Defending Against Yam Discoloration

May 5/Thiruvananthapuram, India/Food Business Week --  According to recent research from Thiruvananthapuram, India, "The use of sweet potato and yams for product development is hindered by the discoloration from enzymatic and non-enzymatic browning The effect of pre-soaking treatments on the nutritional changes and browning index (BI) of sweet potato and yarn (greater yam and white yarn) flours was Investigated Ascorbic acid (AsA), citric acid (CA), acetic acid (AA) and sodium metabisulfite (SMS) were used for soaking at three concentrations (0.25%, 0.50% and 1.00%) and two durations (one hour and two hours) AsA and SMS removed more starch during soaking of sweet potato, while CA and M removed more starch from greater yam and CA removed more starch from white yam. Highest removal of reducing sugars was observed in sweet potato in AA, while CA removed maximum reducing sugars from both the yarns."

"Phenol and total free amino acid (TFA) levels were more in SMS treatment than the control sweet potato flour, and least in AA (two hours) Whilst AsA raised the phenols and TFA in greater yam, it removed phenols to the maximum in white yam. Maximum BI was in MA treatment for the three crops, and least for flour from CA (0.25%) treated yams and AA (1.00%) treated sweet potato.

"Industrial Relevance. Browning resulting from enzymatic and non-enzymatic reactions is a major drawback in the processing of sweet potato and yams for product development," wrote J.G. Krishnan and colleagues. The study showed that this could be successfully tackled through soaking the slices in low-cost chemicals like acetic acid or citric acid and sodium metabisulfite at low concentrations."

Krishnan and colleagues published their study in Innovative Food Science & Emerging Technologies ("Effect of Pre-soaking Treatments on The Nutritional Profile and Browning Index of Sweet Potato and Yam Flours." Innovative Food Science & Emerging Technologies, 2010;11(2):387-393).

For additional information, contact G. Padmaja, Cent. Tuber Crops Research Institute, Division Crop Utilizat, Thiruvananthapuram 695017, Kerala, India.

From the May 10, 2010, Prepared Foods E-dition