Effect of ultrasound on bovine and ovine skins soaking

Ultrasound as the only mechanical effect in the first soaking of bovine rawhides and goatskins were tested. Three different working systems were used at pilot plant level. In the first work system only the soaking float was subjected to the action of ultrasound. In the second and third systems, both the soaking float and the skin were underwent the same action. In the third system a surfactant was added to the soaking float. The variables analyzed were the water absorbed by the skin and its organoleptic properties, the chemical oxygen demand, the suspended solids, and the conductivity of the wastewater. Through analysis of variance in bovine hides, the influence on the results of the hide part (butt, neck or belly) and the work system employed were compared. Related to the values obtained by performing a comparative soaking on stationary way, the use of ultrasound allowed an increase of up to 23% in water absorption of the soaked skins and up to 49% of COD, 58% of SS and 34% of conductivity in soaking floats. For goatskins, due to their thickness and size, a comparison based on the work system was developed. It was proved that for dried goatskins and one of the tested systems of ultrasound application, the skin becomes saturated with water in 36% less time than if it was soaked on stationary way. With the same soaking time, the ultrasound application showed an increase of up to 16% of water absorption in soaked skins and up to 162% of COD, 87% of SS and 9% of conductivity in soaking floats. In both cases, the results were compared with those obtained when the first soaking was performed on stationary way or in drumming. The results show that the use of ultrasound in the first soaking of the skins is a valid alternative that may be useful, at the industrial level, to replace the working systems where the use of drums is not possible.