Colloid chemistry approach to understand the storage stability of fermented carrot juice

Probiotic-fermented carrot juice (PFCJ) is a functional food, for which colloidal stability during storage is essential. The water-soluble polysaccharides (WSPs) it contains provide this stability as colloidal stabilizers; they are pectinic, mainly containing galacturonic acid, galactose and arabinose as monosaccharide units. The particle-size distribution, ζ potential, centrifugal sediment ratio, soluble solids content, total acid and structural features of these WSPs were evaluated as functions of storage time. The PFCJ displayed pseudoplastic fluid behavior. Molecular weight and solid morphology of WSPs did not change significantly with storage, although the molecular weights of WSPs showed a slight decrease. The storage stability is ascribed to its WSPs acting as electrosteric stabilizers (which are very robust colloidal stabilizers) by adsorbing onto the insoluble plant cell wall polysaccharides which comprise the dispersed phase in the suspension. Viscosity and particle size remained relatively stable when stored at 4 °C and 25 °C, while centrifugal sediment ratio, soluble solids content and total acid all increased significantly; these can also be explained in terms of the structure of the WSPs. This can provide guidance to choosing ingredients which improve storage stability and other properties of importance to consumers by using the precepts of electrosteric colloidal stabilization: e.g. the presence of water-soluble polysaccharides with long hydrophilic moieties.