Degree Type

Dissertation

Date of Award

1953

Degree Name

Doctor of Philosophy

Department

Botany

Abstract

The moisture content of samples of corn and soybeans were determined by five different methods, which included oven methods, drying under vacuum over magnesium perchlorate distillation methods, and an electrical conductivity method;The methods yielded varying results. It was observed that vacuum drying at 100°C or 70°C gave the most consistent results, while fluctuations were the greatest at 135°C. The highest moisture values were obtained in the 100°C vacuum oven, while Tag-Heppenstall method, as standardized, always underestimated these results. The Brown-Duvel distillation method underestimated moisture content except at higher moisture levels of the seeds;Vacuum desiccator drying was too slow for the drying of whole seeds but could be used to obtain estimates of bound water content. Constant weight was not reached in 55 days. Corn retained more moisture than soybeans for the same length of drying time;Equilibrium drying to constant weight gave similar results with both the 70°C vacuum oven and the 100°C air oven. The vacuum oven required 23 days and the 100°C, 12 days to reach equilibrium. There was less caramelization of material at 70°C vacuum drying than by other oven methods;Prefreezing effects on moisture content of seeds was negligible when moisture was determined in the 100°C air oven, but the Tag-Heppenstall method gave higher moisture readings for seeds of corn and soybeans frozen at a high moisture level;Freezing decreased germinability of both corn and soybeans at moisture contents greater than 20 percent, but did not affect drier seeds. Errors with the Tag-Heppenstall method were correlated with freezing injury of the seeds;The loss of moisture from corn in a drying oven followed the logistic type of curve, M=ta+bt, 1 where M = percentage of moisture, t = time, and a and b are constants. Since the rate of moisture loss increased linearly with temperature, equation (1) may be written, M=tTc+f+gT t2 where T is the temperature and c, g and f are constants. When t/M was plotted against time, a straight line was obtained for all drying curves. These results indicate the importance of permeability in oven drying of seeds;When corn or soybean seeds were held at constant temperature and humidity, their moisture content approached an equilibrium, Mo, at a rate, k, which was a function of their permeability.

DOI

https://doi.org/10.31274/rtd-180813-14640

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Ashley Monroe Bryan

Language

en

Proquest ID

AAIDP12196

File Format

application/pdf

File Size

75 pages

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