Effect of Transglutaminase on Structural and Functional Properties of Proteins of Three Legumes

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Date
2015-06-16
Authors
Selma Hashim Ahmed Elyass, Elyass
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Publisher
uofk
Abstract
This study was designed to investigate the effect of transglutaminase (TGase) on the structural and functional properties of phaseolus, pigeon pea and cowpea protein isolates at different pH levels or salt (NaCl) concentration. The crude protein content was 28.53%, 23.84% and 20.13% and the protein isolate was 71.93%, 79.80% and 72.63% for phaseolus, cowpea and pigeon pea, respectively. Cross-linking of the protein isolate of each legume with the microbial enzyme transglutaminase, EC 2.3.2.13 resulted in reduction of the total free amino groups (OD 340) of the polymerized protein which indicated that TGase treatment cross linked the protein subunits of each legume. The solubility of the polymerized protein isolates at different pH and NaCl concentration was improved compared to that of native protein isolate. The solubility of the protein polymers of each legume was greatly improved at pH 2 and pH 8-12, whereas at pH 4 and 6 the solubility was slightly decreased. Addition of NaCl to the native and polymerized proteins showed that the solubility increased with salt concentration till certain level and, thereafter, started to decrease due to salting out process. TGase treated proteins were less turbid on heating to higher temperature as compared to untreated ones, and the temperature at which the protein turns turbid also increased after TGase treatment. TGase polymer substantially resisted heat induced aggregation up to 70oC then its solubility slightly decreased. The emulsifying activity of the polymerized protein isolate was improved at all pH levels and salt concentrations. The emulsion stability of the polymerized protein was greatly improved at different pH levels and salt concentrations. However, further increase in ionic strength progressively reduced both emulsifying activity and emulsion stability. The foaming capacity of the legume protein isolate was pH and salt concentration dependant and correlated to their protein solubility. TGase treatment improved foaming capacity of the protein isolate at different pH levels and salt concentrations. The foam stability of the protein isolate was gradually decreased with time. TGase treatment greatly improved foam stability of the protein isolate at different pH and salt concentration
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Effect of Transglutaminase on Structural and Functional Properties of Proteins of Three Legumes
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