Lipid Autoxidation and Amino Acid Changes in Protein—enriched Sweet Potato Flakes

Three sweet potato flake formulations, containing (1) soy flour plus methionine, (2) casein and (3) no supplementary protein, were prepared and stored at room temperature (21–23°C) in air for 16 months. The formulations were analyzed periodically to ascertain changes in carotene content, amino acid levels and water‐binding capacity. On the basis of carotene degradation as a measure of lipid autoxidation, it was found that after an induction period of 19 days required by the flakes supplemented with soy‐methionine, all formulations were oxidized in an identical manner. Among the amino acids, only glutamic acid was lost from all three formulations, and isoleucine levels decreased in the control formulation only. Lysine concentration in the fortified flakes decreased while histidine decreased in the soy‐methionine formulation. Storage had no effect on the water‐binding capacity of any of the three formulations.