Effect of amino and thiol groups of wheat gluten on the quality characteristics of Chinese noodles.

Wheat protein contains a large number of side chain groups, amino, hydroxyl groups and sulfydryl, which influence on the quality of Chinese noodles has not been reported. Amino and thiol groups of wheat gluten were modified by chemical reactions, and acetylated gluten (AG) and reduced gluten with anhydrous sodium sulfite (SG) were obtained. Two types of noodles were made by addition of AG and SG, and the effects of AG and SG on texture and cooking properties were investigated. With the increase of AG amount in the original flour, the sedimentation value of reconstituted flour and the tensile force of fresh and cooked noodles decreased, whereas the hardness and adhesiveness increased. The gluten index and springiness of the reconstituted flour did not vary significantly compared to those of the original flour. In addition, most of the texture and cooking quality properties of the two types of noodles decreased except the adhesiveness and tensile force of fresh noodles with a rising trend along with the increase of SG. Furthermore, the cooking yield was reduced, whereas the cooking and protein losses increased along with the elevation of modified gluten levels. Our results indicated that significant differences (p < 0.05) were present between the texture and cooking properties of Chinese noodles made by flour with AG and SG and those of unmodified samples, except for the springiness of AG noodles, and the reduction of disulfide bond was disadvantageous for the quality of noodles. Therefore, the results of the present study indicate that amino and sulfhydryl groups of wheat gluten have an important role in obtaining high-quality noodles.