Optimization of gelatin extraction from perch (latest niloticus) skin for halal industries

Abstract

Fish gelatin is a possible alternative to all haram sources of gelatin. Gelatin was extracted from Perch skin using four pretreatment solutions combination. They were CH3COOH (A), NaCl then CH3COOH (SA), NaOH then CH3COOH (BA) and NaCl then NaOH followed by CH3COOH (SBA). Out of the four combinations of pretreatment solutions examined, application of three pretreatment solutions gave gelatin with most improved functional properties in terms of viscosity, gel-strength, and gel-yield. Analyses of gel-yield and gel-strength was highest for SBA (22.84%, 185.09±9.55 g), SA (24.11+0.78%, 78.57±0.09 g), BA (19.00±1.73%, 147.80±0.81 g) and A (17.88+0.89%, 5.91+0.59 g). Viscosity was also highest for sample SBA (0.0245+0.0001 pas), while viscosity for others are 0.0155+0.0002 pas, 0.0123+0.0001 pas, and 0.0025+0.0001 pas for samples BA, SA and A, respectively. Structural evaluations of these four samples were conducted using FTIR for functional group analysis, FESEM for nano structure analysis and SDS-PAGE for protein molecular weight distribution. Results showed that each pretreatment gave different nano imaging patterns; sample A (fibril), sample SA (zig-zag cracks), sample BA (straight rods) and sample SBA (cross-linked rods). Cross-linked rods observed in SBA denote adequate removal of non-collagen content of the fish skin and increase its surface area. Consequently, several junctions formed in SBA during gelation enhanced water entrapment, thus highest in gel-strength, gel yield and viscosity. Results of FTIR revealed different spectra for the samples meaning that pretreatment solutions have impacts on the functional group of gelatin. Lower spectra were observed for sample BA, SA and SBA as compared to sample A. Pretreatment with three solution of salt, base and acid is suggested as the best pretreatment for production of high value fish gelatin. Sequential analysis was also done and revealed that pretreatment with solution of base and salt should precede that of acid due to increased bands observed for a and b sized gelatin molecules. Process optimization was conducted using central composite design (CCD) in response surface method (RSM) for concentration of the three pretreatment solutions. The optimum gel strength of gelatin is 165g and protein yield is also high 32% which is comparable to previous work and optimum concentration of solution during pretreatment for improved gel strength and gel yield of gelatin from perch fish are 1.72 M (NaCl), 1.00 M (NaOH) and 0.15 M (CH3COOH).