In this article we will discuss about:- 1. Introduction to Market Milk 2. Definition of Market Milk 3. The Market Milk Industry in India and Abroad 4. Composition of Market Milk 5. Food and Nutritive Value 6. Milk and Public Health 7. Safeguarding the Milk Supply 8. Uses 9. Flavour Defects.
Contents:
- Introduction to Market Milk
- Definition of Market Milk
- The Market Milk Industry in India and Abroad
- Composition of Market Milk
- Food and Nutritive Value of Market Milk
- Milk and Public Health
- Safeguarding the Milk Supply
- Uses of Milk
- Flavour Defects in Milk
Introduction to Market Milk:
As a major enterprise, the market milk industry is of comparatively recent origin even in developed dairying countries (such as the U.S.A.). Though ancient written records report milk as an important food, it’s processing and distribution as a separate commercial business did not develop in those countries until the concentration of population in the cities reached a high level in the middle of the nineteenth century.
During the earlier years, each household in those countries maintained its ‘family cow’ or secured milk from its neighbour who supplied those living close by. As the urban population increased, fewer households could keep a cow for private use. The high cost of milk production, problems of sanitation (which led to sanitary regulations by Public Health Authorities), etc., restricted the practice; and gradually the family cow in the city was eliminated and city cattle were all sent back to the rural areas.
Gradually farmers within easy driving distance began delivering milk over regular routes in the cities. This was the beginning of the fluid milk-sheds which surround the large cities of today. Prior to the 1850s most milk was necessarily produced within a short distance of the place of consumption because of lack of suitable means of transportation and refrigeration.
With modern knowledge of the protection of milk during transportation, it became possible to locate dairies where land was less expensive and crops could be grown more economically. The milk supply of the large cities of the U.S.A. now comes largely from 80-160 kms or more away.
Nearly all the milk in the U.S.A. before 1900 was delivered as raw (natural) milk. Once pasteurization was introduced, it caught on rapidly. Mechanical refrigeration contributed to the rapid development of the factory system of market milk distribution.
In India, the market milk industry may be said to have started in 1950-1 when the Central Dairy of Aarey Milk Colony was commissioned and went into stream. The industry is still in its infancy and barely 10 per cent of our total milk production undergoes organized handling.
Definition of Market Milk:
The term ‘market milk’ refers to fluid whole milk that is sold to individuals usually for direct consumption. It excludes milk consumed on the farm and that used for the manufacture of dairy products.
Milk may be defined as the whole, fresh, clean, lacteal secretion obtained by the complete milking of one or more healthy milch animals, excluding that obtained within 15 days before or 5 days after calving or such periods as may be necessary to render the milk practically colostrum-free, and containing the minimum prescribed percentages of milk fat and milk-solids-not-fat. In India, the term ‘milk’, when unqualified, refers to cow or buffalo milk, or a combination of the two.
The Market Milk Industry in India and Abroad:
Although a beginning in organized milk handling was made in India with the establishment of Military Dairy Farms (oldest: Allahabad, 1889), the salient features of the market milk industry so far have been:
(i) Handling of milk in Co-operative Milk Unions (oldest: Allahabad, 1913) established all over the country on a small scale in the early stages.
(ii) Long distance refrigerated rail-transport of milk from Anand to Bombay since 1945.
(iii) Pasteurization and bottling of milk on a large scale for organized distribution was started at Aarey (1950), Worli (1961), Calcutta (Haringhata, 1959), Delhi (1959), Madras (1963), etc.
(iv) Establishment of Milk Plants under the Five-Year Plans for Dairy Development all over India. These were taken up with the dual object of increasing the national level of milk consumption and ensuring better returns to the primary milk producer. Their main aim was to produce more, better and cheaper milk.
The present status of the market milk industry in this country may be gauged from the following facts and figures:
(i) Total annual milk production in India has been estimated at 25 million tonnes (1976).
(ii) Although India possesses nearly one-fifth of the world’s bovine population (cow, buffalo and goat), milk production in India accounts for only about one-sixteenth of the world’s total of 428 million tonnes (1975).
(iii) Due to the large human population, daily per capita milk consumption today (1975) works out to about 114 g, while that recommended by the Medical Authorities is 280 g.
(iv) The main reasons for this acute shortage of milk are low milk-yielding capacity of the average Indian cow and acute shortage of feeds and fodder.
(v) Lack of organized milk production and collection, restricted transport facilities (especially refrigerated) and shortage of processing and marketing organizations have greatly hampered the growth of the market milk industry.
(vi) Poor-quality milk, widespread adulteration, and lack of quality consciousness among the great majority of consumers have further aggravated the situation.
Composition of Market Milk:
Milk Constituents:
The constituents of milk may be listed diagrammatically as in Fig. 1.1.
The ‘major’ constituents of milk are: water, fat, protein, lactose, ash or mineral matter. The ‘minor’ constituents are- phospholipids, sterols, vitamins, enzymes, pigments, etc. The ‘true’ constituents are: milk fat, casein, lactose.
Composition of Milk:
(i) The average chemical composition of milk of different species is given in Table 1.10.
(ii) The average chemical composition of milk of a few breeds of Indian cows and the Murrah buffalo is given in Table 1.11.
(iii) The average chemical composition of milk of some foreign breeds of cows is given in Table 1.12.
(iv) The detailed composition of milk is given in Table 1.13.
Factors Affecting Composition of Market Milk:
Milk differs widely in composition. All milks contain the same kind of constituents, but in varying amounts. Milk from individual cows shows greater variation than mixed herd milk. The variation is always greater in small herds than in large ones. In general, milk fat shows the greatest daily variation, then comes protein, followed by ash and sugar.
The factors affecting the composition of milk are:
(i) Species:
Each species yields milk of a characteristic composition.
(ii) Breed:
In general, breeds producing the largest amounts of milk yield milk of a lower fat percentage.
(iii) Individuality:
Each cow tends to yield milk of a composition that is characteristic of the individual.
(iv) Interval of Milking:
In general, a longer interval is associated with more milk with a lower fat test.
(v) Completeness of Milking:
If the cow is completely milked, the test is normal; if not, it is usually lower.
(vi) Frequency of Milking:
Whether a cow is milked two, three or four times a day, it has no great effect on the fat test.
(vii) Irregularity of Milking:
Frequent changes in the time and interval of milking result in lower tests.
(viii) Day-to-Day Milking:
May show variations for the individual cow.
(ix) Disease and Abnormal Conditions:
These tend to alter the composition of milk, especially when they result in a fall in yield.
(x) Portion of Milking:
Foremilk is low in fat content (less than I per cent), while strippings are highest (close to 10 per cent). The other milk constituents are only slightly affected on a fat-free basis.
(xi) Stage of Lactation:
The first secretion after calving (colostrum) is very different from milk in its composition and general properties. The change from colostrum to milk takes place within a few days.
(xii) Yield:
For a single cow, there is a tendency-for increased yields to be accompanied by a lower fat percentage, and vice versa.
(xiii) Feeding:
It has temporary effect only.
(xiv) Season:
The percentages of both fat and solids-not-fat show slight but well-defined variations during the course of the year.
(xv) Age:
The fat percentage in milk declines slightly as the cow grows older.
(xvi) Condition of Cow at Calving:
If the cow is in good physical condition when calving, it will yield milk of a higher fat percentage than it would if its physical condition was poor.
(xvii) Excitement:
Both yield and composition of milk are liable to transient fluctuations during periods of excitement, for whatever reason.
(xviii) Administration of Drugs and Hormones:
Certain drugs may effect temporary change in the fat percentage; injection or feeding of hormones results in increase of both milk yield and fat percentage.
Food and Nutritive Value of Milk:
Milk is an almost ideal food. It has high nutritive value. It supplies body-building proteins, bone-forming minerals and health-giving vitamins and furnishes energy-giving lactose and milk fat. Besides supplying certain essential fatty acids, it contains the above nutrients in an easily digestible and assimilable form. All these properties make milk an important food for pregnant mothers, growing children, adolescents, adults, invalids, convalescents and patients alike.
(a) Proteins:
Milk proteins are complete proteins of high quality, i.e., they contain all the essential amino-acids in fairly large quantities.
(b) Minerals:
Practically all the mineral elements found in milk are essential for nutrition. Milk is an excellent source of calcium and phosphorus, both of which, together with vitamin D, are essential for bone formation. Milk is rather low in iron, copper and iodine.
(c) Vitamins:
These are accessory food factors which are essential for normal growth, health and the reproduction of living organisms. Milk is a good source of vitamin A (provided the cow is fed sufficient green feed and fodder), vitamin D (provided the cow is exposed to enough sunlight), thiamine, riboflavin, etc. However, milk is deficient in vitamin C.
(d) Fat:
Milk fat (lipid) plays a significant role in the nutritive value, flavour and physical properties of milk and milk products. Besides serving as a rich source of energy, fat contains significant amounts of so-called essential fatty acids (linoleic ami arachidonic). The most distinctive role which milk fat plays in dairy products concerns flavour.
The rich pleasing flavour of milk lipids is not duplicated by any other type of fat. Milk fat imparts a soft body, smooth texture and rich taste to dairy products. Lastly, milk lipids undoubtedly enhance the consumer acceptability of foods; they also serve the best interests of human nutrition through the incentive of eating what tastes good.
(e) Lactose:
The principal function of lactose (carbohydrate) is to supply energy. However, lactose also helps to establish a mildly acidic reaction in the intestine (which checks the growth of proteolytic bacteria) and facilitates assimilation.
(f) Energy Value:
The energy-giving milk constituents and their individual contributions are as follows:
(g) Effect of Processing:
(i) Pasteurization carried out with reasonable care has no effect on vitamin A, carotene, riboflavin and a number of remaining vitamins B, and vitamin D. Of the remainder, a 10 percent loss of thiamine and a 20 per cent loss of ascorbic acid may be expected,
(ii) Sterilization increases the losses of thiamine and ascorbic acid to 30-50 per cent and 50 per cent respectively, though the remaining vitamins are but little affected.
(h) A balanced diet is essential for proper health and growth. The role of milk and milk products in providing the nutrients required for a balanced diet is indicated in Table 1.14.
Milk and Public Health:
It is well established that milk can be a potential carrier of disease- producing organisms. Milk-borne epidemics have occurred in the past throughout the world. Unless proper precautions are taken, such outbreaks of milk-borne diseases can occur anywhere, anytime, especially if raw milk is consumed.
Diseases which are known to be transmissible through milk are listed below, together with the manner in which they may enter the milk:
(i) Infection of Milk Directly from the Cow:
These diseases are essentially bovine. The causative organisms enter the milk through the mammary glands or through faecal contamination, and may cause a diseased condition in persons who consume the milk. Examples- Bovine tuberculosis; Undulant fever or Malta fever; etc.
(ii) Infection from Man to Cow and then to Milk:
These diseases are essentially human, but can become established in the cow’s udders. Examples- Septic sore throat; Scarlet fever, Diphtheria; etc.
(iii) Direct Contamination of Milk by Human Beings:
These diseases may be transmitted to the milk by direct contamination through human contact, either by carriers or patients. Examples- Septic sore throat; Scarlet fever; Typhoid fever; Paratyphoid fever; Dysentery; Gastroenteritis; Diphtheria; etc.
(iv) Indirect Contamination of Milk by Human Beings:
These are human diseases, the pathogenic organisms of which enter the milk through contaminated bottles or other utensils, water supply, insects and dust. Examples- Typhoid or Paratyphoid fever; Dysentery or Diarrhoea; etc.
Safeguarding the Milk Supply:
Whereas ‘cleanliness’ implies freedom from extraneous matter (such as manure, dust, etc.), safety’ means freedom from pathogenic micro-organisms. For human consumption, milk that is both clean and safe is highly desirable.
The sanitation of the milk supply can be safeguarded in two ways:
(a) Production and handling of raw milk in such a manner as to prevent its contamination by pathogenic organisms.
This will require:
(i) Ensuring the health of dairy cattle by various control measures;
(ii) Safeguarding the health of employees by regular medical examination;
(iii) Protection of the water supply from contamination by pathogenic organisms;
(iv) Flies and their control, etc. Examples- ‘Certified milk’, ‘Grade A raw milk’, etc.
(b) Pasteurization of milk, so as to kill all pathogenic organisms and avoidance of any post-pasteurization contamination.
(a) The following standards, vide Table 1.15, are suggested as a guide for grading raw milk in this country:
(b) The sources of contamination of milk and their control have been given in Table 1.16.
Uses of Milk:
(i) In the daily diet, as a nutritive food for pregnant mothers, growing children, adolescents, adults, the aged, invalids, convalescents and patients alike;
(ii) As raw material for the production of various processed milks and manufactured products;
(iii) In bakeries and confectionaries;
(iv) As an additive to improve the quality of various recipes.
Flavour Defects in Milk:
Milk has a flavour defect (i.e., off-flavour) if it has an undesirable smell, foretaste or aftertaste, and if the mouth does not feel clean and pleasant after it has been tasted. These flavour defects may arise due to faulty methods of production, processing and storage.
1. Barny:
Causes:
(i) Improper ventilation of milking byre/barn;
(ii) Milk not properly covered during production.
Prevention:
(i) Proper ventilation of milking byre/barn;
(ii) Keep milk properly covered during production.
2. Bitter:
Causes:
(i) Intake of bitter weeds by milch animals;
(ii) Using late lactation milk.
Prevention:
(i) Eradicate offending weeds;
(ii) Use normal lactation milk.
3. Cooked:
Causes:
Overheating of milk.
Prevention:
Avoid overheating of milk.
4. Feed:
Causes:
Feeding of milk-tainting feeds (such as silage) within 3 hours before milking.
Prevention:
Feed milk-tainting feeds (such as silage) soon after milking.
5. Foreign:
Causes:
Addition or absorption of foreign smelling substances in milk.
Prevention:
Avoid contact of milk with foreign smelling substances.
6. High-Acid/Sour:
Causes:
Excessive lactic acid development (due to considerable growth of lactic acid producing micro-organisms).
Prevention:
Store milk at 5°C (40°F) or below (to check bacterial growth and acid development).
7. Malty:
Causes:
Growth of Str. lactis var. maitigenes micro-organ- isms in milk.
Prevention:
Store milk at 5°C (40°F) or below to check bacterial growth.
8. Rancid:
Causes:
Fat hydrolysis due to lipase action.
Prevention:
Inactivate lipase by proper pasteurization of milk.
9. Oxidized, Oily, Metallic, Tallowy:
Causes:
Fat oxidation due to- direct contact of milk with copper or iron, exposure of milk to light, etc.
Prevention:
(i) Tin milk – holding vessels properly; or use aluminium alloy/stainless steel as milk-contact surfaces;
(ii) De-aerate/vacuumize pasteurized milk.
10. Salty:
Causes:
Milk of animals suffering from mastitis or far advanced in lactation.
Prevention:
Avoid mastitis or late lactation milk.
11. Weedy:
Causes:
Intake of milk-tainting weeds (within 3 hours of milking).
Prevention:
(i) Eradicate milk-tainting weeds;
(i) Vacuum pasteurization of milk.
Note:
In the scouring of milk, lactic acid is the main fermentation product, but the sour smell is not caused by lactic acid (which is non-volatile). Volatile substances, such as acetic acid, formic acid, propionic acid, acetaldehyde, acetone, diacetyl and methyl-acetyl carbinol, are responsible for the characteristic smell of sour milk.