In vitro fermentation assessment of germination and reconstitution processing for different sorghum grain types

Abstract

The effects of controlled germination and reconstitution processes on fermentability of sorghum grain were investigated using an in vitro fermentation technique. Twenty-two sorghum grain types obtained from the University of Sydney Plant Breeding Institute, Narrabri, NSW Australia, were either dry rolled, reconstituted for 21 d (anaerobic storage) or germinated for 5 d. Grains were then rolled and incubated in buffered rumen liquor, and volatile fatty acid (VFA) production after 5 h was determined. Germination capacity (percent of grains that sprouted after 3 d) and water uptake after soaking for 24 h were also measured to determine their relationship with VFA production from germinated or reconstituted grains. Grain type and processing treatment significantly (P<0.001) affected the fermentability of sorghum grain and there was a significant level (P<0.001) of interaction between these factors. VFA production ranged from 44-69 mmol/L for germinated grains and 36-55 mmol/L for reconstituted grains, and both treatments gave significantly (P<0.05) higher VFA production than VFA production from dry rolled grains (20-28 mmol/L). Fermentability of germinated grains was higher than that of reconstituted grains for all except five grain types. Germination capacity and water uptake were significantly (P<0.001) affected by grain type and ranged from 3-97% and 33-41%, respectively. Germination capacity was significantly (P<0.001) and negatively correlated with water uptake (r = -0.81). VFA production was positively correlated with germination capacity (r = 0.92; P<0.001) but negatively correlated with water uptake (r = -0.80; P<0.001). For reconstituted grains, VFA production was neither correlated with germination capacity (r = -0.06, P= 0.80) nor with water uptake (r= 0.27, P=0.23). It was concluded from this study that controlled germination processing improved the fermentability of sorghum grain more than the conventional method of reconstitution, and the level of response to germination or reconstitution wasdependent on grain type.