Steam explosion as pretreatment to increase gelatin extraction yield from chromium tanned leather wastes

Abstract

Alkaline hydrolysis of chromium tanned leather wastes (CTLW) is a promising process that allows turning this waste into valuable materials, especially into protein, recovered as gelatin. Steam explosion, which is a fast, chemical‐free, and efficient process, was tested in this work as a pretreatment to open up the fibrous structure of CTLW and ease gelatin extraction through subsequent alkaline hydrolysis, increasing the process yield. Two steam explosion temperatures (130 °C and 150 °C) and residence times (5 and 15 min) were tested. The gelatin extracted in aqueous medium was characterized according to its dry mass content, ash content, viscosity, protein content, chromium content, and helix‐to‐coil transition temperature. CTLW steam exploded in more aggressive conditions (150 °C, 15 min) allowed the extraction of three times more protein when compared to CTLW without any pretreatment. However, samples treated at 150 °C produced lower‐quality (partially degraded) gelatin. Steam explosion performed at 130 °C for 15 min almost doubled protein extraction and resulted in a better quality gelatin. This is a promising process for the proper use of CTLW as raw material for the production of high added‐value products. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 367–373, 2019