Module 4. Design aspects of dairy plant

Lesson 15

15. 1 Introduction

Dairy industry in India is growing at fast rate and as such, there is need for Scientific Layout and Planning with a view to have model studies by dairy designers, engineers and architects. The term ‘Dairying’ has been bifurcated into two branches, namely Dairy Husbandry and Dairy Technology. Under the purview of dairy husbandry comes animal breeding, care, health, nutrition of animals, animal housing, clean and safe production of milk, i.e., milching animals in good sanitary conditions. In some organized sectors, milk collection and chilling before milk is transported for processi9ng at dairy factory also forms an activity of dairy husbandry.

The Dairy Technology commences with processing of milk at dairy plant for market milk and various dairy products. The dairy plant layout and design means designing a layout plan for dairy factory, i.e. layout of various sections in dairy building, equipment layout, laying of dairy machines in each section for economical and efficient movement of men and material in the plant. It will deal with all items which are needed for planning and layout of dairy factory, with direct application to fundamental topics, such as location, selection of site for dairy plant, building materials, specific requirement of each section including service sections. It will also touch the practical need of prospective entrepreneurs aspiring to set up a dairy plant. Management and planning of layout of indirectly related sections, such as office and administration block will also find place in this presentation. The treatment of subject matter is descriptive and lucid so that students, teachers and dairy professionals can imbibe the topics discussed easily. Many illustration and diagrams have been given to make the subject crystal clear. Thorough study of the text book will not deprive the learner of various definitions of milk and milk products, terminology of various processing and technical terms as are commonly spelled in dairy technology and engineering.

Milk and milk products, however, impose certain requirements which do not occur elsewhere in food or other industries. These special requirements affect the structure and the layout of the building, the provision and distribution of services and the choice of site. The products of dairy industry – milk for liquid consumption, yoghurt, curd (dahi), cream, butter, ghee and similar products, cheese, milk powder and so on – are foods which play a fundamental part in human nutrition. In any country, therefore, it is in the nation’s interest that milk and milk products be available to everyone at the lowest possible rate. The margin of profit which the dairy entrepreneur can expect is limited. Therefore, every possible economy in capital outlay on building and plant should be sought. Planning must be done wisely to make best use of the labour employed and to keep operating costs to a minimum. Materials and method used in building must be such as to give the longest practical life with the minimum of maintenance, in spite of working conditions which are often relatively severe from both the mechanical and chemical points of view. It should also be seen that most of the repairs, alterations or extensions could be done without stopping the production. These characteristics demand closest attention during planning.

There is need for highest standard of hygiene. Milk is most suitable medium for the growth of microorganisms, therefore, every possible measure should be taken to reduce the possibility of contamination, especially after processing. Failure to maintain adequate control of hygiene will spoil the product, it may not keep well or its flavour may change. This will pose problem to sell the product. A good layout design and use of proper materials and techniques make great contribution towards hygiene. Proper cleaning and maintenance of plant and building is essential, so that, there is no contamination. Care should be taken to provide adequate natural and artificial lighting. Every possible effort should be made to ensure that the building and the site will be pleasant to look at. The architect can provide a good landscape and an attractive outlook. The welfare of the employees must be kept in view. Canteen facilities are essential. Housing for key workers must be provided near the plant at reasonable distance, so that they can reach in time in emergency.

To sum up, dairy plant layout needs careful thought and planning keeping in view manufacture of the products and their commercial aspects.

15.2 Increased Safety and Improved Working Conditions

Good plant layout incorporates safety into the plant by eliminating hazards at work stations, in materials handling, storage activities, maintenance operations and the like. Man hour losses can be cut down to minimum. Reduction in losses of capital equipment and materials is another result of “built in” safety in the layout. The provision of a good physical plant environment improves the overall working conditions. Increased employee moral tends to reduce production costs and helps develop a stable operating force.

15.3 Perishable Nature of Milk

Milk by its nature is perishable. The following three factors contribute to its being perishable;

(a) Contamination with bacteria

(b) Warm temperatures, and

(c) Prolonged time before cooling or processing

In practice, none of these factors can be eliminated completely, so if any one is accentuated, the life of milk will decrease. Therefore, every effort must be made to minimize these factors on the farm, during collection at milk plant and during distribution to consumers. At the farm, the aim must be to cool the milk as soon as possible often milking. Freshly drawn milk has bacteriostatic property, i.e. it contains substances which resist the growth of bacteria for several hours. However, there is a substantial bacterial population. Ideally, the milk should be chilled to 4 oC within two hours after milking. If for any reason this can not be done at farm, quick transport of milk to the plant is essential.

If milk can be stored conveniently at the farm or local collecting depot at low temperature, the organization of transport to milk processing plant is simplified to greater extent by transporting bulk quantity in insulated tankers. The type, size and number of vehicles necessary are, therefore determined not only by the usual factors such as distance or nature of roads but also by the condition of milk production. This applies to cream also. In some cases, the milk may be separated at the farm and only the cream, i.e., milk containing 5 to 30 per cent fat is sent to plant for manufacturing butter or ghee.

15.4 Flexibility

Management should lay stress upon maximum flexibility in production facilities and distribution methods consistent with low cost operations. Production facilities and layout can be designed to attain flexibility and adaptability to meet changing economic and technological conditions. To combat regular fluctuations in the supplies of milk available to processing plant throughout the year, flexibility in the plant layout is essential. Flexibility is necessary since market conditions for the sale of finished products attain flexibility in production changes of the product, and technological advances must be anticipated so that plant equipment does not become obsolete. The amount of production flexibility depends on such factors as the nature of the products, the kind of production facilities can in part be attained by initially selecting universal and standard types of machines, which can perform a variety of operations, such as Tri-process machine used for cream separation, clarification and standardization of milk. Layout flexibility can also be attained by incorporating into the layout as much as possible the process-layout arrangement whenever it is consistent with low cost operations.

Allowance for increases in capacity can be anticipated in a layout by properly arranging production departments and selecting the type of building that can be expanded at low cost. Sound layout engineering attains low cost flexibility in the kind of operations performed and an ease in the increase of output capacity which may be required for the future.

Good plant layout achieves a floor arrangement that contributes in a number of ways to low-cost production planning and control. Materials control can be more easily attained in a well designed plant layout. A steady amount of production capacity is facilitated an idleness of machinery and man is reduced to minimum. The net result is facilitation of dispatching activities on operating floor. Deliveries toi customers on short notices are easily attained.

15.5 Modes of Transportation of Milk

Modes of transportation of milk depends on type of area, type of transportation available and local road conditions. Table 15.1 shows different types of mode of transport used for procurement of milk, for optimum load conditions and distance.

Table 15.1 Various modes of transportation of milk to dairy plant along with optimum load and distance


Table 15.2 Various modes of transportation of milk to dairy plant along with optimum load and distance


15.6 Milk Procurement and Reception at Dairy Plant

In most of the countries, milk production is carried out in rural areas from where it is transported to milk processing plant, and thereafter for distribution to consumers through local depots or milk parlours. Under Indian conditions, milk has to be regularly collected and transported twice a day (morning and evening).

The usual methods of milk collection and reception at dairy plant are:

Milk procurement through individual producers: In this milk is brought to the dairy plant by the individual producers in their own vessels any type. This is possible for those producers who are located nearby milk processing dairy.

Milk collected through co-operative organizations: Here, co-operative societies form an organization which is responsible for uninterrupted supply of milk to the dairy plant. Supply of milk can also be effected by single co-operative society formed by milk producers. This is beneficial to the producers as there is no middle man to share the profit.

Milk procured through contractors: There is less return to the milk producers, as milk contractor will keep his share in the profit.

Milk reception from milk collection cum chilling centers: This method is generally possible and is prevalent in organized sectors, and dairy corporations in India.

Milk is collected at various milk collection centers from nearby villages in 40 litre cans usually belonging to the organization. The milk is weighted, tested for fat content and kept ready to be dispatched to the milk chilling center, where milk cans are emptied, washed through can washer and sent back to milk collection centers for next day collection of milk. Route plan linking villages, milk collecting centers and chilling center is shown in Fig. 1.1. On arrival at milk chilling center, the milk is weighed chilled and transported to milk processing dairy plant through Insulated Road Mill Tankers or Rail Tankers. The important equipment for reception of milk at milk processing plant are

(i) Can conveyor (ii) milk weigh tank

(iii) Weighing scale (iv) dump tank with cover

(v) Can washer (vi) drip saver

(vii) Milk pump (sanitary type) (viii) surface/plate chiller

(ix) Refrigeration unit (suitable capacity), and (x) milk testing laboratory

The milk as soon as it is received at plant, it is weighed, dumped into the dump tar (weigh tank) and has to be chilled before it is stored for processing. This has to be done in quick succession through equipment well planned and installed at milk reception dock and receiving room. If the milk is received in bulk through tankers, the arrangement has to be made for quick transfer of milk through milk pumps installed at milk reception dock to milk storage tanks. The milk received in the evening may be chilled and the stored for processing next day. This all will need careful planning of layout of equipment at milk reception dock and milk receiving room. Roads leading to milk reception dock and dispatch dock have to be planned in such a manner so as to avoid traffic congestion inside the factory or road blockage.

15.7 Contamination and its Prevention

Milk coming from its source to milk plant for processing is prone to contamination as it passes through different stages, hands and environmental conditions. Unless proper precautions are taken, outbreaks of milk-borne diseases can occur any where anytime especially if raw milk is consumed as such. Diseases which are know to be transmissible through milk are given hereunder together with the manner in which they may enter the milk.

Infection of milk directly from the cows: These diseases are essentially bovine. The causative organisms enter the milk through the mammary glands or through contamination, and may cause a diseased condition in persons who consume the milk. Bovine tuberculosis or fever can occur.

Infection from man to cow and to milk: These diseases are essentially human, but can become established in cow’s udders, e.g., septic sore throat, scarlet fever, diptheria etc.

Direct contamination of milk by human beings: These are human diseases, the pathogenic organisms of which enter the milk through contaminated milk bottles or other utensils, water supply, insects and dust, e.g. typhoid or paratyphoid fever, dysentery or diarrhoea etc.

For human consumption, milk must be clean and safe. The sanitation of milk supply can be safeguard in two ways.

(a) Production and handling of raw milk. It should be done in such a way, so as to prevent its contamination by pathogenic organisms. This will require

(1) ensuring the health of dairy cattle by various control measures,

(2) safeguarding health of employees by regular medical check ups,

(3) protection of water supply from contamination by organisms,

(4) straining the milk through milk strainer for any dirt straw etc.

(5) pasteurization of milk. This will kill all pathogenic organisms and avoid any post-pasteurization contamination.

There are many factors which help in preventing contamination, such as design of equipment, effectiveness of cleaning and sterilization, methods of handling and design layout of building, particularly internal finishes. The end products of processing plant are liquid milk in various forms, cream, butter, cheese, milk powder, ghee, etc., each item is produced to meet consumers requirement. In all these conservation processes, highly perishable raw material is given longer life. Although the various processes are different, but they are similar in sense that they control development of bacteria. It is, therefore, recommended to keep the raw material well separated from the processed products. The isolation of dirty bottle reception and bottle washing from pasteurized milk bottling, storage and dispatch is one of the example of this. Similarly, pipelines for raw milk must be completely separate from those carrying processed milk. Every section of the plant must be independent and self contained as far as possible. For instance, many varieties of cheese involve the growth of molds to give their characteristic flavour, whereas the presence of mold in butter would damage it. Most of dairy products quickly absorb flavours not only from one another, but also from any strong smelling contaminants such as oil, ammonia, paint or kerosene.

Table 15.3 Contamination checkup guidelines


15.8 Cleaning and sterilization

The dairy industry is somewhat different from other industries so far as hygiene is concerned, and is comparable with medical practice. Every detail of equipment and building design must have medical rather than industrial approach. Every item of equipment which comes into contact with milk must be cleaned thoroughly and sterilized every day. Anything less than this will quickly lead to problems. In hot climate, the problem is intensified. Once trouble starts, it may quickly spoil large portion of the production it may then take several days to control the situation.

With milk pasteurization, daily cleaning may not be sufficient. Where the plant has to operate for more than five hours at a time, it will be necessary to stop for an intermediate cleaning and sterilizing operation. The reason for this is deposit of milk solids heating surfaces, which causes loss of heat transfer efficiency. Dairy equipment, therefore, must be designed so that it can be easily and thoroughly cleaned. Crevices and small internal radii must be avoid. The equipment may be dismantled and thoroughly cleaned. The material used must be corrosion proof. The building should fulfil high standards of sanitation. Every possible effort must be made to eliminate dust and insects. Floors, walls and ceiling finishes must be such that they can be easily cleaned, thus reducing the contamination. Neat and clean dairy is liked by everyone and also makes a good business.

Last modified: Thursday, 4 October 2012, 7:15 AM