Traditional cheddar, matured in cloth is prized the world over for its characteristic complexity of flavor. This flavor is derived in large part from the way the cheese loses moisture, maturing through the muslin cloth, as well as the flora of flavor-producing molds that develops on the cloth itself.

A consequence of having a cloth-wrapped cheese is that cheese mites (related to common dust mites) are a routine pest for traditional cheesemakers, affecting wheels from around 6 months old.

"The mite" is completely normal on cheese, and harmless when it is kept within certain limits. For instance, all blue Stiltons have it on the rind. However, when mite gets out of control, it has disastrous effects on the appearance of the product and can have a severe impact on sales.

First, cheese mites eat the mold on the cloth, then the lard on the cheese, and then start on the cheese itself. Or, in eating the lard and removing its protective layer, mites dry the cheese out so that it cracks. Both conditions expose the paste to unwanted molds from the rind.

Quickes Cheddar with the cloth pulled back to reveal mite damage.

Cut wheels revealing damage from cracking and bluing as a result of cheese mite

Cheeses on racks are transferred via forklift to the enclosed area/blowing chamber.

Cheeses inside the sealed off chamber about to have high pressure air blown onto them via an air hose.

Mites being blown off the surface of the cheese.

The 6 bar air compressor.

Until 2006, traditional English cheddar makers controlled cheese mite with the fumigant methyl bromide, which was eventually banned by the EC, as it damages the ozone layer. Since then, the only control measures used have been physical – brushing and vacuuming, which is slow and not very effective. As a consequence, mite numbers rose to catastrophic levels in the maturing rooms of all traditional cheddar makers.

There have been numerous articles in the UK about the cheese mite crisis, and the ban on methyl bromide has forced traditional cheddar makers in particular to find new ways of dealing with the issue. Montgomery’s, one of a handful of benchmark English cheddar producers, currently employs five people wielding vacuum cleaners and are looking at a pricey Swiss robot to do the job instead. Meanwhile, five miles away, Keen's is using diatomaceous earth, a desiccant powder, together with higher levels of lard to inhibit mite.

Here at Quicke’s, customers expect cheese to be largely clean of internal mold. Due to the loss of methyl bromide as a tool, it cost us £217,000 ($344,000)—or 10% of our turnover—in waste, control measures and additional labor, to meet this expectation between April 2009 and March 2010.

At that level we did not have a viable business, and we decided not to put any cost price increases in, because we did not know if we could continue as a creamery.

In order to stay afloat, we had to design a system that could blow mites off our cheese and collect them for disposal more efficiently than a simple vacuum. There are four parts to this process:

• Dust extractors
We have two industrial dust extractors, DCE Unimasters, with filters that have a glazed liquid repellant on them to stop the mite from sticking—mites are moist, and clog up vacuum pipes. The filters have a starter/shaker on them so the machine can clean itself into a closed bin after a blowing session.

• Blowing chamber
We’ve attached the dust extractors with 7.8 in (200 mm) ducting to a clear plastic chamber 13.1ft (4 m) long x 9.5 ft (2.9 m) wide and 7.9 ft (2.4m) high. This gives enough clearance for the forklift and room for two people to work.

• Racks
All cheese susceptible to mite on is now stored on forklift-ready racks. Each rack of 24 cheddars, weighing ~1500 lbs (624kg), is moved into the chamber about once every four weeks for the de-miting process.

• High pressure, low volume air
We’ve got two air lines attached to a 90psi (6 bar) compressor, with open ended wands, so we need large tanks for compressed air storage: ~800 cubic feet (23m3) . We blow the mite off the top & sides of each cheese and the dust extractor picks up the mite that has been blown off. The cheeses are in two rows, so to avoid blowing mite onto the cheese you’ve just cleaned, we put a plastic barrier between the rows so you can clean each cheese properly. Having cleaned one side, we turn them and clean the base and far side of the cheese.

Mite is an allergen and the dust extractors are noisy, so we need to wear N95 US / FFP2 Europe dust masks and hearing protection. Despite the protection, people with skin that is very sensitive to mite cannot do the work.

The process described above is several times faster for us than vacuuming, and less unpleasant. Mite busting has stopped being a horrible job that people hate doing. It’s still not the best job on the farm, but people can take pride in what they manage to achieve in a few hours.

We’ve been using the machine since March 2010 and have now reduced mite levels down to a point where they’re only detectable by smell. There is very little visible, as long as we regularly blow cheese aged over 6 months every 4 weeks.

Younger cheeses are coming through less damaged, although it is too soon to tell how long we can keep the cheese clear of mite damage. We don’t know yet if the process will allow us to keep mite from getting under the cloth, when we cannot touch them with physical means.

We are still using very low levels of ozone (same as a bright day at the beach) to hold back mite hatching, but I don’t know if this is effective, or whether it might even be driving mite under the cloth. We won’t know for another year if it will enable us to keep our 2 year old vintage cheddar clean enough to be a sensible option. You can see why cheddar used to be considered mature at 8 months old in the time before methyl bromide – to maintain the wonderful cheddars matured for well over a year we all love, cheddar makers need to be constantly cleaning to have a fighting chance of getting there.

Thanks to the Specialist Cheesemakers Assocation for being very supportive throughout the horrendous process of managing mite without methyl bromide.

Mary Quicke is the award-winning maker of Quicke's Traditional Cheddar. The Quicke family have been farming in Newton St Cyres, Devonshire, for over 450 years.