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Highlights

Sweet potatoes designated for animals contains higher trypsin inhibitor activity.

ABSTRACT. Sweet potatoes are a good food source, but they contain trypsin inhibitors, which reduce the protein utilization rate in animals. This study analyzed the trypsin inhibitor activity of ten sweet potato varieties. Most of the sweet potatoes designated for animals exhibited high trypsin inhibitor activity. The trypsin activities of TNG57 and TNG10, the most popular sweet potato varieties in Taiwan, were 51.5% and 77.1%, respectively. However, the trypsin inhibitor activity of these fresh sweet potatoes was successfully reduced by hot-water treatment. The influence of hot-water temperature and treatment time was analyzed by response surface methodology (RSM). From the RSM regression models, the optimal conditions of hot-water treatment were determined to be 95°C and 14 min. The kinetic parameters (K_m and V_max) of sweet potato extracts were determined from a Lineweaver-Burke plot. The inhibitor in sweet potato extracts was classified as reversible competitive.