Chemical modification of protein products isolated from chromium-containing solid tannery waste and resultant influence on physical and functional properties

Samples of gelatin extracted from chromium-containing leather waste by diff erent protocols were chemically modified with glutaraldehyde, glyoxal and c arbodiimide and compared to similarly modified commercial gelatins. Glutara ldehyde appeared to be a very efficient cross-linker, giving gels that woul d not melt at 70 degrees C with the addition of only 2% glutaraldehyde but with a decrease in their rigidity when the amount of glutaraldehyde was inc reased. Foaming tests on these samples demonstrated that the addition of lo w amounts of glutaraldehyde increased both the foam capacity and the foam s tability of the gelatins. Glyoxal modification did not have such an effect on the gel strength and melting point of the samples. It did not increase f oam capacity but did increase foam stability, it gave better adhesive prope rties to these gelatins and it did increase dramatically their emulsificati on capacity. Carbodiimide had similar effects on gel strength as glyoxal; i t did increase dramatically the melting point of commercial gelatin but had no effect on the melting point of the extracted gelatins. It decreased the foam and adhesive properties; of all the samples, but it did increase the emulsification capacity of the extracted gelatins. The study demonstrates t hat the functional properties of chemically modified gelatin extracted from chromium-containing leather waste were changed, and, as a result, new uses could be identified for these value-added products.