Optimization and characterization of halal gelatin from fish skin using High Pressure Processing (HPP)

Abstract

Gelatin is an essential component in the food industry mainly originated from porcine and bovine’s skin and bones. Due to religious and health concerns, alternative sources of gelatin were explored, including fish skin. However, the current extraction method is time consuming and the chemicals used bring adverse implications to the environment. Besides, fish gelatin is known to have weaker properties as compared to the mammalian gelatin. Chemical treatment is often used to overcome the problem. However the gelatin extract usually has high chemical residues. As such, the High Pressure Processing (HPP) is a novel, efficient and environmental friendly method for gelatin extraction due to reduction in processing time and chemical waste while enhancing the gelatin properties and increasing the gelatin yield. This research studied the performance of the HPP during extraction process. First, HPP was applied either during pretreatment or during thermal hydrolysis for four types of fishes, namely red tilapia (Oreochromis niloticus), black tilapia (Oreochromis mossambicus), grouper (Epinephelus areolatus) and the threadfin fish (Nemipterus tambuloides). Based on the yield of HPP during the pretreatment, red tilapia skin produced the highest amount of extract, followed by grouper, black tilapia and threadfin skin, with 32.1%, 30.1%, 21.75% and 15.75, respectively. In contrast, HPP applied during the thermal hydrolysis produced an insignificant amount of gelatin extract. Thus, red tilapia skin and HPP during pretreatment were chosen for optimization study while parameters of pressure, the pressure holding time, ratio skin to acid and extraction time were chosen as optimization parameters. Results from OFAT and FCCCD in RSM suggested that the optimum parameters for gelatin extracted from red tilapia fish skin pretreated with HPP are 250 MPa pressure, 10 min pressure holding time, 1:7.5 ratio solid to acid and 12 hours extraction time, with maximum protein concentration (19.51 mg/ml) and highest gelatin yield (320.4 mg/g). Later, characterization of the produced gelatin were done. Gel strength and thermal stability of the HPP-treated gelatin have increased significantly as compared to conventional gelatin, caused by the modification of the gelatin structure during pressure treatment. On the other hand, the amount of amino acid content declines when excessive pressure was applied because it damaged the protein structure. Other gelatin’s properties display similar results with the conventional gelatin, showing the optimum pressurization preserved the properties of the gelatin protein. For kinetic modelling study, Power Law Model was selected as the best model with the 0.93 regression coefficient, 0.07 RMSD and 3.45% P. Lastly, the performance of the gelatin-treated with HPP in the food product has been tested using Texture Profile Analysis (TPA) vis-à-vis commercial fish gelatin. Six textural parameters i.e., hardness, adhesiveness, gumminess, chewiness, cohesiveness and springiness were evaluated. Results showed jelly prepared with HPP treated gelatin is preferred because the gummy is more rigid, firm and adhesive. In conclusion, application of HPP in gelatin extraction is effective in enhancing the production and properties of the fish gelatin. These findings are very beneficial to the food industry, especially in the halal food production due to its ability to increase the production and to enhance the properties of halal gelatin, which may enable the HPP-gelatin to replace the use of mammalian gelatin in the industry.