Study On The Effect Of Poly-?-Glutamic Acid On The Characteristic Of Wheat Gluten

Poly-?-glutamic acid(?-PGA),produced by microorganisms during fermentation,is a kind of nontoxic and biodegradable polyamino acid which is mainly composed of glutamic acid units.?-PGA can be widely applied in food industry.Wheat gluten is usually added in flour products as a gluten fortifier.In this study,?-PGA was added in wheat gluten to investigate the effect of ?-PGA on the characteristic of wheat gluten through three aspects including basic properties of wheat gluten,structure properties of wheat gluten and application properties of wheat gluten gel.The main research and results are as follows:?-PGA could make different extent effect on water holding capacity,the soluble protein content,emulsifying activity,emulsion stability,foaming capacity,foam stability and viscoelastic characteristic of wheat gluten.As the increase of ?-PGA concentration,water holding capacity of wheat gluten increased because of waterremaining property of ?-PGA and wheat gluten with 0.75% ?-PGA had the maximum water holding capacity,rising by 26.3% compared with the original wheat gluten.Emulsifying activity and emulsion stability decreased by 32.4% and 36.5% respectively compared with original wheat gluten,and both got the minimum values.The addition of ?-PGA reduced foaming capacity of wheat gluten while enhanced foam stability of it.The analysis of dynamic rheology indicated that ?-PGA was able to improve viscidity and elasticity of wheat gluten and viscidity and elasticity would have greatest values when the concentration of ?-PGA is 0.75%.The addition of ?-PGA could enhance stability of network structure of wheat gluten.The images of SDS-PAGE of gliadin and glutenin extracted from wheat gluten suggested that ?-PGA could not destroy the primary structure of protein.From the determination of free SH content and S-S content and the analysis of thermal properties of wheat gluten,it was known that ?-PGA benefited to intermolecular interaction of proteins,facilitated intermolecular disulfide bonds to form and intermolecular hydrogen bonds to be strengthened.As a result,the network structure of wheat gluten became more stable and the denaturation temperature of wheat gluten was increased.0.75% ?-PGA made wheat gluten have the most stable network structure.By means of Fourier infrared spectroscopy,it was found that the secondary structure of protein in wheat gluten was changed by ?-PGA.And SEM images showed directly that wheat gluten with ?-PGA had more integral,homogenizing and regular network structure.Application properties such as TPA properties and sensory qualities of wheat gluten gel could be optimized to a certain degree by adding ?-PGA.?-PGA made water absorption ratio of gluten gel grow up dramatically and the value gradually approached to 2.80g/g when the concentration of ?-PGA was more than 0.75%.This result was in keeping with the images of microexamination of wheat gluten.The analysis of TPA of boiling wheat gluten gel indicated that ?-PGA could decrease hardness,chewiness and resilience.The evaluation of sensory qualities suggested that boiling wheat gluten gel with ?-PGA had more excellent appearance and shape,internal color and internal structure.?-PGA also could improve edible taste and maintain the original flavor at the same time.The boiling wheat gluten gel with 0.75% ?-PGA had the best taste.