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

[EN] 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.