In this article we will discuss about the steps involved in making butter. The steps are: 1. Receiving Milk/Cream 2. Pre-Heating of Milk 3. Separation of Milk 4. Neutralization of Cream 5. Standardization of Cream 6. Pasteurization of Cream 7. Cooling and Ageing of Cream 8. Ripening of Cream 9. Churning 10. Washing 11. Salting and Working 12. Packaging and Storage.
Step # 1. Receiving Milk/Cream:
This consists of: D
(a) Unloading;
(b) Grading;
(c) Sampling;
(d) Weighing;
(e) Testing.
(a) Unloading:
The cans of cream brought to the creamery/ butter-making factory are unloaded on the receiving platform which is at truck-deck height, and arranged according to the route and the patrons.
(b) Grading:
The purpose of grading is to pay for the product on the basis of its quality. Grading and quality payment are the efforts made by dairies/creameries to establish a reputation for high quality products. Cream is graded on the same principles as is milk, i.e., on examinations for smell, taste (seldom carried out), appearance, touch, acidity and sediment.
The technique for grading cream consists in removing the lid of each can of cream, inverting it and smelling it. The lid will carry the same smell (odour) as the contents of the can. Next, the cream is examined for appearance and the presence of any extraneous matter. Cream for butter-making is graded in accordance with the grades of butter that can be made from it. The cream grades arc: First Grade Cream — Sweet or slightly sour Second Grade Cream — Sour, coagulated Reject Grade Cream — Markedly sour, fermented.
(c) Sampling:
Before sampling, the cream in the can is thoroughly mixed by a combined rotary and vertical movement of the plunger/stirrer. If required, the lidded cans of cream may be sprayed with hot water to reduce cream viscosity, and facilitate mixing. Then a representative sample may be drawn for testing purposes.
(d) Weighing:
The cans of cream, which have been accepted, are then weighed and the weight recorded for accounting and other purposes. First-grade creams are tipped directly into the main neutralizing vats, while second-grade creams are segregated in some factories in a separate vat for separate churning. (The cream adhering to the inner walls of the cans is recovered by inverting the cans over steaming jets for short periods.)
(e) Testing:
The cream samples drawn are then tested for fat, solids-not-fat, acidity, etc., by standard methods.
Step # 2. Pre-Heating of Milk:
To increase efficiency of cream separation.
Step # 3. Separation of Milk:
Separation of milk is done by centrifugal methods.
Step # 4. Neutralization of Cream:
Neutralization of sour cream for butter-making refers to a partial reduction in its acidity.
Objects:
These are:
(a) To avoid excessive fat loss in buttermilk that results from churning highly acid pasteurized cream. (When pasteurizing sour cream, the casein curdles, thereby entrapping fat globules; as the bulk of the curd goes in buttermilk, this causes high fat loss).
(b) To guard against the production of an undesirable off-flavour in cream (which may result when high-acid cream is pasteurized).
(c) To improve the keeping quality of butter made from high- acid cream. Salted-acid-butter develops a fishy flavour during commercial storage at —23 to —29°C (-10 to —20°F).
Note:
If cream is neutralized, the correct method should be followed. Improper methods and over-neutralization are both harmful to the flavour and keeping quality of butter.
Step # 5. Standardization of Cream:
This refers to the adjustment of the fat level in cream to the desired percentage, conforming to standard requirements.
Procedure:
The fat percentage in cream is usually adjusted to the prescribed level by the addition of a calculated amount of skim milk.
Problem:
Given 1,000 kg cream testing 50% fat. How much skim milk testing 0.1% fat must be added to obtain 40% fat in the standardized cream?
Solution:
From the Pearson’s Square above, it will be seen that 39.9 parts by weight of 50% cream, when mixed with 10 parts by weight of 0.1% skim milk, will give 49.9 parts by weight of standardized 40% cream.
As the amount of cream is 1,000 kg, the amount of skim milk (S) is to be calculated by the formula:
39.9: 10 = 1,000: S
Step # 6. Pasteurization of Cream:
Pasteurization of cream refers to the process of heating every particle of cream to not less than 71°C (160°F) and holding it at such a temperature for at least 20 minutes, or to any suitable temperature-time combination, using approved and properly-operated equipment.
Objects:
(i) To destroy the pathogenic micro-organisms in cream so as to make it, and also the resultant butter, safe for human consumption;
(ii) To destroy undesirable micro-organisms and inactivate the enzymes present, so as to prolong the keeping qualities of the cream and butter;
(iii) To complete the neutralization process;
(iv) To eliminate some of the gaseous tainting substances;
(v) To make possible the removal of some volatile off-flavours (such as feed and weed flavours) during vacreation.
Methods:
(i) Holder Pasteurization:
This is a batch process used for small- scale handling. The cream is heated in a batch/holder pasteurizer to 71°C (160°F) for 20 minutes and then promptly cooled. (A multiprocessing vat may be used for cream pasteurization and cooling.)
(ii) HTST (Plate) Pasteurization:
This is a continuous process used for large-scale handling. It allows for much greater regeneration than would be possible with any other process. The plate pasteurizer is better suited to freshly-separated sweet cream than neutralized cream, as the latter more easily forms burnt-on films on the plates. The maximum heating temperature may be 95-100°C (203-212°F) for 15-16 seconds.
(iii) Vacuum Pasteurization (Vacreation):
This is also a continuous process. A noteworthy characteristic of vacuum pasteurization is that a dilution of the initial cream takes place and the fat test may be lowered by 6 to 8 per cent; this fact has to be kept in view when standardizing cream.
Step # 7. Cooling and Ageing of Cream:
Cream is cooled by lowering its temperature, and aged by holding it at this (low) temperature for a few hours. After pasteurization, the cream has to be cooled and then aged to make churning possible.
Cream will not churn until the butterfat in the fat globules has at least partially solidified (crystallized); if insufficiently solid, due to improper cooling and ageing of the cream, the fat loss in the buttermilk will be excessive and the butter obtained will have an unsatisfactory, weak body.
Under Indian conditions, the optimum temperature for the cooling and ageing of cream should preferably be 5-10°C (41-50°F). Cooling cream to abnormally low temperatures, and ageing at near about the same ones, renders the fat globules so firm (solid) that they coalesce with each other during churning only with difficulty, thereby greatly prolonging the churning process.
High cooling and ageing temperatures of cream shorten the churning period, yield large fat losses in buttermilk and produce butter which has a relatively soft body. Low cooling and ageing temperatures prolong the churning period, decrease fat losses and produce a firm body that has a satisfactory standing-up capacity.
The ageing period should be at least 2 to 4 hours, preferably 15-16 hours (overnight). During ageing, crystallization of fat in the fat globules should be satisfactorily completed. The optimum temperature for cooling and ageing cream depends on: composition of fat, size of fat globules, fat percentage of cream, period of ageing, temperature of churning, and acidity of cream.
Adopting the optimum temperature of cooling and ageing (together with the optimum temperature of churning) provides a degree of solidification of fat in cream that may yield a normal churning period, reasonably exhaustive churning, satisfactory washing and a satisfactory firmness in the body of butter.
Note:
‘Shock’ cooling of warm cream with ice is not conducive to proper fat crystallization, since there is a subsequent temperature rise due to latent heat. Consequently, in exhaustive churning and an unsatisfactory, weak-bodied butter results.
Step # 8. Ripening of Cream:
This refers to the fermentation of cream with the help of desirable starter cultures.
Note:
Fermentation means, strictly, the decomposition of carbohydrate (sugars) by micro-organisms only. In the dairy industry, the most important fermentation is lactic acid production or souring of milk; while less important are those for the production of flavour, etc.
Objects:
(i) To produce butter with a pleasing, pronounced characteristic flavour and aroma, uniformly from day to day;
(ii) To obtain exhaustive churning, i.e., a low fat loss in buttermilk.
Procedure:
The butter starter culture containing lactic acid producers such as Str. lactis and/or Str. cremoris, together with aroma (diacetyl) producers such as Str. diacetilactis, Leuc. citrovorum and Leuc. dextranicum, in correct proportions, is added to the standardized, pasteurized and cooled (20-22°C/68-72oF) cream at 0.5-2.0 per cent. After being thoroughly mixed, the cream is incubated at 21°C (70°F) for 15-16 hours.
Role of Diacetyl:
The typical flavour of butter from ripened cream is mainly the effect of diacetyl (biacetyl), and, to a smaller extent, of acetic and propionic acids. There is no diacetyl in sweet cream. The flavour intensity in butter depends on its diacetyl content, as shown in Table 4.2.
Note:
i. The normal content of ripened-cream butter is on average 2.5 p.p.m. and rarely over 4 p.p.m.
ii. Diacetyl is produced from its mother substance acetyl-methyl-carbinol.
Synthetic Flavours:
Cream ripening is expensive, time-consuming and exacting. Further, most of the flavouring substances enter into the buttermilk and wash water, and are lost to the butter. Hence the use of starter, starter-distillate or synthetic flavour compounds, which are mixed with sweet-cream butter during the working process to impart the characteristic flavour of ripened-cream butter to the finished product.
However, the addition of the above ingredients is not entirely satisfactory, for the following reasons:
(i) Such butter has a somewhat harsh unnatural aroma;
(ii) It lacks the pleasing, mellow, uniformly blended aroma of ripened-cream butter;
(iii) The aroma lacks permanence; etc.
Note:
One way to improve the flavour of butter is to increase the citric acid content of cream or milk before fermenting begins.
Step # 9. Churning:
Churning of cream consists of agitation at a suitable temperature until the fat globules adhere, forming larger and larger masses, and until a relatively complete separation of fat and serum occurs.
Factors Contributing towards Stability of Fat-in-Skim-Milk Emulsion:
The object of churning cream is to produce butter. In milk/ cream, the fat exists in the form of an emulsion, i.e., a continuous phase. This emulsion is fairly stable. As long as it remains intact, there is no formation of butter.
The factors contributing towards the stability of this fat-in-skim-milk emulsion are:
(i) Force of surface tension;
(ii) Phenomenon of adsorption;
(iii) Electric charge on the fat globules; and
(iv) Viscosity of cream.
(i) Force of Surface Tension:
This causes the fat globules in milk/cream to retain their individuality and prevent butter formation.
(ii) Phenomenon of Adsorption:
The surface layer of the fat globules contains an adsorbed phospholipid-protein complex, which resists de-emulsification.
(iii) Electric Charge:
The fat globules carry a negative charge and repel each other. This prevents their coalescence. (The charge decreases as cream acidity increases.)
(iv) Viscosity:
Increased viscosity retards churning.
Churning Cream vs. Whole Milk:
A greater concentration of fat globules in cream promotes a more profuse and rapid coalescence and aggregation than in milk.
Agitation in Relation to Temperature of Cream:
Above the melting point of fat (31-36°C/88-97°F), agitation of cream results in subdivision of fat globules. At lower temperatures (maximum effect, at 7-8°C/45-46°F), agitation causes coalescence of fat globules.
Churning of Cream:
Good churnability refers to:
(i) Ease of churning, i.e., a clear breaking stage and churning until the grains of butter are of the correct size;
(ii) Completeness of churning, i.e., exhaustiveness of churning (which refers to fat losses in buttermilk);
(iii) Satisfactory washing, which is possible if the grains of butter are sufficiently firm;
(iv) Optimum churning period- This in turn affects the firmness of body and exhaustiveness of churning.
Factors influencing churnability of cream and body of butter:
(i) Chemical composition of fat;
(ii) Size of fat globules;
(iii) Viscosity of cream;
(iv) Temperature of cream at churning;
(v) Fat percentage of cream;
(vi) Acidity of cream;
(vii) Load of churn;
(viii) Nature of agitation;
(ix) Speed of churn;
(x) Pre-churning holding period.
(i) Chemical Composition of Fat:
Milk fat is a mixture of numerous fats (glycerides) of widely varying melting and solidifying points. Thus, fats with low melting points are known as soft fats (such as tri-butyrin, olein. etc.); while those with high melting points are called ‘hard’ fats (such as stearin, palmitin, etc.).
An increase in the proportion of soft fats shortens the churning period, diminishes the firmness of butter and increases the fat losses in buttermilk and vice versa. Fresh green succulent feeds increase the proportion of soft fats, while dry hard feeds increase the proportion of hard fats.
(ii) Size of Fat Globules:
Small fat globules churn with difficulty, while large ones churn readily. Therefore, the higher the proportion of small-sized fat globules, the longer the churning time and the greater the fat loss in buttermilk, and vice versa.
(iii) Viscosity of Cream:
The greater the viscosity of cream, the greater the churning period, and vice versa.
(iv) Temperature of Cream at Churning:
This is important for controlling the rapidity and exhaustiveness of churning and the body of butter. Under Indian conditions, the optimum churning temperature ranges from 9 to 11°C (48 to 52°F). A higher churning temperature causes a shorter churning time, higher fat loss and a weak body in butter (which is difficult to wash, and from which it is difficult to remove curd particles properly).
A lower churning temperature prolongs the churning period. The optimum churning temperature will give an optimum churning period (30 to 60 minutes), a butter of satisfactory firmness and exhaustive churning.
(v) Fat Percentage of Cream:
The higher the fat percentage of cream, the lower the churning period, and vice versa. The optimum fat level of cream for churning, according to Hunziker, lies within 30 to 35 per cent (average 33 per cent), while McDowall suggests 40 per cent. On the other hand, Indian research seems to indicate 40 per cent for cows and 35 per cent for buffaloes.
(vi) Acidity of Cream:
According to Hunziker, cream churns more rapidly and exhaustively than sweet cream. However, McDowall believes that the reverse is the case.
(vii) Load of Chum:
The optimum load of cream which the churn can take seems to be between one-half and one-third its total capacity. Overloading prolongs churning time, while under-loading reduces the normal capacity of the churn.
(viii) Nature of Agitation:
This is influenced by the size, type (design) and r.p.m. of the churn, and affects the churning period.
(ix) Speed of Churn:
Should be as prescribed by the manufacturer, since this maximizes agitation and shortens the churning period.
(x) Pre-Churning Holding Period:
Refers to cooling and ageing of cream.
Churning Operation:
(i) Preparing the Churn:
A new churn (especially a wooden one) requires careful pre-treatment before use. An old churn (wooden and metal) requires proper sanitization and cooling, to render it clean.
(ii) Filling Cream into the Churn:
The cream should be strained so as to remove lumps and chance objects. The amount then filled should preferably be slightly below the rated capacity.
(iii) Addition of Butter Colour:
This is done to maintain the uniformity of yellow colour in butter throughout the year for consumer satisfaction. The amount of standard colour added (under Indian conditions) varies from 0 to 250 ml or more per 100 kg of butter- fat. The butter colour should preferably be added to the cream in the churn.
Note:
Butter colour should have the following properties: it should be harmless (i.e., non-toxic), free from off-flavours, concentrated, permanent, and oil-soluble.
Butter colours are of the following types:
i. Of Vegetable Origin:
Annatto and carotene. Annatto is obtained from the seeds of the annatto plant (bixa orellana). The yellowish-red colouring substance is extracted from the seeds by dissolving it in a neutral oil (such as castor, ground-nut, sesame or til). The Annatto plant is of tropical origin and is grown in the West Indies, India, Brazil, etc. Carotene is extracted from carrots and other carotene-rich vegetable matter. This colour is slightly on the greenish side. Its use is growing for it increases vitamin A potency.
2. Of Mineral Origin:
Harmless, oil-soluble coal-tar dyes are mixed with-neutral oil as above. Examples are- Yellow AB (Benzene Azo-β-naphthyl-amine), Yellow OB (Ortho Tolune Azo-β-naphthyl- amine). These have the advantages of being more concentrated and permanent. Butter colour should be stored in opaque, air-tight containers at room temperature (18-21°C/60-70°F), and not unduly agitated, so as to ensure long keeping quality and usefulness.
(iv) Operating the Churn:
After initially rotating the churn for 5 to 10 minutes, the liberated gas is removed once or twice by opening the churn vent. Then the cream sample is drawn for the fat test. During the churning process there is invariably a rise in temperature from 1 to 3°C. Churning is accompanied by foaming. Then comes the ‘breaking’ stage, when the cream breaks away from the spy glass which becomes clear.
At this stage the fat in the skim-milk emulsion breaks and very small butter granules of the size of pin- heads make their appearance. It is sometimes necessary, especially in the tropics, to add ‘break water’ at this stage, to reduce the temperature of the churn contents, and thereby control the body of the butter.
The amount and temperature of break-water depends on the temperature reduction required. After the breaking stage, the churning is continued until the butter grains are of the desired size (viz., ‘pea-size’ in large churns).
Note:
In the tropics, addition of break water can be avoided by providing an air-conditioned butter-making room and/or chill-water spray over the butter churn.
Churning Difficulties:
The usual causes are:
(i) Excessive hardness of fat;
(ii) Small-sized fat globules;
(iii) Excessively thin cream;
(iv) Over-loading of the churn;
(v) Excessively low churning temperature of cream;
(vi) Abnormal cream (causing excessive foaming).
Factors Affecting Fat Loss in Buttermilk:
(i) Fat Percentage of Cream at Churning:
The lower the fat percentage of cream, the lower the fat percentage of buttermilk, but the greater is the per cent total fat loss in buttermilk, and vice versa.
(ii) Size of Fat Globules:
The greater the proportion of small- sized fat globules (2 micron or less), the greater the fat loss, and vice versa. The small globules escape churning action and pass on to the buttermilk.
(iii) Acidity of Cream at Churning:
According to Hunziker, sour cream causes a lower fat loss than sweet cream; but according to McDowall, the reverse is true.
(iv) Physical Properties of Fat:
The softer the fat the more the fat loss, and vice versa.
(v) Conditions of Cooling and Ageing:
Insufficient cooling and ageing (i.e., improper fat crystallization) causes more fat loss, and vice versa.
(vi) Conditions of Churning:
Over-loading, gross under-loading and under-churning all cause a greater fat loss.
Step # 10. Washing:
(a) Draining the Buttermilk:
When the cream has been churned, the churn is stopped in the proper position, a drain-plug fixed, and the buttermilk removed through a sieve.
(b) Purpose of Washing:
(i) To remove all loose buttermilk adhering to butter grains so as to reduce the curd content of butter, thereby improving its keeping quality;
(ii) To correct defects in the firmness of butter by proper adjustment of wash water temperatures, and
(iii) To decrease the intensity of certain off-flavours (in case of poor quality cream); etc.
(c) Procedure of Washing:
After it has been drained, chilled water is added to the butter grains in the churn. The temperature of the water is usually 1-2°C lower than the churning temperature of cream, and an amount equal to the quantity of buttermilk removed. After a few revolutions, the wash water is drained out. Normally one wash is enough for good quality butter.
(d) Quality of Wash Water:
Should be physically clean and bacteriologically and chemically safe. It is best to use freshly pasteurized and cooled water.
Step # 11. Salting and Working:
Salting:
This refers to the addition of salt to butter.
Object/Purpose:
(i) To improve keeping quality;
(ii) To enhance taste;
(iii) To increase overrun.
Amount and Quality:
Usually common salt is added at the rate of 2 to 2.5 per cent of butterfat. The quality of salt should be good and it should be free from any extraneous matter and germs. Excessive salt damages the flavour of butter.
The amount of salt added to butter in a churn is calculated as follows:
Problem:
Fat in churn = 850 kg. Butter is to contain 2.0% salt. How much salt should be added to the churn (without loss of salt during working)?
Solution:
Butter is to contain 2.0% salt. Assuming 80% fat in butter, the requirement of salt per 100 kg. fat
Method of Salting:
(i) Dry Salting:
Most common. Consists in adding the desired amount of dry salt (in installments, if required) by sprinkling it over the surface of the butter during working.
(ii) Wet Salting:
The calculated amount of salt is wetted in the least amount of potable water and then sprinkled over the butter during working. Satisfactorily incorporates salt in the butter.
(iii) Brine Salting:
The salt is added in the form of a saturated solution of brine. Practicable when only light salting is required.
Specifications of Butter Salt:
(i) Screen Test (for Particle Size):
It should be coarse grained and free from lumps. It should pass completely through an IS Sieve-85 (aperture 842 microns). The salt should not be used in powder/dust form, as this tends to lump on wetting and does not mix properly.
(ii) Chemical Purity:
99.5 to 99.8 per cent sodium chloride in dry salt.
(iii) Bacteriological Purity:
Bacterial count less than 10/g.
(iv) Solubility:
Complete.
(v) Rate of Solution:
High.
(vi) Sediment:
Negligible.
Note:
1. Salt should be white in colour and free from any visible impurities.
2. Presence of traces of calcium and magnesium chlorides in salt causes it to moisten and cake. It should be stored in air-tight containers and in a dry atmosphere, away from foreign odours such as kerosene, petrol etc., which it readily absorbs.
Working:
This refers to the kneading of butter.
Object/Purpose:
(i) To completely dissolve, uniformly distribute and properly incorporate the salt:
(ii) To expel buttermilk and to control the moisture content of butter;
(iii) To fully incorporate the added make-up water in butter;
(iv) To bring the butter grains together into a compact mass for convenient handling and packaging.
Note:
During working, the moisture in butter is reduced to droplets of microscopic size, which are mostly sterile.
Procedure:
The working should be continued until the butter has a compact body, a closely-knit grain, a tough waxy texture and an even distribution of salt and moisture. There should be no free moisture on the trier plug drawn from the butter. (Indicator paper develops coloured spots if free moisture is present.) Throughout the working process, the temperature should be controlled.
Both overworking and under-working are harmful and should be avoided; the former damages the body and texture of butter, while the latter produces leaky butter. Working increases the air-content of butter. Normally-worked butter has an air-content of 0.5 to 10 ml. (average 4.0 ml.) per 100 g. of butter. The air-content of butter is important because it affects- (i) the density of butter; (ii) its microbial spoilage; and (iii) its oxidative spoilage.
Note:
‘Vacuum churns’ have been developed for working butter under partial vacuum (0 to 68.5 cm. of mercury). The resultant butter is denser, more glossy in appearance and of closer texture. Working tends to reduce the intensity of the colour and flavour of butter.
Moisture Control:
The legal limit for the moisture content in butter in most countries is 16 per cent, although in others (including India today) it is 80 per cent fat. After the addition of salt, working is continued until the butter is ‘dry’.
A representative sample of butter is then taken and the 1st Moisture Test done. After calculation of the amount of ‘make-up’ water, it is added. Working is recontinued until make-up water is thoroughly incorporated and butter has the correct body. The moisture content in the finished butter is then checked.
The rough formula for calculation of makeup water is:
where W = make-up water (kg.), F = fat in chum (kg.), M = final Moisture Test desired (%), and m = 1st Moisture Test (%).
12. Packaging and Storage:
Packaging:
Removing Butter from the Churn:
This is done either manually, or by gravity, or by mechanical means, viz. by means of compressed air (3 to 5 psi). In the last case, the butter has to be soft.
Types of Packs:
(i) Bulk or wholesale- in boxes, tubs, casks (NZ—56 lb.; US—63 lb.; Europe—50 kg.),
(ii) Retail- 1, 2, 4, 8, 16 oz. or 25, 50, 100, 250, 500 g. pats; also in collapsible (metal) tubes.
Objects of Packaging:
(i) To offer protection against contamination and damage (mutilation);
(ii) To protect the butter against loss in weight and degradation (deterioration of flavour);
(iii) To provide ease and safety of transport;
(iv) To provide a convenient form of disposal;
(v) To identify the contents and increase sales appeal, appearance, etc.
Packaging Materials:
These include:
(i) Wood or Timber:
White Ash or Spruce, White Pine, Firkin Teakwood, etc.
(ii) Parchment Paper/Substitutes:
Vegetable parchment paper/butter paper; cellophane; pliofilm; polythene; etc.
(iii) Aluminium Foil/Laminates:
Moisture and greaseproof; non- tainting and non-toxic; opaque; air-tight; etc.
(iv) Tin-Plate Cans:
Advantageous in tropical countries not only in preventing melted butter from escaping in hot weather but also in preventing absorption of foreign flavours.
Technique of Packaging:
(i) Hand Moulding and Wrapping:
Slow and cumbersome.
(ii) Mechanical Moulding, Patting and Wrapping:
Reduces labour costs and losses; suitable for large-scale operations; etc.
Note:
(i) The standard butter packaging machines are either semiautomatic or fully automatic. The well-known brands are. Benhill and Kustner (both German), and SIG (Swiss). The weight of the packaged butter pats should be checked regularly as they come out of the machine.
(ii) Vacuum packaging of butter in tin cans does not significantly improve its keeping quality, because the oxygen enclosed in the butter or dissolved in the fat is only partially removed.
(iii) ‘Canned butter’ is not sterile.
Storage:
The temperature of commercial cold storage of butter ranges from -23°C to -29°C (-10°F to -20°F). There is invariably some flavour deterioration of butter while it is in commercial cold storage. Thus, a fishy flavour develops in salted-acid-butter. Bacterial deterioration plays a negligible part, while chemical degradation plays a leading one.
Shrinkage of Stored Patted Butter:
Shrinkage refers to loss in weight and is caused mainly by evaporation of moisture from the butter pat. Butter packs must contain the correct weight of butter when sold to the consumer. In the patting of butter, allowance must be made for possible shrinkage of the wrapped butter pat.
The extent of shrinkage depends on:
(i) Type of Wrapper:
Moisture proof/greaseproof wrappers cause less shrinkage than other types.
(ii) Condition of Moisture in Butter:
The greater the quantity of ‘free’ moisture in butter, the greater the shrinkage, and vice versa.
(iii) Size of Pat:
The smaller the pat, the greater the shrinkage, and vice versa.
(iv) Temperature of Storage:
The higher the temperature, the greater the shrinkage, and vice versa.
(v) Relative Humidity of Storage Air:
The higher the humidity, the lower the shrinkage, and vice versa. (However, high humidity favours mould growth and is therefore avoided.)
(vi) Period of Storage:
The longer the period, the greater the shrinkage, and vice versa.
Keeping Quality of Stored Butter:
The factors affecting this are:
(i) Temperature of Storage:
The higher the temperature, the lower the keeping quality, and vice versa.
(vii) Raw or Pasteurized Cream:
Pasteurization of cream increases the keeping quality of butter.
(viii) Method of Packaging:
Sanitized high quality packing materials and sanitary methods of packaging increase keeping quality, and vice versa.
(ix) Exposure to Light:
Lowers keeping quality.
Note:
Sweet cream/unsalted butter has the maximum, and acid cream/salted butter the minimum keeping quality under commercial cold storage. Individually, both acid and salt improve keeping quality.