Heteropolysaccharides samples

Ash et al. (1983) studied the chemical stability of xanthan and one novel heteropolysaccharide which they do not identify. They note the earlier findings of Davison and Mentzer (1980), who observed less than 30% loss in viscosity over 500 days at 90 "C in sea water, and the results of Sutherland et al (1986), who found little loss in viscosity at 112" C in 6% brine over 42 days. Ash et al (1983) found considerable variation in stability of xanthan products obtained from different sources. They, like other workers, noted an increase in viscosity over the first few days of the test which has been ascribed to delayed hydration of the polymer. They also noted that the stability of one of the xanthan samples depended strongly on the salinity of the test brine as shown in Figure 4.8. The data in Figure 4.8 refer to stability at 70°C, but a similar pattern is found at 90°C. This increased stability with increasing salinity gave one clue to one of the physical factors which may influence stability—namely the order-disorder (or helix-coil) transition, as... 

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