Detection of a heat-stable and insoluble form of β-amylase in sweet potatoes

Abstract

Many studies have addressed the soluble form of β-amylase contained in sweet potatoes, but to date no information is available concerning insoluble one. We report here for the first time β-amylase bound to cell walls of sweet potatoes.
The total activity of this insoluble form of β-amylase was one-hundredth of that of soluble one, but it was very heat-stable compared to the soluble enzyme. It had an optimal temperature at 75°C, and about 40% of its enzyme activity remained after heat-treatment at 90°C for 3 minutes. So it is considered that this insoluble form of β-amylase is responsible for increasing the maltose content during cooking sweet potatoes.