A new procedure for the analysis of tung fruit

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.

The determination of the oil content of ground tung fruit

Gilbert¹,

Gropp²

1951

Comparison of the whole fruit and component methods of analysis of tung fruit

Pack¹,

Holmes²,

McKinney³

1950

Summary The effect of moisture content and fineness of grinding on the percentages of oil extracted by the whole fruit method were investigated and the results compared with those obtained by the component method. The spacing of the plates on the Bauer laboratory mill used for grinding whole tung fruit for oil analysis was found not to be critical within certain narrow limits. No differences were found in the oil content when samples of fruit were ground with plate spacings from 0.004 inch to 0.012 inch, but the results were lower with plate spacings of 0.020 inch. No difference was found in the percentages of oil obtained by the component and the whole fruit methods when the results were calculated on the basis of the original moist sample and no correction had to be applied in the calculation of the results by the whole fruit method. The average percentage of moisture obtained by the two methods differ, consequently care must be used in comparing oil contents calculated to a moisture‐free basis since the differences in moisture content will be reflected in the values for the apparent oil content. Careful analyses of tung fruit by either the whole fruit or the component method yield reliable results over a wide range of moisture content although in the case of the component method unusually wet kernels (above 10% moisture) must be partially dried before regrinding in a mortar and pestle during the extraction operation.

Loss of oil in hulling tung fruit in the field and at the mill

McKinney¹,

Holmes²,

Minor³

et al. 1953

SummaryMethods for analyzing commercial tung hulls for oil have been developed. Samples of tung hulls from mill and field hulling operations have been collected and analyzed. The loss of oil when the fruit are hulled was found to vary from 0.6% to 7.3% with an average loss of 2.7% based on the total amount of oil in the fruit. The difference in the loss of oil between grove and mill hulling was not significant. With a loss of 2.7% of the oil in hulling, a recovery of 87.9% oil on the hulled nuts would be equivalent to a recovery of 85.5% oil on the whole fruit.