Self-contained Dairy Wagon for added value to raw milk
Foreword Dr Heva Ranjith Phd, CSci, FIFST, MBIAC
The requirement for a suitable mobile unit to provide on-farm training for dairy operatives’ was highlighted in research work and advice in DEFRA’s publication: Vocational Training Scheme Information. Training of staff is one key requirement for various food standards as well as food security compliance. A problem identified here is the inability of the on-farm manufacturers as well as industrial manufacturers to release their staff for training. It is also noted that a small processing facility made available to farms would provide means to demonstrate how to add value to their raw material (for example producing pasteurised milk, cheese making and yoghurt). A small mobile facility would allow staff training at their work place without disruptions to normal work place activities.
To satisfy this need the first dairy wagon was produced in 2007 for the Peak District Dairy Farmers in UK. This unit was equipped with milk pasteuriser, cheese production, yoghurt, milk separation for cream and butter. This unit relied on single phase electricity supply from the farm of factory to run the equipment.
The second mobile dairy wagon (Mark 2) was designed to contain two separate mobile units. The main unit provides processing services required for the first processing unit. The two units ensure that processing can be done independently without the need for external energy supply from the farm or factory. The service unit has the capacity to carry 500 litres of water and the diesel electricity generator that will run for 8 hrs due to its capacity to hold 60 litres of diesel. This Mark 2 version is very well suited for remote rural operation of dairy processing industries world over. A special feature in this model is the environment control in the processing area using an air-conditioning unit making comfortable working conditions in warmer climates.
Farmers in every part of the world suffer from decline of income mainly due to poor return from raw milk sales. The dairy wagon will create a new opportunity for dairy farmers to make more from their milk by leaning new skills and going on to set up new enterprise. This leads to highlight the importance of adding value to increase returns from the market and so improve competitiveness.
Introduction to the Dairy Wagon
The design of the dairy wagon is aimed at facilitating small to medium entrepreneurs to conduct training and liquid processing of food products
For example, milk can be pasteurised for bottle/bag filing or for cheese making. Similarly a liquid food product (i.e. flavoured milks, milk shakes, butter milk, whey drinks) can be pasteurised using the continuous flow, plate pasteuriser or batch pasteuriser.
If raw milk is not available (i.e. cow, goat, buffalo) then reconstituted milk may be an alternative substitute. For reconstitution of powders a suitable fluid bed drier / evaporator is required (optional extra). Heat treated milk can be stored chilled in the 150 litre storage tank fitted with chilled water jacket to the base of the tank. This jacket is also fitted with an electric heater to facilitate further heating of milk to higher temperature then cool to culturing temperature for cheese and yoghurt making. Cheese curd can be pressed using two piston type cheese presses.
Specification/content of the Dairy Wagon
Dairy Wagon consists of two units, Trailer 1 is the main unit which accommodates the processing equipment and Trailer 2 is the services equipment.
Trailer 1: (5.5 meters long, 2.21 meters wide, 2.08 meters high – this is the external body measurements only, excluding tow bar, measurements not from the ground)
Support Trailer 2 Equipment Specifications: (3.73 meters long, 1.73 meters wide and 2.08 meters high , external body measurements only)
Trailer 1 equipment and specifications
Trailer 1 has an air condition unit and hot water supply for surface cleaning as well as hand washing. Water supply into Trailer 1 is sanitised using UV treatment unit. Adequate lighting is provided inside and 240 volt wall sockets are available for suitable appliances.
Pasteuriser
This is a plate type unit and has a throughput of 300l/h and fitted with an automatic flow diversion valve if the set temperature fails. The heat treatment of product is achieved by an electrically heated hot water system where the set temperature is automatically controlled. Heated product is cooled by chilled water to below 15ºC.
Milk storage tank/ batch pasteuriser
This is a 150 litre tank fitted with a slow moving paddle agitator and an exit port to product. The bottom has a jacket to which an electrical heater is fitted. The jacket is supplied with chilled water for product cooling. The tank is supplied with top lids to totally cover and protect product from external contamination.
Liquid filling unit/sealing equipment
This has a piston operated volumetric filler which has a variable fill adjustment to deliver from 50ml to 1000ml, together with heat sealing equipment for polyethylene bags.
Raw milk storage/product mixing tank
Raw milk up to 300 litres can be stored here and it can be used as product mixing tank. A lid is provided to protect the liquid food from external contamination.
Cheese and yoghurt
Equipment for manufacture of cheese and yoghurt is also provided as standard. Ice cream equipment is an optional extra.
Quality Control
Full QC equipment is provided as standard.
Support Trailer 2 equipment/specifications
Electric generator
This is a diesel generator with a power output of 34 amps with outlet sockets for three phase, single phase 240 volts and single phase for 110 volts. Storage capacity of the diesel tank is 60 litres.
Compressed airThe compressed air unit is a small generator with 50 litres reservoir tank capable of supplying pressure up to 6 bars.
Chilled water unit
This unit supplies chilled water for the pasteuriser and product storage/cheese tank.
Water storage tank
Water storage tank has a capacity of 500 litres. This tank supplies water for production when tap water is not available. Please note: this tank should be empty during travelling or any movement of the support trailer.
Pasteurised milk - a safe and healthy drink
The milk of all animals is an opalescent white liquid with a sweetish, palatable taste. Its main constituent is water and in addition it contains fat, sugar, salts, nitrogenous compounds, enzymes and vitamins together with other constituents. These constituents vary from species to species. The original source of our milk supply is considered to come from bovine origin but other species such as buffalo, camel, goat, sheep and yak may equally be in popular demand in some regions of the world. The animal health is an important aspect of hygienic milk production. The modern hygiene regulations stipulate this requirement under animal welfare to ensure animals are free from disease and in thoroughly healthy condition. Milk serves as an excellent culture and protective medium for certain micro-organisms, particularly bacterial pathogens whose multiplication is mainly dependent on temperature and on competing micro-organisms and their metabolic products.
Many pathogenic bacteria (e.g. Mycobacterium tuberculosis, Brucella) do not multiply freely in milk and viruses do not multiply at all. The pathogens depend for their disease producing capacity on the initial load of infection in the milk and on the subsequent dilution, processing time that elapses before milk is consumed by the individual and other factors.
Temperatures below about 10ºC are inhibitory for most pathogens and therefore in almost all dairy operations the storage temperature is in that region preferably about 3-5ºC.
Where the milk is produced under poor hygienic conditions and without adequate cooling, the main contaminants are usually lactic acid producers, which cause rapid souring.
Source of infection/contamination
The pathogens and other disease causing organisms in milk derived from either dairy or animal itself, the dairy operations or from the environment. One of the most important external sources of contamination of infection on the farm and in some instants the cooling equipment is the contaminated water supply. In addition insects, rodents, dirt and manure all play their part in introducing pathogens. In the early period of the 20th century, disease such as typhoid fever, diphtheria, salmonellosis, streptococcosis (‘septic sore throat’, scarlet fever), Q fever, brucellosis and tuberculosis attributable to milk-borne infections have virtually disappeared in modern developing farming community in the world. They have either been eliminated from the animal population (e.g. brucellosis, tuberculosis) reducing to very low in the human population (typhoid fever, diphtheria), or their transmission avoided by the efficient heat treatment regimes and subsequent hygiene control of the milk product.
Disease Control
Diseases are also transmitted through virus to human. For example a tick borne encephalitis virus circulates among invertebrate hosts through the agency of ticks and mites but human infection may take place either through tick bites or by mouth, particularity through drinking unheated milk from infected animals.
Q fever is caused by the organism Coxiella burneti, a rickettsial organism and is widespread in the world. Most countries are free from this disease now. The route for human infection is through cattle, sheep and goats. Oral infection is through drinking raw infected milk.
Some of the other known bacterial infections and intoxications associated with milk are anthrax (Bacillus anthraracis), botulism (Clostridium botulinum, C. parabotulinum), diphtheria (Corynebacterium diphtheria), listeriosis (Listeria monocytogenese), tuberculosis (Tubercle bacillus) etc. The incidence of bovine tuberculosis infection in man depends largely on its presence in cattle and the amount of raw or inadequately heated milk is consumed by the population. Therefore, the raw milk is the principle vehicle for the transfer mechanism from animals to man of tuberculosis and many other diseases. This includes the milk of buffaloes, goats, sheep , camels and other ruminants as well.
It is reported that E.coli 0157:H7 infection causes severe kidney damage and Campylobacter and E. coli infection leads to severe diarrhoea.
Making milk safe to drink by heat treatment
Historically the dairy industry has adapted the method developed by Louis Pasteur (1822-1895) to improve the keeping quality of wine by subjecting it to a heat treatment and then cooled. In milk the aim was to destroy the bacterium that is responsible for tuberculosis. To achieve this, milk temperature is raised to 63ºC and then held for 30 minutes before cooling. This is the batch heat treatment method. Later with the invention of continuous heat treatment (for example using plate packs) a temperature time regime of 72ºC for 15 seconds was suggested by the IDF (International Dairy Federation).
In recent years it was evident that Mycobacterium paratuberculosis could survive the pasteurisation treatment. Therefore, in the dairy industry the temperature regime used is 74 to 76ºC for 25 seconds. Raw milk can never be free from pathogens even in the cleanest environment and it is better to be safe than being a victim of some of the infections listed above.
Most importantly care must be taken to protect milk from post pasteurisation contamination.