88C-16 |
Temperature and concentration dependence of density of model liquid foods |
R. D. BARBOSA, M. O. Balaban, and A. A. Teixeira. Food Science & Human Nutrition Dept., Univ. of Florida, PO Box 110370, Gainesville, FL 32611 Knowledge of physical properties of foods is fundamental in the design and control of food processes, and in quality control assessment. The accurate measurement or prediction of density is vital to the engineering practice in the food industry. Density of liquid foods is affected by composition and temperature. The objective of this study was to measure the density of model aqueous solutions with an accurate method and to fit experimental data to predictive equations. The aqueous solutions investigated were binary solutions and combinations of sucrose, glucose, fructose, citric acid, malic acid, citric pectin, and inorganic salts. The effect of the concentration and temperature were investigated. Density measurements were performed with an oscillating tube density meter (density accuracy ±1x10-5 g ml-1, density precision ±0.5 x10-5 , and temperature precision ±0.01°C). Instrument calibration was performed with air and double-distilled water. Solutions were prepared with analytical grade reagents with double-distilled water at varying concentrations from 1% to 65% (w/v) for sugar solutions, from 0.1% to 10% (w/v) for acid solutions, 0.025% to 2.5% (w/v) for pectin solutions, 0.05% to 5% (w/v) for inorganic salt solutions. Other combinations were tested for component interaction and predictive analysis. The measurements were performed at temperatures of 10°, 20°, 40°, and 60°C. Density of all solutions studied showed a quadratic dependence with temperature, and a linear dependence with concentration. Coefficients of predictive equations were determined by fitting the experimental data. Using these equations, the density can be predicted with accuracy better than 1x10-5 g ml-1 . Literature values agreed well with experimental data. These models can be used for prediction of density of liquid food systems based on composition and temperature. Special interest would be for applications involving fruit juice and beverage processing by using predictive equations with high accuracy and save elaborate experimental work.
Session 88C, Food Engineering: Physical and Chemical Properties
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