Dietary fibre in fermented oat and barley β-glucan rich concentrates

The ability of different lactic acid bacteria to influence the physicochemical characteristics (content, viscosity and molecular weight) of dietary fibre in β-glucan-rich barley and oat concentrates was investigated. The cultures used were Lactobacillus acidophilus and the exopolysaccharide producing strain Pediococcus damnosus 2.6, together with the yoghurt culture, V2 (a mixture (1:1) of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus). Two methodologies, one including filtration and another centrifugation-dialysis, to quantify the dietary fibre, were compared. The centrifugation-dialysis method generally gave significantly (P<0.05) higher values than the filtration method (for example, 79.8 g/100 g DW versus 59.6 g/100 g DW for the total fibre in the native barley fibre concentrate) with the exception of soluble barley fibres. The insoluble fibre content was found to decrease after fermentation (58.8 g/100 g DW to 39.0/37.0 g/100 g DW in barley and 26.0 g/100 g DW to 4.5/3.0 g/100 g DW in oats as analysed by the centrifugation-dialysis method). The soluble fibre in the barley fibre concentrate was apparently not affected by fermentation, while contents and maximum viscosities of the soluble fibre in oat fibre concentrates decreased after fermentation. However, the molecular weight was apparently not affected.