Effect of sugars on aging of gelatin gels by vacuum-ultraviolet circular dichroism and rheological measurements

Many food products based on gelatin contain sugar. Although the effect of sugars on physical properties of gelatin gels has been intensively investigated, aging of gelatin gels containing sugars has not been studied in detail. In the present study, vacuum-ultraviolet circular dichroism (VUVCD) was applied to the study of the aging of gelatin gels with and without sugars and the aging process measured by VUVCD was compared with that measured by rheology and polarimetry. The storage modulus G’ and reduced ellipticity θ/θ0 in the aging process were correlated with each other, indicating VUVCD is a useful tool for detecting the conformation change of gelatin molecules. On the other hand, the behavior of optical rotation Δα was different with that of either G’ or θ/θ0, suggesting that the optical rotation does not represent the conformation change accurately in the case of gelatin gels containing sugars. The relationship between G’ and a fraction χ of helix amount estimated from VUVCD data showed that the critical helix fraction χc for gelation is slightly increased by the addition of sugars, suggesting a change in the network structure.