α- and β-Amylase activity were determined at 4°, -13°, -18°, and -23°C (39.2°, 8.6°, -0.4°, and -9.4°F) in systems with purified enzymes and in a system with sweet potato puree for different periods of time. In the systems with purified enzymes, commercially purified swine pancreatic α-amylase and sweet potato β-amylase at 0, 0.5, 1.0, and 1.5 μg/0.5 ml concentrations were used to react with 0.5 ml of a 2% potato soluble starch substrate for 112 days. In the system with sweet potato puree, samples prepared from cured and uncured roots were frozen and stored for 56 days. The cumulative enzyme activity was determined after different storage times. The stability of the enzymes as affected by low temperatures was determined in the sweet potato puree.

In the systems with purified enzymes, cumulative α- and β-amylase activity at all storage temperatures studied increased as the storage time and enzyme concentration were increased, Both enzymes were still active at -23°C.

In the system with sweet potato puree, α- and β-amylase were active at 4°C for up to 28 days, but were inhibited at -13°, -18°, and -23°C.

In the cured sweet potato puree samples of the Centennial variety, α- and β-amylase were stable for up to 28 days at 4°C. Enzyme stability in samples from uncured roots of two varieties of sweet potatoes was not affected for up to 14 days of storage at 4°C, but decreased considerably thereafter.

α- and β-Amylase stability in all sweet potato puree samples stored for 56 days at -13°, - 18°, and -23°C was not affected.