The purpose of this research was to obtain information on the requirements for successfully drying mechanically harvested Virginia peanuts by artificial means. The work was performed at the Tidewater Research Station, Holland, Virginia. It was performed in bulk-type bins which were seven feet deep. Two tests, which consisted of four treatments and four replications each, were conducted. One of the replication bins in each treatment was divided into one-foot depth sections. The drying tests were conducted using intermittent heat which was designed to give the prescribed temperature rise when the ambient relative humidity was above 75 percent. The drying potential ranged from 12 cfm/ft³ and a 10 F temperature rise to 9 cfm/ft³ and a 3 F temperature rise. Original moisture contents of the peanuts tested were 43 percent and 31 percent. Weights of the bins were taken during the tests, thereby permitting the calculation of the moisture contents at any time. Drying rate curves were obtained from this. Quality analyses of the peanuts after drying were performed in order to determine the best drying treatment. These included: Fat Acidity, Shelling Damage, and Damaged Kernels from Commercial Grade. The Shelling Damage Tests showed that the lowest drying potential was best. The Fat Acidity Test indicated that the drying potential in all of the treatments was satisfactory when drying Virginia peanuts with an original moisture of 31 percent in a seven-foot depth. However, it appeared that the potential was not adequate to dry peanuts with a 43 percent moisture content in a depth greater than five feet. No information was obtained from the damaged kernels in the commercial grade. The resistance to air flow and the analyses of quality of the end product gave no indication that the sectioning of the bins had any effect on drying as compared with the full depth bins. This can be important in later research from the standpoint of obtaining additional data on drying rates and progression of the drying layer through bulk type bins of Virginia peanuts. / Master of Science

Ph. D.

A deep-bed drying model simulating the drying of peanuts in a fixed bed is required for designing energy-efficient and automatically controlled dryers. A deep-bed drying model consists of a thin-layer drying model to calculate the moisture release from the material and a set of mass and energy balances. An experimental setup was constructed to determine drying rates of Virginia-type peanuts under 14 different drying air conditions. Selected empirical and semi-theoretical models available for modeling thin-layer drying rates were fitted to the collected data using nonlinear regression techniques. The modified Page's model and the two-term exponential model fitted the data better than other models considered. A deep-bed drying model PEATECH based on four coupled partial differential equations consisting of four variables, air temperature, peanut temperature, air humidity, and peanut moisture content was developed. Validation of the model was accomplished by using the data collected from 36 deep-bed drying experiments conducted using three laboratory dryers during 1987, 1988, and 1989. PEATECH predicted the variables within a peanut bed with an accuracy of less than ± 6%. The energy saving potential of exhaust-air recirculation was established by conducting simulated experiments using a modified version of PEATECH. / Ph. D.

There has been controversy over the accuracy of grading peanuts for freeze damage by United States Department of Agriculture (USDA) guidelines. Several other tests for estimating freeze damage in peanuts were investigated. The conductivity test, which measures electrolyte leakage from cells, and the tetrazolium test, a test currently used for estimating viability of seed peanuts, were adapted for assessing freeze damage. The dipicrylamine test, a qualitative spot test for potassium, was developed and used to detect potassium leakage from cells onto the surface of the cotyledon. A visual test was developed based on differences in glossiness of the flat surface of the peanut cotyledon. A freezing apparatus was designed and operated so that peanuts could be cooled at a slow, even rate to a series of low temperatures. These peanuts and peanuts exposed to a natural freeze were tested for freeze damage. The USDA visual test underestimated freeze damage compared to all of the tests used in this study. The VPI visual test differentiated damaged from undamaged peanuts using subtle differences in glossiness that are not considered by USDA visual test guidelines. Results of the VPI visual, tetrazolium, and dipicrylamine tests for peanuts exposed to the laboratory freeze treatments were not significantly different. The dipicrylamine test is a rapid test, but interpretation of color differences proved to be difficult. The tetrazolium test revealed the greatest differences between damaged and undamaged peanuts and these differences were easily interpreted. The tetrazolium test is, therefore, favored over the other tests for grading freeze damage in peanuts. / M. S.