29E-8 |
Kinetics of solids leaching during rehydration of particulate dry vegetables |
A. MARABI1, J. Shah2, C. Dilak2, 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 Rehydration kinetics of dry particulate vegetables is typically determined by samples weight gain due to water uptake assuming that solids concentration is constant. However, leaching of solids to the reconstitution medium is significant even for very short periods of rehydration. Understanding the kinetics and the mechanism of the leaching process could provide the necessary information required for accurately simulating the process. The overall objectives of the work were: quantifying the leaching of solids (sugars, and other organic compounds) from dehydrated food particulates utilizing two different methods; studying the kinetics of the process; and assessing the importance of solids leaching on rehydration modeling. Dehydrated particulate vegetables were rehydrated in hot water in a computerized mixing system. Samples analyzed at different times for sugar content (sucrose, glucose and fructose) with HPLC and for Total Organic Carbon (TOC). Values derived from TOC were significantly higher for all the samples tested than the counterpart values calculated from the three sugars determined by HPLC, indicating that other organic components (e.g., amino acids, lipids , nucleotides, fibers) were extracted during the process. The difference between the derived values by TOC and HPLC, varied with time, indicating the existence of a difference in the dissolution rate of the sugars and other organic components. All three sugars showed an exponential rate of dissolution with sucrose having the highest rate, followed by glucose and fructose. The leaching of organic compounds determined by TOC followed also an exponential behavior. The weight loss due to solids leaching is usually disregarded in rehydration experiments. The significant solid dissolution highlights the need to correct the traditional approach. Utilizing the correct values is important for modeling and simulation of the rehydration process and ultimately for product optimization.
Session 29E, Food Engineering: Transport processes and kinetics
|