The determination of the oil content of ground tung fruit

Abstract

SummaryThe Hamilton‐Gilbert method for oil determination has been adapted to the method of grinding and extracting whole tung fruit. A sample of 100 fruit is ground in a Wiley mill with sharp blades. A 10‐gm. portion is then extracted in a Waring Blendor and oil determined by the procedure previously described or a modification herein described. To approximate closely the values that would be obtained by the strictly accurate but more laborious method of separating kernels from hull and shell and extracting the kernels only (component method), a correction is required for non‐oil substances extracted from the hull and for factors such as adsorption of the kernel oil on particles of hull and decreased efficiency of extraction of the kernel oil in the presence of ground hull and shell. This correction factor is not constant throughout the whole range in oil content found in whole tung fruits, and the best estimate of true tung oil content is obtained by the formula:Estimated component value = 0.8958 (value by whole fruit method) + 1.37.The use of a regression equation such as that above in relating results of two empirical chemical methods is believed to be of very general application. The specific formula here arrived at was determined from 97 samples of air dry fruit ranging in oil content from 16.0 to 25.0%. It is not recommended for use with commercial samples of tung fruit, which vary widely in moisture content and usually range from 10.0 to 20.0% in oil content until adequate tests with such samples have been made.