Effect of processing method on the proximate composition, mineral content and antinutritional factors to taro (Colocasia esculenta, L.) grown in Ethiopia

Abstract

Although taro is widely grown in Ethiopia, it is an underutilized crop and little is known about its proximate and micro-element composition and the antinutritional factors of the raw, boiled and fermented products. Boiling and fermentation processing techniques are widely used in the country, especially within the rural community of the Southern region where the crop grows widely. A cultivar of taro grown in the country was analyzed for proximate and mineral composition and antinutritional factors. An investigation was also made on the effects of boiling and fermentation on the nutritional contents. Protein, fat, fiber, total ash and utilizable carbohydrates, respectively were found to be 6.43, 0.47, 2.63, 4.82 and 85.65%, while the Gross Energy was 372.55 Kcal/100g. The contents of the micronutrients namely:Fe, Zn, Mg, Ca, Na, P and Mn were 5.86, 43.08, 7.24, 45.23, 13.81, 7.77 and 3.61mg/100g, respectively. Phytate for the raw product was 115.43 while oxalate and tannin were 243.06 and 47.69 mg/100g, respectively. Cyanide was not detected in all the samples. There was a significant difference (p < 0.05) in the contents of the proximate and mineral composition and antinutritional factors during boiling and fermentation. The protein content was lower by 9.37% and 8.46%, respectively, in the boiled and fermented products, under the sampling and processing conditions used in the study. The crude fat content was significantly different (p < 0.05) from the crude fat content of the boiled product which was 0.87%. On the other hand, analysis of variance conducted showed that the fiber content of raw sample was significantly different from the fermented samples. Fermentation resulted in a lower level of fiber which was 6.44% and phytates of about 84.75%. Boiling of taro resulted in a higher value of oxalate (70.9%). The data presented in this paper provide an evidence of the potential of Boloso I (which is one variety of taro) to serve as a nutrient dense product for the Ethiopian population provided that the techniques of its processing are optimized.