Dietary Fibre in Fermented Oats and Barley
Sammanfattning: The physiological characteristics of native and bacterial exopolysaccharides (EPS) in oats and barley-based fermented products were studied in relation to the physico-chemical properties. Article I presents a parallel-randomized double blind clinical trial using a dairy-based product (control), an oat-based product (fermented with V2, which is a mixture (1:1) of Lactobacillus delbrueckii subsp. Bulgaricus and Streptococcus salivarius subsp. Thermophilus / Lactobacillus acidophilus) and a ropy, oat-based product (fermented with V2/ Pediococcus damnosus 2.6 (Pd)). The total cholesterol level in subjects fed the ropy, oat-based product was significantly reduced from 6.08 mmol/L to 5.82 mmol/L (4.3 %), P = 0.007 and this decrease differed significantly (6 %, P = 0.022) from the value obtained for the group fed the dairy-based (control) product. A drop of 5.5 % in LDL-cholesterol was also observed as compared with the run-in value in the group fed ropy, oat-based product. In article II, the ability of different lactic acid bacteria to influence the physico-chemical characteristics (content, viscosity and molecular weight) of dietary fibre in ?-glucan rich barley and oat concentrates was investigated. Two methodologies, one including filtration and another centrifugation-dialysis, to quantify the dietary fibre, were compared. The centrifugation-dialysis method generally resulted in significantly (P < 0.05) higher values than the filtration method with the exception of soluble barley fibres. The insoluble fibre content was found to decrease after fermentation. The maximum viscosity of the soluble fibre in oat fibre concentrates decreased after fermentation. However, the molecular weight was apparently not affected.In article III, the molar mass and rheological properties of an exopolysaccharide (EPS) from Pediococcus damnosus 2.6 were investigated. The EPS was observed to be a flexible chain polymer with molar mass, 4.0 x 106 gmol-1. Rheological behaviour of the EPS was compared to that of a commercial cereal ?-glucan (0.359 x 106 gmol-1). The maximum storage modulus G´max for EPS solution was lower than that for the cereal ?-glucan at all concentrations while the relaxation time, trelax was higher.In article IV, short-chain fatty acid (SCFA) formation in rats fed fermented oat fibre concentrates was compared with that of rats fed native oat fibre concentrate. All the fermented fibre concentrates resulted in a higher propionic acid concentration in the distal colon (P<0.05), while rats fed Pd fermented fibre concentrate gave lower concentration of butyric acid (P<0.05, P<0.01) in all parts of the hindgut as compared with rats fed the native fibre concentrates. The fermented fibre concentrates seemed to favour the formation of acetic and propionic acid, while the native fibre concentrate favoured the formation of butyric acid.
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