In vitro fermentation of different commercially available pectins using inoculum from rabbit caecum

Abstract

In vitro gas production kinetics of eight different commercially available pectin isolates from apple (4), citrus (2) and sugar beet (2), with a degree of methyl esterification (DMet) ranging from 9 to 73%, were determined twice using the mixture of caecum contents of two rabbits of 78 d of age per repetition as inoculum. The cumulated gas production over 60 h of incubation was modelled with the Gompertz model and the estimated and calculated kinetic parameters of each substrate compared. Total potential gas production (B), gas production till 10 h of incubation, maximum fermentation rate (MFR) and time of maximum fermentation rate (TMFR) were affected (P<0.001) by the DMet, but not by the pectin source. Increasing the DMet of pectins increased total potential gas production. The highest B value was determined for Citrus pectin with 72% DMet (Citrus72, 376 mL/g dry matter (DM)), while the lowest for Citrus pectin with only 10% DMet (Citrus10, 289 mL/g DM). Similar trends were also established for the amount of gas produced up to 10 h of incubation, as Citrus72 produced the highest volume of gas (261 mL/g DM) and Citrus10 the lowest (103 mL/g DM). Increasing DMet increased MFR from 9.9 mL/h for Citrus10 to 34.6 mL/h for Citrus72, while TMFR was shortened with the increasing DMet of pectins from 10.3 h for Citrus10 to 6.0 h for both Citrus72 and 60% DMet Apple pectin.