Lecithin production and properties

Soy lecithins are important emulsifiers used in the food, feed, pharmaceutical, and technical industries. Native lecithin is derived from soybean oil in four steps: hydration of phosphatides, separation of the sludge, drying, and cooling. Such lecithin has both W/O and O/W emulsifying properties. Products with improved emulsifying properties can be obtained by modifications, involving mainly fractionation in alcohol, hydrolysis (enzymatic, acid, or alkali), acetylation, or hydroxylation. Careful processing is required to produce lecithins of a high chemical, physical, and bacteriological quality.     

Emulsifying Properties of Different Modified Sunflower Lecithins

Lecithins are a mixture of acetone-insoluble phospholipids and other minor substances (triglycerides, carbohydrates, etc.). The most commonly processes used for lecithin modification are: fractionation by deoiling to separate oil from phospholipids, fractionation with solvents to produce fractions enriched in specific phospholipids, and introduction of enzymatic and chemical changes in phospholipid molecules. The aim of this work was to evaluate the emulsifying properties of different modified sunflower lecithins in oil-in-water (O/W) emulsions. In this study, five modified sunflower lecithins were assessed, which were obtained by deoiling (deoiled lecithin), fractionation with absolute ethanol (PC and PI enriched fractions), and enzymatic hydrolysis with phospholipase A₂ from pancreatic porcine and microbial sources (hydrolyzed lecithins). Modified lecithins were applied as an emulsifying agent in O/W emulsions (30:70 wt/wt), ranging 0.1–2.0% (wt/wt). Stability of different emulsions was evaluated through the evolution of backscattering profiles (%BS), particle size distribution, and mean particle diameters (D [3, 4], D [3, 2]). PC enriched fraction and both hydrolyzed lecithins presented the best emulsifying properties against the main destabilization processes (creaming and coalescence) for the analyzed emulsions. These modified lecithins represent a good alternative for the production of new bioactive agents.     

Modification of lecithin by physical,chemical and enzymatic methods

The term “lecithin” is commonly used to refer to a complex mixture of naturally occurring phospholipids. A class of phospholipids, lecithins chemically exist as ester derivatives of phosphatidic acid. Lecithins are suitably modified to produce products possessing improved emulsifying properties besides increased dispersibility in aqueous systems. The products are used in a gamut of applications like food, pharmaceuticals, plastics, paints, coatings, cosmetics, pesticides, petroleum etc. The present review explores in great detail the various methods of producing structurally diverse lecithins and elucidates the advantages of these methods with regard to the specific applications of the modified products.     

Polymorphic and microstructural behaviors of palm oil/lecithin blends crystallized under shear

There has been much work on polymorphism and crystal habit of quiescently crystallized palm oil. However, researchers have found it difficult to probe the process of sheared crystallization. The effect of surface-active molecules as nucleation agents or habit modifiers was demonstrated in quiescent systems. The aim of this work is to explore the effects of shear and specific lecithins (soy and sunflower) on palm oil crystallization by monitoring crystallization under shear using a synchrotron radiation source, as well as microscopy and DSC. It was found that increasing shear led to increasing β′ stabilization in all situations. Soybean lecithin had little effect on behavior. Sunflower lecithin led to even greater β′ stabilization. The different lecithins interact with the crystallizing fat changing rates of nucleation and crystal growth. Thus, the structure of the overall system can be dramatically altered. Microscopy revealed very different structures even if the polymorphism of the different systems was similar. Consequently, specific interactions can be manipulated in order to control the system. In particular, control of lecithin composition affects the stability of the different polymorphs. Palm oil crystallization under realistic processing conditions has been characterized. Under these conditions, increasing shear rates give higher β′ stability. Specific lecithins have different effects. In particular, soybean lecithin is β′ stabilizing, whereas sunflower lecithin has limited effects. Thus the overall structure of lecithin is important in determining the efficacy. This can be applied to control the structure and properties of different systems such as shortenings or spreads where crystalline interactions create the macro-structure that determines product properties.     

The function of phospholipids of soybean lecithin in emulsions

A number of commercially available soybean lecithins were analyzed with respect to their phospholipid composition and emulsifying properties. A phosphatidylcholine (PC) from soybean swells to a lamellar liquid crystalline phase which incorporates slightly less than 50% of water. The swelling behavior of the commercially available soybean lecithins may be different depending on the concentration of other phospholipids such as phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidic acid (PA). In the presence of the negatively charged phospholipids PI and PA, the swelling of the lamellar phase of PC was dramatically enhanced while a lecithin with equal amounts of PC and PE and small quantities of PI and PA formed two liquid crystalline phases, i.e., a lamellar and a hexagonal phase. Stable o/w-emulsions can be prepared when the phospholipid composition is such that a lamellar liquid crystalline phase in equilibrium with the oil and water phases incorporates large amounts of water. The minimal amount of emulsifier required to stabilize the emulsions has been estimated to give an interfacial film of ca. 80 Å thickness which corresponds to a thickness of two double lipid layers in the interfacial film. The incorporation of large amounts of water is obtained if the lamellar layers contain dissociated ionic groups.     

Effect of sunflower lecithins on the stability of water-in-oil and oil-in-water emulsions

Lecithins are frequently applied in the food industry as emulsifiers, viscosity regulators, and dispersing agents. The main aim of the present work was to study the emulsifying capability of diverse sunflower lecithins so as to evaluate the functionality of these by-products, which are not extensively used at present. The experimental results obtained for water-in-oil (W/O) emulsions showe that dispersions containing levels of 0.1% lecithins were more stable against coalescence than a control system, whereas those with 1% emulsifying agent exhibited the opposite behavior. On the other hand, faster sedimentation kinetics were observed at a concentration of 0.1% than at 1%. Lecithins with high phospholipid content, especially phosphatidylethanolamine and phosphatidylinositol, were found to be the best emulsifying agents for W/O dispersions. In the case of oil-in-water emulsions, it was possible to observe two processes: creaming of emulsions with the addition of 1% of lecithins, and instant creaming followed by coalescence of the cream phase in those cases corresponding to 0.1% added lecithin.     

Update on vegetable lecithin and phospholipid technologies

This paper reviews the production technologies for sourcing lecithins from the oil‐bearing seeds soybean, rapeseed and sunflower kernel. The phospholipid composition is measured by newly developed HPLC‐LSD and ³¹P‐NMR methods. The phospholipid compositions of the three types of lecithin show small differences, while the fatty acid composition is largely equivalent to the oil source. Regulatory specifications (FAO/WHO, EU, FCC) and DGF and AOCS analytical methods for product quality are compiled. Phospholipid modifications by enzymatic hydrolysis, solvent fractionation, acetylating and hydroxylation processes result in lecithins with specific enhanced hydrophilicity and oil‐in‐water emulsifying properties. New available phospholipase and lipase enzymes represent opportunities for the esterification of phospholipids with special omega fatty acids and serine groups. Application characteristics are given for use in yellow fat spreads, baked goods, chocolate, agglomerated instant powders, liposome encapsulation, animal feed, food supplements and pharmaceutics.     

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.     

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.     

Eine empirische Methode zur Bestimmung der Emulgierfähigkeit von Pflanzenlecithinen in O/W-Systemen

An Empiric Method to Determine the Emulsifiability of Vegetable Lecithins in O/W-Systems The following method has been developed to evaluate the emulsifying effect of native, fractionated and modified vegetable lecithins. The lecithin which is to examine is solved in the ratio 1:9 in a fat mixture with the melting point of 32°C and the solution is given on the surface of 50 ml of water with 50°C, in a graduated cylinder. After 30 min. time of rest the cylinder is turned by hand or by means of a mechanic swinging device 20 times in 20 seconds for 180° about its transverse axis. Afterwards it is placed in a thermostat, with a temperature of 50°C. The time necessary to separate 25 ml water is determined. The thus defined half-life is characteristic for the emulsifying effect of the lecithin. The variation coefficient of the results is about 10% for mechanically emulsifying. The practicability of this method is explicated in many examples.     

Oil-in-water emulsions formulated with sunflower lecithins: Vesicle formation and stability

Oil-in-water emulsions (30∶70, vol/vol) were formulated with sunflower lecithin to characterize the destabilization processes and the vesicles formed. Dispersions containing levels of 0.1% lecithin were more stable against coalescence than the control system. When the lecithin concentration was increased to 0.5%, the presence of spherical structures, such as vesicles, was recorded that occluded the emulsion inside. Vesicles underwent a creaming process, and a narrow coalescence zone was detected in the upper layers of the samples. As the lecithin concentration was increased, more vesicles were formed, representing as much as 80% of the system volume. A reduction in the average size of vesicles was observed at high lecithin concentrations (2.5 and 5.0%). The vesicle size distribution changed as a function of lecithin concentration, decreasing the ratio of large to small particles in the same way. Coalescence took place in zones where large-volume vesicles were in contact in the upper portion of the tube sample. The results obtained suggest that sunflower lecithins present interesting emulsifying properties that may prove useful in food technology.     

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.     

Improvement of lecithin as an emulsifier for water-in-oil emulsions by thermalization

The various forms (granular, liquid, gum) of lecithin can be heated under certain conditions of time and temperature to greatly improve their properties as emulsifiers for water-in-oil emulsions. Viscosity, discontinuous phase-holding capacity, stability and water retention were greatly enhanced in emulsions containing thermalized lecithins as the emulsifier compared to those prepared with corresponding amounts of nonthermalized lecithins. The improved emulsification properties of the thermalized lecithins appeared to be due, at least in part, to an increase in diglycerides and free fatty acids resulting from the thermal degradation of phosphatides.     

Compositions of commercial corn and soybean lecithins

The lipid and fatty acid compositions of commercial corn and soybean lecithins were compared. The types of lipids were similar, but the proportions varied. The ratio of glycolipids to phospholipids was 0.36 for corn lecithin and 0.14 for soybean. Phosphatidylcholine and phosphatidylinositol were major phospholipids in both lecithins. In soybean lecithin, the percentage of phosphatidyleth-anolamine equaled that of phosphatidylinositol, but in corn, the percentage of phosphatidylethanolamine was only about one-fourth the percentage of phosphatidylinositol. High levels of phosphatidic acid in both the corn and soybean preparations indicated some degradation of the phospholipids during processing. The major differences in fatty acid compositions were a higher percentage of oleic acid and lower percentages of stearic and linolenic acids in corn compared to soybean. The lower level of linolenic acid should give corn lecithin greater resistance toward autoxidation and the development of off-flavors.     

Lecithin production and utilization

Commercial lecithin is the most important byproduct of the edible oil processing industry because of its functionality and wide application in food systems and industrial utility. The recovery of lecithin from oil is a relatively simple process. Hydration of the phosphatides by water or steam followed by recovery by centrifuge and drying is all that is required. But in order to maximize lecithin’s utility and functionality, processing conditions all the way back to the bean or seed must be carefully controlled. Bean storage and handling, crude oil storage, refining pretreats, drying processes, bleaching, chemical modification, and storage all can affect lecithin quality and performance. The effects of processing on lecithin quality and performance is one of the major focal points in this presentation. Utilization of lecithins has expanded beyond the traditional application in paints, chocolate, and margarine. Food technologists have used lecithin as a functional ingredient in many modern systems. Its multifunctional properties and its “natural” status make commercial lecithin an ideal food ingredient. The major functional properties include: emulsification, instantizing and particle wetting, release, viscosity modification and nutrition. The nutritional impact of lecithin is currently being assessed in the medical field as an important factor in improving neurochemical disorders. Other medical and health related activity areas include positive changes in cholesterol, blood chemistry and circulatory factors. Lecithin is also used in numerous industrial and nonfood applications such as pigment dispersing, mold release, and animal feeds. The major source of commercial lecithin is from the processing of soybean oil. Evaluation of lecithins from other seed crops such as cotton, corn, and rapeseed is being pursued. The growth of these sources will be a function of demand.     

Toolbox for modification of the lecithin headgroup

In an effort to produce structurally divergent lecithins for testing of their functional properties and use in food products, several tools have been developed to carry out modifications in the polar head group distribution of the native phospholipids in soybean lecithin. These tools include physical, chemical and enzymatic techniques. Using a combination of acetone de‐oiling, ethanol fractionation, N‐acetylation and enzymatic hydrolysis and transphosphatidylation with a phospholipase D from Streptomyces sp., a set of lecithins with modified head group distributions were produced. The kinetics of the enzymatic head group hydrolysis and transphosphatidylation was studied in detail. Reaction rates and selectivity (transphosphatidylation / hydrolysis) were affected by both lecithin concentration and donor alcohol concentration. Hydrolysis, forming phosphatidic acid, was strongly dependent on both concentrations, whilst transphosphatidylation, forming phosphatidyl glycerol (or phosphatidyl ethanolamine or phosphatidyl serine), was only influenced by the donor alcohol. This resulted in a reduction in selectivity at high initial lecithin concentrations and suggested the use of a reactant feeding strategy. Enrichment of the phosphatidyl choline content of native soybean lecithin was achieved by ethanol fractionation and phosphatidyl inositol enrichment was by N‐acetylation with acetic anhydride followed by de‐oiling. The application of these tools, together with others designed to modify the fatty acid composition of phospholipids, was used to produce 10‐100 g quantities of divergent lecithins and can be routinely used at lab‐scale.     

Analytische Möglichkeiten zur qualitativen und quantitativen Bestimmung der Phospholipide in Lecithinen unterschiedlicher Herkunft

Analytical Possibilities of Qualitative and Quantitative Determination of Phospholipids of Different Sources Phospholipids contained in lecithins have a wide range of application. Dependent on the source, each lecithin has a different fatty acids composition. As many detection methods in the chromatographic analysis are based of different fatty acids compositions, the quantitative determination of the phospholipids has become difficult. In our trials we used TLC with different dye solutions. We observed that in case of a reaction between the dy solution and a functional group of phospholipids of quantitative determination of lecithins of different sources was possible. The most important functional group is the phosphate group, which is a component of all phospholipids.     

Effect of lecithins partly replacing rumen‐protected fat on fatty acid digestion and composition of cow milk

The effects on fatty acid digestibility and milk fat composition of calcium soaps of palm oil fatty acids and of a 25% replacement of the Ca soaps by four different lecithins (raw, deoiled and deoiled/partially hydrolysed soy lecithin, raw canola lecithin) and soybean oil were investigated in six lactating cows each. The complete diets contained the lipid supplements at proportions of 30 g fatty acids/kg dry matter. Partial replacement of Ca soaps by soy or canola lecithins and soybean oil had small but significant effects on fatty acid digestion and utilisation, as well as the fatty acid profile in milk. Relative to Ca soaps alone, C 16:0 digestibility was slightly higher with lecithins, and percentage of conjugated linoleic acid and trans C 18:1 in milk fat increased while proportion of C 16:0 decreased. Deoiling of lecithins slightly reduced the effects on C 16:0 digestibility and excretion with milk. The influence of lecithin processing was higher than the differences between raw soy and raw canola lecithin. Nevertheless, most of the few effects observed may be related to the fatty acids supplied with the lecithins but, regarding C 18:1 trans‐11 and odd chain fatty acids, there is some evidence that lecithins impair rumen microbial activity less than soybean oil.     

Analysis of lecithin by near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) was applied to crude and processed lecithins to enable qualitative and quantitative classification. With the calibration models used, NIRS enables a rapid selection of lecithins for further processing in a property specific product line. Quantitative determination was achieved for selected lecithin reference values (acetone insoluble, phosphatidylcholine content, acid value, water content). Validated models showed no significant differences (p = 95%) to conventional chemical methods in statistical testing.     

Micellar-Enhanced Ultrafiltration of Heavy Metals Using Lecithin

Abstract

Conventional treatment methods for removal of heavy metals from metal finishing operations are usually energy-intensive and costly. Micellar-enhanced ultrafiltration (MEUF) with synthetic surfactants is a recently developed technique which can remove heavy metals and other small molecular weight ions from wastestreams at relatively lower costs and without a phase change. Lecithin, a natural, inexpensive, nontoxic, and biodegradable surfactant exhibits emulsifying characteristics which can be used in a MEUF. The binding of various lecithins to cadmium, copper, lead, nickel, and zinc—in a mixture and individually—was studied using a continuous diafiltration method. This technique uses small volumes of toxic waters and produces an entire isotherm with just one experiment. In the presence of all five heavy metals, the lecithin in this study showed the following affinity: Cu > Cd ～ Zn > Ni. In experiments when only one metal was present, lecithin exhibited the following affinity: Ni > Cu ～ Zn > Cd. Lead was not bound significantly in either scenario.