.The research on this project consists of three main parts.Firstly,Glu and Gli were extracted according to their different solubilities and reconstituted in different ratios to investigate the raw material characteristics of the reconstituted powders,the rheological properties of the extruded blend and the effect on the quality of the high moisture textured vegetable protein.The fibrous macro-molecule Glu had a high water absorption and holding capacity of(183.67% and 1.35 g/g)and a high content of intra-and inter-chain disulphide bonds in the protein chain(52.47 umol/g).In addition,Glu contained a high number of non-polar amino acids and exposed hydrophobic residues with a high surface hydrophobicity(103.83 ug).The small,spherical Gli was more oil holding(0.95 g/g),contained only intra-protein chain disulphide bonds(27.79 umol/g)and had a less hydrophobic surface(65.79 ug).In the process of increasing temperature,the extruded blend protein molecular chain unfolding was denatured and inter-molecular interactions were disrupted,followed by the exposure of functional groups hidden inside the protein and an increase in interactions between groups.During the drop in temperature,the protein inter-molecular interactions increased sharply causing aggregation of the protein.Increasing the Gli content increased the tan δ value and Gli facilitated the flow of the melt during extrusion.As the ratio of Glu to Gli decreased,the extruded product showed a decrease in water holding capacity,hardness and chewiness and an increase in brightness,transverse shear,stretch distance and organization.The best quality was achieved with a Glu to Gli ratio of 20:80,with a Glu to Gli ratio of 0:100 resulting in easy fibre breakage.In addition,the combination of gluten and Gli was adjusted to a Glu to Gli ratio of 20:80 and then extruded,resulting in a smooth surface,rich fibre structure and fine fibrils,with organization and texture data close to that of the Glu to Gli ratio of 20:80,confirming that the Glu to Gli ratio of 20:80 was the best quality product.The SEM results showed that Glu had a supportive effect on the network structure of the product,and products with low Glu content had a weak fibre structure that was prone to breakage,while Gli contributed to a rich fibre structure by strengthening the connection of the fibre layers.Next,RP and Zein were compounded in different proportions to investigate the raw material properties of compounded powders,the rheological properties of the extruded blend and the feasibility of replacing gluten in extrusion to produce a gluten-free high moisture textured vegetable protein.The water holding capacity,oil holding capacity,free sulfhydryl groups,disulfide bond content,and surface hydrophobicity values of the RP and Zein blended powders were all higher than those of the gluten.As the ratio of RP to Zein decreased,the water holding capacity,oil holding capacity and disulphide bond content of the blended powders increased significantly,while the free sulfhydryl content and surface hydrophobicity decreased.The overall gel structure formed by the RP and Zein extruded blend was weaker.Compared to the reconstituted powder product,the quality of the RP and Zein blended powder extruded products was relatively poor,mainly in terms of dark color,large hardness and chewiness(21.11 kg～24.17 kg,17.00 kg～20.71 kg),low organization(1.12～1.53),a laminar fibrous structure,but inconspicuous fibrils and low sensory scores(54.92～65.43).In addition,the structure of high moisture textured vegetable protein was maintained by a combination of chemical bonds and interactions,with hydrogen bonds contributing most to the product structure.Finally,the quality of the extruded product was improved by the addition of different TGase levels at the optimum ratio of gluten-free textured vegetable protein,i.e.40:60 RP and Zein.TGase was added to the extrusion to induce protein cross-linking,resulting in increased oil holding,hardness and chewiness,increased fibre layering and a richer fibre structure.However,when the TGase addition was too high(2%),the anisotropic structure of the product was weakened,the fibrous of the texture was reduced and the degree of organization decreased.Low levels of TGase were found to increase the G’ and G’’ of the product,leading to a more stable protein structure.Protein cross-linking was catalyzed by TGase to improve protein polymerization,but high TGase levels were detrimental to product gel formation.The optimum range of TGase addition was 0.2% to 0.5%.In addition,the distribution of water in the extruded product was characterized using LF-NMR and less mobile water was the main form of water present in the product,and TGase was able to facilitate the conversion of bound water into less mobile water in the product.