Semester

Spring

Date of Graduation

2018

Document Type

Problem/Project Report

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Lane Department of Computer Science and Electrical Engineering

Committee Chair

Hailin Li

Committee Co-Chair

Roger Chen

Committee Member

Bhaskaran Gopalakrishnan

Abstract

Drying food is one of the well-known methods of food preservation. Food preservation methods, like drying, slow down the deterioration of foods as well as prevents the growth of microorganisms. Food preservation allows for an extension of shelf life and prevents food from spoiling. The method used in this study is known as convective or direct drying. As the ambient air heats up from a convective source the relative humidity reduces which accelerates the drying force and decreases drying time. The reduction in relative humidity allows for moisture to move from the food, such as banana chips, to the air. As the hot air flows over the solid, the moisture content of the solid begins to decrease, and the solid begins to heat up. Then, the heated solid starts to release water from the interior of the solid to the surface and eventually dissipates into the air. In this project, a Presto® Dehydro™ food dehydrator was used to dehydrate chips of bananas to test different parameters such as the environmental settings, the shape, and size of the bananas, preparation, air flow, and temperature in order to explore its impacts on drying time and moisture loss. There were two sets of tests done. The first set of tests examined the effects of the size of the banana chips, temperature, and pretreatment on drying time and moisture loss. The second set of tests investigated the environmental effects, and air velocity on moisture loss. The impacts of these parameters are then analyzed in this study. Concluding that the shape and size of the banana did affect the drying time. The thicker the banana chips were the longer it took for the chips to dehydrate. The thinner the cut, the less moisture the slice contains, and the less moisture the dehydrator had to remove. The faster the fan air velocity was the better the hot air was distributed throughout the dehydrator system and the more water was expelled from the bananas. The test data displayed, that the high fan speed tests removed moisture at a faster rate than at medium and low fan speeds. A baseline was then established for the relationship between the fan speed and the drying time and equations were created to display it. Through the different environmental settings tested, it was shown that the lower relative humidity allows for more moisture weight to be lost. Therefore, to speed up the drying time there needs to not only be high temperatures but low relative humidity as well to increase the rate of moisture removal.

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