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Pectin potentially can be developed for use as a prebiotic and the effect of pectin on the human faecal microbiota is related to its structure. pH- and temperature-controlled, anaerobic batch fermentation systems with a 5 ml working volume were validated against more widely used fermenters. The relationships between pectin structure and fermentation behaviour were investigated using such systems. Fractions derived from smooth regions (polygalacturonic acid, oligogalacturonides DPS and DP9, methylated citrus pectin and methylated oligogalacturonides), and hairy regions of pectins (oligorhamnogalacturonides, arabinan, oligoarabinosides, galactan and oligogalactosides), together with inulin as a positive prebiotic control, were fermented by human faecal bacteria. Changes in principal gut microbiota components were determined. Bacteroides/Prevotella increased on all substrates tested apart from oligogalacturonides of DPS. Fractions exhibiting a bifidogenic effect were galactan and arabinan type oligosaccharides which were comparable to inulin. To assess whether the arabinose and galactose contents of pectin determined the prebiotic potential of pectin, in vitro batch fermenters of galactose rich (70.6 mole% galactose) and arabinose rich (63.7 mole% arabinose) rhamnogalacturonan type I from potato and apple pulp were carried out and compared with galacturonic acid which was rich in pectins (citrus pectin and polygalacturonic acid). The bifidogenic effect was highest with rhamnogalacturonan type I fractions rich in arabinose and galactose as predicted by above the structure function relationships. Pectins (paS 1, pas 2 and pas TC} were also assessed for their prebiotic potential through in vitro batch fermentation. Methylated homogalacturonan was the major component of pas 1 and pas TC, pas 2 carried 33.7 % w/w arabinose and exhibited the highest arabinose content among the three pass. Bifidobacterial numbers increased with all substrates tested and inulin demonstrated the highest stimulation. Among pass, pas 2 showed the strongest bifidogenic effect which was related to its high arabinose content. pas 2 and inulin resulted in an increase in lactobacilli/enterococci. pass did not show cytotoxicity nor any effect on viability of Caco2 cells following incubation with 0.1-10.0 mg/ml for 24 h. No DNA laddering, as a presumptive indicator of apoptosis, was seen after treating cells with 10 mg/ml pas 1, pas 2 and pas TC for 72 h. In general, pectin has prebiotic potential. Its selectivity toward bifidobacteria can be enhanced by an increased ratio of arabinose and/or galactose per galacturonic acid content.

This thesis reports data on blends of carrageenan (0.3%w/w) and locust bean gum (0.3%w/w) in the presence of biopolymers, particularly gelatin of varying concentration. Particular attention is given to their behaviour on autoclaving since this is relevant to one of the most important applications of these materials as gelling agents in canned meat products. It was shown there is such 3% gelatin could be found in the gelling system as a result of from collagen in the meat. Gelatin at this level generally reduced the strength of non-autoclaved carrageenan and LBG gels but enhanced autoclaved gels. Studies of turbidity and rheology suggested that the effect was due to phase separation. Investigation of viscosity after autoclaving produced evidence to support the hypothesis that gelatin protected LBG from thermal degradation. For industrial LBG this was not, however, observed by direct molecular weight measurement, although such effects were seen for pure LBG. Interesting differences between the gel strength response between low and high ionic strength buffers were found. It was concluded that textural performance in real products was sensitive to a range of factors (salt, impurities, presence of gelatin) and would be interpreted by a combination of degradation and phase separation theory. Implications for the industry are discussed.