P.S. Dimick

The flavor potential of milk fat. A review of its chemical nature and biochemical origin

Actual and potential flavors are among the most important attributes of milk fat. In some dairy products (milk, cream, ice cream, uncul-tured butter) the aim is to retain the faint pleasant flavor associated with the fat of fresh milk. However in cooking, baking, and many processed food applications the object is to gen-erate buttery, creamy, cheesy, and caramel-like flavor qualities from milk fat. Although the ulti-mate chemical characterization of all these fla-vors has not been achieved, the existing infor-mation is reviewed in this paper. Some recent findings concerning the biological variability and significance of the lactone and ketone flavor po-tential of milk fat are also presented. A scheme which outlines means for more effectively utiliz-ing the flavor capabilities of milk fat is included.

Thermal analysis of palm mid-fraction, cocoa butter and milk fat blends by differential scanning calorimetry

Commercial samples of anhydrous milk fat (AMF), Ivory Coast cocoa butter (CB) and palm mid-fraction (PMF) were blended in a ternary system. The melting characteristics of the blends were studied by differential scanning calorimetry (DSC). Results suggest that in the studies of interaction involving more than two fats, partial area (Ai) under the melting peak should be converted to partial enthalpy (ΔHi) rather than to solid fat index. The ΔH values of the blends decreased as the amount of AMF was increased and increased as the amount of CB was increased. In general, the effect of PMF was less pronounced compared to the effect of the other two fats. Eutectic effects within the ternary system could be detected by measuring the deviation of melting enthalpy by DSC, and from the corresponding values that were calculated for the thermodynamically ideal blends. The deviation reached a maximum when the amount of AMF was about 33%. On the binary line of CB/PMF, the eutectic effect was maximum at about 50–75% PMF. The interaction effect in the system was more noticeable at 30 and 20°C than at lower temperatures. Evaluation at 30°C was preferred because both the effect of AMF in the ternary system and the effect of PMF on the binary line were more readily observed.

Chromatographic separation of lactone precursors and tentative identification of the γ-lactones of 4-hydroxy octanoic and 4-hydroxy nonanoic acids in butterfat

A combination of silicic acid column and thin layer chromatography which separates γ- and δ-hydroxy acid containing glycerides from butterfat is described. This procedure facilitates the isolation of the γ- and δ-hydroxy acids (lactone precursors) while avoiding lactonization. The method indicated that the hydroxy acids are entirely esterified to the glyceride in fresh butterfat. Hydrolysis, using pancreatic lipase, showed that these polar acids are located on the α-positions of the glycerides. The γ-lactones of 4-hydroxy octanoic and 4-hydroxy nonanoic acids were tentatively identified by gas liquid chromatography. These occurred in quantities of 0.25–0.5 ppm and approximately 0.2 ppm respectively in the butterfat samples investigated.

Melting and solidification characteristics of confectionery fats: Anhydrous milk fat, cocoa butter and palm kernel stearin blends

Differential scanning calorimetry measurements of crystallization and melting characteristics of commercial samples of anhydrous milk fat (AMF), cocoa butter (CB) and hydrogenated palm kernel stearin (PKS) in ternary blends were studied. Results showed that stabilization at 26°C (either for 40 h or 7 d) did not greatly affect the melting thermogram trace of PKS. However, the effect of stabilization became prominent as CB was added into the system. Deviation of measured enthalpy from the corresponding values, calculated for thermodynamically ideal blends, showed clear interaction between all three fats. At 20°C, the strongest deviation occurred at about the AMF/CB/PKS (1∶1∶1) blend, whereas at 30°C the deviation moved toward the CB/MF (1∶1) blend. The presence of 25% AMF in PKS had little effect on its solidification capability, but solidification was adversely affected with inclusion of CB.

The prevalence of aliphatic delta-lactones or their precursors in animal fats.

Data are presented to show the occurrence of saturated aliphatic delta lactones, namely the δ-C10, δ-C12, δ-C14, and δ-C16, in numerous ruminant and monogastric animal fats. These trace components were isolated by silicic acid adsorption chromatography followed by identification employing gas chromatography. The general prevalence of the delta-lactones or their precursors in animal depot fat, mammary tissue, blood serum lipids and milk fat is suggestive that they occur commonly in animal fats and are related to lipid metabolism.

Incorporation of [1-14C]acetate into the aliphatic δ-lactones of ruminant milk fat

Abstract 1. 1. Gas-liquid radiochromatography was employed to demonstrate that 14C from [1-14C]acetate was incorporated in vivo into the aliphatic δ-lactones (δ-hydroxy fatty acids) of goat milk fat. 2. 2. The δ-C10, δ-C12, δ-C14 and δ-C16 lactones were isolated from milk fat samples collected at 5, 10, 15, 20 and 25 h following intravenous and intramammary administration of [1-14C] acetate to two goats and the specific activities of the δ-lactones were determined. These values, in general, were of comparable magnitude to the specific activities of the saturated milk fatty acids of corresponding carbon chain lengths. 3. 3. Following intravenous administration of [1-14C]acetate both the δ-lactones and the saturated fatty acids exhibited maximum specific activities at 5 h whereas following intramammary administration the δ-lactones and fatty acids exhibited maximum specific activities at 10 h. 4. 4. The results are consistent with the view that acetate is a common precursor of both the δ-lactones (δ-hydroxy fatty acids) and the saturated fatty acids and imply that the (δ-hydroxy fatty acids are produced from acetate in a manner similar to biosynthesis of the corresponding fatty acids rather than as products of long chain fatty acid oxidation.

High levels of acetone found in male turkey skin.

Investigation of the carbonyl compounds in the hexane extractable lipid of raw poultry skin revealed that the only monocarbonyl present was acetone. Furthermore, in male turkeys the level of acetone was significantly greater than the level observed in either chickens or female turkeys. During maturation, increased acetone concentrations were accompanied by low lipid deposition in the tissue.