29C-28 |
Viscometric and sensory analysis of, and sensory-instrumental correlations in, cocoa gels made using different thickeners and dilution factors |
A. H. BARRETT1, A. V. Cardello1, G. M. Marando1, L. L. Lesher2, and J. L. Briggs1. (1) U.S. Army Natick Soldier Center, U.S. Army Research, Development & Engineering Command, Combat Feeding Innovative Science Team, Kansas St., Bldg. 36, Rm. E-108, Natick, MA 01760-5020, (2) Geo-Centers, Inc., Universal Office Bldg., 190 N. Main St., Natick, MA 01760 The military is developing a variety of gel-type foods that are dispensable via tubes, provide carbohydrates, and serve as vehicles for fortification with performance-enhancing ingredients. Various flow profiles result from the thickeners used. Little research has focused on optimizing the texture of these products. Our objectives were: to determine the flow functions of cocoa-sucrose gels thickened with different hydrocolloid systems; to correlate flow parameters with specific sensory attributes; and to determine “optimal” levels of these attributes. A 3x3 gel matrix was developed by thickening cocoa-sucrose gels with xanthan, a synergistic xanthan-konjac blend, or instant starch—-with each series diluted to three viscosity levels. For “similar-viscosity” samples, thickener levels were selected to provide the same apparent viscosity at 24 s-1 using a Brookfield rotational viscometer. Flow curves were fit to the Herschel-Bulkley model, Y=Yo + kX^n, where Y=shear stress, Yo=yield stress, k=consistency index, X=shear rate, and n=shear thinning exponent. A trained sensory panel, using magnitude estimation, evaluated initial resistance to drawing, resistance to compression by the tongue, rapidity of thinning, and other attributes. “Optimal” attribute levels and sensory-instrumental correlations were assessed. While all the gels were shear-thinning, k, n and Yo varied with formulation. Xanthan and starch gels had similar sensory profiles; xanthan-plus-konjac gels were in a different regime, exhibiting higher scores for initial resistance to draw, resistance to compression by the tongue, density, and rapidity of melting. These sensory properties were generally correlated with gel consistency factor. Hypothetical “ideal” levels of these attributes were close to medium-dilution formulations containing either starch or xanthan. Rheological properties of high-viscosity fluids are best described by flow-functions rather than single viscosity measurements. Sensory attributes can be optimized by selection of specific hydrocolloids.
Session 29C, Food Engineering: Rheology and texture
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