Suppression of discoloration after cooking of sweet potato by an enzymatic treatment

Abstract

Utilization of enzymes for suppression of sweet potato discoloration after cooking was examined. A treatment of steamed sweet potato pasts prepared from cultivars of Beniotome and Benihayato with commercially available chlorogenic acid esterase (CAE) suppressed the discoloration of the past significantly. CAE decomposed all chlorogenic acid isomers of caffeic acid and quinic acid, whereas 4 CQA and 5CQA were decomposed faster than 3CQA. Since the intensity of the pigmentation of caffeic acid reacted with ferrous ion was less than that of chlorogenic acids, it was estimated that the suppression of the sweet potato past discoloration by CAE resulted mainly from the decomposition of chlorogenic acids to caffeic acid and quinic acid. Moreover, pectinases slightly contaminated in the CAE preparation were also estimated to suppress the discoloration by acidification of the pasts through the production of uronic acid from sweet potato pectin during the enzyme treatment.