Soybean lecithin fractionation and functionality

Soybean lecithin contains primarity PC, PE, and PI. Fractionation of these phospholipids (PL) is desirable for certain applications. Ethanol was used to fractionate PC and PI, which have different solubilities in this solvent. Various concentrations of ethanol (90, 95, and 100%) and ethanol/gum ratios (0.5, 1.0, 1.5, 2.0, and 2.5) were used. Ethanol concentration significantly influenced the yield of the PC-enriched fraction and the PC and PI fractionation: The highest ethanol concentration resulted in the highest yield of PC fraction, the most PC in the PC fraction, and the most PI in the PI fraction. The ethanol/gum ratio significantly affected the yield of PC-enriched fraction, but did not affect the relative PL composition of the PC-enriched fraction. Ethanol of 90% concentration with a solvent/gum ratio of 3 was used for further large-scale fractionation. Such fractionation resulted in a PC-enriched fraction containing 73% PC, 24% PE, and 3% PI based on the total PL content, whereas the PI fraction contained 26% PC, 35% PE, and 39% PI. Functional properties of these two purified fractions, i.e., surface tension reduction, emulsion stability, and oxidative stability, were investigated. The PI-enriched fraction had a much lower critical micelle concentration than the PC-enriched fraction, which suggests the PI-enriched fraction has a higher surface tension reduction capability. For the emulsion stability test, the PI-enriched fraction performed better than the PC fraction in both water-in-oil and oil-in-water emulsions. An oxidative stability test showed that these PL were very stable to lipid oxidation.     

A review of lecithin chemistry and glandless cottonseed as a potential commercial source

Industrial lecithin can be fractionated as phospholipids and glycolipids after neutral lipids and protein-containing contaminants are removed. The polar lipids are very reactive and are difficult to extract and purify from oilseeds. Their purity and special properties can be improved by a number of methods including solvent fractionation, hydrogenation, sulfonation, and ethoxylation. Studies are determining the role of the polar lipids of lecithin in (a) the synthesis of triglycerides in maturing seeds, (b) the structure of biological membranes, and (c) the molecular basis of the functionality of food ingredients. Lecithin, having both polar and nonpolar groups, has high surface activity and is reactive with both oil and protein, making it an excellent emulsifying agent in food systems; lecithin also slows autoxidation and enzyme hydrolysis of fats. Cottonseed lecithin is low in linolenic acid, prevents flavor deterioration of soybean oil and can be used to stabilize sunflower oil against color change during high temperature use. Gossypol binds to lecithin in oil from glanded cottonseed economically negating it as a commercial source of this product. New cultivars producing glandless, or gossypol-free cottonseed, may have potential as commercial sources of edible lecithin.     

Development of Industrially Scalable Method for Phospholipids and Branch-Chain Fatty Acids of Dairy by-Product

Dairy phospholipids (PL) is of interest due to their health benefits and functional properties. Solvent fractionation of PL has not been commonly used in the dairy industry to fractionate milk fat to obtain or concentrate the PL. The total lipid extracted from the β stream, a waste by-product of dairy processing, was used in this study to investigate suitable solvent and conditions to separate the neutral lipid from PL. A fixed lipid solvent ratio (1:10 g/v) was used at various fractionation temperatures (−20, 2, 15, 23, 40, and 60 °C) depending on the solvents. The use of acetone at 23 °C, not at the lower temperatures, led to a dairy lecithin product with high PL content, such as 71.5%. The more aqueous ethanol, i.e. at 70% concentration compared to 95%, was able to preferentially extract PL to form products with up to 74.7% PL, but the PL yield was much lower (26.3%) compared to acetone precipitation (97.9%). The enrichment of branch chain fatty acids proved to be very challenging due to the overlapping melting points with other fatty acids. The composition of the major fatty acids of polar and neutral lipids also showed interesting patterns that may indicate different nutritional and oxidative properties of the fractionated products.     

Lipids extracted from soy products by different procedures

Lipids in soybean defatted meal, concentrate and isolate were extracted by four procedures: (a) a Soxhlet extract by chloroform-methanol; (b) a Soxhlet extraction by benzene/ethanol; (c) a short extraction by chloroform/methanol; and (d) a short extraction by hexane/ethanol. Procedure 2 extracted more lipid than Procedure 1 from the isolate and meal. Both Soxhlet procedures extracted more lipid than Procedure 3 from the meal only, and more lipid than Procedure 4 from all products. Percent lipid on dry matter basis ranged for the meal, 1.56 to 4.52; concentrate 0.90 to 1.44; and isolate, 0.28 to 0.96. Lipids extracted from each product by Procedures 3 and 4 were fractionated quantitatively into (a) neutral lipids, (b) polar lipids except lecithin, and (c) lecithin. Fatty acid (C12–C20) composition of each lipid fraction was determined, and attempts were made to identify lipids. The larger amount of lipid in any product extracted by either Procedure 3 or 4 was in Fraction 1. Linoleic acid was the most abundant acid found in any lipid fraction. Significantly more oleic acid was found in Fractions I and II Concentrate lipids than in the same fractions of meal or isolate lipids. A number of lipids were found in Fractions I and II, but the only lipid in Fraction III was lecithin.     

Extraction of lipids from a specialist dairy stream

In this work a process for the extraction of neutral and complex lipids from the specialist dairy stream ‘beta-serum’ is described. Beta-serum is a proprietary product obtained from dairy streams containing greater than 60% fat that have been through phase inversion from an oil-in-water to a water-in-oil emulsion. It is an enriched source of milk fat globular membrane proteins and complex lipids, and is distinct from buttermilk in this respect. In the process described here a total lipid extract could be obtained from liquid beta-serum using a continuous near-critical dimethyl ether (DME) antisolvent fractionation process. Protein and water are precipitated from solution when mixed with the DME, whilst lipid and some water are extracted into the DME-rich phase. The extraction yield of lipids depended on the solids content of the feed and the feed to DME flow ratio, but did not depend on the lactose content. Lipids were also extractable from spray dried beta-serum powder, but only when the lactose content had been reduced below 45% by mass. A two step extraction process is described in which neutral lipids are extracted with supercritical CO₂, and then polar lipids using near-critical DME. The polar lipid extract was enriched in phospholipids (∼70% by mass), which included phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin. Other complex lipid components extracted included gangliosides and cerebrosides. Unlike the antisolvent process, proteins were not denatured during either CO₂ or DME processing of the spray dried powders, and the de-fatted powders are therefore suitable for a range of functional foods. A polar lipid extract could also be produced from spray dried powder by extracting first with DME to obtain a mixed neutral/complex lipid extract, then re-extracting the lipid extract with CO₂ to remove neutral lipids.     

Dairy Lecithin from Cheese Whey Fat Globule Membrane: Its Extraction, Composition, Oxidative Stability, and Emulsifying Properties

An ethanol extraction method was studied for the production of dairy lecithin from cheese whey-derived milk fat globule membrane (MFGM). A two-step ethanol extraction of MFGM involving first extraction at pH 6.5, followed by second extraction at pH 4.5 yielded 17.2 % lipids. The extracted material contained about 90 % lipids, 4.5 % ash, and 1.2 % moisture. The phospholipid content of the ethanol extract was 31 % and the remainder was mostly neutral lipids. The phospholipid fraction contained 34 % sphingomyelin, 31 % phosphatidylcholine, 27 % phosphatidylethanolamine, 4.6 % phosphatidylserine, and 3.1 % phosphatidylinositol. Since the ethanol extract contained 31 % phospholipids, it can be technically termed as dairy lecithin. The major fatty acid components were linoleic acid (5.1 %), myristic acid (8.3 %), palmitic acid (29 %), stearic acid (14 %), oleic acid (25 %), and the remainder was minor fatty acids with chain length ranging from C4:0 to C22:5. The dairy lecithin was semi-solid at room temperature and exhibited a major phase transition at about 35 °C. Owing to its low polyunsaturated fatty acid content, the dairy lecithin was reasonably stable to oxidation as measured by the rate and extent of hexanal production during 35 days of storage at 45 °C. Oil-in-water emulsions made with less than 2 % dairy lecithin (relative to the total emulsion weight) were unstable; however, emulsions made with greater than 4 % dairy lecithin were very stable for more than 60 days at room temperature. The results of this study indicated that a highly functional dairy lecithin can be commercially produced using cheese whey-derived MFGM as the starting material.     

Effect of lipid type on water‐in‐oil‐emulsions stabilized by phosphatidylcholine‐depleted lecithin and polyglycerol polyricinoleate

Water‐in‐oil (W/O, 30:70) emulsions were prepared with phosphatidylcholine‐depleted lecithin [PC/(PI,PE) = 0.16] or polyglycerol polyricinoleate (PGPR) as emulsifying agents by means of pressure homogenization. The effect of lipid type (medium‐chain triacylglycerols, sunflower, olive, butter oil, or MCT‐oil/vegetable fat blends) was investigated in relation to particle size distribution, coalescence stability and the sedimentation of the water droplets. A significant correlation (p <0.05) was observed between the interfacial pressure caused by the addition of lecithin to the pure lipids and the specific surface area of the emulsion droplets (r_s = 0.700), and between the viscosity of the lipids used as the continuous phase (reflecting the fatty acid composition) and the specific surface area of the emulsion droplets (r_s = 0.8459) on the other hand. Blends of vegetable fat and MCT‐oil led to reduced coalescence stability due to the attachment of fat crystals to the emulsion droplets. Lecithin‐stabilized W/O emulsions showed significantly higher viscosities compared to those stabilized with PGPR. It was possible to adjust the rheological properties of lecithin‐stabilized emulsions by varying the lipid phase.     

Total and polar lipids in soybean protein meals

Soybean protein meals obtained by various oil extraction methods have different neutral oil content, and they may contain differnet amounts of polar lipids. Three soy protein meals obtained by different processing methods were extracted by two solvents consecutively, chloroform/methanol (2:1, vol/vol) and water-saturated butanol, for total lipid analysis. The organic flour (i.e., ground soybean) containted 15.52% total lipids; the high protein dispersibility index flour from extrusion-expelling processing and the white flour from conventional solvent extraction contained 11.20 and 1.84% total lipids, respectively. Organic flour contained more polar lipids than the other two protein meals on a dry-weight meal basis. Chloroform/methanol extracted most of the lipid from the meals, whereas water-saturated butanol resulted in an extract with more polar lipids than that from chloroform/methanol extraction.     

Extraction of phospholipids from structured dry chicken egg

Chicken egg contains a high level of phospholipids (PL) in the yolk. Recovering yolk total lipids and extracting egg PL with efficiency are important to the availability and utilization of these health‐promoting lipid products. In this study, we prepared two structured dry egg yolk materials and used two common solvents to extract and concentrate the PL. We found that drum‐dried flake‐like yolk is an ideal starting material for lipid extraction. Anhydrous ethanol can extract almost all the neutral lipids and PL. PL with purity over 90% can be prepared by cold acetone precipitation from the total lipids.     

Phospholipid class and FA compositions of modified soybeans processed with two extraction methods

Soybean lecithin is used as an emulsifier in food, cosmetic, and pharmaceutical industries. The proportion of individual phospholipids (PL) and their FA composition may affect the functional properties of lecithin. In this research, lecithins recovered from four modified soybeans and one commodity soybean, which were processed by extrusion-expelling and conventional solvent extraction, were analyzed for proportion of PL class and FA composition. HPLC with an ELSD analysis demonstrated that the percentage of PC in extrusion-expelled lecithin was higher than in solvent-extracted lecithin, whereas the PE content was lower. GC analysis showed that FA compositions of the PL varied with soybean type. The oil extraction method did not significantly affect FA composition. Critical micelle concentration tested with a tensiometer showed differences among the lecithins.     

Lecithins in oil-continuous emulsions. Fat crystal wetting and interfacial tension

Lecithin is a powerful emulsifier widely used in foods, feeds and pharmaceuticals. Several analytical methods have been proposed to characterize lecithins, but they are often inadequate to determine the industrial functionality. The purpose of this study was to find a relationship between the interfacial properties of lecithins (adsorption to oil/water and fat crystal/oil/water interfaces), phospholipid composition and functionality. Results show that all lecithins adsorb to fat crystals at the triglyceride oil/water interface, making their surface more polar (observed as an increase in the contact angle measured through the oil at the interface: fat crystal/oil/water). This adsorption process is quick (less than five minutes) for relatively polar lecithins, such as soybean phosphatidylcholine (PC), and results in highly polar surfaces (contact angle ∼180°). Less polar lecithins give slow adsorption (some hours) and less polar crystals (contact angle ≤90°). The adsorption of different lecithins to the oil/water interface, observed as a decrease in interfacial tension, follows the adsorption pattern to the fat crystals. We found a relation between high-fat crystal polarity and poor lecithin functionality in margarine (margarines spatters during frying), and also between high-fat crystal polarity and a high polar to nonpolar phospholipids [Σ(PI + PA + LPC)/ΣPE; PI, phosphatidylinositol; PA, phosphatidic acid; LPC, lysoPC, PE, phosphatidylethanolamine] ratio in lecithin. The correlations might bevia aggregation properties of lecithin in the oil. We found also that monoolein shifted the adsorption kinetics of lecithin (soybean PC) to fat crystals and the hydrophilicity of adsorbed layers probably due to formation of mixed aggregates between monoolein and soybean PC.     

A rapid method for extraction of total lipids from whey protein concentrates and separation of lipid classes with solid phase extraction

A modified procedure for extraction of total lipids from whey protein concentrates was developed such that stable emulsion with extracting solvents was avoided and the solvent system remained monophasic. Nonlipid contaminants from the extract were removed using gel filtration instead of traditional aqueous washing to prevent any loss of polar lipids. The extraction of total lipids by the modified procedure was complete and comparable with a reference procedure. Traditional thin-layer chromatography is tedious and more qualitative than quantitative for lipid class separation. Total lipids were further separated into free fatty acids, phospholipids, cholesterol ester, triacylglycerol, cholesterol, diacylglycerol, and monoacylglycerol, using modified solid phase extraction procedure. Columns with 2 g amino propyl packing allowed separation of up to 80 mg of total lipids into lipid classes gravimetrically. The values for anhydrous milk fat for all lipid classes agreed with those in the literature. Separation of total lipids into lipid classes with solid phase extraction is easy, quantitative, and can also be performed on a preparative scale.     

Enzymatic hydrolysis of oat and soya lecithin: Effects on functional properties

Enzymatic hydrolysis of oat and soy lecithins and its effects on the functional properties of lecithins were investigated. The phospholipase used was most efficient at low enzyme and substrate concentrations. More fatty acids were released from soy lecithin than from oat lecithin. The maximum degree of hydrolysis was 760 μmol free fatty acids per gram soy lecithin and 170 μmol free fatty acids per gram oat lecithin. On the basis of the total carbohydrate and phosphorus contents in the polar fractions of the lecithins, oat lecithin contained more glycolipids and less phospholipids than soy lecithin. With regard to functional properties, the stability of oil-in-water emulsions was enhanced by hydrolyzed soy lecithin and by crude and hydrolyzed oat lecithins, but only hydrolyzed soy lecithin prevented the recrystallization of barley starch. The dissociation enthalpy of amylose-lipid-complex (AML-complex) was significantly higher when hydrolyzed soy lecithin was present. Hydrolyzed oat lecithin slightly affected the dissociation enthalpy of AML-complex. The other lecithins had no effect on recrystallization or dissociation enthalpies in the barley-starch matrix.     

Extraction of Phospholipids from Egg Yolk Flakes Using Aqueous Alcohols

Two alcohols, ethanol and butanol, with different water contents were evaluated for phospholipids (PL) sequential extraction from drum dried egg yolk flakes. It showed that butanol was more effective in extracting total yolk lipids compared to ethanol, but the PL in the extract had the same concentration as in the original yolk total lipid. The use of aqueous ethanol of 95 and 75% resulted in lipid extracts with higher PL concentration during the initial stages of the sequential extraction. When ethanol was further diluted to a concentration of 55%, the solvent lost its PL extraction ability, and the total lipid recovery also decreased dramatically. When both the PL purity and recovery were considered, 75% ethanol was the most effective aqueous alcohol for PL extraction and enrichment from the yolk flakes. In the first stage of extraction using such a solvent, 67% of the total PL in the original yolk was recovered in a lipid fraction with a PL purity of 75%. This study identified the optimal ethanol concentration for PL extraction from dried egg yolk. With this information, the best solid:solvent ratio can be designed to extract and enrich the polar lipids from lipid-bearing materials with known moisture content using a renewable or “green” solvent, ethanol.     

Embryonic fatty acid composition as a function of yolk fatty acid composition in eggs of the lesser spotted dogfish (Scyliorhinus canicula L.)

Yolk and embryonic total lipids were extracted from spotted dogfish eggs at two developmental stages. Total lipids were fractionated into neutral lipids (NL) and polar lipids (PL), and the fatty acid composition of each group was determined. Yolk lipid composition was found to be quantitatively different (NL/PL≊1) from embryo lipid composition (NL/PL≊0.5), for both stages of development. However, individual fatty acid composition did not differ from younger to older eggs for either yolk or embryo. There were significant differences (p<0.05) in major fatty acid groups from yolk and embryonic PL for saturated fatty acids, monounsaturated fatty acids (MUFA) and n−3 polyunsaturated fatty acids (PUFA) for younger eggs, and for MUFA and n−3 PUFA for older eggs. For NL, only MUFA composition from the oldest eggs showed differences between yolk and embryo. Results are discussed in terms of embryonic needs for highly unsaturated fatty acid (HUFA) biosynthesis, as well as to provide some explanations for the unusually high levels of 20∶4n−6 in both yolk and embryonic neutral lipids and polar lipids.     

Extraction of Phospholipids from Structured Dry Egg Yolk

Chicken egg yolk is a concentrated source of phospholipids (PL). Extracting egg PL with high efficiency is vital to the availability and economics of this high-valued lipid product. In this study, two types of structured dry egg yolk materials, yolk flakes and pellets, were prepared. Two commonly used solvents, hexane and ethanol, were tested on the extraction of total yolk lipids including the PL. The PL fraction was obtained by the conventional cold acetone precipitation. The drum-dried yolk flakes were shown to be an ideal starting material for total lipid and PL extraction. Anhydrous ethanol can extract almost all the neutral lipids and PL with little change to the individual components of the native PL. A PL product with a purity of more than 90 % and a yield of 99 % can be prepared using this method.     

Studies on stability of rapeseed wet gum as a source of pharmaceutical lecithin

Lecithin wet gum with high water content is less stable during storage than dry lecithin. Deoiling and dehydrating the fresh gum can result in a purified lecithin of high quality. The stability of rapeseed wet gum obtained from double-zero rapeseed varieties was determined at various temperatures. The effect of storage time on volatile substances, acetone insolubles, neutral lipids and acid, iodine, and peroxide values were investigated. The rapeseed wet gum stored a little above 20°C is stable for up to ten days, although in the frozen state (−20°C) no changes in general composition, acid, iodine, and peroxide values were observed during 24 mon of storage.     

Total,polar and neutral lipids ofRhizopus arrhizus fischer

The changes in total lipid content, neutral and polar lipids, total fatty acids, and free fatty acids were investigated over a 4 day period in the zygomycete,Rhizopus arrhizus Fischer. The highest concentration of lipids occurred at the 72 hr period. The degree of unsaturation in the total fatty acid fraction increased during the growth period, whereas the degree of unsaturation decreased in the free fatty acid fraction during the same time period. The ratios of neutral to polar lipids over the 4 day period were: 0.75, 0.22, 1.94 and 0.94. The major components of polar lipids were phosphatidyl ethanolamine, lecithin, lysolecithin, and fatty acids. The fatty acids in the mono- and diglycerides were predominately saturated (67–96%). The fatty acids in the triglycerides shifted from a predominately unaturated (69%, 24 hr) to a more saturated pattern (62%, 96 hr).     

The Importance of the Phase Behaviour of Phospholipids for Emulsion Stability

The relationship between the phase behaviour for different combinations of neutral and charged surface active lipids was investigated with regard to the dispersion and stabilization of emulsified systems. When the negatively charged lipids were combined with neutral phospholipids lamellar liquid crystalline phases were formed with large repeat-distances depending on the incorporation of water between the lipid bilayers. Studies of phase equilibria in a water-oil-phospholipid system showed that the lamellar phase was present in that concentration area where the o/w emulsions investigated were produced. The investigation made clear that both the degree of dispersion and the emulsion stability could be brought to optimum values by the addition to neutral phospholipids of negatively charged lipids or by selecting commercial lecithins in which a certain amount of negatively charged phospholipids were present.     

Die antioxidativen Eigenschaften von Lecithin

Antioxidizing Properties of Lecithin In various storage trials with sunflower oil and lard the antioxidizing properties of crude soybean lecithin as well as of its alcohol soluble and alcohol insoluble fraction could be proved. The addition of a very small quantity of these phospholipids to the oil after the refining process (prior to this process crude oil contains approx. 2–3% lecithin) improves the stability of these oils. The antioxidizing properties of phospholipids depend on: 1. composition of phospholipids, 2. tocopherol content of the oil. In our trials the alcohol soluble fraction of soybean lecithin performed the best antioxidizing results in sunflower oil by adding not less than 1%. In lard the same effect could already be reached with 0.1% of this fraction. As shown before, lecithin with a special phospholipid composition has antioxidizing properties and its addition in small quantities is beneficial to increase the stability of oils and fats. In new Japanese literature soybean saponines are the most favoured antioxidizing agents. Our trials did not confirm the results of these publications.