Fresh Goat Milk Research Articles

Stereospecific analysis of fatty acid esters of chloropropanediol isolated from fresh goat milk.

The fatty acid esters of chloropropanediol isolated from goat milk fat in small quantities were subjected to a stereospecific analysis via phospholipase C and phosphocholine esters as intermediates. Synthetic rac-1-chloro-2,3-dioleoyl-propanediol was prepared by standard methods and was used as a control. The stereospecific analyses were performed following a release of the fatty acids from the primary positions of each chloropropanediol diester with pancreatic lipase. The resulting X-1-chloro-2-acylpropanediols were then converted into the corresponding phosphocholine derivatives by a stepwise reaction with phosphorus oxychloride and choline chloride. The X-1-chloro-2-acyl-3-phosphocholinepropanediols were subjected to hydrolysis with phospholipase C (C. perfringens), which hydrolyzed 50% of the phosphatide within two min and the rest of it in two hr. From previous experience with glycerol esters, it was assumed that the more rapidly hydrolyzed molecules were the sn-1-chloro-2-acyl-propanediol derivatives and the more slowly hydrolyzed ones the sn-2-acyl-3-chloropropanediol derivatives. A hydrolysis with phospholipase A2 (Crotalus adamanteus) released 50% of the total fatty acid along with the corresponding lyso compound within 10 min, after which there was no further reaction. The hydrolysis products were assayed directly by gas liquid chromatography (GLC) or were isolated by thin layer chromatography (TLC) prior to quantitation by GLC. Both naturally occurring and synthetic chloropropanediol diesters behaved similarly on stereospecific analysis and were therefore concluded to be racemic.

Characterization of Male Goat Odors: 6-Trans Nonenal

Solvent extraction and nitrogen degassing were employed to collect volatile odors from the lipid complex yielded by swabbing the sebaceous gland areas of the scalps of sexually active bucks from four breeds of goats. Gland tissue samples from freshly slaughtered bucks and does also were obtained for lipid analysis. Identified as the major compound responsible for one of the characteristic odors of the buck was 6-trans nonenal. Isolation of the compound as its 2,4-dinitrophenyl hydrazone was achieved by column and thin-layer chromatography. Tentative identification was based on comparison with known compounds by argentation thin-layer chromatography, retardation factors for the 2,4-dinitrophenyl hydrazone derivatives, and gas liquid chromatography retention times of regenerated compounds. The presence of other nonenals suggests that the compound may be formed by oxidation of the gland lipids.The odor of the male goat in rut often is implicated as a source of the “goaty” flavor problem in fresh goat milk. When added to goat milk, 6-trans nonenal yielded a significant melon-musky flavor response from the flavor panel; the “goaty” flavor response was more significant for added 4-ethyl octanoic acid, 4-methyl octanoic acid, and 4-ethyl oct-2-enoic acid.

Formation of Intracellular Fat Droplets: Interrelation of Newly Synthesized Phosphatidylcholine and Triglyceride in Milk

The lipogenic system of fresh goat milk was used to investigate the relationship of lipid synthesis to formation of fat droplets. The skim milk phase was incubated with [l-carbon-14] palmitate and incorporation of activity into the glycerolipids was assayed. In two representative experiments, 44 and 56% of the label was incorporated into the lipids. Most of this activity (78 to 84%) was in triglycerides. Of 12 and 10% activity in the phospholipids, about 60% was contained in phosphatidylcholine with substantially smaller amounts in the other phospholipids. The synthesis of triglyceride and phosphatidylcholine was further investigated in relation to distribution of labeled lipids in a cream layer and a sedimenting fluff (membrane) fraction derived by centrifuging the skim milks following incubation. The correlation coefficient for the amounts of activity in phosphatidylcholine and triglyceride in the cream layer was .97. The data are consistent with synthesis of phosphatidylcholine and triglyceride to meet the requirements of surface and volume expansion, respectively, in formation of fat droplets. Our findings suggest the interesting working hypothesis that phosphatidylcholine synthesis regulates development of fat droplets.

"Sunbursts" and "christiesomes": cellular fragments in normal cow and goat milk.

Goats' milk includes numerous cell fragments ("christiesomes") which originate from the mammary secretory cells, contain well preserved endoplasmic reticulum, mitochondria and lipid droplets, and are responsible for the considerable triglyceride synthesising capacity of fresh goat milk. Cows' milk shows a few such particles only after repeated oxytocin-aided milkings. Cows' milk does contain quite different particles which have a dense content with a few small vesicles and numerous microvillus-like protrusions on one side ("sunbursts"). These have not been found in goats milk. Cytoplasmic particles similar to sunbursts have been found on the surface of the mammary secretory epithelium. It is suggested that they are residues of dead cells.