Rheological and functional characterization of gelatin and fat extracted from chicken skin for application in food technology

Chicken skin is a major byproduct of the poultry industry. This study was undertaken to extract and characterize fat and gelatin from chicken skin. To do this, the chicken skin was wet-rendered at different temperature-time combinations and the yield and properties of the extracted gelatin and fat were determined. Gelatin and fat were recovered at yield ranges of 0.74%-2.03% and 24.01%-27.91%, respectively. The time and the interaction of time-temperature had a positive effect on gelatin yield (p < .05); however, the fat yield was not affected by the extraction condition. Protein, ash, and hydroxyproline content of gelatin and unsaponifiables and free fatty acids contents, peroxide value, and induction period of oxidation of the fat were affected by the extraction condition. Functional and rheological analyses showed chicken skin gelatin gel/solution had a higher bloom value, viscosity, foaming capacity, storage and loss moduli, and melting and gelling points than the commercial bovine gelatin. Oleic (42.13%), palmitic (24.6%), and linoleic (17.53%) acids were the main fatty acids of chicken skin fat. The storage modulus of chicken skin fat was higher than the loss modulus up to 31°C; however, because of a low slip melting point (22.74°C) and solid fat content, it was fluid at room temperature. The findings of this research can be useful in the development of processes for the extraction and application of chicken skin gelatin and fat.