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Differential thermal analysis (DTA) of water solutions of polydextrose, κ -carrageenan, NaCl and mixture of sorbitol and sucrose

Initial freezing points Ti of water solutions of polydextrose, κ -carrageenan, NaCl and mixture of sorbitol and sucrose in mass ratio 1:1 were determined by use of differential thermal analysis (DTA). Mass fractions of the dissolved substances in samples determined as percent of total mass were in the range from 0 - 10%. The largest effect of cryoscopic depression on initial freezing point Ti were exhibited by the samples of water solutions: a) NaCl (from - 0.91 to - 6.86 °C), b) κ -carrageenan (from - 0.27 to - 1.26 °C), c) mixture of sorbitol and sucrose in mass ratio 1:1 (from - 0.27 to - 1.03 °C), and d) polydextrose (from - 0.05 to - 0.41 °C). Relations between decrease of the initial freezing point Ti as function of mass fractions w of the dissolved substances were determined by linear regression. Coefficients of determination in a range of R^2 = 0.95 - 0.99 for the samples were obtained. This is a result of the relative molecular mass of the added matter, which according to modified Raoult's Law is inversely proportional to cryoscopic depression of the initial freezing point.

initial freezing point; DTA; water solutions

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