Enrichment of barley grain in some biologically active molecules by microbial fermentation and their characterisation by infrared spectroscopy

Abstract

A FTIR-ATR coupled to chemometry method was first-ever tested in monitoring the effects of a range of bacterial, yeast and fungal fermentations on nutrient and chemical composition of barley. Chemically analysed contents of samples taken at 24 h intervals were predicted by a partial least square regression (PLSR) model. Moreover, secondary protein components (SPC) of barley protein were measured by a Gaussian curve fitting of amid I spectral region. The results showed that crude ash content of barley increased significantly in Aspergillus oryzae+Bacillus subtilis fermentation and crude protein content in Lactobacillus salivarius fermentation. Organic acid content (especially lactic acid) increased in all fermentations of barley with bacteria, fungal and yeast, while crude fiber and anti-nutritional contents such as phytic acid and tannin decreased. On the other hand, PLSR model based on second derivate spectral data has highly acceptable performance characteristics in predicting protein, ash, fibre, lipid and starch: low RMSEV (root mean squared error of calibration) of 0.0003–1.24 with r2 = 0.999 and RMSECV (root mean squared error of cross validation) of 0.004–1.88 with R2 = 0.988, high recovery rate (closeness to analysed value) of almost 100.0, high precision VCp% (variance coefficient of prediction) of less than 5.0% and RPD (relative performance determinant) values of over 2.0. Barley protein was seen to be subjected to a useful hydrolysis, degradation and aggregation of microbial fermentation, as measured in SPC percentages. The decreased percentages of β-sheet, α-helix components and random coil associated with increased percentage of β-turn component is more likely an indication of improved protein quality. We recommended the model employed herein is robust and can replace the analytical methods of wet chemistry in feed analysis in nutritional studies and in routine analysis by the industry to monitor in line fermentation processes.