Methods for Percent Oil Analysis of Avocado Fruit

Abstract

The 8% oil criterion for avocado was established in 1925 to insure minimum maturity and quality. However, determination of the oil content of avocado fruit is expensive, time consuming, and tedious, especially for growers who lack the necessary laboratory and equipment. A simpler method would be more useful for growers and also for packers. The standard method for analyzing the oil content is done by the petroleum ether extraction of dried material in a Soxhlet extractor. However, this method is too expensive and requires too much time to be generally useful in the avocado industry. Lesley and Christie (1929) described a relatively short method which uses Halowax oil (monochloronaphthalene) as a solvent and a refractometer for determination of oil content in avocado tissue. Two other methods, the NMR method and the simplified method (oilplus-water constant method), have been tested in connection with oil content determination. The detailed procedures of the Soxhlet, Halowax, NMR, and oil-plus-water constant methods are described and compared.