Enzymatic Hydrolysis of Chicken Rest Raw Material
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The global increase in production and consumption of chicken has lead to the generation of large amounts of rest raw material that often are discarded or used as animal feed. Rest raw material of animal origin, such as chicken, contain valuable biomolecules like proteins and lipids that can be recovered and processed for various applications in the food, pharmacy and cosmetic industry. Therefore, with a growing global demand for food, optimal uses of unexploited or under-utilized resources are increasingly important.The aim of this study was to optimize enzymatic hydrolysis of chicken and to find processing conditions giving hydrolysis products of high quality. Optimization was aimed at minimizing the amount of oil in the protein hydrolysates, to increase the amount of solubilized protein, to reduce the lipid content in sediment and protein hydrolysate and to avoid the formation of an emulsion fraction. Additionally, enzymatic hydrolysis on herring was conducted for interspecies comparisons of degree of hydrolysis (DH), molecular weight distribution, colour and amino acid composition. The chicken rest raw material contained 15.8 ± 0.6% protein, 17.5 ± 2.0% lipids, 5.8 ± 1.9% ash and 37.7 ± 2.2% water. The endogenous activity was low, which may indicate a higher stability and possibly a longer shelf life compared to marine rest raw materials. Hydrolysis for 60 minutes with the commercial enzymes Protamex, Corolase pp, papain and bromelain gave good hydrolysis yields. The oil and sediment fractions had high protein contents and desirable amino acid compositions. Both CPH (chicken protein hydrolysate) and sediment fractions were found to have high contents of the predominant amino acids in collagen (glycine, alanine and hydroxyproline), and could thus be evaluated for gelatine extraction. All CPH powders from 60 minutes of hydrolysis with commercial enzymes had similar compositions with contents of protein (72.8 85.4%), ash (6.2 13.1%), lipid (0.8 1.6%) and water (4.8 6.1 %) respectively. Further, the hydrolysates were found to have good sensory properties, high degrees of hydrolysis (21 25%) and desirable amino acid compositions. CPH and FPH from herring were fond to have similar DH, molecular weight and amino acid composition, which may indicate that they are well suited for applications in human nutrition.