Changes in lipid, fatty acids and protein composition of sweet potato (Ipomoea batatas) after solid-state fungal fermentation

Sweet potato-root meal was fermented with three fungal species, Aspergillus niger, Aspergillus oryzae and Pleurotus ostreatus using solid-state fermentation. The changes in total lipid, fatty acids and total protein composition were determined at specific intervals during the study. The total lipid of sweet potato fermented with A. niger and A. oryzae increased from 1.93% to 3.17% and 1.93% to 8.71% respectively, while it decreased on P. ostreatus from 1.93% to 0.54%. The fatty acid composition of the fermented tuber showed C18:2 and C16:0 to be the most predominant. Protein contents of fermented sweet potato increased significantly above the unfermented samples, and protein enrichment was highest with A. niger, followed by A. oryzae, and lowest on P. ostreatus. This study demonstrated that solid-stale fermentation of sweet potato with A. niger and A. oryzae increased the lipid and protein contents, both of which are limiting nutrients. Overall, A. niger appeared to be the best of the three fungi studied, and it appeared that P. ostreatus was not useful for the current purpose. (C) 1999 Elsevier Science Ltd. All rights reserved.