Interactions between alginates and pectins
Mixtures of pectins with other polysaccharides such as alginate has found that good gels are formed from high methoxy pectin and guluronic rich alginates. A pH above 4 also hinders the gel formation. This finding, with the added evidence of low methoxy pectin gelation with alginate at very low pH, indicates that the chains must be sufficiently charge neutralised before interaction can occur, and that esterification is required only to reduce electrostatic repulsion. These mixed systems work well with cold setting conditions.
Interactions between pectins and proteins
Understanding interactions between pectins and proteins is thought to be central to developing satisfactory food texture. Mixtures of proteins and polysaccharides are prone to incompatibility or undesirable complex formation. However, due to the number of interactions possible with pectins, there are many opportunities to explore different systems. One such system sees LM pectin interacting with poly-L-lysine. In pectins with a DE of 36%, strong gels crosslinked by physical bonds with the protein were obtained at pH’s close to neutrality. These clear, elastic gels had controlled increase in gel strength with added crosslinker up to an optimum. Excess protein caused increased opacity and eventual network collapse. Poly-L-lysine also serves to control network swelling. As with some hydrocolloids, chain length of the protein was found to have an optimum value, which may correspond to the different regions of the pectin molecule.
Interactions with other polymers
Interactions with other hydrocolloids has been studied in depth recently. Gel formation of LM pectins with guar, locust bean gum, oxidised starch, potato maltodextrin and gum arabic have shown there to be specific interactions between polysaccharide complexes. Complex formation between gum arabic and LM pectin (DM 31) was found to be enhanced when there was specific spatial compatibility between the HG areas of the pectin and the gum arabic fibrils. These interactions were found to be non-ionic and were more likely a hydrophobic association and stabilisation which resulted in differing gel properties. Branched hydrocolloids caused faster destabilisation of calcium induced LM pectin than linear polymers. This takes into account the interactions of branched regions in pectins with other branched regions, interactions that are highly hydrophobic and non-ionic.
Additional information on pectin can be accessed using the arrows in the Further Reading box below.