Wheat Gluten Plasticized with Its Own Hydrolysate

Abstract

Proteins can be made into polymer materials through plasticization. Here, wheat gluten is plasticized with its own tryptic hydrolysate. Wheat gluten hydrolysate largely consists of small molecular weight peptides as measured by size exclusion chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Elastic modulus decreases 3.8 times at hydrolyzed wheat gluten contents of 0.2–0.4 mass fraction. Differential scanning calorimetry shows a 100 °C reduction of the glass transition temperature from 0.0 to 0.5 mass fraction hydrolyzed wheat gluten content. Compared to glycerol, hydrolyzed wheat gluten is not as efficient a plasticizer. However, hydrolyzed wheat gluten has a similar effect on the protein structure as glycerol as measured with Fourier transform infrared (FTIR) spectroscopy. The glass transition temperature is found to strongly correlate with the state of glutamine and proline in the protein and FTIR results can be used to predict the glass transition temperature at a given plasticization level.