Kinetic Evaluation of Gelatin Extraction From Chicken Skin and the Effect of Some Extraction Parameters

Abstract

Kinetic models have been extensively studied for the prediction of yield and quality for plant-sourced ingredients although that is very rare for animal-sourced products. This study is designed to evaluate common kinetic models for the prediction of yield in gelatin extraction from chicken skin. Kinetic models used for comparison were the Peleg's, the first order, and the rate law models while extraction parameters studied were solvent pH, solid:liquid ratio, and sample size. Extraction is evaluated based on the protein and hydroxyproline (Hyp) concentrations of each extract. The success of the models is evaluated based on the root-mean-square error (RMSE) and the coefficient of determination (R-2) values calculated for fittings of the models to the experimental data. The protein content of the dried and degreased skin was over 50% before gelatin extraction. Neutral pH led to the highest yield for both protein and Hyp, which were close to 2,100 and 200 mg per 10 g of skin, respectively. Similarly, smaller sample size or lower solid:liquid ratio resulted in a higher yield. In general, the first 60 min of the extraction was by rapid washing and later on by slow diffusion. Peleg's model is found to be the best fit to the experimental data with the highest R-2 values between 0.97 and 0.99 and the lowest RMSE values compared to that of other kinetic models. This is the first report on the kinetics of gelatin extraction as well as one of the few studies on extraction kinetics of animal-sourced products. Practical Applications Extraction parameters including the size of the raw material and raw material:solvent ratio showed significant effects on extraction yield. The smaller the size and the ratio, the higher the yield. Kinetics of gelatin extraction is reported for the first time by this manuscript, dealing with the yield during the whole extraction process. Extraction parameters may create substantial variability in quality and yield; thus, the data presented here may be utilized in minimizing those potential variations, by minimizing the time, energy and solvent required. The gelatin industry may use this report in the design of the gelatin extraction process as the data presented concludes that a high-rate extraction was completed within the first hour of the extraction, leading over 80% of the expected yield. Gelatin manufacturers and researchers in this field may find this manuscript useful as it provides valuable insights on gelatin extraction and its kinetics.