In this article we will discuss about:- 1. Introduction to Continuous Butter Making 2. Basic Principle of Continuous Butter Making 3. Methods 4. Advantages 5. Disadvantages.
Introduction to Continuous Butter Making:
From about 1890, the possibility of producing butter by a continuous process so as to avoid the disadvantages of the batch process, was studied by many research workers, and several prototype machines were built.
While useful theories were tried out, none of the above machines could be applied commercially due to problems caused by operation at the separating temperatures, excessively high butter moisture, unsatisfactory drainage of buttermilk and clogging due to the use of acid cream. It was found difficult to ensure that the severe agitation treated alike every particle of cream.
Interest subsided before World War I (1914-18) and little progress was made until 1932, when high-fat cream by the re-separation of normal cream was developed. Attempts towards continuous butter making were renewed during 1930-40 in Australia, 1937 in Sweden, and during World War II (1935-45) in Germany and the United States. A number of different systems have now been developed for regular commercial use.
Whether these continuous processes will ultimately completely replace the conventional batch system of churning for large-scale production of butter is still an open question. Whatever the final outcome, it is apparent that the transition will be slow, because of- (i) the time required to re-equip the butter factories; and (ii) the cost involved in discarding equipment that may have only partly worn out.
Basic Principle of Continuous Butter Making:
The continuous methods of butter production developed since 1935 may be divided into three main groups:
Group I- The Churning Process:
(Such as Fritz; similar ones are Westfalia, Paasch and Silkeborg, and Contimab.) This involves the use of high-speed beaters to destabilize the fat emulsion in the chilled cream, and thus cause the formation of grains of butter in a matter of seconds. The buttermilk is drained away and the resulting grains worked in a kneading section prior to extrusion.
Group II- The Concentration and Phase Reversal Process:
(Such as Alfa-Laval and Meleshin). This involves a system whereby cream of 30-40 per cent fat is concentrated in a special cream separator to 80-82 per cent fat. After standardization, the concentrated cream or ‘butter mix’ is subjected to combined cooling and mechanical action which causes phase reversal and the formation of butter, followed by its expulsion from the machine.
Group III- The Emulsification Process:
(Such as Creamery Package and Cherry Burrell). This again involves the concentration of 30-40 per cent cream. During concentration, the emulsion is broken and the fat, water and salt content are standardized. This is followed by re-emulsification, cooling, working and finally extrusion.
Note:
In making a study of methods of continuous manufacture, the following points require consideration: treatment of the cream, control of butterfat losses, control of moisture and salt and curd content, capital involved in relation to throughput, labour charges, the effect of the process on the finished product, overall economics of the process, etc.
Most European countries and Australia have concentrated their research and development on the churning process; the USSR has followed the process of high fat separation; and the USA has utilized the principle of re-emulsification of a standardized fat mixture.
Methods of Continuous Butter Making:
One process in each group has been described below:
Group I- Fritz Process:
The milk is pumped from the receiving vats to a separator from which cream of 45-50 per cent is obtained. The cream is pasteurized to 95°C (203°F)/No hold, cooled to 6-10°C (43-50°F) and held for some hours (or overnight) in a storage vat/tank. Next, it is pumped into a small control container which maintains the flow of cream at a constant pressure and adjustable rate.
The cream is then passed into a small water-jacketed cylinder (about 25 cm. long and 25 cm. in diameter) which is kept cool by circulating cold water in the jacket. High-speed vanes in this cylinder churn the cream into butter in 1-2 seconds. The buttermilk and butter granules drop into an inclined section fitted with 2 spiral screws about 45 cm. long and 15 cm. in diameter, which rotate in opposite directions.
Here, the buttermilk runs off and butter is forced through a perforated plate from the farther side of which it is removed by rotating blades. It emerges as a ribbon 7.5 cm. x 3.7 cm. in cross-section, which can be bulk-packed directly, or cut and wrapped into retail sized pats.
(A machine of modified design called Westfalia Buttermatic was later developed and enables accurate moisture control below 16 per cent. It also permits the working and salting of butter. Working is effected by a series of screws, a perforated plate and spinners. It is salted with micro-fined salt by the injection of a 50/50 salt/water slurry in the butter early in the working stage.)
Group II- Alfa-Laval† Process:
The milk is pre-heated to 45- 50°C (113-122°F) and passed on to a hermetic Alfa-Laval separator to produce cream with a 25-35 per cent fat content. This cream is then pasteurized in a vacreator/plate pasteurizer at a temperature of up to 95°C (203°F) in a special cream separator to the fat content desired in the butter.
In a small standardizing vat/tank, the calculated amount of salt, colour, water or skim milk can be added to allow for the adjustment of the composition of butter. The ‘plastic’ cream is then pumped through the transmutator where it changes from cream to butter. The transmutator consists of three jacketed stainless steel cylinders (each about 180 cm. long and 30 cm. in diameter) inside each of which rotates a stainless steel drum fitted with raised spiral strips.
Brine circulates in the jackets at variable temperatures. Phase inversion starts in the first cylinder and is actually completed in the second one. The butter leaves the third cylinder in a semi-fluid form and is packaged immediately. Solidification takes place at once and is completed in the cold store.
Group III- Cherry Burrell’s Process:
The cream is pumped from the receiving vats, through an agitating heater to destabilize the emulsion, and then directly to the centrifugal separator which concentrates the cream at up to 86-90 per cent fat, and breaks the emulsion. An automatic desludging type separator is used. Next, the butter fat containing dispersed serum is pasteurized in a vacreator, cooled to 43-46°C (110-115°F) and passed into standardizing vats.
The standardization of acidity, moisture and salt content is an intermittent process. After standardization, the ‘butter’ mix is pumped through a chiller resembling an ice cream freezer and cooled to 5°C (40°F).
It then passes through a texturator which crystallizes the fat more completely and later works the butter slightly by making it flow through a perforated plate. The butter emerges through a mouth-piece into a packing machine or bulk container. The whole process takes about half an hour.
It has been widely reported that continuous-process butter has a better appearance, finer texture, lower bacterial count and better keeping quality than conventional churned butter; the former is also said to be coliform free. It is, therefore, believed that continuous butter-making machines have come to stay. The change from batch to continuous butter making has been making slow but steady progress throughout the world.
Advantages of Continuous Butter Making:
(i) More economical—due to- lower capital cost, lower running cost (reduced power, labour, refrigeration, steam, detergent, etc.), reduced floor space, no expensive foundations to prepare, no time loss for fat crystallization, less butter wastage, etc.;
(ii) More hygienic due to its being a closed system, free from airborne contamination (so that finished butter has a greater shelf- life).
Disadvantages of Continuous Butter Making:
(i) Lack of uniformity in the quality of butter during the day (unless cream is bulked before conversion into butter);
(ii) Difficulty in selection of sample package for grading and analysis (due to fluctuation in the quality of butter).