THE FLUORESCENCE OF GELATIN AND ITS IMPLICATIONS

In a study designed to elucidate the origin of the variance in the col our of Type B gelatin from bovine hide it was found that there was a s trong correlation between gelatin colour and animal age. Based on the many publications on the nonenzymic (Maillard reaction) cross-linking of collagen, that is, the formation of the pentosidine cross-link, it teas proposed that this in vitro reaction could be the basis for the i ncrease in gelatin colour with animal age. Gelatins derived by a stand ardized process from the hide of animals of known biological age were submitted to fluorescence analysis and it was shown that Type B gelati n exhibited pentosidine (335/385 nm) fluorescence and the intensity of the fluorescence was well correlated with animal age and gelatin colo ur. Type A calfskin gelatin, on the other hand, exhibited both the pen tosidine and the pyridinoline cross-link (295/395 nm) fluorescence whi ch confirmed that the pyridinoline cross-links were alkali labile. Pal e gelatin was incubated with glucose or ribose and the expected increa ses in pentosidine fluorescence and colour formation were observed. In the case of ribose, the mixture eventually gelled, confirming the for mation of cross-links, however, the chromophore produced was not ident ical to the natural chromophore in gelatin. With glucose incubation, t he chromophore was the same as the natural chromophore, thus confirmin g that the colour of gelatin was probably the result of the Maillard r eaction in vivo with glucose as the carbohydrate involved. The stabili ty of the pentosidine cross-link to both alkaline and thermal processi ng would be of significance for both the tanner and the food scientist . To the gelatin manufacturer it explains the variation in gelatin col our with animal age and also the reducing susceptibility of bovine hid e to alkaline conditioning with animal age.