Effect of lactic acid fermentation of wheat and barley whole meal flour on carbohydrate composition and digestibility in mink (Mustela vison)

Summary

Wheat and barley whole meal flours (WMFs) were subjected to treatment by fermentation, autoclaving, and fermentation followed by autoclaving. The WMFs were analysed for chemical composition, formulated into wet diets (282 g kg(-1)) and fed to adult mink (Mustela vison) for determination of total tract digestibility of total starch, total carbohydrate, crude protein and fat. Fermentation of WMF/water mixtures inoculated with a Lactobacillus sp. (strain AD(2)) was performed at 30 degreesC for 16 h. Autoclaving was carried out for 60 min at 120 degreesC. Fermentation increased colony-forming units (CFUs) to about 10(8) g(-1) and lowered pH to 3.7-3.8 in both WMFs. All carbohydrate parameters were affected by type of cereal, and were, except for total starch, affected by treatment. Levels of total dietary fibre and beta -glucans decreased by Fermentation in both WMFs. The decrease in total beta -glucans from 33.5 to 18.4 g kg(-1) in barley WMF, was mainly restricted to the soluble fraction. Glucose levels in barley WMF increased simultaneously from 0.6 to 12.3 g kg-l. The main effects of autoclaving were increased levels of total dietary fibre, maltose, and increased hydration capacity. With fermentation prior to autoclaving, increases in levels of the fibre fractions and maltose were prevented while hydration capacity prevailed as an effect of autoclaving. Compared with fermentation alone, the combined treatment increased damaged starch levels and hydration capacity. Digestibilities of total carbohydrate, crude protein and fat were significantly higher for wheat than for barley. Fermentation had no effect on digestibility of total starch or total carbohydrate of wheat, but increased digestibility of total starch of barley significantly from 0.742 to 0.880, and of total carbohydrate from 0.457 to 0.616. Autoclaving had no significant effect on digestibility of total starch and total carbohydrate of wheat. Digestibility of total starch and total carbohydrate in barley increased significantly after autoclaving. Total starch and total carbohydrate digestibility of both wheat and barley were significantly enhanced by combined fermentation and autoclaving compared with fermentation alone. Compared with autoclaving alone, combined fermentation and autoclaving promoted no significant improvement of total starch and total carbohydrate digestibility in wheat, whereas total carbohydrate digestibility in barley increased from 0.605 to 0.672. Fat digestibility was slightly improved by both fermentation and autoclaving. Autoclaving of cereals reduced significantly the faecal dry matter contents of mink. This effect could be counteracted by preceding fermentation. in conclusion, lactic acid fermentation of wheat and especially barley provided chemical changes of benefit for carbohydrate digestion in the mink. (C) 2001 Elsevier Science B.V. All rights reserved.