FAQ

General

Phospholipids consist of a water-soluble and fat-soluble part. These so-called amphiphilic (“water and fat-loving”) molecules act as emulsifiers between hydrophilic phases (polar, like water) and lipophilic components (non-polar, like oils or fat-soluble vitamins). Phospholipids form a monolayer covering the oil droplets and thereby enable the dispersion of oil droplets in aqueous media. The resulting stable dispersion is called an emulsion and can encapsulate fat-soluble ingredients. In the absence of an oil phase, phospholipids form bilayer structures, called liposomes, when dispersed in water. The liposomes are able to encapsulate water-soluble ingredients. Similar structures are known from cellular membranes, where phospholipids naturally separate the cell from its environment.

Lipoid offers natural phospholipids from sunflower, soybean, and egg yolk, synthetic phospholipids, phospholipid-based formulations, and oils. Lipoid is the only company worldwide that can supply the whole range of phospholipids on a large scale. Phospholipids are the main constituents of natural lecithin which is “generally recognized as safe” (GRAS) by the US Food and Drug Administration. In the EU, lecithin is approved as food additive E 322.

Lecithin is a complex mixture of acetone-insoluble phosphatides (i.e. phospholipids), which consists mainly of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), and phosphatidic acid (PA), present together with various amounts of other substances such as triglycerides, fatty acids, and carbohydrates, as separated from the crude vegetable oil source (United States Pharmacopeial Convention, 2014). During manufacturing of our products by lecithin purification, PC is more and more enriched in the different fractions. The term “lecithin” defines a product with less than 70 % by weight PC; the term “phospholipids” is used when the product contains 70 – 90 % by weight PC. With more than 90 % PC, the product is called “phosphatidylcholine”.

Purified natural phospholipids (> 40 % of PC) are waxy agglomerates that can be dispersed in water or dissolved in oil. Lipoid’s liquid formulations are transparent phospholipid-based formulations.

The typical fatty acid composition of natural, unsaturated phospholipids depends on the source. An overview of the average fatty acid composition [%] of PC from different sources is given in the following table.

The hydrophilic-lipophilic balance (HLB) describes the relative proportions of hydrophilic and lipophilic components in amphiphilic substances, like phospholipids, and is often used to classify emulsifiers. The values range from 1 to 20. Because of the diversity of phospholipid structures with their different head groups and natural fatty acid composition, a strict classification by HLB values is not advisable for phospholipid products of natural origin. Phospholipids are mainly suitable for oil-in-water, but also for water-in-oil emulsions. We do not recommend limiting the application of the emulsifier according to the HLB value.

Technical

High energy input is necessary to generate small particles. This can be best achieved by using high pressure homogenization or ultrasonic systems. On a smaller scale, a rotor-stator mixer is an appropriate alternative but leads to larger particles sizes, which might negatively influence the stability of the final product.

We recommend dispersion of the phospholipids in water. The lipophilic active should be dissolved in an oil component. After that, the oil phase can be slowly added to the aqueous phase. High-shear mixing yields an emulsion. The formulation has to be subjected to a high energy input to generate a homogeneous product.

After dissolving the hydrophilic actives in water, the phospholipids should be added. The formulation has to be treated with a high-shear mixer and in an additional step by a high pressure technique.

The most important parameter is the pH value. It should not be less than 4; the optimal range is between 5 and 6. If necessary, the pH value can be corrected with the help of, e.g., citric acid or sodium hydroxide. Moreover, high concentrations of bivalent cations like Fe2+, Zn2+, Ca2+, Mg2+ may have a negative impact on the stability of the formulation. Compatibility with the respective mineral salt should be checked previously. High temperature over a longer period should also be avoided. However, brief heating, e.g., for filling, is possible.

Visual inspection for phase separation as well as determination of the particle size (should be below 200 nm) are useful measures to evaluate the stability. As phospholipids are prone to oxidation, the peroxide value is an essential parameter. For all liquid formulations of Lipoid the peroxide value is specified as ≤ 10. As is generally the case for food supplements, microbiological examination as well as quantification of the respective active ingredients are recommended.

Phospholipids are susceptible to oxidation and hygroscopic. Therefore, they should be stored at low temperature, low relative humidity, and protected from light (for example in a closed container). The recommended storage temperature for most phospholipids is +5 °C or -20 °C. To prevent oxidation, precautions such as the addition of antioxidants (for example tocopherol), proper processing, and airtight packaging are appropriate. When natural phospholipids are processed in dry form or into dry formulations, the humidity and temperature of the production environment should be controlled. Preferably, the humidity and temperature should not exceed 25 % relative humidity at 30 °C – the lower, the better. In liquid formulations the sensitivity of phospholipids is reduced. Therefore, our delivery systems can be stored refrigerated or at room temperature.