Rotational and Translational Mobility of Small Molecules in Sucrose plus Polysaccharide Solutions

• Published in: Journal of agricultural and food chemistry 2000-04, Vol.48 (4), p.1009-1015
• Main Authors: Contreras-Lopez, Elizabeth, Champion, Dominique, Hervet, Hubert, Blond, Geneviève, Le Meste, Martine
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Dextrans - chemistry; Diffusion; Fluorescein - chemistry; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; Glucans - chemistry; Gum Arabic - chemistry; Methods of analysis, processing and quality control, regulation, standards; Polysaccharides - chemistry; Solutions; Sucrose - chemistry; Thermodynamics; Viscosity
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf990816n

The effect of different polysaccharides on the rotational (D rot) and translational diffusion (D trans) coefficients of small molecules in concentrated systems (sucrose solutions) was investigated. Dextran (1 or 10% w/w) with different molecular masses (from 104 to 2 × 106 Da), gum arabic, or pullulan was added to solutions of sucrose (57.5% w/w). Viscosity measurements of the diffusion medium studied (sucrose and sucrose plus polysaccharide) were made using a Rheometric Scientific viscometer in a temperature range from 20 to −10 °C. The rotational mobility of nitroxide radicals (Tempol) dispersed in the concentrated systems was measured by electron spin resonance. The translational diffusion coefficient of fluorescein was determined by the fluorescence recovery after photobleaching method. The studied temperature range for the latter two techniques was from 20 to −16 °C. For these conditions of concentration and temperature, there was no ice formation in the samples. No effect of the molecular mass of dextran on D rot and D trans was observed when solutions with the same dry matter content were compared. Only pullulan and gum arabic, at 10%, had a significant effect on D trans of fluorescein. Temperature and total dry matter content were observed to be the most important factors controlling D rot and D trans in these concentrated systems. Keywords: Polysaccharide; sucrose; rotational and translational mobility; diffusion coefficient; subzero temperatures