Inactivation of trypsin inhibitors in sweet potato and taro tubers during processing

In order to understand the extent of elimination of trypsininhibitors during processing of sweet potato (Ipomoea batatas) andtaro (Colocasia esculenta) tubers, a detailed study was conductedusing tubers processed by oven drying, cooking, and microwavebaking. Between 80 and 90% trypsin inhibitor (TI) activity wasretained in sweet potato chips up to 2h at 70 °C. Among thefour cultivars of sweet potatoes, RS-III-2 trypsin inhibitors were more heatlabile. Heating at 100 °C led to rapid inactivation of TI of sweetpotatoes. Varietal differences in thermal stability were more pronouncedfor the trypsin inhibitors of taro than sweet potatoes. Taro inhibitors werealso more rapidly inactivated than sweet potato TI. Between 17 and31% TI activity was retained in cooked tuber pieces of sweet potatoes,while only 3–10% were retained in taro cultivars. Very effectiveinactivation of trypsin inhibitors of sweet potatoes and taro could beobtained through microwave baking. Flour prepared from taro was devoidof TI activity, while 5–12% TI activity was retained in the flour preparedfrom sweet potatoes. The study clearly established that among the fourtechniques used, microwave baking and flour preparation were the best methods to eliminate TI from sweet potatoes and taro.