18A-20 |
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C. KUSNADI and G. Kaletunç. Dept. of Food, Agricultural & Biological Engineering, Ohio State Univ., 590 Woody Hayes Dr., 210 Agricultural Engineering Bldg., Columbus, OH 43210-1058 Moisture migration from high moisture to low moisture domain during storage of a multi domain food occurs, compromising its quality attributes and safety. The moisture migration between the domains is accelerated by temperature increase leading to reduction of shelf-life. This study aims to apply the Fick's equation of unsteady state diffusion to predict effective moisture diffusivity in a cheese and bread sandwich. Moisture sorption isotherms for rye bread and provolone cheese were developed using dessicators containing saturated salt solutions at various relative humidity levels. The data were fitted to GAB equation to establish the equilibrium relationship between the water activity and moisture content at 4, 10, and 23 oC. Sandwich samples of bread (5cm) and cheese (2 cm) were prepared, sealed, and stored at constant temperature. Water activity of the 0.5 cm slices of bread was measured as a function of time using a temperature controlled water activity meter. The moisture content of bread slices was calculated by using GAB parameters. Effective moisture diffusivity was calculated by fitting the moisture content data to the solution of unsteady state diffusion equation for a finite slab. The GAB equation parameters were material specific and temperature dependent. For both cheese and rye bread, the monolayer moisture content and constant C decreased while constant k increased as the temperature increased. Moisture content values were calculated using the GAB equation parameters and were fitted to unsteady state diffusion equation. Effective moisture diffusivity in bread was calculated to be 1.56x 10-9 m2/s at 23 o C. Control of moisture migration in foods is critical for food industry. The knowledge of effective moisture diffusivity provides a quantitative measure of moisture migration between the domains of a multi-domain food system. Such information can be utilized for more accurate prediction of physical stability and shelf life of multi domain foods.
Session 18A, Carbohydrate: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |