MODELING THE GELLING BEHAVIOR OF LINSEED POLYSACCHARIDE - EFFECT OF SALTS AND PH

The rheological properties of linseed polysaccharide gels in the prese nce of citric acid, calcium and magnesium carbonates were studied usin g a factorial design and the Herschel-Bulkley model. The yield stress and consistency index increased with the concentration of calcium and magnesium ions, while the flow behaviour index decreased, imparting st ability to the gel. With citric acid, sigma(o) and k reached a maxima and then decreased, while n increased after an initial dip. The effect of pH (3.4-9.3), sucrose (45-55%), and polysaccharide (0.6-0.8%) on t heological constants were modelled using polynomials where up to fifth power of pH was required. Ln(sigma(o)), In(k), and n were fitted to t he standardised (normalised)forms of pH, In (sucrose) and In (polysacc haride) with multiple correlations of 0.95, 0.97 and 0.98, respectivel y. The two optima (with pH) were computed using Nelder and Mead's flex ible polyhedral search method. Both required 55% sucrose and 0.8% poly saccharide with pH of 4.3 and 7.3, respectively. The models at the two optima are discussed through 3-D graphs. The technological implicatio ns of the dual optima have been indicated This is, probably, the first report where two optima, with pH, have been observed for a gel formin g polysaccharide.