REDUCED BROWNING IN RAW ORIENTAL NOODLES BY HEAT AND MOISTURE TREATMENT OF WHEAT

Flours milled from heat- and moisture-treated hard white wheat (KS-196 ) contained reduced levels of polyphenol oxidase (PPO), but not peroxi dase (PO). With a 12-min heating period, the PPO activity decreased wi th increasing moisture content (MC) from 13 to 15%, whereas with 4- an d 8-min heating periods, the PPO activity was insensitive to moisture level. When the tempering period was increased from 1 to 4 hr at 19% M C, PPO activity in the heat-treated wheat was unaffected. Three other wheat cultivars, tempered to 15% MC for 1 hr and then heat-treated for 8 min at 100 degrees C, yielded flours with approximate to 50% reduct ion in PPO activity. Heating the KS-196 wheat for 12 min at 100 degree s C reduced PPO activity in flour by as much as 76%, but destroyed the elasticity of gluten as determined by mixograms. White noodles and ye llow alkaline noodles, made from heat-treated (15% MC, 8 min, 100 degr ees C) KS-196 wheat, had improved brightness in the raw state and show ed little change in cooking quality and cooked texture, except for red uced firmness. When KS-196 wheat was pearled to remove 28% of its weig ht, and the pearled kernels were heat- and moisture-treated at 15% MC for 8 min at 100 degrees C, the straight-grade flour contained 75% les s PPO activity than the untreated wheat flour. White noodles made from pearled, heat- and moisture-treated wheat were brighter than those ma de from pearled untreated wheat. A white noodle dough, made from heat- and moisture-treated wheat with aminoguanidine bicarbonate added, had the brightest dough (L = 75) after 24 hr at 25 degrees C.