Effect of processing on the oxalate concentration of Com Hen and Canh Chua Bac Ha, two local dishes prepared from the petioles of taro grown in central Viet Nam

Abstract

Petioles of Mon Ngot (Sweet taro, Colocasia esculenta) are widely grown in Thua Thien Hue Province in Viet Nam and they are an important ingredient in the popular local dishes Com Hen and Canh Chua Bac Ha. During the preparation of the petioles the tough, fibrous outer skin, known to cause itchy throats, is removed. In the preparation of Com Hen the outer skin is removed sliced and washed while the preparation of Canh Chua Bac Ha, involves the natural fermentation of the peeled petioles with Lactobacillus to give a more even taste. This experiment investigated the effect of removing the outer skin on the oxalate composition of the washed and cooked stems, the effect of cooking the these petioles for 10, 15 and 20 minutes to encourage increased leaching of soluble oxalates into the cooking water and the effect of fermentation of the petioles with Lactobacilllus for 24, 48 and 72 hours. Taro petioles constitute between 30% and 40% of the final local dishes. These dishes do not include foods high in calcium that would bind soluble oxalate. This emphasises the importance of adequate processes for removing soluble oxalates prior to consumption.