Improvement of Functional Properties of Wheat Gluten Using Acid Protease from Aspergillus usamii.

Lingli Deng,Sheng Yang,Fei Que,Junmei Song,Hui Zhang,Zhaoxia Wang,Fengqin Feng,Vijai Gupta

doi:10.1371/journal.pone.0160101

Abstract

Hydrolysis parameters (temperature, E/S ratio, pH, and time) for acid protease (from Aspergillus usamii) hydrolysis of wheat gluten were optimized by response surface methodology (RSM) using emulsifying activity index (EAI) as the response factor. A temperature of 48.9°C, E/S ratio of 1.60%, pH 3.0, hydrolysis time of 2.5 h was found to be the optimum condition to obtain wheat gluten hydrolysate with higher EAI. The solubility of wheat gluten was greatly improved by hydrolysis and became independent of pH over the studied range. Enzymatic hydrolysis resulted in dramatically increase in EAI, water and oil holding capacity. Molecular weight distribution results showed that most of the peptides above 10 kDa have been hydrolyzed into smaller peptides. The results of FTIR spectra and disulfide bond (SS) and sulfhydryl (SH) content suggested that a more extensional conformation was formed after hydrolysis, which could account for the improved functional properties.

Highlights

Wheat gluten is an economically important coproduct in the recovery of wheat starch in wet milling of wheat flour
Analysis of variances indicates that the regression model for emulsifying activity index (EAI) is significant at p < 0.0001, while the lack of fit is not significant at p < 0.05
The coefficient of determination (R2) of 0.93 obtained for the model indicates a high degree of reliability for predictions of the EAI response

Summary

Introduction

Wheat gluten is an economically important coproduct in the recovery of wheat starch in wet milling of wheat flour. With the expansion of wheat starch production, the utilization of wheat gluten is getting diversified. The poor water solubility of wheat gluten hinders its application as a functional ingredient in food industry. Even though the price of wheat gluten is lower compared to that of protein isolates from animal sources, it has a narrower range of industrial applications [1]. In order to broaden the utilization of wheat gluten, the functional properties such as solubility and emulsifying capacity need to be improved. A lot of work has been done to improve the functional properties by physical [2, 3], chemical [4, 5], and enzymatic modifications [1, 6, 7]

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Conclusion