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Table 1

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Table 1

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  1. Table 1 Parameters of length ratio (length to initial length) variation model for beans during drying (L/L0 = A + B MR) L:D ratio A B R2 1:1 0.6731 0.3757 0.80 2:1 0.7189 0.3189 0.80 3:1 0.7832 0.2203 0.82 Table 2 Parameters of diameter ratio ( diameter to initial diameter) variation model for beans during drying (D/D0 = A + B MR) L:D ratio A B R2 1:1 0.3948 0.5940 0.87 2:1 0.3539 0.6736 0.87 3:1 0.3875 0.6275 0.87 Table 3 Parameters of length ratio ( length to initial length) variation model for potato during drying (L/L0 = A + B MR) Aspect ratio A B R2 1:1 0.5552 0.4753 0.83 2:1 0.7164 0.3203 0.82 3:1 0.7382 0.2855 0.80 Figure 1 Diameter variation of peas with moisture ratio during drying INTRODUCTION Food particulates come in various sizes and shapes, and often irregular in nature. When those particulates are subjected to any thermal treatment, their shape and size changes according to the nature and intensity of applied treatment. Drying is one such treatment commonly applied in the food processing industry. During drying, shape and size of the food particulate are constantly changing as a result of water removal and internal collapse of the structure of the material. The objective of this study was to investigate the dimensional changes of three different shaped foods during drying. MATERIALS AND METHODS Three major geometrical shapes and their major dimensions were taken into consideration. The shapes considered were, spherical, cylindrical and pararalellpiped. Materials were selected according to these geometrical shapes. Green peas, diced green beans and diced potato were used for spherical,cylindrical and parralallpiped shapes respectively. Fresh green beans (Labrador), green peas (Bounty), and potato (Sebago) were purchased. Beans were cut and three length:diameter ratos of 3:1, 2:1 and 1:1 were prepared. Potatos in parallelpiped shape with aspect ratios 3:1, 2:1 and 1:1 were diced. Peas were shelled and graded according to size of 10mm. Before each drying experimentation, samples were kept in a cold room for 24 hours at 40 Cto achieve an even moisture throughout the samples. The drying in fixed bed was conducted using a heat pump dehumidifier dryer at a temperature of 50+20 C and 13+2 % RH. The variation of length, diameter, width, length to diameter ratio, and aspect ratio were investigated separately. Empirical models of linear form (Y = A + B MR) were fitted for these variations with moisture. In each case A is the dimension at zero moisture and B is the rate of change of the dimension with the moisture ratio. DIMENSIONAL CHANGES OF DIFFERENT SHAPED FOOD PARTICULATES DURING DRYINGW. Senadeera1, B. R. Bhandari1, G. Y. Young1 and B. Wijesinghe21Food science and Technology, School of Land and Food, The University of Queensland, Gatton College, Queensland 4345, Australia.2Centre for Food Technology, Queensland Department of Primary industries, Hamilton, Queensland 4407, Australia. RESULTS AND DISCUSSION Length and diameter variation of the green beans, were correlated to a linear model and their parameters are shown in Table 1 and Table 2. For beans radial shrinkage was more pronounced than axial shrinkage. Length was reduced by 22 - 32 %, while diameter is by 60 - 65 % (Table 1 and Table 2). The rate of change of axial shrinkage with respect to moisture removal was lower at higher L:D ratios. As L:D ratio increased, the axial shrinkage was decreased where as the radial shrinkage remained relatively similar. The change of diameter with respect to moisture loss was less significant than the axial shrinkage. Variation of length to diameter ratio of the potato with moisture ratio was also found to be behaving according to a linear model. Its parameters are given in Table 3. The final length ratios were increased as aspect ratio increased. The rate of change of length ratio with moisture removal was lowered as aspect ratio increased. Diameter change of green peas was correlated to the model D/D0 = 0.6015 + 0.4265 MR (r 2 = 0.92 ) (see Figure 1). This indicates that 40 % reduction in diameter. CONCLUSION The dimensional changes (L/L0 or D/D0) of beans, potato and peas can be related to moisture loss (moisture ratio) linearly. For similar initial diameter for sphere (peas) and cylinder (beans), diametral shrinkage of sphere (peas) is less than the radial shrinkage of the cylinder (bean). As the length of cylindrical (beans) and parallelpiped (potato) increased the final shrinkage is decreased. Find us at: E-mail: ws@burger.uqg.uq.edu.au Web: http://www.laf.uq.edu.au