River Cottage A-Z

Vin aigre is simply sour wine or, more accurately, the natural end state of wine, or any alcoholic liquor, if fermentation is not halted. Certain specialised, booze-loving bacteria work on the alcohol, turning it into acetic acid, which is the source of vinegar’s sharpness.

During the process, a vinegar ‘mother’ is formed – this is a gel-like layer of cellulose produced by the bacteria and containing many of them. You may find it forming in organic, unpasteurised shop-bought vinegars – and some brands actually advertise the mother as a positive health benefit, since it means the product is essentially ‘live’. Whatever your view, vinegar mother is not going to do you any harm – you can just strain it out.

Traditional vinegars, where wine or cider is simply inoculated with vinegar mother and allowed to ferment, take months to produce – and the process is rather unpredictable. There are not many of these around any more – health food shops and the internet are your best hunting grounds. Vinegar bacteria need oxygen to work and modern vinegar-making methods focus on ways to increase the amount of oxygen they get, thus speeding the process. Most vinegar is now produced by ‘submerged fermentation’, where the alcoholic liquid is housed in large, temperature-controlled vats called acetators. Acetobacter (essentially, vinegar mother) is added to the liquid and air is pumped through it. This system can turn out vinegar in 24 hours.

It’s easy to be reticent about using vinegar. It’s so very sharp, harsh and bold and too much really is too much. Like salt, it’s a flavour you can’t take back. But acidity is such a crucial element in well-balanced cooking, it pays to get to grips with the sharp stuff. Just add it drop by cautious drop.

Don’t be afraid to add vinegar to ingredients that are already acidic, like fruit or tomatoes. Just like lemon juice, vinegar’s acidity has a seasoning effect – although you should choose one of the sweeter vinegars, like balsamic or sherry, here. One of my favourite ways to serve strawberries is coated in a sauce made by blitzing raspberries, sugar and balsamic vinegar into a purée, then sieving out the pips.

Conversely, vinegar is a welcome counterpoint to the sweet and rich. It’s crucial in mayonnaise and, combined with honey or sugar, mustard and garlic, it forms the basis of a classic vinaigrette dressing, the embroidery on the olive oil backdrop. But a tiny dash of vinegar in rich stews and soups, often added right at the end, can be the thing that defines their flavours.

Vinegar can be infused with herbs to make flavoured vinegars. Its make-up means it dissolves aromatic compounds more readily than water so it can really bring out the flavours of other things. Choose a good quality, light vinegar such as rice, white wine or cider with an acidity of at least 5 per cent (check the label). Pack your chosen flavouring – anything from raspberries to rose petals, grated horseradish to lemon peel – into a sterilised jar and pour over the cold vinegar. Make sure the flavourings are completely submerged and leave to infuse for at least 2 weeks in the fridge before straining the vinegar and decanting into a clean bottle. White wine vinegar infused with tarragon is one of the best (use it in salad dressings with olive oil, or in béarnaise sauce), while a syrupy, sweetened raspberry vinegar can be used like a cordial in drinks.

Vinegar is an ingredient we use for its chemical properties as much as its flavour. Once one of the only reliable methods of preserving food, since it is so inhospitable to harmful bacteria, it remains essential in pickles and chutneys. Vinegar is also crucial in some meat marinades, where the acetic acid ‘denatures’ protein, altering it on a molecular level so that it becomes softer.

TYPES OF VINEGAR

Malt vinegar Made from a basic malted barley beer, this is strident in character and dark in colour. It’s great for fish and chips, and hearty chutneys, but too harsh for subtle dressings. Barley contains gluten but the fermentation process renders the amount in malt vinegar negligible.

White wine vinegar This is one of the great all-rounder vinegars, perfect for a classic vinaigrette and ideal for herb-flavoured vinegars.

Red wine vinegar With its lovely, full, winey quality, this is great for seasoning meaty stews and gravies.

Cider vinegar Having a distinct fruitiness and a softer, mellower flavour than wine vinegars, cider vinegar is hugely versatile. Use it for everything from subtle vinaigrettes to pickles. Unfiltered versions are cloudy and may be sold with the ‘mother’ still in the bottle.

Distilled vinegar Made from malted barley or corn, distilled vinegars have little flavour beyond their acetic tang, but they are useful for pickles where you want other flavours to dominate. They are also very handy for descaling your kettle.

Rice vinegar With a light, sweet character, this is good with Asian flavours: soy sauce, garlic, ginger, chilli. Use in dipping sauces, dressings for noodles and sweet-sour stir-fries.

Sherry vinegar Dark, glossy and richly flavoured, this has a lovely caramel sweetness. Like traditional balsamic, fine sherry vinegars are aged in a range of wooden barrels. The method is known as the solera system.

Balsamic vinegar True, traditional balsamic is technically not a vinegar at all because it is made not from wine, but from concentrated, cooked-down fresh grape juice – known as grape must or mosto. Fermentation begins only after it has been reduced. The slowly fermenting, acidifying mosto is aged – for at least 12 years – in a succession of barrels made from different woods that impart a spectrum of subtle flavours. Really good balsamico is aged for much longer and is so rich and sweet that it can be enjoyed as a digestif. Look for the label Aceto Balsamico Tradizionale di Modena, DOP (Denominazione di Origine Protetta). The price tag is another good indication – tradizionale starts at £50–60 for 100ml. Use neat, in tiny, precious droplets on the finest ingredients, such as aged Parmesan, milky mozzarella di bufala or a dish of perfect strawberries.

Nearly all the balsamic vinegar on our shop shelves is the cheaper aceto balsamico di Modena. Confusingly, this may have an IGP (Indicazione Geografica Protteta), but not a DOP. This is still made from grape must, but it has actual vinegar added, and sometimes sugar and colouring too. These vinegars may still be aged and can be excellent (and expensive, though not tradizionale expensive), but the cheaper ones are thin and disappointing. British apple balsamic vinegar is a nice ingredient, however: an appley approximation of grape-based balsamic, using concentrated apple juice (essentially the mosto) and cider vinegar (and colour). There is also a white balsamic – a lighter, clearer alternative, but still with the sweetness that comes from the cooked-down mosto.