Wednesday, 25 November 2015

History of Good Ole Lettuce

After harvesting my fist cos lettuce at of the new veggie garden I got thinking about where do lettuces originate from and what it's history. So here it is a very interesting overview of the humble lettuce.

Lettuce has been described as a "weedy Cinderella" by T. W. Whitaker (1974) and as the "queen of the salad plants" by Franklin W. Martin and Ruth M. Ruberté (1975). What is this plant that merits two such disparate descriptions? It is certainly the most commonly used salad vegetable, occurring in or under most salads. Many types exist, varying in size, form, leaf shape, color, and taste. All of these types may have evolved from a weedy form that was used in ancient Egypt as a source of cooking oil from pressed seeds, so both descriptions are probably justified. 

Among the several lettuce types, most of which are consumed as raw leaves, one is used for its stem instead of its leaves. This lettuce is depicted on the walls of tombs dating back to about 2500 b.c.e., during the Middle Kingdom of ancient Egypt. Lettuce is shown as a long stem with marks indicating where leaves had been removed. At the top of the stem is a tuft of elongated leaves, bluish green in color. This lettuce may have been the one that first was eaten and may have been derived in turn from the type used for seed oil. The blue color is associated with the process in the growth of lettuce called bolting or stem formation. Leaves that form in the development of the head are green. As the process of bolting begins, the leaves become bluish green, signaling the elongation of the stem, which emerges from the interior of the head and eventually produces many small, yellow flowers that mature into small, narrow fruits. The fruits are less than four millimeters long. They look like seeds and usually go by that name.

Oilseed lettuce is a primitive, wild-looking plant that forms no head or rosette of leaves. It bolts early in its growth cycle, forming a thin stem with elongated, narrow leaves. The seeds produced on this stem are about 50 percent larger than those formed on cultivated lettuce. The seeds are pressed to express an oil used in cooking. This is an ancient custom still practiced in twenty-first century Egypt.

Evolution of Lettuce

One can speculate that somewhere in time ancient Egyptians selected, perhaps from oilseed lettuce, plants that bolted more slowly and formed a thick stem that was less bitter than the more primitive type and therefore edible. This new stem lettuce also had somewhat broader leaves. Later, perhaps many centuries later, further selection may have yielded a newer form with a still shorter stem and broader leaves that were appealing enough to eat, the romaine type. From Egypt, romaine lettuce moved around the Mediterranean Sea and to the Middle East. In these areas it was the most commonly grown lettuce in the twenty-first century. The original stem type traveled eastward, eventually reaching China. Numerous mentions of lettuce in ancient literature, beginning with Herodotus in 550 b.c.e., document its travels into Persia, Greece, Rome, and Sicily and later into France, Germany, and England. Use of descriptive names, such as crispa and purpurea, and place names, such as Cappadocian and Cyprian, indicate further proliferation into various distinctive types differing in color, size, leaf shape, and adaptation to specific environments. The various modern butterhead, leaf, and crisphead forms undoubtedly were selected and developed as lettuce spread through Europe. Lettuce reached the shores of the New World with the second voyage of Christopher Columbus in 1494. Many varieties within the different types were brought to the Western Hemisphere in subsequent years.

The scientific name of lettuce is Lactuca sativa. Lactuca means 'milk forming', sativa means 'common'. It is related to over one hundred wild species of Lactuca and also to sunflower, artichoke, aster, and chrysanthemum. Among the modern types of lettuce are two crisphead forms, iceberg, which forms a large, firm head, and Batavia, which is slightly softer and smaller than iceberg and is popular in Europe. Romaine lettuce has long leaves in a loaf-shaped head. Butterhead lettuce is quite small with oily, soft textured leaves. Red and green leaf lettuces form no head and have leaves with a variety of shapes. Less commonly found are the Latin type, which looks like a small romaine, and the aforementioned stem and oilseed lettuces.

Preparing a Salad

Since lettuce is used mainly in salads, preparation methods are simple, rapid, and informal. The ubiquitous tossed salad is made of lettuce leaves cut up into various-sized pieces. To some people the use of a knife is anathema, and they tear the leaves by hand. The salad maker may use one type of lettuce alone or a mixture of two or more kinds. Depending upon the ingenuity of the salad maker and the availability of edibles, any combination of other vegetables, fruits, and even cheeses or meats can be added to the lettuce. A dressing is added, and the ingredients are mixed together. Salads are vital to many slimming diets, the effectiveness of which can be reinforced or negated by the calorie value of the chosen dressing.

In the United States head lettuce was for many years commonly cut and served as a wedge, covered with mayonnaise or another dressing, and eaten with a knife and fork. This simple salad was served less frequently by the beginning of the twenty-first century. The popular Caesar salad is made only with leaves of romaine lettuce tossed with a special dressing, including a raw egg and small pieces of anchovy. A relative newcomer to the salad scene is mesclun, a mixture of baby leaves consisting of several lettuce types and other leafy vegetables, some of which are fairly exotic. These may include arugula or rocket, actually a partially domesticated weed; a fine-leaved endive called frisée ; mizuna, a small, dark green round leaf from Japan; spinach, beet tops, or chard; red chicory (radicchio); and romaine, butterhead, and red and green leaf lettuces. These leaves are cut in the field by hand, or mowed, when they are no more than ten centimeters long. In parts of the American Southwest wilted lettuce is a favorite salad made by pouring bacon fat over lettuce leaves.

Some salads consist primarily of other vegetables or fruits, such as sliced tomatoes or a scoop of cottage cheese. These are often arranged in a more formal manner than a tossed salad. Lettuce may find its way into these salads as whole or shredded leaves serving as a base for the main constituent.
Lettuce may also be used to make soup, as part of the filling for sandwiches, or as a wrap for holding cooked meat and vegetable mixes. Stem lettuce is consumed raw, like a stalk of celery, in Egypt or as a cooked vegetable in China.

The Biological Human Connection

Lettuce relates to human biology in several ways. The most obvious way is in its role as a food. Some less well-known relationships to human consumption also exist.
As a green vegetable, lettuce contains many of the same nutrients found in other green vegetables, although mostly in lesser amounts. These include vitamins, minerals, water, and fiber but essentially no protein or fat (Table 1). Lettuce is a low to moderate source of vitamins and minerals. Among the various types of lettuce, romaine and leaf varieties exceed crisphead and butter-head varieties for most of the common nutrients. This is directly related to the proportion of dark green leaves in the edible portion. The nutrient contribution of lettuce
Selected nutritional values per 100 grams for crisp, butter, romaine, and leaf lettuces
  Minerals (g) Vitamins Water Fiber
  Ca P Fe Na K A (IU) C (g) % g
Crisp 22 26 1.5 7 166 470 7 95.5 0.5
Butter 35 26 1.8 7 260 1,065 8 95.1 0.5
Romaine 44 35 1.3 9 277 1,925 22 94.9 0.7
Leaf 68 25 1.4 9 264 1,900 18 94.0 0.7
source: Adapted from Rubatzky and Yamaguchi (1997) as compiled from several original sources.

compared to other vegetables is affected by the amount consumed. For example, a study by M. A. Stevens in 1974 showed that broccoli has considerably more vitamins and minerals than lettuce but that much more lettuce was consumed than broccoli; therefore the total contribution of nutrients to the diet by lettuce was greater than that of broccoli. This relationship may have changed somewhat as consumption habits changed. Nonetheless lettuce is important for its nutrient content, which complements its usefulness as a diet food because of its high water and fiber content.

Symbolism: Fresh, Cool, Green

The obvious symbolism associated with lettuce is three words, "fresh," "cool," and "green." "Fresh" is a word that many think of as important to health. Lettuce is eaten fresh and raw. In the gardening months many can cut it and eat it almost immediately. It is not that fresh in the store bin of course, but it is still only a few days old. Even the leaves in a packaged salad were growing in the soil shortly before they appeared on the shelf. Lettuce is never frozen or canned.

Lettuce is kept cool. After being cut in the field it is transported to a cooler, where the temperature is quickly reduced to just one degree above freezing. It is transported in refrigerated trucks to a market, where it is kept in a cooler before being placed in a refrigerated bin. Finally, it is purchased by the consumer, taken home, and placed in the refrigerator. This sequence is called the cold chain and is designed to maintain the quality of the lettuce at the time of harvest in the field as long as possible.

Finally, lettuce comes in various shades of green. Even red lettuce contains chlorophyll, which confers the green color, though it may be hidden in the red parts of the leaf. Green means vitamins. Green is a cool color. Many also associate greenness with the health of the planet and with personal health. The process of photosynthesis produces oxygen and sugar converted from carbon dioxide and water. The absorption of carbon dioxide by green plants, from lettuce to trees, helps prevent its accumulation in the air, thus mitigating the greenhouse effect and possible global warming.

The symbolism of these words is so strong that they and similar words, such as "ice," "crisp," "winter," and "spring," have been used repeatedly in various combinations in the names of lettuce varieties. Consider the names Green Ice, Iceberg, Crisp as Ice, Coolguard, Green Towers, Valverde, Valspring, and Winterset.

In ancient Egypt lettuce had sexual symbolism. After completing its vegetative development with the formation of a head or a rosette of leaves, the plant goes into its reproductive phase with the formation of an erect seed stalk bearing flowers. The amount of latex in the plant increases and is under pressure, so if the top of the flowering stalk is cut off, the latex spurts out in a manner reminiscent of ejaculation. The same tomb paintings portraying the ancient stem lettuce also picture the god Min with an erect phallus. Consumption of lettuce may therefore have been thought to increase sexual prowess.

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