The effect of storage temperature on reducing sugars, pH, and phosphorylase enzyme activity in potato tubers

Summary

The influence of storage at 40 and 70 F on reducing sugars, pH, phosphorylase enzyme activity in potato tubers, and the effect on chipping quality, was investigated. In addition to the expected increase in reducing sugars and decline in chip color during storage at 40 F, the pH decreased markedly and phosphorylase enzyme activity increased. Conditioning at 70 F, after storage at 40 F, lowered reducing sugars, increased the level of pH, and improved chip color.

Although continuous storage at 70 F after harvest caused little variation in reducing sugars, pH declined, and phosphorylase activity increased, but both to a lesser extent than occurred at 40 F. Chip color was still good after 4 weeks at 70 F although slightly poorer than at harvest.

Phosphorylase activity was high in tubers stored at 40 F and since this enzyme catalyzes the breakdown of starch, it could be a factor influencing sugar accumulation and chip quality. Varieties differed significantly in phosphorylase activity.

The pH of the juice correlated negatively with reducing sugar levels in the tubers and offered an excellent guide for estimating chip quality. This rapid test was more easily performed than chemical analysis for reducing sugars or preparation of chips and measurement of the color.