Resistance of Nile tilapia leather subjected to pickling with different salt concentrations and exposure times of skins in salt-free water

Resumo

The skins discarded during the filleting process, when subjected to an appropriate tanning process, can be transformed into high-quality leather. Thus, the objective of this study was to analyze the effect of salt concentration and acid swelling as a function of the exposure time of Nile tilapia skins acidified in salt-free water. To this end, three tests were conducted: Test I – Evaluation of pickled skins; Test II – Evaluation of the effect of salt concentration in the pickling stage; and Test III – Evaluation of the effect of pickled skins at different exposure times in salt-free water. The removal of acidified skins to salt-free water promotes acid swelling, which can significantly reduce the leather’s resistance, tear strength, elongation, and tensile strength. A salt concentration below the recommended level leads to acid swelling, while an excessive concentration prevents proper tanning, resulting in collagen fiber densification. Regarding the exposure time of skins in salt-free water, significant losses in their properties were already observed after ten minutes. It is concluded that salt is essential in the pickling stage, requiring a Baumé degree of 7. Skins should not be exposed to a salt-free solution to prevent acid swelling, which compromises their resistance quality. Exposure to salt-free water can reduce elasticity, tensile strength, and progressive tearing, regardless of the exposure duration.