Composition of bovine milk lipids

Recent literature on the composition of milk lipids is reviewed and discussed. Many additional exotic fatty acids, mainly branched chain, keto, hydroxy and isomers containing double bonds, have been identified, often with the aid of mass spectrometry. It is estimated that ca. 500 fatty acids have been found in milk lipids. Components of lipid classes have been isolated and their structure determined, e.g., glucosyl and lactosyl ceramide, sphingomyelin, ether lipids, etc. The fatty acid composition of “protected” milk is discussed. This milk, obtained from cows fed polyunsaturated oils encapsulated with formaldehyde-treated casein, contains about five times more linoleic acid than regular milk. The future of research on milk lipids is promising, as there are still many intriguing problems of separation and identification. One of eight papers presented in the symposium “Milk Lipids,” AOCS Meeting, Ottawa, September 1972. Contribution No. 528, Storrs Agricultural Experiment Station, University of Connecticut, Storrs.     

Fatty acid composition of monkey milk lipids

Milk from 6 species of monkeys contained 2.2–8.5% total lipids, and 11.5–16.5% total solids. The fatty acid composition of the milks, as determined by an improved gas liquid chromatographic techniques, was generally similar among the six species. The predominant fatty acids (by wt) were capric (7.5–14.6%), palmitic (19.4–23.3%), oleic (22.4–30.3%), and linoleic (13.6–15.2%). Small amounts of butyric (0.1–1.2%) and caproic (0.5–0.8%) acids were present in all samples. The averaged data were compared with the fatty acid compositions of primate and cow milks. Milks of the nonhuman primates contained less myristic, but more caprylic and capric acids, than did human or cows' milk. Data taken from thesis of S. Hardjo submitted in partial fulfillment of the requirements for the Masters' degree in food science.     

Fatty acid composition of baboon milk lipids

The predominant fatty acids of mature baboon milk were shown by gas-liquid chromatography to be (by weight) palmitic (16%), oleic (23%), and linoleic (38%) acids. The high proportion of linoleic acid was attributed to the corn oil in the diet. Less myristic acid (1.3%), but more caprylic (5%) and capric (8%) acids, were present in baboon milk than in human milk. The proportions of these short-chain fatty acids were highest during early lactation.     

Composition of the lipids in human milk: A review

Recent publications on the composition of human milk are reviewed. The importance of proper sampling is discussed. Fat contents of 2.6–4.5% and cholesterol amounts of 200–650 mg/100 g fat were reported. The phytosterols in milk were increased by the consumption of these sterols. Phytosterols could contribute to the “total cholesterol” in milk if analyses are done colorimetrically. The fatty acid composition is remarkably uniform unless bizarre diets are consumed; the amounts of linoleic acid vary the most. Phospholipids contained more long chain polyunsaturated fatty acids than triacylglycerols. Scientific Contribution No. 786, Storrs Agricultural Experiment Station, University of Connecticut, Storrs, CT 06268.     

The simultaneous separation and quantitation of human milk lipids

A protocol using a dry column method was modified for the extraction of total lipids and the simultaneous separation and quantitation of neutral and polar lipids in human milk. The triacylglycerol, cholesterol, phospholipid and vitamin E contents of the lipid extracts were determined and compared with lipids extracted using a modified Folch procedure. Good precision for the extraction of neutral, polar and total lipids, as well as the different lipid classes, was demonstrated. No significant differences were found between the two methods with respect to the amount of cholesterol, phospholipid, total lipid or vitamin E extracted, thus validating the method as an extraction technique. We discuss the relationship between vitamin E and the three major milk lipids as an indicator of the vitamin's place of origin in the mammary gland. Our findings do not support the idea that vitamin E in mature milk has its original location in the apical membrane. Scientific Contribution No. 1254, Storrs Agricultural Experiment Station, University of Connecticut, Storrs, CT 06269.     

Differences in CLA isomer distribution of cow's milk lipids

The uniqueness of ruminant milk lipids is based on their high concentration of CLA. Maximal CLA concentrations in milk lipids require optimal conditions of ruminal fermentation and substrate availability, conditions like those present in pasture-fed cows. Our previous work showed that farm management (indoor feeding vs. pasture feeding) markedly influenced the CLA concentration. In this study, the objective was to evaluate the influence of the farm management system as dependent on different locations. Milk samples from different locations (Thuringia and the Alps, representing diverse altitudes) were collected during the summer months and analyzed for FA profile and CLA isomer distribution. The proportion of PUFA and total CLA in milk fat was significantly lower in milk from indoor cows compared with the pasture cows in the Alps. The trans-11 18∶1 in milk fat of Alpine cows was elevated, in contrast to lower values for trans-10 18∶1. Milk from cows grazing pasture in the Alps was higher in EPA and lower in arachidonic acid than milk from indoor-fed cows. The proportion of cis,trans/trans,cis isomers of CLA was 10 times higher from the indoor cows than from the Alpine cows. In addition to the major isomer cis-9,trans-11, this difference also occurred for the trans-11,cis-13 isomer, which represented more than a fourth of the total CLA present in milk fat. This is the first report showing a special isomer distribution in the milk fat of cows living under very natural conditions. We hypothesize that the CLA isomer trans-11,cis-13 is formed in large quantity as a result of grazing mountain pasture, which is rich in α-linolenic acid.     

Fatty acid composition of polar lipids in goats' milk

Silicic acid column chromatography was used to separate the polar lipids of goats' milk into glycolipid, phosphatidylethanolamine, phosphatidylserine plus phosphatidylinositol, phosphatidylcholine, and sphingomyelin fractions. Each fraction was purified by column chromatography and its fatty acid profile determined by gas liquid chromatography and mass spectrometry. The glycerophospholipids each contained 18∶1 as the predominant fatty acid (∼45%). The sphingolipids contained a high percentage of long-chain saturated fatty acids (C₂₂ to C₂₄>45%); the glycolipid fraction also contained ca. 2% 2-hydroxy fatty acids. The data represent a comprehensive cross-sectional study of the major polar lipids found in goats' milks.     

"国际建筑密封胶/胶粘剂耐久性会议"简介

简要介绍了美国ASTM C24分会主办的“国际建筑密封胶服粘剂耐久性会议”的内容。     

The phytanic acid content of the lipids of bovine tissues and milk

In three steers which were given grass silage for six months, the content of phytanic acid (i.e. 3,7,11,15-tetramethylhexadecanoic acid) in plasma lipid increased to about 8% of the total fatty acids, whereas after this time the proportion in the total fatty acids of liver and heart lipids was about 1%, and only 0.1% in those of kidney lipids; the acid was present in trace amounts in adipose-tissue triglycerides and was apparently absent from brain lipids. In eight lactating cows which were given grass silage for about 3 months, the content of phytanic acid in the total long chain fatty acids of milk and of plasma was 0.7% and 13%, respectively. In the plasma lipids of both steers and lactating cows, phytanic acid constituted a substantial proportion of the total fatty acids of the triglycerides and phospholipids; the acid was present in lowest proportion in the cholesteryl esters.     

The effect of dietary fat on the fatty acid composition of lipids secreted in rats' milk

During pregnancy and lactation, female rats were fed diets containing either 28% partially hydrogenated marine oil (28MO), 2% arachis oil (2AO), or no fat (FF). Milk lipid composition was examined by gas chromatographic analysis of the gastric content of 10-day-old suckling pups. An increase to 45% in the milk content of long chain monoenoic acids, 18∶1, 20∶1 and 22∶1, reflects the fatty acid composition of the marine oil. Milk fatty acids of medium chain length comprised 6%, 31% and 24% of total fatty acids in the (28MO), (2AO) and (FF) groups, respectively, suggesting that a high-fat diet (28MO) inhibits the lipid synthetic activity of mammary glands. The amount of dienoic C₁₈-acids (6%) in the group fed (28MO) containing no essential fatty acids (EFA) was similar to the amount of 18∶2 in the group receiving a low-fat, EFA-rich diet (2AO). However, only half the dienoic acid from the milk of the (28MO)-fed animals was linoleic acid, which was most likely mobilized from fat depots.     

On the probable origin of some milk fat acids in rumen microbial lipids

The quantity and character of the microbial lipid isolated from rumen digesta are interpreted as indicating that significant quantities of milk fat acids originate from rumen microbial synthesis of long chain acids from volatile fatty acids. Component fatty acid patterns are presented of rumen bacterial lipid, crude rumen protozoal lipid, blood serum lipid, and milk lipid isolated from samples taken from a lactating Holstein. Certain rumen bacterial lipid fractions are shown to be very rich sources of odd carbon acids and branched acids, and it is suggested that the major source of these acids in ruminant fats is from bacterial synthesis rather than animal synthesis. Scientific Article No. A950, Contribution No. 3313 of the Maryland Agricultural Experiment Station (Dairy Department).     

Trans- and cis-octadecenoic acid isomers in the hump and milk lipids from Camelus dromedarius

The distribution profiles of individual trans- as well as cis-18∶1 isomers from the fat prepared from the hump adipose tissue and the milk from Camelus dromedarius (the single-humped Arabian species) are described. Gas-liquid chromatography on two capillary columns with different polarities and lengths were used for this purpose in combination with argentation thin-layer chromatography. A comparison of the profiles established is made with that of true ruminant fats. In the fats from the dromedarius as well as from true ruminants, the trans-18∶1 isomers have their ethylenic bonds in all positions between Δ4 and Δ16. The prominent trans isomer is the 11–18∶1 (vaccenic) acid in all species, and the complete distribution profiles are quite similar. Concerning the cis isomers, the prominent isomer is oleic acid, followed by cis-vaccenic acid, as in true ruminant fats. Other cis isomers encompass the Δ6–8 and the Δ12 to Δ15 isomers. Camelidae (suborder Tylopoda) and Bovidae (suborder Ruminantia) have evolved independently since the Eocene, that is for approximately 50 million years. Despite this considerable period, and the profound differences in anatomy, morphology, physiology, ecological and dietary habits between the extant species of these suborders, the rumen microflora has continued to synthesize the same trans- and cis-octadecenoic acid isomers, in comparable proportions, at least as deduced from their composition profiles. We conclude that the trans-18∶1 acid profile is not intrinsically species-dependent, but it can be affected by the nature and the proportions of dietary unsaturated fatty acids that themselves depend on the feed, and that may be species-specific.     

Changes in lipids of pigeon “milk” in the first week of its secretion

Pigeon “milk” (PM) collected from the crop of 1- to 5-day-old squabs was analyzed to examine whether there were changes in lipid composition during the first week of secretion. The high PM fat content (9–11%) remained fairly constant in the first 5 days of secretion. The mean percentage of neutral lipids, glycolipids and phospholipids was 80, 12 and 8%, respectively. Unlike the content of neutral lipids, glycolipid and phospholipid levels increased significantly between day 1 and day 5 of secretion. Triglycerides, the major neutral lipids, decreased by 24% between day 1 and day 5, while free sterols, monoglycerides and hydrocarbons increased by 8%, 11% and 2.5%, respectively, during the same period; diglycerides and sterol esters, however, remained unchanged. The ratio of saturated to unsaturated fatty acids was 0.27 and it remained unchanged. Medium-chain (C₁₀, C₁₂ and C₁₄) and oddchain (C₁₅ and C₁₇) fatty acid contents were low. Fatty acids longer than C₂₀ were absent. Palmitic acid, the major saturated fatty acid, increased by 42% from day 1 to day 5, whereas stearic acid decreased by 48% during the same period. Oleic acid, the predominant unsaturated fatty acid, also decreased from 51 to 45% between the first and fifth day of PM secretion. Polyunsaturated acids (18∶2, 18∶3 and 20∶4) accounted for 26% and 30% of the total fatty acids on day 1 and day 5, respectively. Although lipid changes in the crop of squabs prior to collection of samples cannot totally be ruled out, the nature of lipid changes is likely to reflect cellular breakdown that precedes PM secretion by parent pigeons.     

Effects of minor lipids on crystallization of milk fat-cocoa butter blends and bloom formation in chocolate

Minor lipids, such as diacylglycerols, monoacylglycerols, cholesterol, and phospholipids play a key role in crystallization of fats. In this study, the effects of minor lipid components on crystallization of blends of cocoa butter (CB) with 10% milk fat or milk-fat fractions, and on bloom formation of chocolate were investigated. Both removing the minor lipids from milk fat and doubling the level of minor lipids from milk fat resulted in longer nucleation onset time, slower crystallization rate, and rapid bloom development in chocolate. Removal of minor lipids resulted in the formation of irregular primary and secondary crystals with inclusions of liquid fat, whereas the crystals were spherical and uniform in shape in the presence of minor lipids. Minor lipids from milk fat, even at the low concentrations typically found in nature, affected the crystallization of milk fat-CB blends, impacted the chocolate microstructure, and affected bloom development in chocolate.     

Visual acuity and blood lipids in term infants fed human milk or formulae

This multicenter, parallel group study determined plasma phospholipid and red blood cell (RBC) phosphatidylcholine and phosphatidylethanolamine fatty acids, plasma cholesterol, apo A-1 and B, growth and visual acuity (using the acuity card procedure) in term infants fed from birth to 90 d of age with formula containing palm-olein, high oleic sunflower, coconut and soy oil (22.2% 16∶0, 36.2% 18∶1, 18% 18∶2n−6, 1.9% 18∶3n−3) (n=59) or coconut and soy oil (10.3% 16∶0 18∶6% 18∶1, 34.2% 18∶2n−6, 4.7% 18∶3n−3) (n=57) or breast-fed (n=56) with no formula supplementation. Different centers in North America were included to overcome potential bias due to differences in n−6 or n−3 fatty acids at birth or in breast-fed infants that might occur in a single-site study. Plasma and RBC phospholipid docosahexaenoic acid (DHA, 22∶6n−3) and arachidonic acid (AA, 20∶4n−6), cholesterol and apo B were significantly lower in the formula- than breast-fed infants. There were no differences in looking acuity or growth among the breast-fed and formula-fed infants. No significant relations were found between DHA and looking acuity, or AA and growth within or among any of the infant groups. This study provides no evidence to suggest the formula provided inadequate n−6 or n−3 fatty acids for growth and looking acuity for the first 3 mon after birth.