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Dairy industry - Cream and butter

Dairy industry - Cream and butter


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Cream and butter

According to Italian law, butter is the fatty substance of cow's milk, obtained by separating buttermilk by various mechanical operations. Quality butter is obtained only from milk cream.

Cream (natural outcrop and centrifugation)

The cream consists of milk enriched with fat. We distinguish creams with low lipid content, such as cooking cream (minimum 21%) or whipping cream (minimum 30%) and those with medium or high content (40-70%), used in the process of making. The whipping and whipping cream are subjected to pasteurization, giving rise to the fresh cream that can be stored for 6-7 days in the refrigerator, or to UHT sterilization, giving rise to the long-life cream (4 months).
It can be obtained by two methods: by surfacing or by centrifugation. The outcrop of the cream occurs by leaving the milk to rest for 12 hours at 15 ° C in stainless steel containers with a capacity of 1.5-2 quintals, 15 cm high and 2 m wide. The surface that emerges is called cream and contains 20-30% of fat. The natural surfacing process is no longer followed for the industrial preparation of butter, since it requires long times and does not separate all the fat from the milk, but is still practiced today in the preparation of some semi-fat cheeses, such as Grana. The cream obtained by outcrop is partially acidic for the development and reproduction of bacteria, which promotes buttering, and a more aromatic but difficult to preserve butter is obtained from it.
In industrial buttering processes, the cream is obtained by subjecting the milk to centrifugation. The centrifugal skimmers are made up of a series of truncated conical plates, mounted on a rotating drum, and spaced a few millimeters apart. The plates have a series of holes that allow the upward movement of the milk. When the milk has reached the last disk, the separation is completed: the cream comes out of a central duct and the skimmed milk from a lateral one. By varying the number of plates and the rotation speed, a different degree of skimming is obtained. The cream obtained by centrifugation is sweet as lactic ferments have not yet developed.
Since the buttering process takes place better if the cream has a certain degree of acidity, the one obtained by centrifugation is previously pasteurized, then inoculated with selected acidifying ferments and left to rest for about 18-20 hours in special tanks kept at 12-15 ° C. During this maturation process, the cream acidifies, aromatizes and becomes more consistent.

Discontinuous (churning) and continuous buttering

To obtain butter, the cream must be violently beaten, which allows you to break the fat globules and mix them, making the residual part of the water escape. This process is called churning and is favored by acidity conditions and temperatures below 15 ° C which make the fat globule more fragile. The churns, once made of wood, are now made up of stainless steel containers that rotate on their axis. Internally they may have rollers that mix the butter and mix it. The liquid that is eliminated by churning is called buttermilk and contains a minimum part of fat (0.3-0.4%) and proteins, deriving from the external envelopes of the fat globule.
Before being mixed, the butter is washed with water two or three times, in order to favor a complete bleeding of the buttermilk. It can then be subjected to light salting or the addition of natural dyes, such as saffron, and subsequently packaged.
Continuous buttering systems are also spreading which, starting from creams with a high fat content, carry out the process without interruption. The butter obtained is not always of good quality and of the right consistency.
The last operation to which the butter is subjected before putting it for direct consumption is the forming: from one hecto to one kg, with its packaging.

Butter composition; butter defects and alterations

The yield of milk in butter is extremely variable depending on the fat content of the milk and the buttering systems; an average of 23-25 ​​kg of milk is needed to obtain one kilogram of butter.
Butter has on average the following composition: maximum humidity 17%, minimum fat 82%, proteins, sugars and salts 1-2% in total.
Commercially, an important character of the butter is the structure, which is a consequence of the buttering process, more precisely of the percentage of globular fat contained in the butter, and of the cooling rate, which affects the greater and lesser homogeneity of the crystallization of the fat. A butter subjected to the action of low temperatures and limited mechanical treatment, loses the ability to harden. The biochemical defects, much more serious than the previous ones, are: the hydrolytic rancidity resulting from the activity of the lipase which releases volatile fatty acids all with an unpleasant smell; ketone rancidity due to mold attacks; the acid taste induced by insufficient washing of the product. The chemical defects all derive from oxidation, which must be distinguished in autoxidation and photooxidation. Self-oxidation or oxidative rancidity is a process to which all fatty substances spontaneously undergo in the presence of oxygen and is catalyzed by heavy metals. Photooxidation is a deterioration caused by light.

Margarine

The oils of various seeds (soy, corn, sunflower, peanut, palm, etc.) can be subjected to an industrial hydrogenation process: with this operation the fatty acids of the oils are saturated which then take on a solid consistency turning into fats. Margarine can be colored with annatto, flavored with vegetable flavors and added with sorbic acid (as a preservative).


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