Pickling Foods
Immersing fresh vegetables and other foods in a liquid solution of salt brine was a fairly common practice in medieval Europe. In fact, although the term "pickle" didn't come into use in English until the late Middle Ages, the practice of pickling goes back to ancient times. Not only would this method preserve fresh food for months so that it could be eaten out of season, but it could infuse it with strong, piquant flavors.
The simplest pickling was done with water, salt and an herb or two, but a variety of spices and herbs as well as the use of vinegar, verjuice or (after the 12th century) lemon led to a range of pickling flavors. Pickling might require boiling the foods in the salt mixture, but it could also be done by simply leaving the food items in an open pot, tub or vat of salt brine with the desired flavorings for hours and sometimes days. Once the food had been thoroughly infused by the pickling solution, it was placed in a jar, crock, or other airtight container, sometimes with a fresh brine but often in the juice in which it had marinated.
Confits
Although the term confit has come to refer to virtually any food that has been immersed in a substance for preservation (and, today, can sometimes refer to a type of fruit preserve), in the Middle Ages confits were potted meat. Confits were most usually, but not solely, made from fowl or pork (fatty fowl like goose were particularly suitable).
To make a confit, the meat was salted and cooked for a very long time in its own fat, then allowed to cool in its own fat. It was then sealed up -- in its own fat, of course -- and stored in a cool place, where it could last for months.
Confits should not be confused with comfits, which were sugar-coated nuts and seeds eaten at the end of a banquet to freshen the breath and aid the digestion.
Sweet Preserves
Fruits were often dried, but a far more tasty method of preserving them past their season was to seal them up in honey. Occasionally, they might be boiled in a sugar mixture, but sugar was an expensive import, so only the cooks of the wealthiest families were likely to use it. Honey had been used as a preservative for thousands of years, and it wasn't limited to preserving fruit; meats were also stored in honey on occasion.
Fermentation
Most methods of preserving food involved stopping or slowing down the process of decay. Fermentation accelerated it.
The most common product of fermentation was alcohol -- wine was fermented from grapes, mead from honey, beer from grain. Wine and mead could keep for months, but beer had to be drunk fairly quickly. Cider was fermented from apples, and the Anglo-Saxons made a drink called "perry" from fermented pears.
Cheese is also a product of fermentation. Cow's milk could be used, but the milk from sheep and goats was a more common source for cheese in the Middle Ages.
Freezing and Cooling
The weather of the greater part of Europe throughout much of the Middle Ages was rather temperate; in fact, there is often some discussion of the "medieval warm period" overlapping the end of the Early Middle Ages and the beginning of High Medieval Europe (the exact dates depend on who you consult). So freezing was not an obvious method of preserving foods.
However, most areas of Europe did see snowy winters, and freezing was at times a viable option, especially in northern regions. In castles and large homes with cellars, an underground room could be used to keep foods packed in winter ice through the cooler spring months and into the summer. In the long, frigid Scandinavian winters, an underground room wasn't necessary.
Supplying an ice-room with ice was a labor-intensive and sometimes travel-intensive business, so it was not particularly common; but it wasn't completely unknown, either. More common was the use of underground rooms to keep foods cool, the all-important last step of most of the above preservation methods.
Sources and Suggested Reading
Medieval Science, Technology, and Medicine: An Encyclopedia
(Routledge Encyclopedias of the Middle Ages)
edited by Thomas F. Glick, Steven John Livesey, and Faith Wallis
Food in Medieval Times
by Melitta Weiss Adamson
The Goodman of Paris
translated by Eileen Power
Food and Eating in Medieval Europe
edited by Martha Carlin and Joel T. Rosenthal
Food in Medieval England: Diet and Nutrition
edited by by C.M. Woolgar, D. Serjeantson and T. Waldron
Food in the Middle Ages: A Book of Essays
by Melitta Weiss Adamson
