Utilisation of model pectins reveals the effect of demethylated block size frequency on calcium gel formation.

Calcium-mediated gelation of LMP is thought to arise from formation of a dense network of Ca(2+)-cross-linked DMB meeting a required minimum average length along pectin chains. The use of MP containing specific average DMB size (BS) types, in the range of 3-100 and in varying proportion (0-100%), has afforded further insights into the gelling behaviour of pectins with a certain DM in the presence of Ca(2+) ions. It clearly appeared that a required minimum BS and a required minimum average frequency (BSF) of the required minimum BS are conditions that must be satisfied by a pectin for formation of a highly dense Ca(2+)-cross-linked DMB network equaling an elastically stable, strong, and cohesive gel. Furthermore, there is a clear contribution of the pectin branched domains to gelation and formation of a firmer and more cohesive gel. The results suggest that this pectin portion may function, not only as a "maintainer" of the pectin molecular weight to a sufficiently high level which fosters good gelation regarding the gelling rate and the strength and nature of the gel formed, but also as junction-zone-terminating structural elements that limit the appearance of undesirable phenomena, notably turbidity, syneresis, and precipitation.