36D-29 |
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R. KARNJANOLARN, M. J. McCarthy, and K. L. McCarthy. Dept. of Food Science and Technology, Univ. of California, Davis, One Shields Avenue, 150D Cruess Hall, Davis, CA 95616 In chocolate enrobing processes, rheological properties have a great impact on quality and final product properties. There are several factors influencing rheological properties of chocolate, e.g., emulsifier content, particle size, temperature, and degree of temper. These factors are interlinked; the modification of one factor may impact another. Our objective was to investigate the effect and the interaction of emulsifier on the rheological properties and coating thickness of a dip-coated milk chocolate system. The experimental factors and levels were: emulsifier type, soy lecithin and PGPR; and level of emulsifier, 0.1, 0.2, 0.3, 0.4, and 0.5% w/w. The experiment was conducted on glossy acrylic plates. The shear viscosity and yield stress were examined according to IOCCC method. The thickness of the chocolate was obtained by a gravimetric method. The thickness of dip-coating chocolate decreased to a certain point with increasing emulsifier levels. With no lecithin added, the thickness of the coating was 0.90 mm and decreased to 0.54 mm as the emulsifier concentration increased to 0.1%w/w. As the levels increased to 0.3%, the thickness of the chocolate decreased minimally to 0.47 mm and increased to 0.51 mm at the concentrations of 0.4 and 0.5% w/w. The rheological parameters were incorporated into a drainage theory model to predict coating thicknesses in the enrobing process. The model was solved numerically and yielded good approximations to the experimental values. The level of the emulsifiers had a significant impact on the thickness of dip-coating milk chocolate. Nonetheless, the effect of emulsifiers is limited. The incorporation of other control factors is essential for an effective method of controlling the coating thickness.
Session 36D, Food Engineering: Rheology
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |