17H-12 |
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G. H. LEE1, W. Ratphitagsanti2, and F. Hsieh2. (1) Division of Agricultural Engineering, Kangwon National Univ., Chuncheon, 200-701, South Korea, (2) Dept. of Biological Engineering, Univ. of Missouri, 254 Ag. Eng. Bldg., 1406 E. Rollins St., Columbia, MO 65211-5200 Fruit leather is a confectionery product manufactured by dehydrating fruit puree into leathery sheets. Fruit leathers add value to fruit which may otherwise not acceptable for the fresh produce market. Hot air drying is one the common unit operations in the food processing industry. The objective of this study was to determine the drying characteristics of strawberry leather by hot air drying and to investigate the effect of process parameters such as drying temperature and sample thickness. Strawberry leathers were prepared by blending strawberry puree, corn syrup, pectin and citric acid in 200:40:2:1 ratios, spread into thin layers, and dried in a convective oven. The independent variables were product thickness (1.8, 2.7, and 3.6 mm) and drying temperature (50, 60, 70, and 80°C). Moisture losses were recorded at constant time intervals during drying for the determination of drying curves. Drying times for strawberry leather samples to reach the moisture content of 12% (wb) for safe storage were found to vary from 80 to 600 min depending on drying temperature and sample thickness. The drying rate curves showed that drying of strawberry leathers for all samples took place in the falling rate period. Both drying air temperature and sample thickness had pronounced influences on the values of the apparent moisture diffusion coefficient, Deff. The values of Deff varied from 2.40E-09 to 1.21E-8 m²/s. The activation energy (Ea) for water diffusion was estimated using an Arrhenius-type equation. The values of Ea were found to be 35.57 (r²=0.98), 33.14 (r²=0.98), and 30.46 (r²=1.0) kJ/mol for strawberry leather samples with 1.8, 2.7, and 3.6 mm thickness, respectively.
Session 17H, Food Engineering: Thermal processes
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