HIDROGRAFIA: CUENCAS, MASAS Y SU ESTADO

F.C. Garg Scientist (SG) Dairy Technology Division NDRI, Karnal-132001 1.0 INTRODUCTION

During II World War period several attempts were made in Australia and New Zealand, for finding a convenient method of supplying butter-fat to meet the army requirement, saving refrigeration and minimizing the storage space and also for satisfactory disposal of butter and second-grade creamery butter.

After trying various methods of manufacturing, wrapping and packaging butter it was concluded that the most practicable method of dealing with butter was to extract from it dry butter-fat, which packed in suitable containers, could be shifted without marked deterioration and saving shipping space. This was followed by the development of continuous method of factory scale manufacturing of butter oil under partial vacuum, applying minimum heat treatment to preserve nutritive value of the product.

2.0 DEFINITION

Butter oil may be defined as fat concentrate obtained exclusively from butter and also cream and resulting from the removal of practically the entire water and solid-not-fat content.

According to the norms of the FAO/WHO,anhydrous milk fat should have a minimum fat content of 99.8%, and the water content should not exceed 0.1% (Edgar Spreer,1998).

Taking this into consideration, ghee in India and Pakistan or Samna of Egypt produced, long long ago before man knew anything about technology could come under the group of butter oil. However, the product “butter oil” popular in continental countries differs from ghee or Samna in colour, granularity and flavour resulting from difference in method of manufacture. Unlike ghee or Samna it is darker in colour, less granular in appearance and has a bland/flat flavour.

3.0 METHODS OF MANUFACTURE OF ANHYDROUS MILK FAT

Continuous process lines are available for the manufacturing of anhydrous milk fat from frozen butter and also directly from cream (Alfa-Laval ).

3.1 Butter as the raw material

Though it is normally more economical to produce butter oil directly from cream and thus eliminating the need for the churning process, the process line using butter as the raw material is used to convert excess amount of available butter into butter oil which is simpler

93

manufacture of butter oil after proper treatments. In this process butter is taken directly from cold storage to the butter melting equipment, where it is melted by using steam. The molten butter is forced outward by centrifugal force towards the periphery, where it is collected and transferred by positive displacement pump 3 to a heating system consisting of plate heat exchanger 4 with a jacketed pipe, through which hot water is circulated.(Fig.1)

From plate heat exchanger 4 the molten butter is transferred to holding tank 5, where it is held for certain period of time. The purpose of the holding time is to give protein sufficient time to agglomerate and to liberate any air entrained in the molten butter. This procedure facilitates the subsequent separation process. From holding tank 5 the molten butter is transferred to separator 7, where the fat is concentrated to more than 99% purity.

The butter milk is discharged to the butter milk tank and used further if possible. If the butter is of poor quality and contains significant amount of FFA, it can be neutralized with a warm alkaline solution.

Since the fat still contains a small quantity of water, as much as possible of this water is removed in the vacuum dryer 10. Before drying, the fat is heated in plate heat exchanger 9 and, after drying, it is cooled in the cooling section of the same heat exchanger, and than transferred to butter tank 11 before packaging.

3.2 Cream as the raw material

This method utilizes the principle of the de-emulsification of concentrated cream.

The fat globules are broken down mechanically by using clarifixator with a line capacities between 500 and 1000 kgs of butter oil per hour or centrifixator with a line capacity of 1500-2000 kgs or even more kgs of butter oil per hour. This forms a continuous fat phase containing dispersed water droplets which can be separated from fat phase.

Raw material should be of good quality. Sour milk is completely unsuitable, even though fat may not be affected. However, the cream from such milk can be improved to certain extend by pre-treatment in the form of “cream washing” i.e. dilution with water, followed by separation.

Cream with a fat content of 35-40% is generally used for the production of anhydrous fat. In order to ensure effective inactivation of lipase enzym, the cream is pasteurized in heat exchanger 3 (Fig-2) and is then cooled regeneratively to 55-58°C. This treatment is recommended even though pasteurized cream may be used as the raw material, since the effect of reactivated enzymes is thus avoided.

After heat treatment, the cream is concentrated in centrifuge. This is of the solids-ejecting type. The cream is concentrated to a fat content of 70-75%. The skim milk from contrifuge 4 is separated in separator 9, and the cream thus obtained is transferred back into the process across float hopper 1, upstream of heat exchanger 3. The skim milk discharged by separator 9 is cooled regeneratively in the first heating stage for unseparated cream in plate heat exchanger 3.

The concentrated cream flows to the centrifixator 5, where the milk fat is subjected to heavy mechanical working and most of the fat globules membranes are broken down. This liberates the fat and a continuous fat phase is formed (emulsion splitting). The raw butter milk still contains a small percentage of fat in globular form, i.e. the membranes of some fat globules are still intact. This globular fat is removed in separator 6. After this treatment, the fat phase is purified so that it contains up to 99.5% fat. The fat phase, with a water content of about 0.4-0.5%, is pumped to plate heat exchanger 7, where it is preheated to 90-95°C. The oil is then transferred to vacuum dryer 8, where the water content is further removed to below 0.1%. The dehydrated milk fat is cooled to about 35-40°C and is then ready for packaging.

During packaging of butter oil, care should be taken to exclude oxygen. Butter fat as it comes out of the vacuum dehydrater it is practically or completely de-aerated. Reaeration should be avoided and air-containing head-space in the container should be minimized. If fat is to be carried through regions of high atmospheric temperature, allowances must be made

95

for expansion of butter-fat which has a fairly high co-efficient of expansion. Both for bulk and retail packaging tin-cans are satisfactory.

4.0 STORAGE

One reason for its popularity is its long shelf-life. Even in tropical climate, anhydrous milk fat can be stored for months at room temperature, provided that the packaging is not translucent and is gas-tight. In chill storage, the shelf life of anhydrous milk fat is up to one year.

The natural antioxidants of butter fat, pass mainly into separated serum, except for dry butter fat prepared by direct evaporation. The resistance of butter fat to oxidation can be improved by addition of permitted anti-oxidants, butylated hydroxytoluene anisole (BHA) not exceeding 0.02% by weight except gollate which shall not exceed 0.01% by weight.

5.0 USES

i) Conversion of butter/cream to butter oil is a convenient method of preservation of butter fat if refrigerated storage is not available.

ii) It is suitable for recombining and reconstitution of milk, cream & butter.

iii) In ice-cream manufacture as a source of fat.

iv) As a cooking fat.

v) For manufacture of toffee, chocolate and other confections.

vi) For manufacture of various type of fat spreads.

vii) For conversion into ghee.

5.1 SELECTED REFERENCES:

Alfa-Laval, Dairy Hand Book. Alfa-Laval AB Dairy and Food Engineering Division, S-22103 Lund, Sweden.

Edgar Spreer, Milk and Dairy Products Technology. Marcel Dekker, Inc. New York (1998).

FRe Frederick Henry Mc Dowall, The butter Maker’s Manual Volume 2, (1953).

FAO/New Zealand Dairy Training Course (14 January to 25 February, 1974) Vol. I

Robert Jenness and Stuwart, Principle of Dairy Chemistry. John Wiley and Sons, INC. New York (1959).

W.B. Sanderson, XIX International Dairy Congress Vol. II (1974).