Separation and characterization of alpha-chain subunits from tilapia (Tilapia zillii) skin gelatin using ultrafiltration

Abstract

Alpha-chain subunits were separated from tilapia skin gelatin using ultrafiltration, and the physicochemical properties of obtained subunits were investigated. As a result, α 1 -subunit and α 2 -subunit could be successfully separated by 100 kDa MWCO regenerated cellulose membranes and 150 kDa MWCO polyethersulfone membranes, respectively. Glycine was the most dominant amino acid in both α 1 -subunit and α 2 -subunit. However, the tyrosine content was higher in α 2 -subunit than in α 1 -subunit, resulting in strong absorption near 280 nm observed in the UV absorption spectrum. Based on the DSC analysis, it was found that the glass transition temperatures of gelatin, α 1 -subunit and α 2 -subunit were 136.48 °C, 126.77 °C and 119.43 °C, respectively. Moreover, the reduced viscosity and denaturation temperature of α 1 -subunit were higher than those of α 2 -subunit, and the reduced viscosity reached the highest when α-subunits were mixed with α 1 /α 2 ratio of approximately 2, suggesting that α 1 -subunit plays a more important role in the thermostability of gelatin than α 2 -subunit.