Physico-chemical properties of purified starch affect their in vitro fermentation characteristics and are linked to in vivo fermentation characteristics in pigs

Abstract

Fermentation characteristics and short-chain fatty acid (SCFA) production of purified starch sources differing in physico-chemical properties and in vitro digestion kinetics were investigated using an in vitro porcine model. Four starch sources (rapidly digestible, RD; moderately rapid digestible, MRD; moderately slow digestible, MSD; and slowly digestible, SD) were used. These starch sources were previously fed to growing pigs to determine their net portal appearance (NPA) of SCFA and glucagon-like peptide-1 (GLP-1) and fecal SCFA. Samples were incubated in a buffered mineral solution inoculated with pig feces. Gas production was measured for 72 h and fermentation kinetics were modeled. The fermented solution was analyzed for SCFA at the end of the fermentation. The SD had the greatest (P < 0.05) lag time (2.7 h) while RD to MSD did not differ (mean 2.3 h). Total gas production was greatest (P < 0.05) for MSD (239 ml/g sample) followed by RD, MRD, and SD (236, 226 and 219 ml/g sample, respectively). The fractional rate of degradation was greatest (P < 0.05) for RD (0.19/h), intermediate for MRD and MSD (0.17/h) and lowest for SD (0.11/h). Starch types did not differ (P = 0.749) in total SCFA production (5.8–6.0 mmol/g sample). Amylose content and crystallinity of starches was correlated to in vitro fermentation kinetics, total gas production, and SCFA profile. For example, fractional rate of degradation was negatively correlated with amylose content (r = −0.90, P < 0.001). Butyrate content from starch fermentation was associated with increased in vitro fractional rate of degradation and total gas production and in vivo fermentation metabolites and NPA of SCFA and GLP-1. In conclusion, physico-chemical properties and in vitro digestion kinetics of starch affect in vitro fermentation characteristics and SCFA production and are associated with NPA of SCFA and GLP-1 in pigs. Thus, the in vitro fermentation model can serve to screen starch sources to determine their fermentation characteristics in pigs.