Effect of phosphorylation on gel properties of gelatin from the skin of unicorn leatherjacket

Phosphorylation of gelatin from the skin of unicorn leatherjacket was carried out by incorporating sodium tripolyphosphate (STPP) at varying concentrations during pretreatment and extraction. Phosphate attached to gelatin during pretreatment and extraction was found at levels of 12.43 and 18.25 μmol/g, respectively. Based on zeta potential analysis, phosphorylated gelatin became negatively charged, reconfirming the charge modification mediated by phosphorylation. For gelatin phosphorylated during pretreatment, that using 0.2% STPP had the highest gel strength (128.3 g). Amongst all gelatins incorporated with STPP during extraction, that added with 0.08% STPP showed the highest gel strength (146.0 g). Slight differences in FTIR spectra were observed when gelatin was phosphorylated, compared with the control gelatin. Gel of gelatin phosphorylated with 0.08% STPP during extraction exhibited a finer and more compact structure with smaller pores and was able to set at 4 °C at the fastest rate, compared with other gelatins. Thus, the phosphorylation under the appropriate condition could improve gelling property of gelatin from skin of unicorn leatherjacket.