Special processes and products
Milk fat fractionation
Milk fat (butter) comprising numerous different triclycerides can be separated industrially by purely physical methods, i.e. fractionating. Thus today it is possible to produce stearin fractions with a clear melting point of over 40°C (to 48°C) and olein fractions with a melting point below 10°C. This means that processes like transesterification or hydrogenation are decreasing in importance.
Dry fractionation (Tirtiaux process) begins with anhydrous milk fat which is heated to a temperature of 60-80°C. It is then cooled to crystallisation temperature and crystallisation is initiated. The crystals can be separated off in special-purpose centrifuges or vacuum filtration systems (band filtration, drum filtration). Pressure filtration systems have also been used recently.
Fractionation techniques used in other fields of fat production, e.g. flash distillation or supercritical gas extraction, have not yet become established in the milk fat product sector. The same applies to wet fractionation (crystallisation in solvents) or suspension in aqueous detergent solutions, as both processes cause residue problems.
Cholesterol-free or low-cholesterol products
For health reasons many consumers are forced to choose low-cholesterol or cholesterol-free foods. It is practical to remove cholesterol, at least free cholesterol, in quantity from milk fat. Processes such as steam extraction and extraction by aqueous cyclodextrin solutions have proved suitable for large-scale production. Supercritical gas extraction still appears to be too expensive.
The milk fat freed by the cholesterol can be used in numerous reconstituted products, although the market share in Europe is small.
Incidentally. dry fractionation produces a slight decrease of cholesterol in the stearin fractions, whereas the level in the olein fractions is increased slightly.
Low-calorie milk fat products are characterised by low fat content and a comparatively high level of protein (3-7 %) and water.
The starting products may be cream or butter, milk proteins in the form of powder or UF concentrate, as well as skim milk, buttermilk or whey. Lactic acid concentrates and aromatic concentrates are also added.
Crystal modification of milk fat
In fat products intensive use is made of the fact that fats may occur in various crystal modifications. It has proved very useful that these modifications not only have different energy content, but also crystallise in different forms and even cross-link to a greater or lesser extent.
Due to the large number of triglycerides, however, this fact cannot be put to such good use in milk fat as, for instance, in vegetable fats. Even so, attempts are increasingly being made to exploit the differences between the ß and ß‘ modification in milk fat products as well. In this respect high hopes are being placed on ultra high pressure technology, although conclusive results are not yet available.