Screening of probes for specific localisation of polysaccharides

Polysaccharides can be used as gelling or stabilising agents in foods. In order to investigate how polysaccharides affects the rheology and sensory characteristics of foods, an in situ method for direct localisation is required. The aim of this study was to investigate the specificity and stability of the monoclonal pectin antibody JIM7, anti-carrageenan polyclonal antibody and the lectins wheat germ agglutinin (WGA) and concanavalin A (ConA). An enzyme-linked immunosorbent assay (ELISA) was used to test the affinity of these probes for compounds frequently found in dairy products. The compounds chosen were pectins, carrageenans, galactomannans, starches, exopolysaccharides (EPS), alginate, xanthan gum, gelatine and skimmed milk powder. The impact of exposure to low pH, 0-2% salt and 0-40% sugar on the antigen-binding activity of the probes was tested. The results showed that WGA bound specifically to chitosan and hetero-EPS at neutral pH, and while ConA bound strongly to hetero-EPS, it also exhibited various degrees of affinity for all the other hydrocolloids tested. However, the ability of the investigated lectins to bind to hetero-EPS almost disappeared under conditions similar to those in yogurt. JIM7 was very stable and highly specific for pectins, also under conditions similar to those present in yogurt. The polyclonal antibody was very stable and displayed potential as probe for all the polysaccharides tested. Due to the broad specificity, however, the identity of the polysaccharides present must be known. Confocal laser scanning microscopy (CLSM) images using the probes for specific localisation of pectin and carrageenan in dairy products are shown.