Soluble fibre concentration effects during in vitro fermentation: Higher concentration leads to increased butyrate proportion

• Published in: Food hydrocolloids 2022-09, Vol.130, p.107728, Article 107728
• Main Authors: Yao, Hong, Williams, Barbara A., Flanagan, Bernadine M., Lisle, Allan, Mikkelsen, Deirdre, Gidley, Michael J.
• Format: Article
• Language: English
• Subjects: Concentration; Dietary fibres; Functional property; Gas kinetics; Short-chain fatty acids
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2022.107728

Dietary fibre (DF) fermentation outcomes are often thought to be based on their chemical structure and molecular weight, but less is known about concentration effects. In this study, two oligosaccharides: raffinose (Raff), fructo-oligosaccharides (FOS); and two polysaccharides: β-glucan from oats (BGlu) and pectin from apple (Pect), at different concentrations (0.1, 0.2, 0.3 and 0.4 g/43 mL bottle), were subjected to in vitro batch fermentation using a pooled human faecal inoculum. The DF type and concentration effects on the fermentation properties of these DF were investigated. Results showed that DF types had no obvious effects on the total gas volume, maximum rate of gas production, total short chain fatty acid (SCFA) or ammonia concentration, although polysaccharides took longer to reach maximum gas production. Higher DF concentration led to higher total gas volume, total SCFA concentration, maximum rate of gas production and time to reach maximum rate, but lower ammonia concentration. The most interesting observation was that for all DF, while the total SCFA concentrations increased linearly with DF concentration, the proportion of butyrate increased significantly as the DF concentration increased. It was hypothesised that increased butyrate was because of acetate to butyrate conversion, via butyryl-CoA:acetate-CoA transferase, but a further in vitro fermentation experiment using different concentrations of FOS and Pect, (0.2 and 0.4 g/bottle) with the addition of sodium acetate did not show enhanced butyrate production. It is concluded that concentration is a critical functional property of DF as it is closely related to fermentation kinetics and outcomes, particularly butyrate proportion. [Display omitted] •DF concentration and chemistry both affected fermentation outcomes.•Higher DF concentration led to lower proportion of acetate concentration.•Higher DF concentration led to higher proportion of butyrate concentration.•Butyrate proportion was not increased by addition of acetate to medium.