Total milk fat extraction and quantification of polar and neutral lipids of cow, goat, and ewe milk by using a pressurized liquid system and chromatographic techniques

Abstract

Although milk polar lipids such as phospholipids and sphingolipids located in the milk fat globule membrane constitute 0.1 to 1% of the total milk fat, those lipid fractions are gaining increasing interest because of their potential beneficial effects on human health and technological properties. In this context, the accurate quantification of the milk polar lipids is crucial for comparison of different milk species, products, or dairy treatments. Although the official International Organization for Standardization-International Dairy Federation method for milk lipid extraction gives satisfactory results for neutral lipids, it has important disadvantages in terms of polar lipid losses. Other methods using mixtures of solvents such as chloroform:methanol are highly efficient for extracting polar lipids but are also associated with low sample throughput, long time, and large solvent consumption. As an alternative, we have optimized the milk fat extraction yield by using a pressurized liquid extraction (PLE) method at different temperatures and times in comparison with those traditional lipid extraction procedures using 2:1 chloroform:methanol as a mixture of solvents. Comparison of classical extraction methods with the developed PLE procedure were carried out using raw whole milk from different species (cows, ewes, and goats) and considering fat yield, fatty acid methyl ester composition, triacylglyceride species, cholesterol content, and lipid class compositions, with special attention to polar lipids such as phospholipids and sphingolipids. The developed PLE procedure was validated for milk fat extraction and the results show that this method performs a complete or close to complete extraction of all lipid classes and in less time than the official and Folch methods. In conclusion, the PLE method optimized in this study could be an alternative to carry out milk fat extraction as a routine method.

Comprehensive Study of the Lipid Classes of Krill Oil by Fractionation and Identification of Triacylglycerols, Diacylglycerols, and Phospholipid Molecular Species by Using UPLC/QToF-MS

“…Krill Oil Analysis by HPLC-ELSD, Fractionation by FC-ELSD, and Characterization of Lipid Classes Figure 1 shows the profile of lipid classes of KO analyzed by HPLC-ELSD for the separation of neutral and/or polar lipids in qualitative and quantitative conditions following the procedure described by Castro-Gomez et al (2014). The results revealed that KO was mainly composed of TAGs and PLs (43.7 and 48.9 %, respectively) and other minor compounds (Table 1).…”

“…Samples of KO as well as the isolated KO fractions were prepared at 5 mg/mL, and the injection volume was 50 μL. Solvent gradient was as detailed in Castro-Gomez et al (2014). Analyses were carried out with solvents freshly prepared.…”

Effect of ewe’s (semi-skimmed and whole) and cow’s milk yogurt consumption on the lipid profile of control subjects: a crossover study

“…Yogurt fat was extracted from the freeze-dried yogurt samples following the Folch method modified according to Castro-Gómez et al [47]. The fat samples were derivatized following the method described in Castro-Gómez et al [48].…”

Isolation and Analysis of Phospholipids in Dairy Foods

“…However, these data have been further updated/completed by the works carried out on small ruminants' milk and some of its products by Yao et al [36], Castro-Gómez et al [37], Zancada et al [38], Contarini and Povolo [39], Rodríguez-Alcalá and Fontecha [40] (this latter also focused on powder buttermilk), and Park [41]. Moreover Barry et al [42] reported the PL composition of butter, butterserum, cream, butteroil, and whole and skimmed milk while Fong et al [43] analysed infant formulas and Ferreiro et al [44] described the evolution of PL concentration during the production of quark cheese.…”

“…Some approaches to the development of faster methods (10 minutes) have been focused on the utilization of pressurized liquid extraction (PLE) for the isolation of milk fat from goats', ewes', and cows' milk with a dichloromethane/methanol solution (2 : 1 v/v) as solvent mixture at 10.3 MPa and 60°C [37]. These authors did not find differences between the molecular species composition of TG and the total fatty acid profile of the assayed milks by PLE or Folch's method.…”