Date of Award
Master of Science
Biosystems Engineering Technology
Luther R. Wilhelm
Fred Tompkins, J.L. Collins
The purpose of this study was to identify both a rapid method for determining moisture and a standard oven drying procedure for determining moisture in snap beans. Parameters of interest were sample size, sample preparation, sample condition (fresh vs. frozen), drying time. oven pressure, and a comparison of microwave, vacuum, and convection oven drying.
The experiment was divided into four phases, each concentrating on selected parameters. The results of one phase determined parameter values used in later phases. Two convection ovens, two vacuum ovens, and one microwave oven were used. For the convection and vacuum oven drying, treatment effects were combinations of drying temperature and oven pressure. Treatment effects for microwave drying were combinations of sample size and power setting (energy level) coupled with drying time. Fresh and frozen samples were evaluated in all three types.
For convection and vacuum oven drying, oven pressure, drying temperature and sample condition had little effect on indicated moisture content for the ranges tested. However, indicated moisture content was more sensitive to temperature than any other factor. Samples used in the microwave oven had to be ground in a food processor before drying. The indicated moisture contents given by the microwave oven were significantly affected by sample size, sample condition, and power setting. The larger samples and higher power settings produced higher indicated moisture contents. Frozen samples consistently gave higher Indicated moisture contents than fresh samples.
For determination of moisture in snap beans, convection ovens at 100°C or vacuum ovens at 100°C with absolute pressures between 760 and 60 mm of mercury gave the same results. Both methods required a 24-hour drying period. Indicated moisture contents given by drying 10-gram samples in the microwave oven for 12 minutes were significantly different than convection or vacuum dried samples at the 95 percent level of probability. Even though they were statistically different, the moisture contents given by the three methods were within 1 percent of each other. Thus, the great time reduction from 24 hours to 12 minutes offered by microwave drying has potential for moisture determination in snap beans.
Perrin, David Ray, "Evaluation of methods for determining moisture in snap beans using microwave and conventional oven drying. " Master's Thesis, University of Tennessee, 1980.