The effect of peeling and cooking processes on nutrient composition of Oromo dinich (Plectranthus edulis) tuber

Abstract

The effects of peeling and cooking processes (boiling, steaming and baking) on the proximate, amino acids, mono, and disaccharides content of Oromo dinich (Plectranthus edulis) tubers from selected landraces were investigated. The effect of peeling on the crude protein, reducing sugars and sucrose content of the tuber was not consistent across the landraces. Crude protein reduced in landraces DHSer, IWsh, DGArr, and DGArw but increased in landrace CWsh. Reducing sugars (fructose, glucose, and maltose) increase in landraces LWsh, CWsh, DGArr, and DOJiw but reduced in landrace DOSu. Sucrose reduced in landraces IWsh and LWsh but increased in landrace CWsh on dry matter basis. Peeling significantly reduced the dry matter, ash and crude fiber content of the tubers. Dry matter reduced in landraces CWsh, DGArr, and DGArw; ash reduced in landraces DHSer and DGArw; crude-fiber reduced in landraces DOSu, DOSer, LWsh, CWsh, DGArr, and DGArw. On contrary, peeling significantly increased the crude fat, sum of total amino acids content and energy density of the tubers. Crude fat increased in landrace DOSu, IWsh, CWsh, DGArr, and DOJiw. Sum of total amino acids increased in landraces DOSu, DOJiw, and DGArw. Energy density (KJ/100 g dm) increased in landraces DOSu, DHSer, IWsh, and DOJiw. Boiling and steaming significantly increased the ash content of the tubers in landrace LWsh. Steaming and baking significantly increased crude fiber in landraces IWch and CWsh, and carbohydrate content of the tubers in landrace LWsh. Boiling, steaming and baking significantly reduced the crude fiber and the energy density of the tubers in landrace LWsh. Baking significantly reduced the moisture content of the tubers in landraces IWch, LWsh and CWsh. Boiling significantly reduced reducing sugars and crude fat content of the tubers in landraces IWch, LWsh and CWsh. The reduction in reducing sugar and crude fat content most likely is due to leaching and the presence of essential oils respectively. Thus to get the best possible nutritional benefits from P.edulis tubers, cooking with their skin under optimized operation recommended.