Effect of fermentation on protein fractions and in vitro protein digestibility of maize

Changes in pH, titratable acidity, total soluble solids and protein of maize during natural fermentation at 37 degrees C up to 36 h were monitored. The pH of the fermenting material decreased sharply with concomitant increase in the titratable acidity. Total soluble solids increased with progressive fermentation time. The crude protein and non-protein nitrogen increased during the first stages of fermentation. The in vitro protein digestibility markedly increased as a result of fermentation. The globulin and albumin fraction increased significantly (P less than or equal to 0.05) during the first 16 h of fermentation. The zein fraction was the major protein fraction, which decreased during the first 16 h of fermentation but increased sharply with progressive fermentation. G(1)-glutelin increased during the first 16 h but fluctuated thereafter. The G(2)-glutelin, which is the minor fraction and G(3)-glutelin the second most abundant fraction, together with insoluble protein, fluctuated during the fermentation process. The results indicated that natural fermentation of corn significantly improves in vitro protein digestibility. (C) 2000 Elsevier Science Ltd. All rights reserved.