In this article we will discuss about:- 1. Definition of Butteroil 2. Composition of Butteroil 3. Methods of Manufacturing 4. Packaging, Storage and Distribution 5. Market Quality 6. Keeping Quality 7. Judging and Grading 8. Defects in Butteroil, Their Causes and Prevention 9. Uses.
Definition of Butteroil:
Butteroil refers to the fat-concentrate obtained mainly from butter or cream by the removal of practically all the water and solids-not- fat content. The terms milk fat, anhydrous milk fat, dry butter fat and dehydrated butter fat are used synonymously with butteroil, but the raw material for their preparation is usually cream.
Conversion of butter or cream into butter oil is a convenient method for the preservation of fat in the absence of refrigerated storage.
Composition of Butteroil:
This may be as given in Table 5.1.
Note:
The United States Army Quartermaster Corps’ specifications for butter-oil are as given below:
Food and Nutritive Value:
Butter-oil is the richest source of milk fat amongst western dairy products and is also expected to be high in fat-soluble vitamins A and D.
Methods of Manufacturing Butteroil:
These are:
(a) Direct Evaporation:
(i) At atmospheric pressure
(ii) Under vacuum
(b) Decantation
(c) Centrifugation followed by vacuum drying
(d) Direct from cream by de-emulsification and centrifugation.
Note:
The first three methods use butter as raw material.
(a) Direct Evaporation:
This is a batch process and may be carried out either at atmospheric pressure or under vacuum. The former resembles the Indian method of ghee production. Butter is placed in a large open vat/pan which can be heated through a steam jacket or coil. At first the heat is applied slowly till the butter melts.
The temperature is then gradually raised, and the butter stirred, usually to 108-110°C (226-230°F). When all the moisture has evaporated, the residual butter fat is drained from the curd and filtered.
The product obtained (butteroil) has a somewhat darker colour when compared with other methods; it has also got a cooked flavour. Direct evaporation under vacuum does not yield much advantage, either in the efficiency of production or in the quality of the finished product.
(b) Decantation:
This is also a batch process. The butter is melted and allowed to stand undisturbed for sufficient time, until it stratifies into three layers, viz., top-scum, middle-fat and bottom- serum. The fat layer is drawn off from the top and cooled. A clean separation cannot be obtained by this process and fat recovery is low. As such this method is uneconomic, especially when employed on a large scale.
(c) Centrifugal Separation Followed by Vacuum Drying:
This is a more or less continuous method and yields a high quality product. Different variants of this process have been used in many countries for large-scale production of butteroil from butter.
A typical method has been described below:
Flow Diagram of Manufacture:
Details of Manufacture:
Butter (unsalted) is dumped in the butter melter which is a vertical jacketed stainless steel cylindrical tank fitted with an agitator (provided with reduction gear to work on variable speeds). If the butter is very cold and hard, it should be cut into small pieces before heating. Then a steam inlet to the jacket is opened and the agitator run at low speed.
The tipping tank, which is jacketed at the bottom, is filled with clean water and heated to 77-79°C (170-174°F) by opening the steam inlet of the jacket. The centrifugal oil separator is then started and when it has attained full speed, the hot water from the tipping tank is run into it.
When the water has completely run out, the discharge valve of the butter melter is gradually opened to allow the melt to enter into the oil separator. The rate of flow of the melt is so regulated as to avoid overflow. The melt is now separated into oil and serum.
The oil flows into the float-controlled balance tank and thence into the vacuum pan due to suction. Here it is dehydrated at 56-63°C (133-145°F) under a vacuum of 57-62 cm. of mercury. At the end of the operation, the vacuum is broken and butteroil allowed to flow by gravity into the receiving kettle for subsequent cooling, packaging and storage at room temperature.
(d) Directly from Cream by De-Emulsification and Centrifugal Separation:
This process utilizes the principle of de-emulsification of cream used in various continuous butter-making processes. De-emulsified fat may then be melted and clarified by centrifuging and vacuum heating. However, the direct production of anhydrous milk fat from cream has yet to achieve significant commercial application.
Cooling:
This is an important aspect. Butteroil should be cooled and crystallized under careful control, so as to form a large number of fine crystals. The desired result may be obtained by rapidly super-cooling (to 13-18°C) and stirring the mass during forced crystallization (by adding 5-15 per cent of finely crystalline fat from a previous batch); this yields a smooth homogeneous mass which does not separate into solid and liquid layers on standing.
Packaging, Storage and Distribution of Butteroil:
Packaging:
When packaging butteroil, care should be taken to exclude oxygen. Thus, it is important to avoid re-aeration of the product as it comes out of the vacuum dehydrator in a partially or a completely de-aerated form. Care should also be taken to leave a minimum of air in the head-space of the container, or to replace the air in the head-space with an inert gas.
In tropical countries, allowance must be made for expansion of the product in deciding upon the size of the container to use. While filling, the fat should run into the bottom of the container in such a way as to avoid contact with the air.
Tin cans are satisfactory for both bulk and retail packaging. Wooden casks and tubs with suitable liners (butter- paper or plastic film) may be used. Cardboard containers, waxed or plastic-coated, can also serve the purpose.
Note:
The cans should preferably be lacquered on the inside surface with ‘food enamel’ in order to prevent corrosion.
Storage:
Under atmospheric conditions, dehydrated butter fat develops a perceptible oxidized flavour in the course of a month. Use of anti-oxidant ethyl gallate in a concentration of 0.05 per cent increases its shelf life to 3 months. Alternatively, packing the product in a 1 -kg. container under 50 cm. vacuum prior to sealing, ensures satisfactory storage quality.
Distribution:
This is done in the original packing under atmospheric conditions.
Market Quality of Butteroil:
The colour of butteroil prepared from cow milk is deep yellow, while that produced from buffalo milk is white when solid, and colourless when liquid. The product from both cow and buffalo milk has a raw (bland) or slightly cooked (caramelized) flavour, depending on the quality of the raw material and the method of production. The texture of the product, when no special conditions for cooling are adopted, is pasty,
Keeping Quality of Butteroil:
Butter fat free from suspended moisture is immune to microbial attack; but when more than 0.3 per cent of water is present, mould growth can develop and cause a musty, rancid flavour in the fat. If the butter fat is water-free, the only deterioration to which it is readily subject is oxidation, development of a tallowy flavour and, frequently, bleaching of the colour.
Butteroil is more susceptible to oxidative deterioration than butter, because portions of the anti-oxidants present in the butter, e.g., the phospholipid-protein complex, are lost in the butter serum. High grade dry butter fat will retain its quality for at least 6-12 months if properly packed and stored.
Influencing Factors:
The resistance of fat to oxidation, i.e., its keeping quality, will depend on:
(i) The Copper and Iron Content:
These hasten the absorption of oxygen by fat, leading to the development of an oxidized flavour. A good sample of dry butter fat should have a copper content of not more than 0.02-0.03 p.p.m. and iron content of not more than 0.10 p.p.m. (All butteroil-making equipment should preferably be of stainless steel; alternatively, copper and iron vessels should be well-tinned.)
(ii) Amount of Air Present:
Fat dissolves oxygen from air and the dissolved oxygen is only slowly removed from the fat. Vacuumizing and gas-packing help increase the keeping quality of the product. Fat, with oxygen content of less than 0.5 p.p.m. and stored in nitrogen, has been found to have good keeping quality.
(iii) The Holding Temperature:
Within the normal range of variation of atmospheric shade temperatures, this does not greatly influence the keeping quality of anhydrous milk fat which has been properly de-aerated and sealed from contact with air and light; but there is some increase in the speed of oxidation with rise in temperature, and the product is best kept in cold storage (5-10°C).
(iv) Absence of Light:
Fat readily bleaches and goes tallowy if exposed to light, especially bright sunlight. Light accelerates the effect of copper and iron contamination in causing tallowiness.
(v) Heat-Treatment during Extraction:
Dry butter fat obtained by a direct evaporation process has a keeping quality under open storage superior to that obtained by decantation or by centrifugal extraction. This is due to the retention in the butter fat of a portion of the anti-oxidant phospholipid. Some heat-treatment of the butter fat during its production is necessary for the destruction of lipase.
(vi) Initial Quality of Butter Fat:
The best butter fat for long storage is made from sweet cream butter.
Anti-Oxidants as Preservatives:
Anti-oxidants are substances which prevent or delay the development of an oxidized flavour in fat, when added. It appears that they themselves undergo oxidation and are, therefore, able to break the chain reaction which occurs during fat oxidation. The natural antioxidants of butter fat (such as lecithin) are retained by the direct evaporation process.
The resistance of butteroil to oxidation can be improved by the addition of synthetic anti-oxidants, some of which are mentioned below:
(i) Nordihydroguiaretic acid (NDGA)—0.01 to 0.05 per cent
(ii) Ethyl gallate—0.005 to 0.01 per cent
(iii) Hydroquinone—0.01 to 0.10 per cent.
Note:
The use of anti-oxidants is not permitted under the Food and Health Regulations of many countries. In India, the permitted anti-oxidant is Butylated Hydroxy Anisole (BHA). It can be added @ 0.02 per cent to ghee and butter and @ 0.01 per cent to whole milk powder and partly skim milk powder (by weight of the finished product).
Judging and Grading of Butteroil:
Score Card:
A tentative score card has been suggested in Table 5.1.
Procedure for Examination and Scoring:
Examine the container for cleanliness, and in the case of tin-containers also determine whether they are rust-free on the outside and inside when emptied. Open the container and examine aroma and colour. Then pour a small sample and observe the texture. Put a few drops in the mouth and note the taste. Determine percentage acidity (oleic), moisture and peroxide value.
(c) Requirements of High Grade Butteroil:
The package should be clean and bright on the outside and rust-free inside. The product should have a deep yellow colour for cow fat and a white colour with a greenish tinge for buffalo fat, a fine crystalline (pasty) texture, a characteristic bland smell and a butter-like pleasant taste.
Defects in Butteroil, Their Causes and Prevention:
Defects in butteroil may arise due to low quality milk or cream or butter, and faulty methods of production, processing and storage of butteroil. The common defects in butteroil, their causes and prevention are given in Table 5.2.
Uses of Butteroil:
(i) In the production of recombined milk;
(ii) For reconstitution into butter;
(iii) In ice cream manufacture;
(iv) As cooking fat;
(v) In the confectionary industry;
(vi) In the manufacture of various types of fat spreads.