"Free fat" solvent extraction methods damage milkfat globules

The "free fat" solvent extraction method is used to assess milkfat globule damage in milk and cream and is based on the supposition that, in contrast to fat from damaged globules, fat from intact globules is not extracted. Th e present study showed that the amount of "free fat" extracted was signific antly affected by the conditions under which the extraction was performed. Increasing the extraction time, the number of extractions, the degree of ag itation during the extraction and the ratio "sample weight:solvent volume", all resulted in a greater amount of "free fat". Two extraction temperature s, and 5 different solvents, n-hexane, iso-octane, toluene, tert-butyl meth yl ether and n-butanol, were also investigated. More "free fat" was extract ed at 22 degreesC than at 40 degreesC, and of the solvents, the highest amo unts of "free fat" were obtained from tert-butyl methyl ether (12% of total fat) and n-butanol (46% of total fat) after one extraction. Depending on t he parameters chosen, the amount of "free fat" ranged from 2-40% of total f at for raw milk, and 2-70% of total fat for raw cream. It appears that the "free fat" result is either partly or wholly an artefact of the method, and the supposition underlying the method does not seem plausible.