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Microbiology in a Devon lane

The science behind cider

Philip Strange 14 February 2011

Stop press: ciders apples await their fate

There are reports of cows becoming drunk and disorderly after having been fed old pomace residue

The countryside in this part of Devon consists of rolling hills, green fields and hidden river valleys and it was a brilliantly sunny morning as we searched for the cider farm called Heron Valley. I knew which lane to take but beyond that I was lost, so we carried on for a mile between high banks with the river Avon hidden but close by all the time. The first leaves were changing colour and sparkled in the bright light, but the brightness was misleading. Where the sun had failed to reach the fields there were still patches of frost. I looked for farm signs but in the end I was led by the apples. A yard littered with a mosaic of bright red, green and yellow cider apples in deep wooden boxes told us that we had arrived.

These cider apples are not good-looking. They are small and many have pocked skins with black marks. Their flavour is disappointing, sometimes tart, sometimes bland. Cider apples make up for their poor looks by their picturesque names that recall different times: Hangy Down Clusters, Foxwhelp, Slack-Ma-Girdle, Pig’s Snout. They also have special properties. They are more fibrous than eating apples and this helps in getting the juice out. Some are rich in tannins, the complex phenolic compounds that give cider its interesting flavour. They can be high in natural sugars if they are allowed to ripen properly and this may mean waiting until they have fallen off the tree. It’s worth waiting, as it is this sugar that makes the alcohol.

The cider apples here come from local orchards, the sort that don’t use chemical sprays. As if to prove this point, a huge tractor entered the yard while we were there, pulling a truck full of apples, and we had to jump out of its way. Apparently the farmer had driven 17 miles across the countryside with his unusual cargo. I imagined the traffic problems this must have caused. He left, well pleased, with several flagons of cider, off to disturb the traffic again.

The apple press

I had been told that they would be pressing apples that day and the fragrant aroma of apple juice lead us to the apple press at the back of the modern barn attached to the yard. The rest of the barn was full of packing cases stuffed with bottles of apple juice and bottles of cider. Liz was our friendly guide, not that we could see much of her. She was swathed in sweaters and protective clothing for warmth and cleanliness. You can’t crush whole apples, she told us; they have to be milled before crushing in the press. Traditionally, apples were milled to what cider makers call a ‘pomace’ using a horse-drawn stone wheel in a stone trough but nowadays, they use machines. The pomace is loaded into the press in layers, given solidity by hessian sheets or long straws; cider makers call this ‘forming the cheese’. As the pressure is increased, juice oozes freely from the layers of crushed apple. The dark juice is collected and pumped into large plastic tanks. The juice is sweet but it’s not typical apple juice. When you sip it, you can taste the tannins and already get a hint of the cider to come. The apple residue after pressing is very popular with farm animals but beware, there are reports of cows becoming drunk and disorderly after having been fed old pomace residue.

At this point, a tall blonde woman arrived, exuding warmth and an almost palpable enthusiasm. This was Natasha Bradley, the boss of the Heron Valley operation and artisan cider maker. She welcomed us and explained what happens next. The tanks filled with juice are taken to the cider barn down the road. This is a traditional stone barn containing several large plastic tanks and neat rows of wooden barrels, rather like a winery.

Barrels for aging

“We use traditional methods,” she said. “Nothing is added to the tanks other than apple juice. We are an example of natural chemistry in action.”

Many cider makers use sulphites to control fermentation. Heron Valley runs the risk of sometimes ending up with cider vinegar but, with careful cleanliness, this rarely happens.

In the cider barn we also met Adrian, who runs this part of the operation. He is fascinated by the combination of skill and science needed to make good cider. He explained that the tanks filled with juice are sealed loosely and left in the barn. The microbiology now begins: because the apples and the pressing equipment contain wild yeasts, these end up in the juice and are enough to start the fermentation. There is much bubbling and frothing as the yeasts get to work, and the rate of the fermentation will be influenced by the ambient temperature. There is no heat in the barn and it was cold the day we went. A cold winter will slow things down but as the weather warms up, it will take off again. Adrian can tell what is happening by tasting the brew, but he also measures the specific gravity of the liquid because this reflects the sugar levels: as the sugars are used up, the specific gravity falls and the alcohol rises. The Heron Valley ciders contain about 6% alcohol when they are finished.

Fermentation carries on from October to January and when the New Year celebrations are finished, the fermenting liquid is put into a fresh tank, leaving dead yeast and sediment behind. By March the primary fermentation is almost over and another transfer takes place. This time it is into oak barrels for ageing and conditioning, with the barrels adding more flavour in the form of tannins. Some of the barrels have been used for storing rum or port and this prior treatment also adds flavour. As spring arrives, the trees in the apple orchards come into flower again as the weather warms up, and this also wakes up the cider. At this point, there may be additional fermentation, but this time it is bacterial. The bacteria convert malic acid in the cider into lactic acid and carbon dioxide gas. This “malolactic” fermentation – the same chemistry that creates the taste in a Chardonnay wine – imparts a buttery flavour. The secondary fermentation also reduces acidity, and the carbon dioxide gas gives the cider a sparkle. According to Natasha, drinking this young, energetic, sparkling cider in May is “as good as it gets”.

Later, cider from different barrels will be blended to create a more uniform flavour and some will be aged again or stored for sale later. This is a traditional farmhouse cider, dryish but not unduly so and with a strong appley flavour. It is a product of art and science and will vary depending on the apples, the weather and the microbiology. But it bears no relation to mass-produced, industrialised cider or to rough “scrumpy”. A delicious drink with complex flavours, providing echoes of the summer when the apples were on the trees, this cider should be taken as seriously as a good wine.

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All photos taken by Hazel Strange