CONTINUOUS BUTTER MAKING
Continuous butter making, introduced after World War II, increased the efficiency and output of butter manufacture. To overcome the disadvantage of batch method of production continuous method is evolved and it has the following advantages:
Continuous butter making, introduced after World War II, increased the efficiency and output of butter manufacture. To overcome the disadvantage of batch method of production continuous method is evolved and it has the following advantages:
1. Highly economical: Due to reduced labour cost, reduced power consumption.
2. More hygienic: Because it is processed under closed system, no manual handling is necessary and no chance for air borne contamination.
3. Quicker: Butter can be produced in a span of few minutes from cream.
4. Large volume can be easily produced.
5. Can be connected directly to packaging lines.
1. Churning or frothing:
In this method butter grain is formed by aggregation of the fat globules under the action of air present in the cream. During churning, air is beaten into the cream and is dispersed into small bubbles. The fat globules touch these bubbles, often spread part of their membrane substances and some of their liquid fat over the air–water interface, and become attached to the bubbles. one bubble can catches several globules. This resembles flotation, although in true flotation the foam is collected. In the churning process, however, the air bubbles keep moving through the liquid and collide with each other due to the rotation of beater. They thus coalesce and adhering together In this way small fat clumps are formed. This involves the use of high-speed beaters to destabilize the fat emulsion in chilled cream, and cause the formation of grains of butter in few seconds. The buttermilk is then drained out and butter granules are worked in kneading section consists of screw type kneader.
The proportion of solid fat is crucial, if the globules contain very little solid fat, then the cream does not churn. Higher the proportion of solid fat, the slower the churning, and the lower the fat content in the buttermilk. The temperature will therefore have a considerable effect on the churning.
Eg. Fritz. Fritz Eisenrich process. Contimob (Simon Frever) Westfalia and Silkborg are based on this principle.
Concentration and phase Reversal:
In this method the concentrated cream will be subjected to combined effects of cooling and working and bring about a direct conversion of cream to butter. Thus it by-passes the butter grain stage.
Eg. Alfa Process and maleshin (Russian) Process.
Emulsification:
In this process, liquid butter fat and serum are emulsified and emulsion is cooled and worked to form butter.
Eg. Creamery Package and Gold’s flow process.
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| Formation of butter granules according Forthing Principle |
2.Fritz-Eisenri Process:
Fritz butter making machine; it contains only one churning cylinder and twin screw working device. This was only suitable for sweet cream of 40-50% fat.
1. First Churning Section:
Beater rotates at a high speed (600-2800 rpm) which can be adjusted according to the requirement. Cream containing 40-50% fat is passed to this section at a temperature of 7-10°C. Butter granules are formed here within 3-5 seconds. Cream is set into the rapid motion in the form of a thin film. Fine cream froth is produced. Through the breaking of these froth bubbles and through the action of the very vigorous mechanical action the cream is churned to butter granules and buttermilk.
2. Second Churning Section:
This is also in cylinder shape and rotates at 10-25 rpm. In this section cylinder is cooled and butter granules are able to form loose agglomerates. Metal rods are attached to this cylinder so they rotate at the same speed loosen the mass and prevent the formation of lumps. In the buttermilk discharge section major part of the buttermilk is drawn off through a wire mesh which covers the perforated cylinder. Removal of buttermilk is almost complete and water is in very fine state of dispersion. Washing of butter granules can be done in wash compartment but it is hardly necessary.
3. Twin screw working device
Butter granules are collected by two rotating screws and worked intensively. Buttermilk is pressed out here, to reduce the moisture content of butter. Screws force the butter through a number of perforated plates arranged in series. This treatment serves to produce a fine dispersion of water in the butter. Process is assisted by mixing vanes which are assisted between the plates and attached to the shaft.
In this working section water or salt solution may be added through an opening immediately in front of the perforated plates to adjust moisture or salt.
Modern butter making machine have vacuum compartments to reduce the air content of the butter and improve the spreadability to some extent.
3. Contimab Process
In this method, cream churns into butter granules in 1-2 seconds, churning cylinder rotates at 600 – 800rpm. Two major working sections are provided, one is wet and another one is dry. In wet working section washing and cooling of butter granules and removal of buttermilk takes place. In dry working section, butter is further worked and reduces the moisture content to 13 to 14%. Further butter travels to dosing section, where adjustment of salt and moisture will be happen. At the end vacuum chamber is provided to reduce the air content of the butter.
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| Contimab process of continuous butter manufacturing |
1. Churning cylinder.
2. Separation section.
3. Squeeze-drying section.
4. Second working section.
4. Alfa Process
Cream of 30% fat is pasteurized at 900C, degassed, cooled to 45 – 500C and separated at this temperature in a cream separator to 82% fat. The cream, which is still in the form of oil in water emulsion, but it is almost the composition of butter. In this cream fat globules are so closely packed that their fat globule membranes are in contact with each other. As fat crystallizes and fat crystals perforate the fat globule membrane and free fat is released out. Rubbing together of the fat globules helps this process as they move in the cooler. Thus phase inversion takes place and water-in-oil emulsion (butter) is formed. It contains all the fat globule membrane material, thus it has high phospholipids content and no buttermilk is produced in this process. Process flow diagram for Alfa process is given below:
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| Alfa process flow diagram of continuous butter making |
Salting in Continuous Butter Making:
Salt is added only after removal of buttermilk and preferably entry is in between 1st & 2nd perforated plates. Salt is commonly injected in the form of 50:50 water salt slurry. Only 26% salt is soluble, so half the salt remain undissolved in slurry.
5. Cherry-Burrell Gold’n Flow Process
This process essentially includes following steps:
1. Destabilizing cream and separating it to 88-90% fat.
2. Pasteurizing the high fat concentrate.
3. Standardizing to the composition of butter.
4. Chilling and working into butter.
The process starts with 18°C cream that is pumped through a high-speed destabilizing unit and then to a cream separator, from which a 90% fat plastic cream is discharged. Destabilization is a process of packing small fat globules together to form large ones. Destabilizing unit consists of a perforated blade travelling at high speed, beating chamber, an adjustable hold back valve and an air inlet valve. The blade travelling at high speed packs the fat globules together by mechanical force. The adjustable hold-back valve insures that the cream is held in beating chamber long enough.
It is then vacuum pasteurized and held in agitated tanks, wherein color and salt are added. Now, product is in the form of 80% fat-water emulsion, which is maintained at 490 degree C, is cooled to 40 degree C by use of scraped surface-heat exchangers. It then passes through a crystallizing tube and then a perforated plate that works the butter. Before chilling, 5% nitrogen gas is injected into the emulsion. It is possible to manufacture butter from high-fat cream (>82% milk fat) on a continuous basis.
6. Salt Quality & Slurry Preparation:
If the butter is to be salted, salt is spread over the surface in batch production, or added in slurry form during the working stage in continuous butter making. Very finely grounded salt to be used and which is of high quality (TBC <10/g) and Purity (99.5 – 99.8% Sod. Chloride). Salt grain should be fine, all pass through IS: Sieve-85(aperture 8424). Salt slurry should be made before 30min and vigorously agitated. Need a proper working after salting otherwise “loose moisture” or mottling defect may happen.
THEORIES OF CHURNING
There are three main theories of the churning of cream into butter. These are
Fisher and Hooker’s Phase-Reversal Theory, Rahn’s Foam Theory, and King’s
Modern Theory.
1. Fisher and Hooker’s Phase-Reversal Theory:
According to this theory, churning is a process of phase reversal, i.e. changing an oil-in-water type emulsion (such as cream) to a water-in-oil type emulsion (such as butter).
Agitation of cream in the churning process causes coalescence and clumping of fat globules until eventually the ratio of the surface area to the volume of fat units becomes so small that it can no longer contain all the buttermilk in stable form. The fat-in-water emulsion then suddenly breaks, yielding butter grains (consisting of an emulsion of water-in-butter-fat) and free buttermilk.
But this theory fails to explain the results of microscopic studies, which reveal
that a proportion of fat globules in butter are still intact in the worked butter.
Hence butter is not a true water-in-fat emulsion whereas this theory assumes
that butter is a water-in-oil type of emulsion.
2. Rahn’s Foam Theory:
According to this theory, the presence of foam/froth is essential for churning. It also postulates that there is a ‘foam-producing’ substance present in cream (and milk) and which gradually solidifies as the cream or milk is agitated. Foam is created during the churning period. The fat globules, due to surface tension effects, tend to concentrate and clump on the foam bubbles. The foam-producing substance assumes a solid character and causes the foam to collapse. The fat globules then coalesce and butter is formed.
This theory also fails to explain continuous butter-making processes where in some cases foam formation (i.e. the presence of air) is not required. This theory assumes that the presence of foam is essential for churning.
3. King’s Modern Theory:
According to this theory, the true explanation of what takes place during churning appears to lie midway between the first two theories. The current concept of mechanism of the churning process may be summarized as follows:
A. In cooled cream at churning temperature, the fat is present as clusters
(clumps) of fat globules and within each globule it is present partly in solid
and partly in liquid form.
B. Churning breaks up the clusters and causes foam/froth formation. The globules
become concentrated to some extent in the film around the air bubbles in the
foam and are thus brought into close contact with each other.
The movement of the globules over one another in the foam film and the direct concussion between them causes a gradual wearing away of the emulsion-protecting surface layer of the phospholipids-protein complex. The globules then adhere together to form larger and larger particles. Eventually these particles become visible as butter grains (granules). As the granules form, they enclose some of the air from the foam. The fat in the granules is still mainly in globular form.
C. The working of butter grains causes the globules to move over one another.
Under the effect of friction and pressure, some of them yield up a portion of the liquid fat. Others are broken up during working. Finally there is enough free liquid fat present to enclose all the water droplets, air bubbles and intact fat globules.
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