FAT RICH DAIRY PRODUCTS

Module 9. Butter making equipment

Lesson 29
HISTORY OF BUTTER CHURN DEVELOPMENT, CONSTRUCTION, OPERATION AND SANITARY CARE

29.1 Introduction

Two major types of churns are classified mainly as a batch churns and continuous butter making churns. In batch churns there are wooden and metallic churns. Presently wooden churns are obsolete and metallic batch and continuous butter making equipments are popular.

29.2 History of Butter Churn Development

Role of churn is to agitate the cream, today’s churn design is the modification of several earlier designs, and following are the types of churn design evolved over the time. During the ancient time wooden churns were popular and in recent time metallic churn are widely adapted.

1. Swinging Churns: In this, cream moves backward and forward in horizontal plane, they were first used by the Arabs, a wooden made vessel is suspended and swung from a tripod

2. Rotating Churns: A barrel rotating on its axis at the centre of the axis or at the centre of the ends. Shelves are provided to increase the agitation effect and barrel suspended from one side slightly eccentrically to provide movement to the cream inside the barrel.

3. Dash Churns: Have agitator or dash which rotates to convert cream into butter while the containing vessel remains stationary. Ther are two major types of dash churns, they are;

a. Plunger type: in which plunger usually made of wood, is moved up and down in a tall open vessel containing the cream.

b. Rotating-agitator type: in which an agitator is immersed in the cream itself. The dash may be rotated on either a horizontal or a vertical axis. Simplest type of vertical dash churn is Indian paddle churn consisting of earthenware vessel in which a wooden paddle is operated by means of double rope around the long handle.

Fig. 29.1 operation of Batch type butter churns
1. Cubical 2. Cylindrical-Conical 3. Double Cone

(Source: Ing and Kessler, 1981)

There are three major designs in batch type churns; 1. Cubical, 2. Cylindrical-Conical and 3. Double Cone, all these will not have any interior fittings and they rotate at the speed of 20 to 30 rpm and this varies with capacity of the churn. The interior corners, edges and other irregularities on inner surface of the churn support whipping. Interior surface of the churn is roughened to prevent the sticking of butter granules to the walls of the churn.

Degree of mixing predominantly depends upon the amount of cream in the churn and rate of revolution of the churn. Too low a rate of revolution results in insufficient turbulent for whipping and yield more loss of fat in skim milk. Too high rate of revolution causes centrifugal force to exceed the gravitational force, thus cream will stick to the periphery and rotate there with the drum and cream may not churn or delay churning of cream. Therefore, best condition for churning is when force of gravity is just exceeds the centrifugal force that causes maximum turbulence. Following equation provide the detailed information on how to adjust centrifugal force slightly less than the gravitational force for ideal churning.

Centrifugal force < force of gravity

mω²R < m.g

Where,

m – mass,

ω- angular velocity,

R –radius of the path

g – gravitational force.

→ (2πn)2 . R. < g, because ω=2πn,

→ n < (√(g/R)). 1/(2π), since g and π are constant

So, n < 1/ 2√R assume if the furthest point of the interior of the churn from axis of rotation is 1m, then n < 0.5 per second or 30 per minute.

29.4 History of Continuous Butter Churns

Between 1930 and 1960 a number of continuous processes were developed. In the Alfa, Alfa-Laval, New Way, and Meleshin processes phase inversion takes place by cooling and mechanical treatment of the concentrated cream. In the Cherry-Burrel Gold'n Flow and Creamery Package processes, phase inversion takes place during or immediately after concentration, producing a liquid identical to melted butter, prior to cooling and working. The Alfa, Alfa-Laval, and New Way processes were unsuccessful commercially. The Meleshin process, however, was adopted successfully in the Republic of Russia. The Cherry-Burrel Gold'n Flow process appears to have been the more successful of the two American processes.

The Fritz continuous butter-making process, which is based on the same principles as traditional batch churn, is now the predominant process for butter manufacture in most butter-producing countries. In the churning process crystallization of milk fat is carried out in the cream, with phase inversion and milk fat concentration taking place during the churning and draining steps. However, because of the discovery that cream could be concentrated to a fat content equal to or greater than that of butter, methods have been sought for converting the concentrated or plastic cream directly into butter. Such methods would carry out the principal butter-making steps essentially in reverse order, with concentration of cream in a centrifugal separator, followed by a phase inversion, cooling, and crystallizing of the milk fat.

Increased demands on the keeping qualities of butter require that, in addition to careful construction, operation, and cleaning of the milk and cream processing equipment, research to develop machines that will ensure butter production and packing under conditions eliminating contamination and air admixture must be carried out. It has been demonstrated that butter produced under closed conditions has a better keeping quality than butter produced in open systems.

There are two classes of continuous processes in use: one using 40% cream, such as the Fritz process, and the other using 80% cream, such as the Cherry-Burrell Gold'n Flow. As much as 85% of the butter in France is made by the Fritz process. In this process 40% fat cream is churned as it passes through a cylindrical beater in a matter of seconds. The butter granules are fed through an auger where the buttermilk is drained and the product is squeeze dried to a low moisture content. It then passes through a second working stage where brine and water are injected to standardize the moisture and salt contents.

The Cherry-Burrell Gold'n Flow process is similar to margarine manufacture. The process starts with 18.3°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. It is then vacuum pasteurized and held in agitated tanks to which color, flavor, salt, and milk are added. Then this 80% fat-water emulsion, which is maintained at 48.9°C , is cooled by use of scraped surface heat exchangers to 4.4°C. It then passes through a crystallizing tube, followed by a perforated plate that works the butter. Prior to chilling, 5% nitrogen gas is injected into the emulsion.

Although the Meleshin process continues to be in widespread use in the former USSR, the use of alternative continuous butter-making processes based on high-fat cream has declined in Western countries during the past 20 years. The principal reasons for this decline appear to be the economics and butter quality, particularly when compared with the Fritz process. A Fritz manufacturing process can be installed in existing batch churn factories with almost no modification to cream-handling or butter-packing equipment. The churns could be retained in case the Fritz breaks down. However, very little batch plant equipment could be reused in the alternative systems (ie, Gold'n Flow). Butter from the Fritz process is nearly identical in its physical and flavor characteristics to batch-churned butter, whereas butter produced by the alternative processes tends to be different. These differences may be perceived as defects by the consumer, and manufacturers have been reluctant to alter a traditional product.

29.5 Construction of Continuous Butter Churns

Continuous butter churns essentially consists of double jacketed cylinder and extruder (Fig. 29.1). Product contacting surfaces should made of stainless steel AISI 304. Double jacketed cylinder has been used to make butter granules from cream of 35 – 45% fat, wherein baffles are provided inside to break the fat globule membrane and thus release the free fat by rotating the cylindrical at higher rpm. In this type of equipment provision has made to wash the butter granules and to take out buttermilk out of the process by introducing another perforated cylindrical rotating drum after formation of butter granules. Perforated cylinder is positioned at inclined angle to drain out buttermilk. Working of butter takes place in extruder. Common type of extruder is rotating screw type, few manufacturer also adopts contra-rotating double screw worker wherein two screws contra rotates thus assist in proper working of butter. Moisture and salt adjustment can also be done in extruder.

Fig. 29.1 Line diagram of continuous butter making machine(CBMM)

1. Churning cylinder first stage

2. Churning cylinder second stage

3. Working screw

4. Mixing vanes

5. Butter outlet

29.6 Operation of Batch Type Churns

1. Cool the cream after pasteurization to 10°C and maintain temperature of cream in between 10 to 13°C for overnight. During storage cream should not be agitated at higher speed that may cause partial churning of the cream resulting in short grained butter.

2. Cream having fat percentage of 35 to 40 percent fat is ideal for churning. Churning temperature should adjust in such a way that small peas size granules should form in 40 to 50 minutes. Churning temperature should be in between 13 to 15°C .

3. Churn should not be overload, slightly under loading is preferable.

4. Spray the granules with a small amount of pasteurized chilled water and allow the rinsed water to drain from the churn.

5. For washing and chilling add enough pasteurized chilled water at a temperature of 7°C .

6. Revolve the churn in high speed gear (i.e. 12 to 15 revolutions per minute).

7. Drain the wash water and work the granules until they have formed into mass. This allows the removal of considerable amount of water.

8. Drain the water from the churn and then add calculated quantity of salt and some minimum quantity of chilled water of 7°C .

9. Work the butter until it is fairly dry and test the moisture in the product. If the level of moisture is less then calculate the required amount of water and add into the churn. Te temperature of water should be same as temperature of butter.

10. Work the butter thoroughly and compete the working.

11. When there is clear visible sight glass without any butter sticking to the surface that is time to stop the churn and unload the butter.

12. Store the butter in a refrigerator at 4 – 7°C .

29.7 Operation of Continuous Butter Making Machine (CBMM) Using Fritz Process is Explained Below

1. After overnight storage of standardized cream, then pump the cream to small supply tank for steady flow of cream.

2. Then cream flows into water jacketed horizontal cylinder wherein cold water (at 4 – 5°C ) is circulated through the jacket. Cream strikes the baffles as cylinder rotates at higher rpm (~600 to 3000rpm). Butter granules are formed in 2-3seconds. Ideal churning temperature is 7 to 10°C .

3. Then butter granules are conveyed to buttermilk separating section, where butter milk got separated through perforated drum.

4. Then butter granules are passed through the Butter granules are collected by two contra rotating screws and worked intensively to press out buttermilk.

5. 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.

6. Process is assisted by mixing vanes which are assisted between the plates and attached to the shaft.

13. Water or salt solution(usually 50% solution) may be added through an opening immediately in front of the perforated plates to adjust moisture or salt

14. Modern butter making machine have vacuum compartments to reduce the air content of the butter and improve the spreadibility to some extent.

15. The evacuation is done in the last stage of working screw, this also extends the working time which helps to improve the spreadibility.

Operation of Contimob CBMM is also similar to Fritz process, It has one churning cylinder and two working sections, in first working section it removes buttermilk and in second working section it reduces the moisture content to 13 to 14 % level.

Operations in other CBMM methods such as Alfa and New Way processes of follow this

1. Cream of 30% fat is pasteurized at 90°C , degassed, cooled to 45 – 50°C and separated at this temperature in a cream separator to 82% fat.

2. The cream, which is still in the form of oil in water emulsion, but it has almost the composition of butter.

3. In this cream fat globules are so closely packed that their fat globule membranes are in contact with each other

4. This cream is then passed through a two or three stage screw cooler where it is cooled to 8 – 13°C

5. There the fat crystallizes and fat crystals perforate the fat globule membrane so that free fat escape

6. This process is helped by rubbing together of the fat globules as they move in the cooler

7. 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.

29.8 Cleaning and Sanitary Care of the Batch Churn

1. Routine Cleaning of metallic churn:

· Add hot water 80 to 90°C , equivalent to 10 to 12% of the churn capacity.

· Add 0.2 to 0.3% of the fat emulsifying cleaner such as trisodium phosphate.

· Revolve the churn at high speed for 5 minutes.

· Stop the churn and drain the water.

· Rinse the interior and then add water at near boiling temperature and revolve the churn for few minutes followed by draining.

· Rinse air escape valve

2. To remove milk stone following schedule to be practiced at certain intervals.

· Revolve the churn at working speed with a 2% solution of caustic soda (at a temperature of 60°C ) for about 15minutes. Volume of caustic soda should be 5% of its capacity.

· Drain the solution and rinse with hot water several times.

· Add 0.5% nitric acid solution (approximately 5% of the churn capacity) at 60°C and revolve the churn at working speed for 15 min.

· Drain the acid solution from the churn and rinse with hot water several times.

3. Cleaning of pumps and fittings associated with butter churn:

· Before use, the pumps, pipes and filters should be rinsed with hot water of 90 – 95°C or steamed or rinsed with chlorine solution containing 100ppm available chlorine.

· These pumps and fittings should be cooled before running the product using portable water.

29.9 Cleaning and Sanitary Care of Continuous Butter Churns

Hot water rinsing is the first step to melt the fat in the churn, pump the hot water of 70 – 80°C through the churning cylinder, washing unit and through extruder for 20 to 30 min.

· Caustic soda of 0.5% strength can be circulated after hot water rinse, intermittently to remove the adhered milk soil.

· Then wash with hot water to flush out the residues of alkali.

· Sanitization using chlorine solution can be achieved by circulating hypochlorites or chloride of lime with 200 - 250ppm of available chlorine.