Biochemical and microbiological properties of a cereal mix fermented with whey, wet wheat distillers' grain or water at different temperatures

摘要

Microbiological and biochemical properties of three different liquid diets fermented at 10, 15 or 20pC were studied. The liquid diets consisted of a cereal grain mix of wheat, barley and triticale, blended with whey (diet WH), wet wheat distillers' grain (diet WDG) or water (diet WAT). The diets were fermented for 5 days without disturbance, followed by 14 days of daily feed replacements, where 4/5 of the contents were replaced with fresh feed mixtures. Starting pH values were 5.1, 3.9 and 6.3 in WH, WDG and WAT, respectively. For most diets, the pH decreased to approximately 4.0 by day 5. However, the WAT diet fermented at 10pC required 7 days to reach a pH of 4.0. A higher (P<0.001) pH was seen in the WH diet fermented at 10pC than in the other diets. Composition of the diets was determined during day 17-19 of fermentation to allow the microbial populations to stabilise and to reflect conditions in practice. Lactic acid bacteria (LAB) grew in all diets during fermentation and the growth was affected by temperature and type of diet (P<0.001), and the interaction between these two factors (P<0.001). The highest LAB counts were found at higher temperatures in the WAT and WH diets and the lowest counts were found in diet WDG. The highest levels of acetic, succinic and propionic acids were found in diet WDG (P<0.001). Lactic acid concentrations increased with temperature (P<0.001) and were highest in the WAT and WH diets. In vitro digestibility of organic matter was highest for diet WH and lowest for diet WDG (P<0.001). Inositol hexaphosphate-bound phosphorus (P) and total P in the cereal grain mix were 2.2 and 3.7gkgp# dry matter, respectively. No inositol phosphate-bound P was found in any of the diets after fermentation. Some moulds, probably originating from spores in the cereal grain mix, were detected in the fermented diets, but total numbers did not increase with time. Enterobacteriaceae detected in diet WH, probably originated from the cereal grain mix and the whey. Yeasts were present in all diet ingredients. In conclusion, fermentation processes and biochemical properties differed greatly due to temperature, type of diet and the interaction of these two factors. Dietary inositol hexaphosphate was completely degraded in all fermented diets.