Determination of Fat in Dairy Products Using Pressurized Solvent Extraction

Abstract

Gravimetric fat data were obtained for a wide range of dairy products with fat contents ranging from 0.5 to 83% using pressurized solvent extraction at elevated temperatures and pressure (80–120°C; 10.3 MPa). Extraction performance was sensitive to solvent composition, temperature, and sample matrix. By optimizing solvent mixtures, sample–solvent contact times of 8–10 min were sufficient for high recoveries from all products tested. The most successful solvents with regard to speed of extraction, selectivity, and recovery (average recovery, %) were various mixtures of hexane (or petroleum ether)–dichloromethane–methanol for dried cream (99.8%), dried whole milk (99.6%), dried buttermilk (98.2%), dried skim milk (97.0%), dried whey protein concentrate (97.5%), casein (95.0%), and caseinate (102.1%); petroleum ether–acetone–ethanol or petroleum ether–acetone–isopropanol for cheddar-type cheese (99.4%); petroleum ether–acetone for butter (99.9%); petroleum ether–acetone–isopropanol for cream (100.3%); and petroleum ether–isopropanol for liquid milks (99.0%). Relative standard deviations for repeatability were obtained for dried whole milk (0.2%), dried whey protein concentrate (0.7%), cheese (0.3%), butter (0.1%), and ultraheat treated (UHT) milk (0.7%). Solvent removal and drying of extracts with a heated block evaporator saved time compared with conventional drying ovens. Estimated savings in labor (50–75%) and solvents (80%) were substantial compared with the manual Mojonnier methods.

Gas chromatographic quantification of fatty acid methyl esters: Flame ionization detection vs. Electron impact mass spectrometry

“…By contrast, the SRM values were determined by 18-24 h Soxhlet extractions of 2.5 g tissue homogenate samples with hexane/acetone. Although the performance of accelerated solvent extraction for lipid extraction has been addressed elsewhere and deemed sat-isfactory (21)(22)(23)(24)(25)(26)(27), these different approaches may be partly responsible for some of the minor discrepancies between the present results and the NIST SRM certified values; however, since the same extract was analyzed by all methods, the results are indeed suitable for direct comparison among the various quantification methods.…”

“…The tissue homogenate was extracted using a Dionex ASE 200 accelerated solvent extractor (Sunnyvale, CA) (20). Conditions similar to those previously described for lipid extraction were used (21)(22)(23)(24)(25)(26)(27).…”

Microscale recovery of total lipids from fish tissue by accelerated solvent extraction

“…Compared with other methodologies, there have to date been relatively few accounts of lipid recovery by ASE. The presently available reports describe the application of ASE for lipid isolation from plant and animal tissue (10)(11)(12)(13), eggcontaining foods (14), and dairy products (15). Although these studies have established ASE as a viable lipid extraction method, several avenues of further development remain to be pursued.…”

Rapid extraction of total lipids and lipophilic POPs from all EU-regulated foods of animal origin: Smedes’ method revisited and enhanced

“…Recoveries of polycyclic aromatic hydrocarbons (PAHs) from urban dust and marine sediment samples and of PCBs from sewage sludge and oyster tissue are reported as quantitative [69]. ASE may further be applied for lipid extraction from (marine) animal tissue [74][75][76][77], egg containing foods [78] or dairy products [79]. Chloroform-methanol, hexane-propane-2-ol, or methylene chloride have been used to extract fish tissue [74], egg yolk can be extracted with propan-2-ol:hexane (2:3, v/v) [75], egg-containing foods with chloroform:methanol (2:1, v/v) and hexane:propan-2-ol (3:2, v/v) [76], and poultry tissue with chloroform:methanol (2:1, v/v) [75,76].…”