In vitro gas production profiles and fermentation end-products in processed barley, maize and milo

Abstract

BACKGROUND: An experiment was carried out to establish whether using a pre-compacting device (expander) changes the contribution of dry matter (DM) and degradative behaviour of grains of barley, maize and milo pre-processed by grinding over the different DM fractions (non-washable (NWF), insoluble washable (ISWF) and soluble washable (SWF) fractions). Samples of the entire concentrate ingredients (WHO ingredients) and their different fractions (NWF, ISWF and SWF) were subjected to three processes (Retsch-milled (R), expander-treated (E) and expander-pelleted (EP) samples) and their fermentation characteristics were evaluated using an in vitro gas production technique. RESULTS: The E process increased the size of the NWF and decreased that of the SWF compared with the R process. The ISWF of R samples was very rich in starch. The maximum fractional rate of substrate degradation and maximum rate of gas production were higher in EP samples than in R samples (P < 0.05). In maize and milo the E and EP processes shifted the pattern of fermentation towards a more glucogenic fermentation, as represented by a lower non-glucogenic/glucogenic ratio (NGR). In all grains the ammonia concentration (NH3-N) and branched chain ratio (BCR) of E and EP samples were significantly (P < 0.05) lower than those of R samples. CONCLUSION: It is concluded that the E and EP processes have the potential to synchronise the fermentation of dietary proteins and carbohydrates and shift the pattern of fermentation towards a more glucogenic fermentation. © 2009 Society of Chemical Industry.