Milk phospholipids have a surfactant effect. The term “surfactant” refers to the ability of a substance to lower the surface tension between two immiscible phases, such as water and fat. This functionality makes them very interesting as emulsifiers for oil in water (O/W) systems to replace the classic synthetic emulsifiers which, in addition to being additives, do not have a particularly attractive names for the final consumer.
Milk phospholipids are mainly composed of phosphatidylcholine, a complex fat composed of several molecules of fatty acids linked to a phosphoric group and a nitrogenous base, a composition which gives natural emulsifying properties by forming a lipid membrane which surrounds the drops of fat present in the milk, preventing them from their coalescence and separation from the aqueous phase. This helps to maintain a uniform distribution of the fat and to avoid the formation of layers of cream especially after the homogenization phase.
It is important to know that the quantity of phosphatidylcholine present in milk can vary according to various factors, such as the breed of the animal, the diet and the stage of lactation and can therefore be optimized for industrial purposes. The main sources of phospholipids for the food industry are found in powdered buttermilk or whey protein powder. In both cases the lipid percentage in the powder is rarely less than 13-15% and part of this phase is composed of phospholipids. Depending on what has been said above with regard to genetics but also to the concentration systems, powders with lower or higher concentration of emulsifying product can be obtained.
The surfactant effect of milk phospholipids is particularly important in the production of dairy products where emulsion is important, such as ice cream or RTD beverages. In the first matrix, phospholipids help stabilize the emulsion of fat and water, improving the structure and preventing the formation of ice crystals, often accompanied by highly absorbent vegetable fibers.
The application of buttermilk or whey phospholipids can be equivalent in terms of functionality but can be discriminating in the case of the matrix in which they are applied. Since the main purpose is to emulsify without negative effects on the ingredients list, in the ice cream matrix the whey protein phase can strongly contribute to the reduction/simplification of the stabilizing phase given their gelling effect especially after high pasteurization (the most common technique for the preparation of mix except in some special countries).
The choice of buttermilk can instead be made for finished products where gelation is a partially or totally undesirable effect such as in RTD beverages or in systems where gelation must be controlled in a precise way (for example fresh spoon desserts). Even the organoleptic part has a considerable importance on relatively simple systems such as RTD beverages, which normally favors the powdered buttermilk matrix rather than the whey protein one.
As a general rule, the use of a buttermilk or a whey protein high in phospholipids replaces a classic synthetic emulsifier in a ratio of about 4-5:1 and for this reason the part exceeding the lipid phase must be well considered because it brings benefits to the recipe by eliminating from it ingredients that affect the cost of the general formula. The results obtained in the experimental and industrial phases are particularly positive, with a clean taste and, in the case of ice cream, an increase in the general creaminess on the palate even after long periods of storage. In the RTD beverages, products without creaming effects were obtained at room or refrigerator temperature for the desired shelf life. In both cases, the label may simply indicate “buttermilk” or “milk proteins”.