The purpose of this investigation was to modify the procedure
of Bills, Khatri and Day for use in the development of a suitable
method for determining the quantitative distribution of the free fatty
acids (FFA) in normal, heated, and rancid milk and milk fractions
The method consists of extracting the FFA from lyophilized
milk, separating the FFA from neutral fat, converting the FFA to
methyl esters, and analyzing the methyl esters by gas-liquid chromatography
(GLC). The salts of FFA present in lyophilized milk or milk
fractions were released by lowering the pH of the sample with H₂SO₄,
and subsequently extracted with ethyl ether. The extracted FFA were
simultaneously isolated from the extract and methylated by using the
one-step procedure of Bills, Khatri and Day. A specially designed
concentration flask was employed with a reflux system to concentrate
the methyl esters. The esters were then separated by GLC. Quantitative
calculations were made from the GLC peak areas using internal
standards.
The major esterified fatty acids of milk are n-saturated, evennumbered
4:0-18:0 and unsaturated 18:1 and 18:2 acids. The distribution
of major FFA in whole milks was found to be essentially the
same as that of the esterified fatty acids of milk fat.
Heat treatments of milk, whether pasturization or extended
holding at 100°C, effect a progressive reduction in total FFA. Decreases
in long chain fatty acids are also characteristic of extended
heating.
Milks determined to be rancid by acid degree value and organoleptic
analysis showed high levels of FFA, 1.5-3.6% of the fat content
of the sample. The increases in 6:0-12:0 resulting from lipase hydrolysis
approximate the amounts shown by Al-Shabibi and co-authors
to produce rancid flavor when added to good quality milk.
Milk triglycerides, fat globule membrane, skim milk, and buttermilk
show characteristic FFA patterns which appear to be related
to the solubility properties of the individual acids. Seventy-one percent
of the total FFA in a given portion of 40% cream was found in the
triglyceride fraction, 26% in the crudie fat globule membrane preparation
and 3% in the skim milk fraction.
The total concentrations of FFA were found to be: 1% of the fat
in whole milk or 0.04% of the fluid milk weight; 0.16% of the total
weight of 40% cream; 0.28% of centrifuged triglycerides; 1.7% of the
fat globule membrane; and 0.008% of the fluid weight of skim milk. / Graduation date: 1965
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26779 |
| Date | 29 September 1964 |
| Creators | Kintner, Judith Ann |
| Contributors | Day, Edgar Allen |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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