Solubility and Volatility of Fatty Acids Involved in Lipolysis in Homogenized Raw Milk

Abstract

Homogenization of raw milk, a process known to greatly accelerate lipase activity, results in immediate increase in the free fat ty acid content of the fat with homogenization at 1500 pounds pressure increasing the free fat ty acids approximately five-fold within a few minutes following processing (6). Since information relative to the characteristics of the fat ty acids involved in this lipolysis is meager, experiments were Conducted to ascertain their solubility and volatility. The results of these experiments are herein presented. Steam distillation procedures have been used to study the volatility of free fat ty acids in milk and milk products. Roahen and Sommer (9) used this procedure to measure the extent of lipolysis in milk and cream and Fouts (4) studied the volatility of free fat ty acids in butteroil of varying acid degrees secured from butter by steam distillation of 10 grams of fat and collecting and titrating 200 ml. of distillate. He secured values for volatile fat ty acids approximating 15 per of the total fat acidity. Davies (2) reports that volatile acids account for less than five per cent of the total titratable value of the fat ty acids, whereas oleic acid is responsible for 60-70 per cent of this value. Dyer (3), and Hiscox and Harrison (7), used steam distillation in the study of pure volatile organic acids. Hiscox and Harrison (7) steam distilled acetic, butyric, caproic, caprylic, capric, and lauric acids (acids neutralized with NaOH and then acidified to pH 2 with H2S04) and secured complete recovery from water when distillate volume was 5 times original volume. Recovery of these acids from cheese was retarded, the retardation being especially marked for acetic, caprylic, caproic, and lauric acids. Butterfat and cheese fat also retarded distillation of the water-insoluble fatsoluble acids. Methods of preparing samples of cheese for steam distillation were studied by Hiscox, Harrison, and Wolf (8). They found that a method involving warm water washing of the cheese to obtain the fat, ether extraction of the fat, washing of the fat with NaOH, acidifying and steam-distilling this rinse, resulted in volatile acid values which were about 4.5 times as high as those from direct steam distillation in the case of Stilton cheese and about twice as high in the case of Cheddar.