Optimizing Oxalate Reduction in Taro Leaves (Colocasia esculenta (L.) through Soaking and Drying Techniques for Inclusion in a Farmed Fish Feed
Kelvin E. Vulla
*
Department of Food Biotechnology and Nutrition Sciences, The Nelson Mandela African Institution of Science and Technology (NM-AIST), P.O. Box 447, Arusha, Tanzania.
Francis P. Mmanda
Institute of Marine Sciences (IMS), University of Dar es Salaam, P. O. Box 668, Zanzibar, Tanzania.
*Author to whom correspondence should be addressed.
Abstract
The utilization of Taro leaves as fish feed is hampered by high levels of oxalates. An investigative study was carried out to assess the efficacy of soaking and drying method on oxalate content reduction in taro leaves. During this study, the taro (Colocasia esculenta) leaves samples were collected along the river bank and washed before transported to laboratory for further processing and analysis. The leaves samples subjected to different processing method (soaking and drying) were crushed or grinded into a fine paste or powder using pestle and mortar to obtain extract for oxalate analysis, respectively. The soluble oxalate content in all samples was extracted using acidic solutions, and then analysed by titration methods using potassium permanganate solution (LOBA Chemie, India). The insoluble oxalate content (calcium oxalate) was obtained by subtracting soluble oxalate from total oxalate. The results showed that soaked and dried Taro leaves contained low level of oxalate compared to unprocessed leaves. The oxalate content of unprocessed leaves was 43 mg/100 g WM, while that of soaked and dried leaves were 23 and 4.2 mg/100 g WM, respectively. Therefore, the study has proven the efficacy of soaking and drying on oxalate reduction in taro leaves before used in a fish feed formulation.
Keywords: Taro leaves, anti-nutritional factors, oxalate, fish diet, processing techniques