18A-1 |
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Y. -C. TSENG and Y. L. Xiong. Dept. of Animal Sciences, Univ. of Kentucky, 103 W.P. Garrigus Bldg., Lexington, KY 40546 Inulin/oligofructose have been used as prebiotics in many food applications. Little is known about the effect of these fructans on the thermal stability and gelation of soy globular proteins. The objective of this study was to examine the effect of 3 commercial inulin/oligofructose (mean degree of polymerization or DP=5, 10, and 23) on the thermal and rheological properties of soy protein isolate (SPI) during gelation. Samples of 5% SPI dispersions containing 10% inulin/oligofructose were subjected to differential scanning calorimetry (20-110°C), and those of 8% preheated SPI with 8%inulin/oliogofructose to oscillatory shear analysis (0.1 Hz). Gelation of the latter samples was induced by heating from 20° C to 90° C at a constant rate (1° C/min) using glucono-delta-lactone (0.4%) as a coagulant. Storage modulus (G') and loss modulus (G”) were constantly recorded. The microstructure of SPI gels was examined using scanning electron microscopy. Treatment with 10% Raftiline® HP-gel produced 1.77° C and 2.37° C increases (P < 0.05) in the denaturation temperatures of 7S and 11S proteins, respectively, over the control SPI sample. The addition of all fructans lowered the onset gelling temperature (by an average of 4.6° C, P < 0.05) and increased (P < 0.05) the G' and G” values. Fructans with higher DP showed greater effects on the protein gelation. Samples with Raftiline® HP-gel (highest DP) had 43.8% and 52.7% improvements (P < 0.05) in the final G' and G”, respectively, than control counterpart sample. Consistent with the viscoelastic behavior, the fructan-treated SPI gels exhibited a finer texture than the SPI-alone gel. Results indicated that inulin/oligofructose promoted protein-protein interactions during gelation of soy proteins, probably through affecting protein-solvent association and not protein conformation, suggesting that they can be used to improve the texture of soy protein gel products.
Session 18A, Carbohydrate: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |