Butter manufacturing technology

Overview

At the physico-chemical, butter consists mostly of milk fat, the state of emulsion type water in oil. Its manufacturing process has precisely the effect of reversing the original emulsion of milk or cream in which fat globules are dispersed in the serum.

Butter is made from cream. Until the advent of centrifugal creamer in 1879, we got the cream-skimming by spontaneous or natural, ie by gravity, in deep containers. At the end of the last century and during the following decades, the creamer farm spread gradually, so that around 1930. Almost all milk for the manufacture of butter was skimmed on the farm: the cream was delivered to the butter and skimmed milk used in animal feed. Receipt of whole milk to the butter has become widespread during the Second World War.

The fat globule

It should add some notions on the fat globule, which plays a role in making butter. The physical and chemical properties of the milk fat of cattle vary with race, the period of lactation and food, resulting in fluctuations during the year. Thus in summer, the proportion of unsaturated fat, softer (iodine number higher), is greater in winter, which is reflected in the texture and spreadability of butter. The firmness of the fat fluctuates with the degree of unsaturation, chain length and position of fatty acids on the glycerol molecule (melting point variables).

The fat is in the form of corpuscles spherical or slightly ovoid. It can also take the form of clusters of fat globules. Thus, agglutination may be associated with the device layer of fat globules and individuals promote their juxtaposition in the form of clusters (several hundreds of units), thus facilitating the rise of the fat (Stokes law). In addition, there may be blood in which the membrane is more or less to form and wrap different types of agglomeration of fat globules. The stability of emulsion globules is mainly attributed to a membrane complex are related or associated proteins, glycolipids and phospholipids other minor constituents.

With its heterogeneous structure, milk or cream gives the fat a weakness in the balance of three phases: colloidal, soluble and emulsified. Surrounded by a membrane active in the serum, the blood fat is sensitive to treatment technologies and chemical, enzymatic and microbiological. Agitation, pumping and cooling energy result in the disruption of the lipoprotein membrane of fat globules to bring the serum and the presence of triglycerides to the surface. Crystallization stage of triglycerides is starting with those most saturated: there is then a contraction of the core of fat globules, resulting in cracks that allow liquid triglycerides of walking towards the outside. These are released on the membrane surface to form a collection of blood. During the churning of cream, this membrane will be distorted, and then failed to release both the content of the blood, ie fat or butter, and on the other hand, the serum of the cream together with remnants of the membrane or buttermilk. The mechanical action promotes the sudden approximation and welding blood and destabilizes the emulsion.

The duration of churning will be influenced by the pH of the continuous phase, ie the serum, the latter being in direct contact with the organic protective film of blood. The development of acid by lactic acid bacteria results in partial neutralization of electronegative charges on the surface of the membrane, thus disrupting the membrane arrangement and allow the contents of the blood to free more easily. If the pH reaches the isoelectric point of fat globules (pH 4.1 to 4.5), it occurs spontaneously churning of the cream or the destabilization of the emulsion. Similarly, the direct action of some microorganisms secrete a Lecithinase decreases the stability of fat globules in hydrolysing lecithin membrane, so there désémulsification.

Manufacturing butter batch

Figure 10 relates the various stages of production of butter. Although most of these operations are so fundamental to certain manufacturing processes continuously, they are discussed in this section specifically related to the conventional batch system.

Figure 10 (Click on image to enlarge)

Deacidification cream

The generalized method of rapid cooling of milk and its conservation on the farm helps prevent the development of acidity. Also, under normal conditions, cream-skimming is obtained by good quality: its acidity generally ranging from 0.08 to 0.12%. However, if it is accidentally subjected to adverse conditions, it can acquire a higher acidity and thereafter affect the quality of butter. Thus, a cream with an acidity level of 0.20% may cause abnormal fish flavors, oxidation and storage in the conservation of butter prolonged and produce excessive losses of fat in buttermilk . Therefore, in these cases, to normalize the acidity of the cream.

This treatment, also known as neutralization butter, is to reduce acidity by the addition of an alkaline producing reactions like:

CH3CHOHCOOH + NaHCO3     —>   CH3CHOHCOONa + H2O  + CO2
lactic       sodium           lactate
acid         bicarbonate      sodium

CH3CHOHCOOH + Ca(OH)2    —>  (CH3CHOHCOO)2Ca  +  2H2O
lactic       calcium         lactate
acid         hydroxide       calcium

Neutralizing the sodium are often used in combination and include sodium bicarbonate (NaHCO₃), sodium carbonate (Na₂CO₃) and sodium hydroxide (NaOH). They must be handled with care to avoid foaming caused by abundant carbon dioxide. They have the advantage of being easily soluble. Of this group, the most used are carbonates.

The neutralizing calcium, commonly known as the lime is calcium hydroxide containing a proportion of magnesium. Less popular because of their low solubility, however, they possess a power greater than the neutralizing neutralizing sodium.

Neutralization must be done quickly and accurately. The amount of neutralizer is calculated taking into account:

• molar equivalence between the lactic acid to neutralize and neutralizing;
• to neutralize acidity: initial acidity acidity least desired;
• fat content of cream: it is, in effect, neutralize the serum of the cream, where there are elements of the titratable acidity.

The neutralizing solution is added to the warm cream, 25 ° to 30 ° C before pasteurization, making sure to mix quickly to avoid local concentration.

One should not go too far the acidification of the cream because it would result in a supportive environment while the development of proteolytic bacteria. The optimum acidity of the serum of the butter varies from pH 6.9 to 7.1. It must also avoid a sudden break, ie carried out at temperatures too high or too high dose of neutralizing sodium, which in effect cause saponification of fat giving a taste of butter soap.

After pasteurization, it is recommended to check the acidity of the cream and make corrections if necessary. Indeed, the heat treatment can affect the acidity of the cream.

Pasteurization and cooling

Cream is subjected to pasteurization more severe than that of milk at least 74 ° C for 16 seconds. This is justified by the increasing resistance of microorganisms to heat due to the protective effect exercised by the layer of fat. The heating must be sufficient to destroy the yeasts and molds, as much as possible of bacteria and enzymes, including lipase and peroxidase. In practice, pasteurizes beyond the standards for better conservation of butter. With the rapid methods of pasteurization, the cream is processed at temperatures of 95 ° C or more.

Heating at high temperatures promotes the development of a slight taste of cooked, which is associated with increased antioxidant properties desirable environment.

Eventually, we may suffer as a cream heat treatment under vacuum in order to extract the volatile substances responsible for unpleasant odors and flavors: the process vacréation. The subjects vacréateur first heating cream or an injection of steam under pressure, then runs in a compartment where a partial vacuum, which initiates the process of cooling and evaporation. The vacréation may affect the texture and consistency of butter and reduce performance. This treatment is especially useful when problems are found abnormal flavors due to the presence of certain aromatic plants in pastures.

During pasteurization, a restraint too long or too high a temperature, a heating or cooling too slow to cause destabilization of the fat and tend to promote a floury texture in butter. However, pasteurization goods helps to control the texture and consistency. Fat liquefied in the heat crystallizes in various ways depending on the cooling mode. Thus, the rapid cooling of the cream promotes the formation of many small crystals, while with slow cooling, it produces large crystals, less numerous. Cooling is more energetic, more solid phase increases, leaving less free of fat or liquid fat in the blood. As the size of crystals depends on their diameters, their sizes and their numbers, a greater proportion of liquid fat is adsorbed on their surface, which will reduce the quantity in this state after the mixing and churning. The result, therefore, in this case, a firm-textured butter. On the contrary, a slow and gradual cooling of the cream leaves a greater amount of liquid fat in the blood, resulting in a butter soft texture, and loss of fat in the buttermilk. The program of cooling the pasteurized cream has a great importance, as affecting the mode of crystallization of the fat it can control the texture and consistency of butter.

Physical maturation of the cream

Without controlled cooling of the cream, the consistency and firmness of butter depend exclusively on the composition and properties of the fat and therefore vary with the seasons.

To avoid this situation, it is to adapt production to changes in the composition and properties of the fat. For this purpose we shall, cold, physical maturation of the pasteurized cream. The principle is to cool and maintain the low temperature long enough to obtain an optimal fat solidified fat compared to liquid. This treatment should therefore be longer in summer than in winter, due to the higher proportion of unsaturated fatty acids with low melting points.

Thanks to the physical maturation of the cream, it is possible to control the degree and pattern of crystallization of fat in the blood and obtain a regularity of his physical condition. The size, shape, arrangement and number of crystals, and an optimal ratio of solid and liquid phases should provide a good phase inversion during the churning and a uniform consistency of the butter produced.

After pasteurization, the cream is cooled rapidly in a tubular heat exchanger or a plate at a temperature below an average of 3 ° C to the churning. In general, applying a cooling by 7 ° to 10 ° C in summer and 10 ° to 12.5 ° C in winter, with a retention period of at least three to four hours, preferably up twenty hours to allow partial solidification desirable blood fat. At the beginning of the maturation period, the latent heat of crystallization (the phenomenon of surfusion) has the effect of increasing the temperature of the cream by about 1 ° to 3 ° C. In the case where you do the churning after a very short period of maturation, should be a few degrees lower temperature usual churning.

Churning the cream

The manufacture of butter requires two separate operations: the inversion of the emulsion of the cream and buttermilk expulsion. This process is called churning.

Principle of churning

Several theories were proposed to explain the phenomenon of butyrification when churning. The main ones are those of the agglomeration, concentration and combination. Making butter from the conventional, discontinuous or method is an application of the principle of locality and is based on the theory of foam. The cream is agitated under conditions that favor the formation of butter by the coalescence of fat globules. The agitation of the cream results in the production of abundant foam, the fat globules agglomerate granules becoming larger, then the foam collapses suddenly and butter grains are separated from the serum. The incorporation of air during agitation increases the viscosity of the cream, and closely directs the fat globules in the walls of bubbles whose interface consists of surfactants, water and air. Cooling, the foam and shocks promote blood abrasive effect, break the membrane and cause the rupture of the inner layer, which facilitates the release of liquid fat and the coalescence of several granules, with scattered very fine droplets of buttermilk. The phenomenon is increasing in the process, and when the proportion of liquid fat is sufficiently available in relation to fat solid, there is formation of larger granules or grains of butter. The emulsion is suddenly reversed and buttermilk is expelled. The mass of butter is then mixed in order to weld the grains of butter evenly.

Regardless of the method of making butter, the electric charge on the fat globules alter their degree of attraction. The acid neutralizing negative electrical charges of the protein in the membrane facilitates the approximation of the blood and activates the process of agglomeration.

Types of churns

The churns are conventional stainless steel and an inner surface rough. They can be shapes and various capacities, rotating around a horizontal axis. They are provided with means to facilitate the agitation of the cream, butter and mixing control their temperature. Are actually churns mixers. The design of walls, faces and edges as well as bars and axial fixed shelves on the inside, takes into account the shape, size and the ideal arrangement, important factors influencing the quality of butter. Churns Some are fitted with a device that allows you to select the speed to meet the various parameters of the finished product and ensure a perfect mixing with a regular distribution of tiny droplets of water in the butter.

Churning temperature

In the conventional manufacture of sweet cream butter, churning the temperature should vary depending on the firmness of the fat (depending on its melting point), the size of fat globules, acidity, richness and viscosity of the cream . In principle, for a butter consistency and satisfactory texture, preventing excessive losses of fat in the buttermilk and allow a good preservation of the finished product, you have to choose a temperature that allows a period of churning from 40 to 60 minutes. In spring and summer, the average temperature is 7 ° to 10 ° C in autumn and winter, fat is generally stronger, it may be between 10 ° and 13 ° C.

Salting

This step is reserved for the production of salted butter salt which helps to enhance flavor and prolong the conservation of butter. Its antiseptic properties help to restrict microbial growth and prevent defects. However, it also has effects that limit their use. Droplets of salt water, being more difficult to divide, tend to be larger, which affects the waxy texture of the butter in a more coarse. That is why it is important to mix more salted butter to better incorporate moisture into droplets the finest possible. Too much salt has a tendency to create more open water in the finished product and also to promote certain defects in butter flavor conservation extended.

Salting is normally done at a rate of 1 to 3% depending on regulatory requirements and those of consumers, the salt must be chemically pure, extra fine, quickly and completely soluble. It is normally added to the dry state. In the case of a low salt, we added in solution in water of standardization. It is important that it be incorporated evenly with butter, otherwise there would be a sandy texture and mottled color.

Kneading

The mixing process is designed to intimately mix the granules of butter between them, to ensure product consistency and texture desired, it can also finely disperse the water and salt in the continuous phase or the fat. It also has the effect of expelling the fat crystals and liquid fat globules.

For these purposes, churns (or mixers) are fitted with internal pallets or other devices can lead to clumps of butter at the top, where they fall to mix vigorously to the mass of butter in the bottom of the device.

We continue mixing until the results of the test identical humidity made on samples taken from several locations of the mass of butter. We must proceed with care in mixing, for poorly made, this will affect the consistency of butter and harm to its conservation.