17B-3 |
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P. SPAGNUOLO1, H. D. Goff1, D. G. Dalgleish1, and E. Morris2. (1) Dept. of Food Science, Univ. of Guelph, Ontario Agricultural College, Guelph, ON N1G 2W1, Canada, (2) Univ. College Cork, Western Rd., Cork, Ireland Polysaccharides, i.e. locust bean gum, are commonly used in dairy products such as ice cream mix to impart solution viscosity and enhance the overall sensory attributes of the final product. In the presence of milk proteins, most specifically the caseins, incompatibility results and two distinct phases are formed, one rich in casein micelles and the other devoid of casein micelles. kappa-carrageenan is able to prevent this undesirable phenomenon and is therefore used in these systems to provide stability. The mechanism by which kappa-carrageenan is able to suspend the casein micelles and prevent their flocculation is unknown. Two theories exist; one that a specific interaction occurs between the two biopolymers and the other that the carrageenan forms a weak gel entrapping the casein micelles. Recent work in our lab on conventional soft-serve ice cream mixes has demonstrated that 0.015% kappa-carrageenan is the minimum concentration required to achieve stability. However, stability is only achieved at the macroscopic level while microscopic phase separation is still evident. This research project is focused on the mechanism by which kappa-carrageenan achieves macroscopic stability. Images from field emission scanning electron microscopy suggest that kappa-carrageenan adheres to the casein micelle surface. Dynamic light scattering data shows casein micelle diameter linearly increasing (r2=0.947) as kappa-carrageenan concentration increases, within the concentration range of 0-0.02% (w/w). These results indicate that an interaction occurs between the two biopolymers. Phase separation experiments using the non-gelling lambda-carrageenan, which is known to interact with the casein micelle and increase its diameter, shows that lambda-carrageenan is unable to prevent separation. Also, by manipulating the ionic environment to block kappa-carrageenan gelation phase separation was evident. These experiments have verified that a weak kappa-carrageenan gel is also required in addition to direct micelle surface interaction to prevent phase separation in systems containing polysaccharide and casein micelles.
Session 17B, Dairy Foods: General
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