Glycerophospholipids and sphingolipids are quantitatively the most important phospholipids (PLs) in milk. They are located on the milk fat globule membrane (MFGM) and in other membranous material of the skim milk phase. They include principally phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine, while sphingomyelin is the dominant species of sphingolipids There is considerable evidence that PLs have beneficial health effects, such as regulation of the inflammatory reactions, chemopreventive and chemotherapeutic activity on some types of cancer, and inhibition of the cholesterol absorption. PLs show good emulsifying properties and can be used as a delivery system for liposoluble constituents. Due to the amphiphilic characteristics of these molecules, their extraction, separation and detection are critical points in the analytical approach. The extraction by using chloroform and methanol, followed by the determination by high pressure liquid chromatography (HPLC), coupled with evaporative light scattering (ELSD) or mass detector (MS), are the most applied procedures for the PL evaluation. More recently, nuclear magnetic resonance spectrometry (NMR) was also used, but despite it demonstrating high sensitivity, it requires more studies to obtain accurate results. This review is focused on milk fat phospholipids; their composition, biological activity, technological properties, and significance in the structure of milk fat. Different analytical methodologies are also discussed.

Objectives:The objective of this study was to quantify human milk supply and intake of breastfed infants up to age 12 months. Additionally, human milk composition was quantified per energetic macronutrient and fatty acid composition in a subsample of lactating mothers. Methods:174 Italian breastfed children were followed using test-weighing and 3-day food protocols from birth to age twelve months. From a sub-sample of thirty mothers breast milk samples were collected at child ages one (T1), two (T2), three (T3), and six (T6) months, and were analyzed for the amount of protein, digestible carbohydrates, total lipids and fatty acid composition. Results:142 (82%) filled in at least one three-day food protocol within the first 12 months of life and complied with test-weighing of all milk feeds. The number of valid food protocols declined from 126 infants at one month to 77 at twelve months of age. Only galactose, non-protein nitrogen and protein decreased significantly from age one to age six months of lactation. Maternal BMI and age affected fatty acid levels in human milk. Median human milk intake decreased from 625ml at T1, over 724ml at T3 to 477ml/day at T6.Average energy and %energy from protein intake per day increased from 419 kcal (SD 99) and 8.4% (1.0) at T1, respectively, to 860 kcal (145) and 16.1% (2.6) at T12. Conclusion:These data provide a reference range of nutrient intakes in breastfed infants and may provide guidance for defining optimal nutrient intakes for infants that cannot be fully breastfed.4

In this work dynamic headspace capillary gas chromatography coupled with multivariate statistical techniques was applied to distinguish milks subjected to different heat treatments (pasteurization, direct ultrahigh-temperature method, and “in-bottle” sterilization). Results were obtained by taking into account a reduced, though significant, number of volatile compounds (acetone, 2-butanone, 2-pentanone, 2-heptanone, 3-methylbutanal, pentanal, hexanal, heptanal, dimethyl disulfide, toluene, and limonene). Moreover, the concentration of these volatile compounds, especially aldehydes and ketones, provided discriminant information about storage time and storage temperature in both whole and partially skimmed UHT milk. The analytical method was quite simple, rapid, and reliable and permitted the analysis of a large number of milks to be carried out by using a small volume of sample. This work represents an attempt to apply a method, generally used only for research purposes, to the quality assessment of heat-treated milk. Keywords: Milk volatile compounds; heat treatment; storage; thermal cold trapping (TCT)

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The aim of this research was to validate the results obtained previously by purge and trap (PT) and to investigate the ability of solid phase microextraction (SPME), a more rapid and less expensive technique, to discriminate drinking milk subjected to different heat treatments (i.e., pasteurization, ultrahigh temperature, "in-bottle" sterilization) and produced at different factories. The data obtained by both methods were processed by multivariate statistical analysis. PT and SPME showed comparable repeatability, although with different performances for the yield of extraction, and allowed the three milk categories to be distinguished. Within the chemical class of methyl ketones, 2-heptanone was found to be the most discriminating compound, and the possibility of using the concentration of this volatile as a marker for heat treatment was investigated.

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Despite the great interest paid to protein components in colostrum, fat also plays an important role in the supply of essential nutrients to provide energy, increase metabolism, and protect the newborn calf against microbial infections. This work aimed to elucidate levels of different fat components in colostrum, in particular fatty acid (FA), triglyceride (TG), cholesterol, and phospholipid contents. Colostrum samples from primiparous and multiparous (3-5 lactations) Holstein dams, fed the same ration indoors, were collected on the first 5d after parturition, analyzed, and compared with milk samples from the same cows collected at 5mo of lactation. Fat content during the first 5d of milking did not vary. However, the proportion of short-chain saturated FA increased and that of long-chain FA decreased. The concentration of n-3 FA was higher on the first day of calving than on the other days, with clear differences in the number and type of n-3 FA. Conjugated linoleic isomers and trans FA slowly increased from d 1 to 5, reaching a maximum at 5mo of lactation. Changes in the distribution profile of TG were observed as lactation progressed, with a shift from a prevalence of high-carbon-number TG (C48-50) on d 1 to a bimodal distribution (maxima at C38 and C50) on d 5, characteristic of mid-lactation milk. Cholesterol content was high in the first hours after calving and rapidly decreased within 48h. Colostrum sampled on d 1 also had a high content of phospholipids. Phosphatidylethanolamine and sphingomyelin were, respectively, lower and higher in the first 5d than in mid-lactation milk. The influence of lactation number on colostrum fat composition was also considered and significant results were obtained for all FA groups (except for polyunsaturated and n-6 FA) and TG content.

The effect of the stearoyl-CoA desaturase (SCD) gene on milk fatty acid composition was tested. Cows of 3 breeds of northern Italy, Piedmontese, Valdostana, and Jersey, were genotyped at exon 5 of the SCD gene. This has been suggested as a primary candidate gene to change the proportion of saturated vs. unsaturated fatty acids in milk, wherein a single nucleotide polymorphism (C/T) gives rise to a different AA codon. It was possible to ascribe a reduced desaturase activity to the T allele only in the case of caproleic and myristoleic fatty acids. In contrast with the findings of SCD effects on carcass fat, it was not possible to confirm the higher desaturation activity of this single nucleotide polymorphism on long-chain fatty acids, due to the different pathways that originate milk fatty acids of different carbon length; long-chain fatty acids are highly influenced by the complex metabolic events that affect the ingested nutrients during their transfer to milk fat.