Abstract
Fish gelatin extraction from wastes of fish Herring species (
Tenualosa ilisha) was carried out by a series of pretreatment with 0.2
M Ca(OH)
2 followed by 0.1
M citric acid and final water extraction at 50
°C for 3
h. The resulting fish gelatin preparation was evaluated for its dynamic viscoelastic properties, gelling and melting temperatures and gel strength. The gelling and melting temperatures of gelatin samples (at 6.67%, w/v) were obtained from differential scanning calorimetry and rheological studies. The melting temperature of extracted fish gelatin (EFG) obtained ranged from 16.2 to 16.7
°C compared to that of commercial fish gelatin gel (CFG), from 23.7 to 25.6
°C and halal bovine gelatin (HBG), from 26.5 to 28.7
°C. On the other hand, gelling temperatures of EFG, CFG and HBG ranged from 5.1 to 5.2
°C, 11.9 to 17.46
°C, and 12.6 to 19.33
°C, respectively. EFG gave gels with a considerably lower
G′ values than CFG and HBG. The bloom strength of EFG gels at 6.67% (w/v) was 69.03
g which was much lower than HBG (336.2
g) and CFG (435.9
g). Enzyme transglutaminase was added in the amounts of 0.5, 1.0, 3.0 and 5.0
mg/g gelatin to modify the gel properties of the extracted fish gelatin. The modified EFG gels obtained had higher gel strengths of 101.1
g and 90.56
g with added transglutaminase of 1.0 and 3.0
mg/g, respectively. However with addition of 5.0
mg/g enzyme the gel strength increased only up to 75.06
g. SDS-PAGE of extracted gelatin gel showed protein band intensities for α1-chains and 53
kDa but in gels added with higher concentration of transglutaminase, these protein band intensities seemed to disappear.