GN Limited recommends that small farmers use a batch pasteuriser to get more from milk.


"It used to be said that you never see a poor farmer and that perception still persists, especially amongst those who don't know much about the dairying industry.

"Here at GN Ltd., we get phone calls every week from dairy farmers struggling to make ends meet. The milk processing companies get squeezed hard by the supermarkets and this filters all the way down the chain. We hear stories of farmers getting less than 25p a litre for their milk, even below 15p in some cases! Usually it is costing them more to produce the milk than they are getting in return, which of course puts them in an unsustainable situation. In more than one case we've been told that the smallholding or farm is about to go broke and buying a pasteuriser represents the last roll of the dice for them.

"It is usually thought that the smallest herds have suffered the hardest financial hit, so let us consider one in this bracket.

"Our farmer has just a dozen milkers and each cow is producing on average just 18 litres of milk a day, (well below the 25 litres per day national average). This means our farmer has about 216 litres in the bulk tank every day, ready for collection by the milk tanker. For this quantity, the farmer is currently receiving say £54 - £64 per day, or typically about £400 - £450 per week and from this has to pay feed bills, vets bills, power, water, and everything else.

"Our farmer now buys a batch pasteuriser. Once pasteurised, the milk can now legally be sold directly to the public, using a vending machine, through a small farm shop, or supplying local retail outlets. In many cases it can be used for doorstop deliveries; either directly or indirectly. The average price for the first 2 retail options is about £1.30 a litre and whilst the farmer has all the work, pasteurising, bottling, transporting etc. as well as other expenses including the cost of the electricity, packaging, etc., our farmer should now receive about £1965 per week...and with careful management, half of that should be profit.

"However, our farmer is clever and wants to expand and widen the range, so on one day a week, the milk in the batch pasteuriser is allowed to cool to 40C, before the temperature is set to 42C; one heater element is then switched on to achieve this lower temperature and when it has stabilised, yogurt culture is added and the batch is left to incubate for 5 - 6 hours. Our farmer now has enough "artisan yogurt" to fill over 1400 x 150g (5 ounce) pots, adding strawberries, raspberries etc. grown in the greenhouse to make the final varieties. This yogurt will have a retail value of about £600.

"I now hear that he's/she’s keen to start using their batch pasteuriser to produce soft cheese, kefir, clotted cream...

"So what does the batch pasteurisation process entail and what is the difference between a batch and a continuous-flow pasteuriser? A batch pasteuriser is basically a great big bains-marie, i.e. a simple jacketted vessel where there is water in the outside jacket and milk in the inner compartment. It is only the water in the jacket that is directly heated, usually by electric elements and this provides a very gentle transfer of heat through the walls and base of the vessel that warms and pasteurises the milk. The milk must be stirred at all times to transfer this heat in a steady sustained manner and ensure there are no cold spots. When the milk reaches the pre-set temperature, it is held at that temperature for a set time before being cooled and filled off.

"There must be a probe in the milk to measure its temperature and this temperature profile must be recorded to satisfy the appropriate authorities. These days it is usually recorded digitally and the latest data loggers will text your i-phone if anything is not quite right - e.g. if the temperature goes outside the prescribed limits or there is a power cut etc..

"That is basically the batch pasteurisation process. On the other hand continuous-flow pasteuriser does exactly that - i.e. it allows milk to pass through the masses of stainless steel heat-exchange plates in an extremely efficient manner so that the milk is pumped in at one end and basically comes out pasteurised at the other, all within a very short time.

"Both systems have their advantages and disadvantages:

"For continuous-flow pasteurisers, these are brilliant at processing thousands of litres of milk efficiently on regular, daily basis. Some have unbelievably vast throughputs and the supermarkets depend upon them to supply more or less all of their milk.

On the negative side, by their very nature they can only operate using the HTST system: High Temperature Short Time method means that the milk is pasteurised by usually holding at around 72C for 15 seconds and there is no other option available. Other disadvantages are that they are very expensive to purchase and to maintain and they need regular servicing and changes of seals etc. to ensure they are operating at their optimum. The smallest continuous-flow pasteuriser I have come across will pasteurise 500 litres per hour and there is considerable wastage of milk during the priming of pipework and pumps and subsequent cleaning. Finally they can only be used to pasteurise milk and by their very design can have no other function.

"For the batch pasteuriser, these vessels are useless for processing large quantities of milk: the biggest ones we manufacture has a capacity of 500 litres although bigger ones do exist. They are also very slow, taking about 30 minutes just to heat up. On the other hand, they are extremely versatile and can be used for pasteurising milk and colostrum as well as for the production of yogurt, cheese and many other dairy (and non-dairy) products. Once installed they are simple to run and we supply them in sizes right down to 35 litres capacity. However, the big advantage that they have over their continuous-flow counterparts is the fact that they can, if required, pasteurise the milk using the Low Temperature Long Time method. This means the milk is processed at the lowest acceptable temperature (about 63C) although it must be held at this point for at least 30 minutes before it can be legally classified as pasteurised.

The benefit of using this method is that the milk tastes unbelievably good and similar to raw milk - the cream still rises to the top and the milk will make the finest yogurts and cheeses (unlike the homogenised milk that is the only type usually available from supermarkets). In fact one of our pasteuriser customers has just won the prestigious Quality Food (Chilled Dairy) 2017 award in the West End, with his whole milk, beating Asda, Waitrose and many others.

"Pasteurising your own milk, cutting out the middle man and retailing milk and dairy products directly is, in effect, taking back control - this is how dairying always used to operate and returning to these methods means farming dairy cows can truly become viable once again."