Experimental study and modelling of gelatin production from bone powder: elaboration of an overall kinetic scheme for the acid process

Abstract

This paper deals with the production of gelatin by acid extraction from animal bones. Experimental data show that during the extraction the “extraction yield” and the mean molecular weight reach a maximum and then decrease, which is attributable to chain degradation. The purpose of this paper is to establish a kinetic scheme that can be included in a global process model able to predict both the yield and the quality (molecular weight) of the gelatin produced. We propose an experimental study of the extraction from hard bones for different particle sizes at 75 °C and pH 2.25 and an interpretation of the results by means of the shrinking core model: it is shown that the kinetic limitations are chemical ones and a kinetic constant is computed. A detailed study of the influence of temperature and pH on extraction and degradation (60–85 °C, pH 1.75–2.50) is then presented. A model is proposed: gelatin products are represented by four classes, and the kinetic laws for extraction and degradation are determined; parameters are computed from experimental data. The overall kinetic scheme can predict the main trends observed for acid production of gelatin and can be included in a process model.