Diffusion of sucrose and aspartame in kappa-carrageenan and gellan gum gels

In the process of sweetness release from the food to the human papillae, diffusion of the sweetener through the food is one of the steps. Information on diffusion behaviour of small molecules like sucrose has been studied mainly in connection with blanching or osmotic processes. In this paper, diffusion constants (D) of both sucrose (100 and 150 g/l) and aspartame (0.8 and 1.2 g/l) in model systems—kappa-carrageenan and gellan gum gels at two different concentrations—have been determined at 37°C (mouth temperature). Mean D values for sucrose (5.9–7.3×10−10 m2 s−1) and for aspartame (6.1–7.7×10−10 m2s−1) in soft kappa-carrageenan gels were significantly higher than in the other gels (3.8–5.1×10−10 m2s−1 for sucrose and 3.9–5.9×10−10 m2s−1 for aspartame). Higher concentrations of sweetener detected in the diffusing medium in the case of soft kappa–carrageenan gels could be partially affected by incipient melting of the gel. Upper values in these ranges corresponded to higher initial sweetener contents.