Separating fat from milk

Most milk plants separate milk for standardization or the obtain cream for bottling purpose and skim milk for butter milk and cottage cheese.

A layer of cream will form on the top of fresh milk, as it comes from cow, if it is allowed to stand for twenty or thirty minutes. This known as gravity creaming and it was very important prior to the invention of the cream separator. For many years it was customary to heat milk to 85 to 95 °F separation, because at this temperature the difference in density between the fat and skim milk is greatest and results in the most efficient separation of fat from skim milk.

Cream is separated form milk in a cream separator. Cream separator is a heavy metal bowl spinning at a very high speed which sediments the skim milk phase of incoming milk toward the wall of the bowl and displaces the cream inward along the centre of the bowl.

The cream and skim milk can then be recombined in desired ratios to obtain low-fat, light and whole milk with 1%, 2% and 3.25% fat respectively. This standardization usually is performed in a continuous manner.
Separating fat from milk

The reasons of hydrogenation process

Hydrogenation is a major type of chemical process. Hydrogenation of triglyceride oils may be defined as the reaction of the carbon-carbon double bonds of the fatty acids with hydrogen. The reaction is carried out in the presence of a catalyst, to form a solid or semi-solid mixture.

Consequently the fatty acid become saturated and thus, less prone to oxidation and attain a high melting point.

The first patent for the hydrogenation process was by William Norman in 1903. The process has affected the whole food industry because the lipid by-product from the manufacture of high-protein feeds from soybeans, cottonseeds, etc.

The hydrogenation process is an important tool for the edible fats and oils processor. With hydrogenation, liquid oils can be converted into plastic or hard fats more suitable for a particular food product.

The purpose to hydrogenate fat or oil:
*To change the physical form for product functionality improvement
*To improve oxidative stability

It is a complex process, requiring the right catalyst type and quantity, the right combination of process conditions and the optimum processing time, reflecting upstream and downstream, capacity; it is mass transfer limited.

Hydrogenation is used to convert liquid oils to semi-solid plastic fats that are suitable for margarine, shortening and specialty products.
The reasons of hydrogenation process

What are the characteristics of butter?

Butter is one of the main fat products used as spreads. Both of these products are water in oil emulsions.

Butter usually contains about 80% fat. In England, butter must not contain more than 16% water.

Other constituents of butter include protein (1%), lactose (0.4%), mill ash (0.15%), and salt.

The natural color of butter is due to carotene and other fat soluble pigments.

The major proportion of the butter consumed in many countries is sweet cream butter. That is butter manufactured from fresh cream.

Lactic butter, which is more popular is some other countries is manufactured from cream which is first cultured to develop aromatic flavored compounds, e.g. diacetyl.

Both types of butter may be slated (up to 2% salt) depending on market requirements.

Production of butter
Butter making is synonymous with churning of cream in batch or in continuous buttermakers, the latter having been established since the 1930s.

While both processes have been optimized over the years, batch churns are mainly used in smaller dairies and cheese factories (where the cream recovered from whey is churned into whey butter)and continuous plants are used in large scale operations productions 1 – 4 ton of butter.

What are the characteristics of butter?

Decreaming Process

Decreaming Process
During processing, milk fat is removed partially or completely in order to:

• Obtain a fat-reduced or fat free

• Concentrate milk fat or the production of high fat products

• Standardize the fat content of milk

Decreaming (separation, centrifugation) is the mechanical separation of milk into cream and skim milk by means of centrifugal forces.

The decreaming process has significant economic importance, as it controls the efficiency of the fat separation.

The key objective is to manufacture a skim milk with the lowest possible fat content, which corresponds to good decreaming efficiency.

Knowledge of the basics of the fat separation is important for an optimal decreaming process.

Decreaming is based on the facts that fat exists in polydisperse system in an emulsified state and that the specific density difference between milkfat and skim milk is fairly large.

Basically two processes for fat separation are possible, natural decreaming and separation with machine. Natural creaming has no industrial significance.
Decreaming Process