SIZE AND SHAPE EFFECT ON NONUNIFORMITY OF TEMPERATURE AND MOISTURE DISTRIBUTIONS IN MICROWAVE HEATED FOOD MATERIALS - PART I SIMULATION

Temperature and moisture distributions were calculated using a finite element model (FEM) in potato samples of different shapes (brick-, cyl inder-, and hexagonal prism-shaped), sizes (75, 90 and 105 cm(3)) and height to base dimension ratios (DR = 0.25 to 1.75). For each of the t hree product volumes considered, the nonuniformity in temperature dist ribution las indicated by the standard deviation of temperature (SDT) distribution within the product) was found to be lower in the case of hexagonal prism-shaped products (SDT ranged from 4.9 to 6.4C for produ ct volume of 90 cm(3)) when compared with brick (7.0 to 7.5C) and cyli nder-shaped products (5.2 to 8.2C). The time to reach the same maximum temperature of 80C, however, was longer in hexagonal prism-shaped pro ducts (61 s for product volume of 90 cm(3) and DR = 1.0) when compared to brick (48 s) and cylinder-shapes (44 s). For the cases considered, the nonuniformity of temperature and moisture distribution increased as the product volume increased from 75 to 105 cm(3) in the case of br ick- and hexagonal-shaped products. Cylindrical products of low volume s (75 cm(3)) and low radii showed high temperature nonuniformity. The moisture nonuniformity in all the product shapes considered was influe nced by the area.