Wheat flour is the main part of bakery products and improving its quality leads to improving the quality of the final product. The viscoelastic properties of wheat gluten play an important role in determining and improving the quality of the final product. Among the factors that affect the viscoelastic properties of wheat gluten is the sunn pest (Eurygaster integriceps) of the wheat. This pest injects a protease enzyme into wheat and reduces the quantity and quality of gluten. The purpose of this research was to investigate the effect of thermal treatments including dry oven treatment with temperatures of 60, 70 and 80 C˚ for the duration of 1, 3 and 5 min, microwave treatment with power of 160 W and for the duration of 2 and 3 min, non-thermal treatments including ultrasound treatment with fixed frequency of 15 kHz, a power source of 96 W at different power levels of 50, 60 and 70% for the duration of 1, 3 and 5 min and plasma treatment with a voltage of 18 V and air gas for the duration of 5 and 10 min on three undamaged , 5% and 8% sunn pest-damaged wheat grain samples. The effects of the treatments on solvent retention capacity, degree of hydrolysis, wet gluten, and gluten index were investigated. The results showed that microwave treatment for 3 min reduced the degree of hydrolysis of the sunn pest-damaged samples, but did not affect the solvent retention capacity. The inactivation of the protease enzyme by microwave occurs due to the volumetric heating. In the dry oven, with increasing temperature and time, the degree of hydrolysis of the damaged samples decreased, but after monitoring the solvent retention capacity, the quality of gluten decreased due to the degradation of glutenin at high temperature. The best eva‎luated temperature and time for dry oven treatment are 70 ˚C and 1 min. Plasma treatment in both durations of 5 and 10 min decreased the degree of hydrolysis of the damaged samples and increased the solvent retention capacity. Plasma treatment improved the quality of undamaged and damaged wheat through enzyme inactivation and oxidation of wheat proteins. Protease enzyme inactivation by ultrasound treatment occurs through the tension created on the outer part of the wheat grain where the enzyme is active. The best power level was 70% and 5 min time, in which the degree of hydrolysis decreased and did not have a negative effect on gluten quality. According to the comparison between thermal and non-thermal treatments it was found that non- thermal treatments have better results due to the lack of negative effects on gluten structure. Among the non-thermal treatments, plasma treatment is a more appropriate treatment to improve damaged wheat due to enzyme inactivation and flour protein oxidation (even in undamaged wheat).

مهدي كديور , مرتضي صادقي

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هاجر شكرچي زاده , علي قاسمي