The determination of moisture in tung fruit

Abstract

Summary and ConclusionsSix methods for determining moisture in tung fruit and seeds were compared.The highest moisture values, and probably those most reliable, were obtained by drying the ground tung fruit in the vaccuum oven at 101°C. for 2.5 hours under 12‐mm. pressure, and by the Karl Fischer titration method. In using the Karl Fischer method on tung products, the sample must be digested in methanol at 60°C. Of these two methods the vacuum oven method is simpler and generally preferable.Somewhat lower moisture values were obtained by the forced draft oven and toluene‐distillation methods. The results obtained in the forced draft oven method were low because of oxidation of the oil in the samples. One hour at 101°C. in the forced draft oven seems to be the optimum time for moisture determination, and no appreciable error in the oil content results from using the percentages of moisture so determined to calculate the oil content to basis of sample as received.For routine analysis, heating the ground tung fruit sample in a hot air blower for 15 minutes at 126.7°C. (260°F.) and adding a correction of 1.35% to the percentage of moisture obtained gives sufficiently accurate values for factory control purposes.The radio frequency meter gave values close to those obtained in the vaccum oven method against which it was standardized. It was necessary to standardize the meter separately for fruit, seeds, and kernels. In practice many samples of wet fruit would be encountered which would exceed the range of the particular instrument used.