Résumé : |
The objective of this study was to evaluate the resistance of bullfrog skin, Lithobates catesbeianus, tanned with chromium salts and vegetable tannin. We also checked the influence of chemicals on the skin during the beamhouse operations. We adopted a completely randomized design for the resistance test, in a 22 factoriel arrangement: two tanning agents (vegetable tannins and chromium) and two cutting directions (longitudinal and transverse). Skin semples were collected during the beamhouse operations (soaking, liming, deliming, bating and degreasing) and analyzed for moisture, crude protein, ether extract and minerai matter. The tensile strength and elongation test, the results revealed that there was an interaction between factors (tanning agent and direction) for strength and tensile strength, indicating that both are important for best results of resistance. On the other hand, for progressive tearing tests, only the tanning agent was significant, chromium salts being the most efficient. The composition analysis showed that there was little variation in the amount of lipids during processing and there is no need for degreasing, because the skin of frogs has a low fat content which is removed in previous stages of processing. |