Use of wheat-sweet potato composite flours in yellow-alkaline and white- salted noodles

Abstract

Chinese-style yellow alkaline noodles (YAN) and Japanese-style white salted noodles (WSN) were prepared from a standard brand of hard red winter wheat flour (Red Bicycle) and from composite flours containing the wheat flour plus 25% sweet potato flour (SPF). SPF from four Philippine genotypes (CL-946-25, Miracle L, CN-941 32, and CL-1489-89) was used. The composite flours showed two distinct gelatinization endotherms corresponding to the two types of starch present. The gelatinization enthalpies of the composite flours were generally slightly lower than all-wheat flour, except for CL- 1489-89, which had minimal amylase activity. Rapid Visco-Analyzer (RVA) viscoamylographs of composite flours were significantly different under slightly acidic conditions (pH 5.7-6.0) but not under alkaline conditions (pH 10), primarily due to differences in SPF amylase activity. Correspondingly, YAN were firmer and had lower cooking loss than WSN. Sweet potato genotypes differed significantly in the color imparted to the composite flour noodles. The modified Pekar Slick test was conducted on SPF under alkaline and under slightly acidic conditions to show the extent of discoloration during processing. For wheat-sweet potato composite flours, the addition of ascorbic acid tended to increase noodle firmness. However, a higher degree of browning after 24 hr of storage at 4°C was observed in noodles containing ascorbic acid. RVA viscoamylographs and the modified Pekar slick test results can be used to screen sweet potato cultivars for noodle quality.