29E-7 |
Rehydration of dry particulates |
A. MARABI1, M. Jacobson2, S. J. Livings2, and I. S. Saguy1. (1) Institute of Biochemistry & Food Science, Hebrew Univ. of Jerusalem, Faculty of Agricultural, Food & Environmental Quality Sciences, POB 12, Rehovot, 76100, Israel, (2) Nestle R&D Ctr., Inc., 201 Housatonic Ave., New Milford, CT 06776 Ready-to-eat meals is a fast growing market, with increasing consumers demand for better quality products. Rehydration and reconstitution speed of dry food particulates is one of the rate limiting steps related to the nature and the history of the particulates. Studying the rehydration kinetics and mechanism, and the effect of various dehydration processes is paramount for improving quality, reduce processing costs and custom-made products for each application. The objectives were developing the appropriate methodologies for studying the kinetics of water absorption and uptake during short time periods, and identifying the pertinent variables affecting the rehydration process. Rehydration experiments were designed to follow water uptake during a short time-frame (up to 3 min). A computerized mixing unit was developed to study the kinetics of the particulates under controlled conditions (temperature, viscosity, RPM, weight). The particulates tested were dehydrated vegetables using several drying methods (i.e., freeze drying, air drying). The weight gain was recorded continuously. Samples open porosity values played a significant role in the rehydration kinetics. The higher porous samples (freeze dried) rehydrated faster. In the presence of starch in the rehydration medium the porosity effect diminished and similar rehydration rates for both air- and freeze- dried samples were observed. Mixing speed showed only a small effect on the rehydration kinetics at low medium viscosity (water), and was significant with increased viscosity due to the presence of starch in the medium. Rehydration rate increased linearly with sample surface area. The observed differences in the samples rehydration kinetics, and the interaction with the reconstitution media and system, should be considered for selecting the appropriate food particulates, and conditions to ultimately improve final product quality.
Session 29E, Food Engineering: Transport processes and kinetics
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