Effect of tea extract on starch gelatinisation, gluten aggregation and quality characteristics of dry yellow alkaline noodle

Three kinds of tea extracts (green tea extract, black tea extract and oolong tea extract) were incorporated into a dry yellow alkaline noodle (YAN) at a concentration of 0.5%-2.0% to investigate their effects on starch gelatinisation, gluten aggregation and noodle quality characteristics. Due to the starch-polyphenol interaction, the temperature and enthalpy required for starch gelatinisation were decreased by 0.90-1.10 degrees C and 2.85-3.31 J/g, respectively, when 2.0% tea extract was added compared with the control. Furthermore, the dry noodles showed lower starch pasting viscosities (reduced by 28.35%-55.20%) and increased resistance to breakdown and retrogradation. Through the hydrogen bonding between gliadins and tea polyphenols, the conformation of gluten was modified (15.41%-24.62% and 15.19%-22.95% increases in alpha-helix and beta-sheet contents, respectively) and its structure was strengthened. The combined effect of tea extracts on starch gelatinisation and gluten formation behaviour resulted in the restricted water permeability and mobility in the structure of cooked noodles, which was associated with increased hardness (13.15-16.34 N), cohesiveness (0.63-0.69), chewiness (7.47-10.88) and resilience (0.34-0.42). It also decreased the absolute adhesiveness (0.11-0.13 N.sec) of cooked YANs. In the alkaline noodle system, three kinds of tea extracts exhibited similar effects on the quality characteristics of YAN. The results suggest that tea extracts are capable of improving YAN texture.