In this article, we will be studying about properties of milk, its processing methods, packing and distribution as well as its products. In Nigeria for instance, the development of the dairy industry is mainly in the hands of the Fulani women.
Development and marketing have been static because of their limitation in Western education. Transporting and the Nomadic way of life have little or no government participation or control of the traditional dairy industry.
Milk is a fluid food produced in the mammary system of female animals following parturition. It is an emulsion of butterfat and water aqueous phase containing proteins, lactose, minerals, and enzymes.
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Properties of Milk
1. Taste and Odour: Milk has a slightly sweet taste and a milk aromatic flavour. The sweet taste comes from lactose while the flavour comes from the fat.
2. Labour: Normal milk has a yellow-white colour because of the presence of fat and small amounts of colouring matter. The breed of the animal and type of feed affect the colour of the milk is deeper yellow when animals are on pasture than when they are concentrated feed.
3. Specific Density: Milk is heavier than water because of the dissolved constituents. The specific gravity of milk is between 1.02 and 1.034.
4. Acid-Base State of Milk: Milk has a pH of 6.6 – 6.8 and is slightly acidic. The substances giving milk its apparent acidity are phosphates, citrates, casein, albumin, and dissolved carbon dioxide.
5. Freezing and Boiling Points of Milk: Milk freezes from about 31°F milk and whole milk has the same freezing point. The boiling point of milk is higher than that of 14°F.
6. Cream Rising: When whole milk stands for a while. The fat rises to the top because it is lighter than water. eventually forms a layer packed with fat globules called cream. When the cream is agitated by chumming, a larger clump forms to yield butter.
7. Foaming: Milk foams on heating. This is due to air which becomes incorporated into the thin layers of milk formed by coagulating proteins.
Processing of Diary Products
This is the application of some treatments to raw milk to make it safe for human consumption or to convert it to other desirable products treatment could involve heating and cooling for separation of milk constituents or fermentation.
Reasons for Processing Milk
Raw milk goes sour when kept at ambient temperature over some time. Milk obtained from the udder of an animal contains different types of bacteria some of which could cause disease. So milk needs so many forms of processing for various reasons.
1. Safeguard Public Health: This is achieved through either pasteurization or sterilization of milk and milk products. The process ensures the domination of disease-causing pathogens.
2. Reduction of Water Content of Milk: This reduces the bulkiness of milk and the cost of transportation. Milk contains about 87% water. Thus evaporated or condensed milk products are cheaper to transport.
Enhances shelf life and reduces storage space processed milk has longer without getting and then condensed the balkiness is reduced.
Production of other desirable products milk can be processed into other products such as cream, cheese, and butter. To confirm industrial and health regulations.
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Milk Processing Methods
1. Pasteurization: This is a process by which milk or milk products are heated to a specific temperature and held there for a specific time to destroy all pathogenic bacteria. There are two types of pasteurization.
(a) Holding VAT or batch method
(b) High temperatures short-time method.
In the holding vat method, milk is heated in the holder pasteurizer at a temperature of 62°C for about 30 minutes. The pasteurized product is then cooled for packaging.
The short-time method involves heating the product at a high temperature usually at 72°C for 15 seconds.
Pasteurization kills about 99.6% of all bacteria in milk.
2. Sterilized Milk: This is a product obtained from raw milk that is treated to a high temperature of 92.97°C for a period of between 16-30 minutes so that all micro-organisms are destroyed. The flavor of pasteurized milk is not very pleasant and such high-temperature heating may result in a decrease in vitamin content.
3. Evaporated Milk: This is the product of evaporating water from whole milk at 70-73°C in a vacuum. About 50% of the water in the original milk is boiled off. This process can be achieved in a home by slowly boiling milk in a pot. Commercially this product is filled into tins and sterilized under pressure.
The storage life of the product is unlimited at normal temperatures as long as the tin or container is not opened.
4. Other Process: A few other processes are used to make milk more acceptable and to improve it keeping quantity. Milk can be homogenized before heat treatment to reduce fat globule size so that will remain dispersed and will not form a cream layer.
Milk is sometimes frozen as a means of having a regular supply throughout the year. A rancid flavour often develops in cow milk as the fat globule membrane is broken by freezing.
Milk Powders
Dried Milk Powders are very suitable products for developing countries because dried milk can be kept without
1. Refrigeration
2. Be transported easily
3. Be easy with other foodstuffs
4. Available all year round
Whereas milk, skim milk, and buttermilk can all be successfully dried. This involves pasteurization condensation into one-third of its volume then drying by roller or spray drying.
Packaging and Distribution of Milk
Methods of packaging and distribution are tailored to the customers, requirements, and income. In many cases, milk is best left unpackaged from containers to provide the cheapest possible supply to low-income customers.
In most countries, some customers are willing to pay for packaged milk. Despite the higher cost, the advantages of packaged milk to the customer are:
1. Convenience.
2. Milk that has better keeping qualities.
3. Milk is accurately measured safe from adulteration.
A variety of packaging methods are used including returnable glass bottles, plastic bottles, card-board cartons, plastic sachets, and sealed cans.
Dried Milk Powders is a very suitable produced for developing countries.
In summary, milk is an important product that contains all the essential nutrients. The properties of milk in most cases are determined by its constituents. Processing of milk is necessary and the various processing methods have been highlighted.
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