Influence of pepsin and trypsin on chemical and physical properties of isolated gelatin from chrome shavings

During the last century, proteolytic enzymes have been used to solubilize collagen. Each enzyme attacks the molecule in a different way; the specificity of each enzyme is already known. After enzymatic digestion, either gelatin or peptides can be obtained from pure collagen. Enzymes have been also applied to gelatin isolation from chrome shavings. In previous work, the effects of different enzymes such as alkaline protease, pepsin, papain, trypsin and chymotrypsin were surveyed, with the discovery that the choice of enzyme had much more influence than the conditions of the experiment. In the current study, pepsin and trypsin, the most promising enzymes from the previous study, were used to study their effects in depth. Chrome shavings were pretreated for 6 to 24 hours with an enzymic solution, at the optimum pH for the enzyme, and at room temperature; only selected bonds were broken. Gelatin was extracted at 70 degrees C; pH 8 was used at this stage to avoid chrome solubilization. Chemical and physical properties moisture, ash, nitrogen, and chrome content, gel strength, viscosity, and molecular weight distribution - were determined for the isolated gelatin. The results were used to compare the effectiveness of both enzymes. Whereas pepsin behaved as a mild enzyme with a controllable effect on leather wastes, trypsin gave a better yield. The isolation of high quality products from wastes will allow a more cost-effective recycling procedure, an incentive to the tanning industry not to dispose of this waste material in landfills.