Otimização da extração de gelatina a partir de pele de tambaqui (Colossoma macropomum)

Abstract

The aim of this study was to optimize the extraction of gelatin obtained from skin tambaqui (Colossoma macropomum). Were first studied eleven variables: concentration, immersion time and weight/weight (w/w) solutions of NaCl, NaOH and acetic acid, extraction time and extraction temperature as a function of the dependent variable total yield (%). A fractional planning Plackett Burman (PB) was used. Variables that showed significant effects were: w/w NaOH and acetic acid, extraction time and extraction temperature. They were then studied through a central composite design (CCD) and analyzed by Response Surface Methodology (RSM). The other variables that showed no significant effect, have had their fixed values. The responses evaluated were the total yield (%) viscosity (cP) and melting point (°C). From there a CCRD was produced twentyeight trials with sixteen factorial trials, four trials at the center point and eight trials on the axial levels. The models for all responses obtained F value higher than the tabulated value, being considered significant and predictive. The value of lack of fit was found lower than the tabulated for models of three responses value. The R2 values for the models were 0,947 for total yield, 0,969 for viscosity and 0,946 melting point. The choice of the optimal extraction conditions happened at the center point area, where these conditions were 1/5 (w/w) NaOH, 1/5 (w/w) acetic acid, extraction time of 12 hours of temperature extraction of 60ºC. After that, the physical and physico-chemical characterization and total amino acid amount of the skin and the gelatin extracted with the optimized conditions was performed, and instrumental color in gelatin. The skin moisture showed 38,11%, fat contents of of 26,56%, protein content of 30,39%, ash content of 1,37%, pH and total acidity of 6,35 ± 2,28 0.06 mL NaOH/100g skin. Gelatin had 9.43% moisture, fat contents of of 1,23%, protein content of 85,99%, ash content of 2,99%, pH 6,12, acidity of 2,94 mL NaOH/100g gelatin and water activity of 0,436. In addition, the process of extracting gelatin showed total yield of 29.06%. The gelatin had a viscosity of 3,48 cP, gel strength (Bloom) 124,5 g and melting point of 25,63 ° C. Also presented as instrumental color parameters L * (lightness) of 74,01, a * 4,17 and b * -10,25, Chroma 11,06 and Hue angle of -22,14°. The amino acid profile of skin gelatin were practically the same, except for cysteine. The amino acids in greater quantity in the gelatin were glycine, proline and hydroxyproline. These last two amino acids are classified as imino acids, and their content of 21.03% is considered high and is associated with higher viscoelastic properties.