Cheese – like wine, beer and bread – is about as old as human history itself. There is a theory that the basic chemistry behind its production was stumbled upon thousands of years ago when milk was stored in flasks made from sheep’s stomachs; the residual rennet worked its magic and cheese curds and whey were born.
Since then, it has become one of the world’s favourite foods. And over time a vast repertoire of types has established itself, reflecting – again, like wine – the climate, ecology and traditional craft practices of different parts of the world. Countless generations of cheesemakers have warmed, fermented and coagulated the milk; separated, drained and pressed the curds; and salted and shaped the end result before ripening and finishing according to custom.
Innovations in the realms of science and technology have played their part, too. Cheese has become safer to eat thanks to improvements in our understanding of how to eliminate harmful microorganisms from the manufacturing process – from the discovery of pasteurisation in the nineteenth century to more recent developments in the techniques of microfiltration. And process engineering has brought to cheese making a scale, and consistency of standard, unachievable in the world of craft production.
Variable speed drives, enhancing both the accuracy and efficiency of motors, may be found in two roughly distinct areas of the cheese factory: the fluid pumps and the various equipment that handles the product and moves it along the manufacturing line.
Whichever kind of pump is used for the transfer of milk and curds – centrifugal being the most usual – VSDs contribute towards gentle fluid treatment. Besides pre-empting systemic problems common across the food and drink industry, such as cavitation, sensitive pump pressure here protects the quality of the product itself. Without it, rough and turbulent flow creates shear forces in the liquid that damage its structure, precipitating unusable fragments of protein and fat (called fines) and reducing overall yield.
Pumps are also to be found in a cheese factory’s Clean-in-Place operations – the procedure by which fluid-handling equipment is flushed clean and sanitised without having to be disassembled. (These systems come in pairs: one for the section that handles raw milk, one for the pasteurised part.) Larger examples manage the chemical dosing automatically, based on flow and conductivity, and do so by means of a combination of VSDs, controllers and monitors.
Further down the production line, once the cheese starts to look more like cheese, machines continue to keep the product on the move. As the fresh curds are drained and dried they are directed from stage to stage by a combination of conveyors and elevator modules run by drives and controllers executing bespoke positional software.
When it comes to the art of maturing the finished article – the delicate set of practices connoisseurs call affinage – sensitive, finely managed handling of the product continues to be crucial. Alpine cheeses, for example, although commercially produced in the form of great, metre-wide wheels weighing up to 50kg, require continuous turning and washing with brine. (The resultant moist, salty surface encourages colonisation by flavoursome microbes.) The industrial machines that do the rotating and washing achieve the precision of manoeuvre along each axis by means of dedicated drive control.
Fully-fledged robots have in fact been developed to take on the taxing labour of tending to cheeses as they mature – such as the one recently commissioned by a small cheddar producer in Somerset. Ageing cheddars also require rotating regularly. Rather than brining, though, they need to be constantly brushed free of mites. Hence the laser-guided autonomous assistant that glides up and down the aisles of the Calvers’ cheese cave, lifting, turning and vacuuming the cheeses; and doing so carefully enough not to crack them.
As contemporary an example of robotic engineering as it is, the device is not otherwise typical of the way in which electronics are currently used in industrial cheese making. It operates, after all, contrary to the assembly line principle of keeping the product on the move (rather than the equipment moving to the product). At their most automated, cheese factories aim for a digitally monitored, seamlessly integrated, conveyor-based sequence of events all the way from the controlled pumping of the milk through to the precise cutting and packing of the cheese blocks.
From this point of view, the importance of variable speed drives is collective. They act in concert to keep the assembly line working as a unified system: both by modifying the speed at specific junctures (in response, for example, to information from load cells in a buffering surge vessel) and through the relationship between their particular software and the larger control platform.
There was a time when factory production methods – particularly when it came to certain foodstuffs – were viewed by the purist with apprehension. It was unclear how an ingredient as naturally various and delicate as milk could sit easily within the kind of mechanised model of manufacture associated with processed products like that patented by James L Kraft in 1916.
But technology has altered that picture, just as in a range of ways it has changed the face of Big Dairy. Automated farms, for example, are credited with improving standards of herd welfare through advances such as sensor-based motor control in robotic milking. And at the other end of the industry, for the cheese manufacturer, intelligent drive engineering is helping to deliver total process control: of the kind that is now more likely to deliver an authentic wheel of local Swiss Gruyère than it is any of the factory favourites of yesteryear.