Rapid Lipid Extraction from Egg Yolks

Abstract

Total or crude fat determination is commonly measured in lipid chemistry by traditional methods such as Soxhlet or Goldfisch extraction. These methods require hours of solvent reflux extraction, which may be necessary when lipids are well embedded into tissues and the surface area to weight ratio is low. However, many food materials may have oil that can be readily extracted without such exhaustive solvent extraction. Simple, practical, rapid extraction techniques are more cost effective when dealing with large number of samples if the lipids can be readily extracted from the food matrix.Clark and Snyder [1] developed a rapid, 1-min equilibrium extraction method of a 1-2-g soy flour sample with hexane at ambient temperature that produced results similar to those obtained by Goldfisch extraction to allow rapid screening of soybean cultivars. Subsequently, we developed a rapid, 1-min method for total lipid extraction with hexane and isopropanol of 2 g of rice bran samples for free fatty acid determination that produced the same results as the Goldfisch extraction [2]. Similarly, the oil contents of milled rice and potato chips were determined by rapid solvent extraction [3,4].However, we have not developed any rapid animal lipid extraction methods. We anticipate incorporating CLA-rich oil [5] in eggs through poultry feed. Therefore, a rapid egg yolk lipid extraction technique would be invaluable prior to egg fatty acid analysis by FAMES GC-FID analysis. The Folch method [6] is a commonly used procedure for total lipid extraction from eggs, but uses chloroform-methanol (2:1, v/v) to extract the lipids, followed by a water wash using 0.2 times the volume of sample. This method is both time consuming and constitutes a significant health hazard because of the use of chloroform. The development of a practical, simple, rapid extraction technique would be more cost effective, particularly when dealing with a large number of samples. Hara and Radin [7] described an efficient 1-min extraction procedure that is particularly adapted to nervous tissues using hexane/isopropanol (3:2, v/v). Using this method, the whole liquid phase is evaporated, eliminating a phase separation step. The objective of this study was to determine if a rapid hexane/isopropanol extraction would extract the same amount of lipid and have the same fatty acid profile as lipids obtained by the Folch method.Six eggs were collected from the University of Arkansas Poultry Science Department. Egg yolks were separated, combined and well mixed in a beaker with a stir-bar. Yolk samples were then diluted with distilled water to obtain 100, 75, 50 and 25 % dilutions of the original yolk mixture. Duplicate extractions of each dilution were made by the Folch method [6] and the following rapid extraction method. Duplicate 4-g samples were accurately weighed and vortexed with ten times the volume of hexane/isopropanol (1:1, v/v) for 5 min at room temperature. Homogenate was filtered using a funnel with Whatman no. 4 110-mm filter paper to recover only the liquid phase...

Survey of egg quality in commercially available table eggs

“…An accelerated lipid oxidation study was performed on egg yolks to determine the amount of free fatty acids and peroxides present in eggs day 1, and again 7 d later, at an incubation of 29°C following the study by Latimer (2012) . Lipids were extracted from triplicate pooled samples for each of the egg brands following the study by Shinn and Proctor (2013) . For lipid extraction, 2 yolks were homogenized in a single 50-mL centrifuge tube for a total of 3 tubes per bsrand.…”

Effect of trans, trans CLA Egg Enrichment from CLA-Rich Soy Oil on Yolk Fatty Acid Composition, Viscosity and Physical Properties

“…Total yolk lipids were extracted from quadruplicate eggs from each treatment and storage duration [N = 120] using a rapid hexane/isopropanol method. 17 A 0.5 g yolk sample was collected in a 7 mL glass vial and dissolved in 5 mL hexane/isopropanol (1:1, v/v), vortexed for 5 min, and allowed to settle. The liquid containing the lipid extract was decanted into a 50 mL plastic centrifuge tube and used for subsequent FAME preparation.…”

Using MALDI MS for rapid analysis of food lipids

“…Our methods for edible lipid analysis have been described and are robust and general in nature [1][2][3][4][5]. It is useful to note that modifying both the lipid extraction and mass spectral procedures to make use of available organic solvents and instrument parameters will still provide similar, reproducible results.…”

“…For food oils, the samples were combined with DHB matrix in a ratio of 1 : 100. For lipid‐rich foods, either the Folch method or a rapid hexane/isopropanol extraction, which we have previously compared, was used before MS analysis . Mass spectra were obtained using a Bruker Ultraflex II MALDI time‐of‐flight (TOF) MS with typical operating conditions.…”