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Hardening of an oil can be done with binding of pure hydrogen to the unsatisfied fatty acids. This is called hydrogenation. Hydrogenation is fastened with the use of a catalyst. Under high pressure the hydrogen is added to the oil. The hardness of the oil can be focused by controlling the melting point during hydrogenation.
Another method of stipulating the melting point and hardness of the oil or fat is fractionating. Therefore the oil is separated into an oil (oleine) and fat fraction (stearine). The ratio of the oil and fat fraction defines the hardness of the fat. Separating of the two fractions is done in a slow stirring tank. The oil is heated and cooled slowly. The triglycerides with a high melting point (the stearine fraction) form crystals and can be separated.
Third method is changing the fatty acids of the oil. This means that the fatty acids of triglycerides are exchanged, so that the oil gets different properties like firmness and spreadability. The oil is heated to 90ºC in a cone formed tank and mixed with a catalyst. The process continues until the desired melting point is reached.
To give the margarine the required properties, like stability, colour, taste and vitamin content, several additions are made. First the additions which are soluble in oil (melted fat) are done. An emulsifier, for example a monoglycerid, ensures that the moisture drops remain well divided. Lecithin ensures that the margarine does not splash during cooking. Dyes gives the margarine colour. Vegetable dyes are used mostly. To give the margarine the required taste, taste substances (like aromas or taste substances from butter) are added. To increase the quality and nutritional value vitamins A and D are added. Fat is a natural source of vitamin E.
The moisture part of margarine consists of water and skimmed milk. The milk is fermented lightly, by lactic acid bacteria, to develop the natural taste substances. To get sourness, citric acid is added. To give the margarine more taste and a longer shelf life salt is added. In some margarines there is no milk used for the moisture part.
The moisture is emulsified into the fat by mixing at a very high speed, after that the emulsion is cooled and kneaded. In an ideal emulsion there are millions of moisture drops in one gram of margarine. An emulsion like this is more stable and resistant to microbiological spoilage. A micro-organism can only survive in the water fraction, but such small drop does not provide enough space and nutrition to survive than a continuous waterphase. The size of a waterdrop is not bigger than one or two micro-organisms.
Halvarine should be stored at a low temperature of maximum 7ºC. Because micro-organisms can grow in halvarine, in this water is a continuous phase.