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Modeling the dielectric properties of pineapples during drying

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1008552.(doi:10.13031/2013.34843)
Authors:   Grace P Okiror, Carol L Jones
Keywords:   Dielectric spectroscopy, moisture content measurement, pineapples, partial least squares

The pineapple (Ananas comosus L.) is among the most important commercial tropical fruits in the world, second only to bananas. However, due to the seasonal nature of the fruit production there is an imbalance in the demand and supply of the product. During the harvest season, there is a surplus leading to considerable losses of the excess product. On the other hand, there is scarcity when the product is off-season. Drying is one of the main technologies used to reduce post harvest losses. The objective of this study was to investigate the relationship between moisture content and dielectric properties of peeled pineapple slices during drying. A vector network analyzer with two types of antennas (parallel-plate and waveguide horn) was used to measure the signal attenuation and phase shift by dehydrated slices in the frequencies of 10 MHz to 2.5 GHz at three antenna separations: 3, 30 and 50 cm apart. The results showed a strong linear relationship (R2 > 0.90) between phase shift and attenuation with moisture content at frequencies of around 1 GHz for the horn-guide antennas. The partial least squares algorithm confirmed these results with strong predictive models.

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