It is a truth almost universally unacknowledged that pickling is the supreme demonstration of human civilisation. This Entry pays homage to the various forms of pickle, beloved by humankind over the millennia.

What Are Pickles?

Pickles are edible products (vegetables, fruit and sometimes fish, eggs or meat¹) which are preserved in an acid solution. There is often confusion here, because some pickles are stored in salt, brine or sugar solution (syrup or honey). However, the effect of these is to decrease the pH of the pickle itself, delivering a similar preservative effect. There is a separate (and, thankfully, small²) category of lye-based pickle in which the alkali effects of the solution break down the foodstuff into an edible form. Edible oils can also play a part as an oxygen-excluding covering for pre-pickled matter. In some cases, 'interesting' flavours emerge in pickles as the result of fermentation processes. Fermentation also produces the acid which does the preserving. The addition of flavouring ingredients (sugar, herbs and spices) is also commonplace. Pickles can also refer to a mélange of ingredients to form a sort of thick sauce, and this category includes chutneys and relishes.

Many things can be pickled. In the United Kingdom, the default 'pickle' is a small onion in vinegar³. In the United States, it is a small cucumber  (or large gherkin) in brine (originally from central Europe and associated with Jewish culture). More outré examples include watermelon rinds, nasturtium seeds, lime keys⁴, sausages, ducks' tongues, durians⁵ and nopalitas⁶.

The History of Pickles

Pickles are found across all cultures. The earliest known examples are cucumbers, that are known to have been pickled some time around 2030 BC in Mesopotamia⁷, when inhabitants from northern India brought cucumber seeds to the Tigris valley.

Pickles are mentioned twice in the Bible⁸, were known to the ancient Egyptians (Cleopatra attributed some of her beauty to pickles), and Aristotle praised the healing effects of pickled cucumbers. The Romans imported all sorts of foods from the countries they conquered, pickling them for the journey in vinegar, oil, brine and sometimes honey. Garum or Liquamen, a fermented, salted fish-based condiment⁹ was a dietary staple and has been found as far north as the Antonine Wall¹⁰.

Lest we remain overly Eurocentric, Asia also has a fine history of pickling. For example, the origins of the noble Korean kimchi or kimchee (of which more later) has a history that can be traced back up to 3000 years. It probably originated in Chinese pickles which were brought into Korea and were modified to form several types of kimchi of common raw materials to suit the taste of Koreans during the Shilla (654 – 935 AD) and Korea (918 – 1392 AD) dynasties.

Back in Europe, a pickle crossover occurred when there was a large increase in food preservation in the 16th Century owing to the arrival of new foods in Europe. Ketchup was an oriental fish brine that arrived via the spice route to Europe and eventually to America, where someone finally added sugar to it. Spices were added to these pickling sauces to make clever recipes. Soon chutneys, relishes, piccalillis, mustards, and ketchups were commonplace. Worcester Sauce was an accident from a forgotten barrel of special relish. It aged for many years in the basement of the Lea & Perrins Chemist shop.

Notable pickle-lovers from history include: Emperors Julius Caesar and Tiberius, King John and Queen Elizabeth I of England, Samuel Pepys, Amerigo Vespucci, George Washington, Thomas Jefferson and Napoleon Bonaparte¹¹.

The English word 'pickle' derives from the Middle English pikel, first recorded around 1400 and meaning 'a spicy sauce or gravy served with meat or fowl'. This is different to, but obviously related to the Middle Dutch source, pekel, meaning a solution, such as spiced brine, for preserving and flavouring food.

How Pickling Works

Pickling is necessary to counteract the growth of microorganisms that are always present on food. Left unchecked, these can cause spoilage and illness (if eaten). When the acidity of a pickled food is high, harmful bacteria like Clostridium botulinum can't grow.

Increasing a foodstuff's acidity is the basis of the pickling process. Acid can either be added, or produced by natural fermentation processes. Fermentation is the anaerobic or partially anaerobic oxidation of carbohydrates by either microorganisms or enzymes (as opposed to putrefaction which is the oxidation of proteins). Fermentation can have both positive and negative effects. When the fermentation occurs in a controlled way, it yields lactic acid which inhibits the growth of undesirable microorganisms. The pickling process is biologically complex (and has been studied in detail for only a few economically-important pickles), but consists in part of the actions of yeasts from the Saccharomyces family, especially S. cerevisiae, which convert carbohydrates to alcohols and bacteria of the Lactobacillaceae family which produce enzymes which oxidise the alcohols to lactic and acetic acid.

There are two basic types of pickling:

• Long, fermentation-based pickling requires a period (up to several weeks) of 'curing' at room temperature. During this period, colours and flavours change. Acid is produced as lactic acid bacteria grow. Most commonly the bacteria are stimulated by the addition of salt, usually in the form of brine.
• Quick, unfermented pickling made by adding acid (eg, vinegar, tamarind juice). It's critical to add enough acid to prevent bacterial growth.

The Many Varieties of Pickle

For purposes of discussion, it is useful to cover the various techniques and elements of pickling separately. In practice, however, there are considerable overlaps between these categories.

Acid-based Pickles

The most common liquid for acid pickling is vinegar. This is an impure, dilute solution of acetic acid, obtained by the fermentation beyond the alcohol stage of fruit (usually grapes, but also apples) or grain (usually barley, malt or rice). Examples of vinegar-based pickles include:

• Pickled onions (silverskin or other, in malt or white vinegar)
• Pickled eggs (as found in some British chip shops)
• Pickled red cabbage (the traditional accompaniment to Lancashire Hotpot)
• Pickled ginger (those mysterious pink slices found alongside sushi)
• Italian pickled vegetables (a crunchy mixture of - usually - onions, carrots, cauliflower and sliced gherkins)
• Rollmop herrings (good for hangovers!)
• Pickled pigs' feet ('soul food' of the American south)
• Pickled sausages (eaten in Poland and the Czech Republic)
• Pickled beetroot (gak!)

Dry-salted Pickles

Salt has two effects when added to fruit or vegetables. Firstly it draws water from them by the process of osmosis. Secondly, the salt in the resultant brine triggers the fermentation process of the lactic bacteria. The resultant fermentation tends to be bacteriologically complex and delivers a particularly rich range of complex flavours. In Europe and North America, the most common dry-cured pickle is sauerkraut (or choucroute, if you prefer), a pickled, white cabbage.

Dry salted pickled limes and lemons are also popular in many parts of Asia, and are an essential ingredient of Moroccan food. The lemons can be either dry-salted or brined and may be dried afterwards.

In Japan, plums are dry-salted to make umeboshi - a mouth-puckering delight often eaten for breakfast. A related product (preserved plums) can be found in some Chinese supermarkets. Dried and with added sugar and liquorice, they are intended as sweets.

Brine-based Pickles

Like dry-salting, brine-pickling works by a combination of osmosis and awakening lactic fermentation. In practice, many pickles which should traditionally be brine-fermented include vinegar at varying proportions in their pickling medium. Gherkins and similar small cucumbers are traditionally pickled in brine along with other flavourings to yield the various species of what Americans know simply as 'pickles' (eg, dill pickles, kosher pickles¹², Polish pickles¹³).

It seems very likely that the art of cucumber-pickling was carried to Europe by the Jewish Diaspora, since the many brine-pickled vegetables found in Middle Eastern cuisines represent the pinnacle of brine pickling. Almost any vegetable is pickled here, from aubergines to chillies to garlic to okra to green beans. Pickles are an essential accompaniment to any Middle Eastern meal. Of particular note are pickled turnips, which turn a delightfully vivid, almost artificial-looking shade of pink.

Fermentation and Pickles

In addition to the basic process of acidulation, fermentation yields other products which add additional flavours, and this is why properly pickled vegetables taste so much better than just vegetables dunked in acid. Aromatic esters, for example, provide much of the characteristic taste of sauerkraut.

However, the acme is surely kimchi, a wondrous Korean pickle. This can be made from various vegetables, and can be brine pickled or dry-salted. The most common variety involves Chinese cabbage. Kimchis are generally heavily laced with chillies and sometimes other flavourings (garlic, spring onions, ginger, fish sauce). Microbiology contributes many wonderful flavours to kimchi as well as a whole range of health-giving compounds. Although kimchi is repulsive to many at first tasting, the acquisition of a taste for it will enhance your life¹⁴. Bejaysus, it's good! Most Koreans eat kimchi daily, and often about three varieties will be served with every meal - including breakfast. It is big business and consequently has been studied extensively: there are whole journals devoted to 'kimchi science'.

Lye Pickling

Lye is an alkali (a mixture of sodium and potassium hydroxides) traditionally obtained by leaching wood ashes. We have to be a little cautious with regard to the role of lye in pickling. Firstly, it does not, being alkali, contribute to the pickling process per se, but to the breaking down of food matter as an aid or adjunct to pickling. Secondly, with one honourable exception, pickles involving lye tend to be... well... disgusting. However, chacun à son goût.

The exception is the noble olive, which has been eaten for thousands of years and is a staple of the Mediterranean and Middle Eastern diets. Olives cannot be eaten in their raw state and require pickling to render them digestible¹⁵. Before pickling, they require treatment with lye to remove substances which would be toxic to the fermentation bacteria (black¹⁶ olives also require pre-soaking in brine to allow the lye to penetrate). Once pickled, olives are packaged in various forms, with the addition of various herbs and spices, in brine, vinegar, oil or dried and salted.

Turning to the less desirable lye products. Okay, admittedly many Chinese people swear by 'thousand-year-old eggs'¹⁷. These are not, in fact, ancient eggs. They are made by coating duck or chicken eggs in a paste of clay, wood ash, tea, lime and salt, then burying them - separated by rice straw to stop them sticking together - for a mere 100 days or so. The resultant egg, once you have washed off the foul-smelling gunk and peeled and sliced it, has a grey-green yolk and a dark, translucent, bottle green 'white'. They are eaten in wedges with a dipping sauce or with more sensible pickles. Their flavour has been inaccurately described as 'cheese-like'. On putting a piece in one's mouth, one first notices a not too unpleasant egginess, which quickly builds up until one's whole being is permeated by a powerful, nauseating, tangy, sulphurosity. They are also found in the centre of a peculiar variety of sweet bun. Nevertheless, they have their aficionados.

Lutefisk is another kettle of fish¹⁸. A Norwegian delicacy, it is a piece of dried, salted cod¹⁹ that has been soaked in a bucket of lye for several days. The lye breaks down the fish to achieve a gelatinous consistency. To eat lutefisk is a badge of national pride amongst Norwegians - but even they do not pretend that one has to actually like it! Lutefisk is traditionally accompanied by mashed potatoes, a species of pease pudding, grease and bacon. More importantly, akvavit²⁰ is deemed essential to the consumption of lutefisk. One must drink in preparation²¹. There is also surstroming - a Swedish pickled, canned herring - dealt with in much the same way, but with tiny new potatoes rather than mash²². Still, it could be worse. In Iceland they bury sharks for several months before eating them.

Pickles in Sugar

Fruits are sometimes first pickled (usually in vinegar) before being stored in a syrup or honey. Pickled peaches are a traditional American dish.

Alternately, a sweet-sour syrup is often made by adding sugar to vinegar. Examples of pickling by this method include watermelon rinds (another tradition of the US south), mostarda di Cremona (an Italian pickle of mixed fruit and mustard seeds) and pickled walnuts (a British tradition).

Such pickles are normally served as accompaniments to savoury meats or cheeses.

Oily Pickles

Oil finds its way into pickles too. Italian antipasti include aubergines and various species of mushroom which are brine-pickled before storage in olive oil. Mustard oil and other vegetable oils are added to dry salted fruit and vegetables (limes, mangoes, tinda²³, karandas²⁴, chillies, aubergines) along with spices to form various Indian pickles.

Pickle Flavourings

In many cases, additional flavouring items are added to the brine or vinegar medium to enhance the general tastiness of the pickle. For example, British pickled onions (but not the silverskin variety, for some reason) are commonly flavoured with various combinations of coriander seeds, cinnamon, bay, cloves and mace (pre-spiced vinegar can be bought for home pickling). Dill is the norm in European and American pickled cucumbers (they are often known as 'dill pickles') and any number of things are added to olives (lemons, oranges, coriander, chilli, garlic, anchovies, wine).

Chutneys and relishes.

Chutneys and relishes can be thought of as mixtures of various pickled elements and flavourings (spices and sugar) to provide a thickish tangy substance for the accompaniment of savoury dishes. Varieties include the various American relishes of the type that accompany burgers. These generally include tomatoes, onions, cucumbers and chillies in various combinations, but can also be made from other foods (sweetcorn, peaches, green tomatoes). They are generally heavily sweetened.

In Britain, piccalilli - a mixture of pickled vegetables (onions, gherkins, cauliflower) in a mustard sauce - is traditional, as is Branston pickle and its cousins - mixtures of various vegetables (carrots, swedes²⁵). There is also a tradition, particularly amongst members of the Women's Institute, of making various chutneys from vinegar, sugar and fruit. These pale imitations of Indian pickles, half-remembered from the Raj, are probably not meant to be eaten but rather as booby prizes at village fête tombola²⁶ stalls.

The prize for chutneys and relishes surely belongs to Asia. Various sambals are known in Asia, including sambal oelek. Not all of these are pickled, but some are. Across the Indian subcontinent, relish-like pickles (achaar) and chutneys are embedded in the culture²⁷. In fact, the English word 'chutney' is derived from the Hindi chatni²⁸. Visitors to British restaurants will be familiar with the lime pickle and mango chutney that accompany the poppadom stage (but should properly be left on the table for the rest of the meal). Many, many varieties are available, ranging from the sweet and mild to the fiery and tangy. Patak's Mixed Pickle is particularly tasty and is commonly available in the UK.

The Health Benefits of Pickles

Although some may be put off by the role of salt in the pickling process, pickles need not be regarded as unhealthy. There is considerable controversy over whether reasonable levels of dietary salt are harmful to all, or only to those pre-disposed towards cardiovascular disease. In any case, life is short, and we may as well get some pleasure while we're here.

In fact, there is increasing interest in the potential health benefits of pickles. The most obvious benefit, especially in undeveloped economies, is that pickling fruit and vegetables allows crops to be preserved to supply a valuable source of vitamins over the scarce winter months.

There is also some evidence that pickles can promote digestive health and lower cholesterol. All manner of claims have been made for kimchi as a preventative for diabetes, cancer and even SARS.

Just as importantly - tasty food promotes well-being and contributes to a healthy and happy life. Eat pickles and enjoy!

Suggested Reading

• Fermented Fruits and Vegetables: A Global Perspective by Mr Mike Battcock and Dr Sue Azam Ali: Everything you could ever wish to know about pickling and other fermentation-based food preservation processes.
• Picklenet: A site about pickles and pickling, including many recipes.
• All About Kimchi by the Korea Food Research Institute (in Korean or English).
• Patak's Pickles: Providers of Indian pickles and other Indian food products across the UK, USA and Canada.
• Karandas (sic): All about this elusive fruit.