36D-1 |
|
A. MARABI and I. S. Saguy. Institute of Biochemistry and Food Science, Hebrew Univ. of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, POB 12, Rehovot, 76100, Israel Utilization of dried foods such as ready-to-eat soups requires adequate rehydration. One of the parameters influencing liquid uptake is related to the properties of the thickening agent utilized to achieve an acceptable viscosity in the food product. Medium viscosity and particle size of different starches markedly affect the process kinetics and could reduce the rehydration achieved. This is especially important during short time processes. However, the factors responsible for this impaired rehydartion are unknown. The objectives were to elucidate the effects of particle size distribution, concentration, dispersion and viscosity of different thickening agents; and to study the interrelation of typical ingredients such as fat and salt concentration of ready-to-eat soup mix on the rehydration kinetics of dried particulates. Thickening agents utilized were: carboxy-methyl cellulose (CMC), natural and pre-gelatinized starches from different botanical sources. The particle size distribution of the thickeners was characterized by microscopy and image analysis. Different concentrations, dispersion characteristics and viscosities obtained by dissolving the thickening agents in water were utilized as the rehydrating medium for freeze-dried and air-dried carrots. Typical ready-to-eat soup formulations containing salt and oil in addition to the thickening agent were also evaluated. The kinetics of the rehydration process was assessed utilizing the normalized Weibull distribution function. The rehydration of dried carrot particulates was influenced by, among other factors, the thickening agent utilized and the dispersion characteristics. Different types of starches showed very different rates of liquid uptake. Viscosity, particles size and their dispersion influenced the rehydration kinetics. The shape of the rehydartion curve followed the normalized Weibull distribution function. The mechanism of liquid uptake was characterized based on the derived Weibull parameters. The effect of the rehydration medium characteristics was demonstrated. Medium uptake during rehydration could be improved and customized by choosing the most appropriate thickening agent and process.
Session 36D, Food Engineering: Rheology
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |