36D-35 |
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P. ZHOU, S. J. Mulvaney, and J. M. Regenstein. Dept. of Food Science, Cornell Univ., Stocking Hall, Ithaca, NY 14853-7201 Gelatin is an important functional biopolymer widely used in foods to provide elasticity, viscosity and stability. Most commercial gelatins are made from pork or non-religiously slaughtered beef and unacceptable to Jews and Muslims, but fish gelatins could satisfy their requirements. Alaska pollock is a cold-water fish, and gelatin from pollock skins may have different rheological properties than gelatins from warm-water fish or mammals. Our objective was to compare the rheological properties of gelatins from different sources under small strain deformation. Alaska pollock Gelatin (AG, 100 bloom), tilapia gelatin (TG, 275 bloom) and pork gelatins (PG1, 110 bloom; PG2, 250 bloom) were evaluated. Gelatin gels were prepared with distilled water and stored at 2~4 ºC for 24 h. Shear storage modulus (G') and loss modulus (G”) were determined as functions of gelatin type, concentration (1.5% to 10%) and frequency (0.01 to 10 Hz) at 0.5% strain. Gel melting was monitored by the change of G' with temperature increasing at the rate of 0.2º C/min. For most gelatin gels, G' was almost independent of frequency, while AG gels showed a slight dependence of G' and a minimum in G”. The value of G' as a function of gelatin concentration followed a power law, G'=k×Cn. The value of n was around 2, with AG having the highest n value (2.25). AG had the lowest melting temperature and sharpest melting transition region. For all gelatin gels, increasing gelatin concentration resulted in a higher melting temperature and a broader melting region. Synergistic increases in G' were observed in mixed gelatin gels. With increasing AG fraction in mixed gels of AG/TG and AG/PG2, melting temperatures decreased and melting regions narrowed. The results suggest that Alaska pollock gelatin has unique melting property and may offer new opportunities for food and pharmaceutical product development.
Session 36D, Food Engineering: Rheology
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |