Influence of crosslinkers and crosslinking method on the properties of gelatin films extracted from leather solid waste

Gelatin was extracted from chrome tanned leather waste with the aim to produce a durable coating or film. Crosslinking has shown to improve the physical performance of a film/coating. The effect of the method of crosslinking and the use of different crosslinking agents were studied. The extracted gelatin was crosslinked either by immersion of preformed films into a crosslinker solution (Method A) or by the addition of the crosslinking reagent to the gelatin solution prior to film formation (Method B). The different results obtained between both methods may be due to: the relative concentration of crosslinking reagent, the introduction of crosslinks within different regions of gelatin (triple helical regions and random coil regions), and the reaction rate. Method A of crosslinking is more likely to form crosslinks outside but close to the triple helical regions, disrupting the order and stability of the helical structure. Crosslinks may form preferentially within the random coil regions when Method B of crosslinking is used. Both methods led to the formation of chemical crosslinks in the extracted gelatin films, as demonstrated by the reduction of the degree of aqueous swelling and the proportion of low molecular weight fractions