Development of antioxidant releasing edible films from carp gelatin and fucoidan
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Date
2015
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Fisheries college and Research Institute, Thoothukudi, Tamil Nadu Fisheries University
Abstract
Gelatin obtained from rohu swimbladder (Labeo rohita) and fucoidan from brown seaweed (Padina tetrastromatica) were used to develop antioxidant releasing edible films. The average yields of gelatin from swimbladder and fucoidan from brown seaweed were 6.96% on wet weight basis and 6.83% on dry weight basis, respectively. Fucoidan had the maximum DPPH radical scavenging activity of 89% at 10 mg/ml; ABTS radical scavenging activity was 96.39% at 20 mg/ml and ferric reducing power of 0.85 absorbance units at 28 mg/ml concentration. Gelatin-fucoidan films were prepared using 3% gelatin and fucoidan at different concentrations (5, 10, 15 and 20% of protein concentration) with sorbitol (30% of protein concentration) as plasticizer. The fucoidan incorporated gelatin films were designated as GF-5, GF-10, GF-15 and GF-20. The films developed with gelatin alone was designated as GC and those along with sorbitol as GS. The physico-chemical and antioxidant properties of developed films were characterized. Maximum thickness of 64.25µm was obtained in GF-20 film. Tensile strength (TS) and elastic modulus (EM) of gelatin-fucoidan films increased from 55.37 to 63.37 MPa and from 1278.40 to 1482.20 MPa, respectively, while the elongation at break (EAB) values decreased from 42.01 to 18.34% with the increase in fucoidan concentration, which make them the most suitable edible packaging films of mechanical integrity. WVTR and water solubility of gelatin-fucoidan films decreased from 917.44 to 634 g/m2/day and 91 to 82%, respectively with the addition of fucoidan. Low WVTR and water solubility in GF-20 films make them as good barrier films. Films with higher fucoidan had significantly lowered the whiteness values from 55.79 to 39.59 in comparision with control films. Microstructures of gelatin-fucoidan films at x1000 magnification showed that gelatin-fucoidan films with lower fucoidan had smooth surface, while those with higher fucoidan (GF-15 and GF-20) had rough surface with several undulations and white precipitation, indicating incomplete dissolution of fucoidan with gelatin. The cross sectional morphology at x1000 and x1500 magnifications indicated that smooth and compact pattern in GF-10 and GF-15 films as a result of perfect electrostatic interactions among gelatin and fucoidan molecules, thus making them as good gas barrier films. FTIR spectra revealed that addition of sorbitol and fucoidan to gelatin films had shifted the amide A, B, I, II and III peaks either to low or high wavenumbers as a result of intramolecular hydrogen bonding, and electrostatic interaction between fucoidan and gelatin. GF-20 film had the maximum DPPH radical scavenging activity, ABTS radical scavenging activity and ferric reducing power of 46.26% 49.95% and 0.12 absorbance units, respectively. However, owing to the other advantages and properties, GF15 film is recommended as an active antioxidant releasing edible films. Further this study clearly proved that the antioxidative properties of fucoidan was retained even after its interaction with gelatin in the film formation process.
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