Lettuce

Often described in Dutch as cabbage lettuce. In science we call the plant Lactuca sativa. All lettuce varieties originated from the kompassla (Lactuca serriola). It occurs from Asia and North Africa to northern Europe, in open spaces, in the forest, on rock faces and on fallow fields. The word Lactuca indicates that lettuce has a milk juice. The last name Sativa says that it was grown. The word is also related to the French word salé (= salt, salted)? The vegetable was formerly kept in the salt. A bit later, the binds in the Netherlands were even cooked for a short while and it owes its old nickname “stew”. Only the word lettuce is confusing. Not so long ago we used the word lettuce (in cookbooks) as a synonym of salad. You had chicory lettuce, asparagus salad, hussarensla, etc. Many names abroad also have the word salad. Such as Hagesalat (Norway) Kerti saláta (Hungarian). Originally, lettuce was mainly distributed throughout Europe by the Roman Empire. From China it is spread to Asian countries like Indonesia, Malaysia, Japan, etc. Europe has introduced the lettuce in America in (1494) and only really got off the ground after 1904. The main markets for lettuce were, until the end of the twentieth century, Western Europe and North America, later in the Mediterranean, followed by movement to Northern Europe and then to the New World. At the end of the twentieth century, lettuce was important in Japan, China, Hong Kong, Australia and some countries in South America and Africa. In Nature.com an extensive research has been done into the origin of lettuce.

On wall paintings in some Egyptian tombs you can see pictures of a plant that is probably a slender precursor of the binds. Probably that plant was not eaten as a salad, but grown for the cooking oil in the seeds. After the Romans, the lettuce was first mentioned in John Gerard’s “Herball” of 1597. He talks about eight varieties. In the past, lettuce was known in medicine as a drug. Hippocrates, born in 456 BC, already mentions this application. The bitter milk juice was widely used as a substitute for opium. Dr. Duncan from Edinburgh studied the effects of the milk juice of lettuce, and called it lactucarium. Fresh lettuce consists of 95% water and contains milk juice with substances that are toxic in large quantities.

In the Dutch seed catalogs from 1852 to 1945 we find 256 names of lettuce varieties. Of these, 33 varieties are now available under 105 variety names. The varieties have many synonyms, as described by Rodenburg (1960: Varieties of Lettuce, an international monograph). The first clear indication for lettuce cultivation in Western Europe can be found in the “Ortis Sanitatis” (Schöffer, 1485). Already in the 16th century, lettuce was a popular vegetable as is evident from the herb books (including Dodoens, 1554). We have to indicate that these are medicinal applications of lettuce and not as consumption vegetables. At the end of the 16th century there was already a large variety of lettuce varieties, indicating that lettuce was already selected at that time.
In the 19th century there was a real explosion in the increase of selections (varieties) that are grown under the most diverse names. Especially in the 60s of the last century. For example, the number of seed companies gradually increased until the 1960s, but declined sharply again in the period thereafter. The supply of different varieties, on the other hand, increased very strongly. Between 1880 and 1890, horticulturists in the Netherlands could choose from less than 50 different lettuce varieties, more than a century later this had increased to over 350. In the beginning of the last century there was a large overlap between the assortment of the various companies, whereby one variety was offered by many different companies. After the sixties this changed, and in the 1990s almost all varieties were offered by only one company. From 1900 you also see that lettuce becomes an important export product. In many countries it is introduced as a healthy western vegetable

Explosion lettuce in the world

Anno 2018 you can talk about a huge development of lettuce cultivation all over the world. The worldwide commercial hydroponics industry has grown 4 to 5 times in the past ten years. And to think that hydroponic production has only been used commercially since the 1970s. But the perception and the facts indicate that the industry has really become large-scale commercial production in the last 5 years and is an alternative to traditional agriculture. It started with the sawdust-based hydroponic systems to the use of peat, straw and sand-based media. which eventually developed in the 1970s to the Nutrient Film Technique (NFT) and had its own medium known as rockwool (Carruthers, 1999). Other developments in the 1970s included the use of fine mist sprays (Ein Gedi system) and various Japanese deep-flowing systems for the recycling of nutrients (Hanger, 1993).

Why Hydroponics

You can harvest lettuce almost all year round. Lettuce is a low-light, low-temperature crop. This means that additional lighting and heating are minimal compared to other crops. On the other hand, lettuce is also a very perishable crop. You have to pick it fresh every day and deliver it. If not, the costs can rise rapidly through the necessary temperature-controlled containers. And the longer the transport, the more can be lost as waste. On the other hand, local growers who guarantee a constant supply of fresh produce of gourmet quality can often also adjust the price upwards!
Cabbage lettuce, such as iceberg lettuce, are usually not recommended for hydroponics, but there are plenty of other types of leaf lettuce and leafy vegetables that are very suitable for hydroponics. Butter lettuce is the most popular and has a fast turnaround time and excellent quality. I myself have been able to grow oak leaf lettuce fairly quickly. Roman lettuce takes a little longer to grow, but you can ask for a higher price. It is bigger and has more volume. Another emerging market for hydroponics is the micro-vegetables. Micro vegetables are the babies of lettuce, mustard and herbs that are sown and harvested close together. Harvest is of course even faster.

Growth systems

Various hydroponic systems are used in the world for the cultivation of lettuce. In different countries, lettuce is produced in rooms (containers, buildings, warehouses) under artificial light. Here they can produce lettuce from seed to harvest in just 30 days. Mostly they use a so-called aeroponically system. Nutrient solution is sprayed on the bare roots. Computers automate the entire growth process. Only manual labor comes in handy when sowing and harvesting. Dressed in space suits. The lettuce is grown indoors in filtered air, which allows the products to be certified as “bacteria free”, and the concerns about possible bacterial contamination are removed. In Canada and also in the Netherlands, there are a number of large commercial companies that use a smooth system for the production of lettuce. The lettuce is grown in styrofoam plates (or else) that float on water with a nutrient solution in it. The rafts with lettuce start at the beginning of the channel and slowly move towards the end of the channel when the lettuce is fully grown.

But by far the most popular hydroponics system for lettuce production in the United States, Indonesia, and Europe is the NFT system. NFT stands for Nutrient Film Technique. The lettuce is placed in plastic channels, usually 2-1 / 2 “to 6” wide, and a thin film of feed water flows through the bare root. The nutrient solution is stored in a reservoir, and a submersible pump pumps the solution from the end to the channels.

Healthy or not

In the beginning and especially in Egyptian culture the lettuce seeds were ground for oil (The mature seeds contain up to 35% oil) and the ancient Egyptians considered lettuce as a medicine for male fertility. In old cultures, lettuce was respected as both appetite stimulant and sleep aid. In the 19th century attempts were made to sort out the knowledge of lettuce as a medicinal plant. Information in Polish medical studies of the 19th century about lettuce also refers to the toxic species, Lactuca virosa. The ordinary garden lettuce or Lactuca sativa v. And Lactuca hortensis, were used as a medicinal plant. In that period, especially the dried-out lactescent juice and lactucarium were considered an intoxicant and were used as a sedative and an analgesic. The effect of the substance was weaker than that of opium but free from the side effects. In practice, lactucarium showed that in some cases it had better curative effects than opium. The old masters describe that there are many types of lettuce, one is grown and grows in the garden and one may use it for eating, but eaten raw it is harmful to the stomach. Goethe describes in 1787: “Der Salat of Zartheit und Gesmack wie eine Milch” therefore the lettuce was called by the ancients in Latin lactuca, from lac: milk. In 1847, the plant in the area of the Mosel was cultivated a lot and the lactucarium was shipped to North America via England. Cultivation in this time also increased in other European countries. Of course, several studies have been done on the juice to confirm this.

The possibility of obtaining lactucarium from lettuce has led to the fact that it has been bred in Poland, and that Polish pharmacists and doctors have shown interest in the stuff and their own research of lettuce and the resulting juice of lactate have started up. Results of research on lettuce were published in 19th-century magazines by, among others, Jan Fryderyk Wolfgang, Florian Sawiczewski and Józef Orkisz. Lettuce is also widely used in Chinese medicine. The dried juice is recommended as a wound disinfectant and the seeds are used as galactogots (to increase the milk flow in nursing mothers.) More recently, opium products from lettuce marketed as narcotic substitutes intended to be smoked alone or in combination with marijuana to improve the effect and taste, so it was in the seventies the plant was popular in the US where it was sold under names like: Lettuce Opium, L’Opium Lettucene, Thousands of American youngsters used in the hippie -time this legal drug. As in 1898 the United States Pharmacopoeia and in 1911 the British Pharmaceutical Codex described the use of lactucarium in lozenges, tinctures and syrups as a tranquilizer in irritable cough or as a mild hypnotic (sleep problem) for insomnia.
Of course, lettuce also contains potassium, iron, vitamins C, A and K and folic acid. Modern marketing makes full use of it, and also talks about the healthy effects of the antioxidants in lettuce. The antioxidant value of iceberg lettuce / crisphead lettuce, raw described in ORAC units is: 438 μ mol TE/100g. These numbers are relative, especially when compared with other vegetables (image). Moreover, this depends on the season (summer higher and winter lower) and disappears very quickly when processing the lettuce. Such as cleaning / washing, trimming, coring, cutting, drying by centrifugation, etc. In addition, it depends on where the lettuce comes from. The concentrations of two major phenolic compounds, chicory acid and chlorogenic acid, were about 2.5-5.5 times higher in both cultivars when grown in open fields than in high tunnels. The health claims must therefore also be seen in the perspective of other vegetables. And then lettuce turns out to play a minor role. But more important is that you must approach lettuce objectively and should not separate from the harmful effects of lettuce on the human body.
It is advisable not to buy the pre-packed salad leaves that are often found in supermarkets. Once they have been picked, cut, washed, packaged, exposed to light and then stood on a supermarket shelf for a few days, reduced to 99% of water you buy, so little nutritional value.

The juice lactucarium

Lettuce produces a milky latex of different chemical compounds. 587 latex proteins were identified from the slalatex using multidimensional protein identification technology. A bioinformatics analysis showed that the most frequently encountered proteins in the latex are organelle proteins, followed by nucleic and cytoplasmic proteins. And the latex also contains various bitter compounds, such as sesquiterpene-lactones called lactucine and lactucopicrin. Interestingly, the same compounds are responsible for the bitterness in chicory and radicchio (Cichorium intybus), both also closely related to lettuce. In 2009, Korean researchers showed that the concentrations of these bitter compounds were much higher in leaves on flower stalks than in leaves at the base of the plant. You see this happening when the plants are still very small, or when they are planted very close to each other for the production of salad mixes and or are exposed to stress. The juice is obtained by cutting off the upper part of the stem, so that the latex can run out. After twenty-four hours a thin slab is made. The collected latex is then cut into pieces and dried. It gradually acquires a brownish color during the drying process. The smell is characteristic, and recalling that of opium. The main ingredients are lactucerin or lactulose. Lactucarium reportedly contains about 0.2% lactucine, a sesquiterpinoid lactone. (sesquiterpene lactones act anti-inflammatory) In addition, the mixture contains a volatile oil, caoutchouc, mannitol and lactucerol (taraxasterol) (about 50%). In France in Aubière, it was so popular that pharmacist H. Aubergier employed women from the village to cut the plants and harvest the juice by hand. Nowadays it is done by a tailor-made extraction with water and alcohol in a modern laboratory. Various patents have been deposited using lactucerin. As in a pharmaceutical substance for treatment or neurological disorders with lactucarium from lettuce. But you can also find it in a dietary supplement, or in cough drops.

Lactuca sativa is not a vegetable?

Historically, Lactuca sativa is almost not used as vegetables. In the ancient Egyptian empire 2680 BCE, lettuce was mainly used for pressing its seeds for oil and as a sacrifice. The classic Greeks and Romans probably ate it raw as a side dish or as a basis for soups. The thoughts here were that the latex-like juice was absorbed into the vulgar rites of Min as an aphrodisiac to enhance masculinity during copulation. Not because it was so healthy. That is often written. There was an important association of lettuce with the god Min (later confused with Amon). He was a god of fertility and procreation. He is shown in different configurations, but the most important characteristics of his representations are: an ostrich feather headdress, a scourge or flagellum, signifying power, an offering stand with large upright lettuce plants behind him and an upright phallus for him (Bleeker, 1956). The god is often portrayed on temple or tomb walls, but if you have seen one Min, you have seen them all well. However, the lettuce plants behind him are shown in a wide variety of treatments that over the years have not caused any confusion for scholars. Prof. Harlan’s work) It is clear that in ancient times lettuce was valued as a painkiller, sedative , narcotic and also by the Egyptians and Romans as an aphrodisiac. It was certainly not seen as food.
Until the middle ages, lettuce was seen as a medicinal vegetable because of its lactucarium. Therefore you wil not find it before the Middle Ages in cookbooks. Only after the Middle Ages you will encounter the word Latuwe. under the name “close taluwe” or “krop-latuwe” / “krop falaat” (f pronounced as s). It was then known as vegetable garden herb and was used in the salad (1777). Here the word salad has a different meaning than it has now. In cookbooks you come across as crop-falà. greasy stocking and latitude. Usually these were grown in country houses, pleasure gardens and plantations. For lettuce then had the reputation of inhibiting indecent desires, erotic dreams and the resulting nightly emissions. When the nightly visits of seductive incubi and succubi it hits the poor nuns and monks in the cloisters, there was hardly a monastery without lettuce and another inhibitor like dill and chaste tree (monk pepper). The monks knew the writings of for example Dioscorides (~ 40-90 AD), who wrote: “Lettuce is good for the stomach, cools a bit, relaxes, softens the stomach and helps with breastfeeding.” In a decoction, those who suffer from involuntary nighttime ejaculation and coitus discourage Pythagorean philosophers, who tried to prevent them from dissimulating sexual energy but sublimating before, also used lettuce in their diet. In the old theory of humor, known to all monastic residents, this vegetable plant was classified as moist and cooling to the third degree: it cools both the body and the passions.Characteristic were the outer red leaves. In the Den Nederland herbarius or herb book of the most important herbs of 1698, one speaks of the Bastaart Hasen-latouw, or wild lathe an herb for which actually no name was yet. Known was the Court-salad or Hof-latouw … latuw (Lactuca sativa) The prunes called it Nipple-herb, (breastfeeding). In other countries such as the Asian countries, it was used by the introduction of lettuce from China, but it was first cooked. Again, it was originally a cooking vegetables and a garnish. The lettuce or mainly the butter lettuce was used as a garnish. And often it was only eaten during holidays in the form of a soup. Raw lettuce was unthinkable. In India the lactuca serriola (Kahu) was used for its seeds and for its medicinal properties (ayurveda)

Lettuce in the kitchen

In Chinese culture, lettuce is generally regarded as good fortune and is served on special occasions such as birthdays and New Year’s Day. In other countries it was mainly in the form of, for example, Sorrel soup (Green Borscht) a spring delicacy in Eastern European cuisine was used, but also in France it was used as soup. In Vietnamese dishes in soups and spring rolls. In the Arab world is now said that lettuce is a main ingredient of salad, but when you look at the real Arabic salad in the old cookbooks you read that this salad contains no lettuce. You will not find salad in almost all traditional salads. One of the reasons is that vegetables throughout the centuries, and also in other cultures, was depending as a part of religion, customs, money, health and legislation. Until the Middle Ages, the church and traditions had a strong influence on what people could eat. The vegetables in the Middle Ages, for example, had an image problem in the Netherlands and England: they were unhealthy according to the dietetic theory at the time, and had a low status. Except for the people who could afford a cook sometimes used lettuce (cooked). The first indications are on a 1759 painting by Pietro Longhi. Moreover, it was quite common in the Middle Ages to know everything that people ate, to which element it belonged, because all food was subdivided into one of these four temperaments. So food was used purposefully. Food was associated with symbolic meanings. And eaters of fruit and vegetables are short-lived. Because these products are bad for the digestion and give little food according the view in the 17th century. Only at the end of the seventeenth century when the Dutch East India Company was founded, a period of great prosperity began and this changed our diet. There were more tropical products in our meal and on the still lifes from the Golden Age you see mainly summer fruit and artichokes, but regular lettuce or garden herbs unfortunately not. Slowly, large-scale agriculture began to develop in the 18th century.
In the Netherlands you see in the 20th century that the rise of the domestic schools brings about a major change among the population about food. After World War II, the development of mass production of food began. The development in the 20th century of new packaging, storage and transport has improved the lifespan and transportability of lettuce, among other things, and resulted in a considerable increase in availability. It took until the 1950s before lettuce really got off the ground due to the development of vacuum cooling and ice cooling. At the moment you can see that the number of countries that suddenly consume lettuce as vegetables is increasing enormously due to the development of Hydroponics. Indonesia is a good example of this. Lettuce was used as a decoration for the introduction of hydroponics. Probably because Indonesia does not have a real climate for lettuce and it is now possible. There are thousands of hydroponics companies that grow lettuce. What is worse is that lettuce is also grown in tropical countries and in the desert, while climatologically it does not belong there.

The dangers of lettuce

Lettuce has a bad name among professionals. In the US, half a billion kilos of salad vegetables per year are not eaten and therefore thrown away. In addition, lettuce (together with other leafy green vegetables) is the largest carrier of pathogens for food-related diseases. According to the Centers for Disease Control (CDC), between 1998 and 2008 (raw eaten lettuce) accounted for 22% of all food-related illnesses. In addition, conventionally cultivated lettuce is involved in several recent outbreaks of Salmonella, E. coli and Listeria, the most recent of which was a lettuce collapse (due to Salmonella infection) in March of this year. Most of the recent outbreaks come from the increasingly popular “bagged lettuce” – lettuce that has been cut and “pre-washed”, mostly in chlorinated water. The centralization of food processing in conventional (and so-called “Big Organic”) agriculture means that thousands of lettuce leaves are processed in one facility. So if one leaf is contaminated (from soil, animal waste or other pollutants), the entire batch of processed lettuce can become contaminated (similar to problems in the production of ground meat). Experiments showed that juice from broken leaves increased salmonella growth in water by 110%. And when the juice was added to a nutrient medium that supports salmonella, the growth of the bacterium was increased by more than 2400 times. (University of Leicester in England) Recently an outbreak in December in Canada and January in the US. We know that cabbage lettuce is an economically important and popular vegetable, but until now little was known about possible contamination with Salmonella and E. coli O157: H7. That is why Inge Van der Linden examined in her doctorate how well Salmonella and E. coli can survive on lettuce. The research that she conducted at ILVO and Ghent University shows that they can actually survive on lettuce seeds, in irrigation water and on the lettuce itself, but also that the bacteria find their stay on the lettuce rather stressful. So our ancestors already knew that you should cook lettuce … However, the following is more dangerous

Nitrate

Nitrogen is an essential element for plant growth and development. What we see is that due to, among other things, environmental pollution and artificial fertilizer, high nitrate concentrations accumulate in the edible parts of our leafy vegetables. Especially if excessive nitrogen fertilizer is used. It is clear that the total nitrogen concentration in the soil and the nitrate concentration in lettuce, among others, increase as the amount of nitrogen fertilizer increases. If the recommended amount of inorganic fertilizer (100 kg • N • ha-1) is used as comparison standard, lettuce supplemented with organic fertilizers (200 kg • N • ha-1) have significantly longer and wider leaves, higher shoot formation, and lower concentrations of nitrate. Also within the hydroponics we see that lettuce grown in NO3 -N solution produces larger biomass and a larger number of leaves per plant. It is also clear that the more NO3 is used in food, the higher the nitrate content is. Only in the “academic” community are there still controversies about the safety of humans and their nitrate and nitrite content in the diet. The fact is that the level of nitrate varies enormously per country, region or cultivation method. Traditional organic agriculture has half less nitrate than on hydroponics. Bio-dynamic agriculture even lower. It becomes more strangely when you look at the political development with respect to the permissible of the nitrate content. And stranger than it is when Vitamin C vegetables are promoted while you know that too high a nitrate content is not associated with a high vitamin C content. Light is needed for more energy to fix CO2 to speed up vitamin C synthesis and nitrate assimilation in plants. The whole story about nitrate reads in the other article

Business and commercial importance

Lettuce is the most valuable vegetable crop, because on the global market, lettuce accounts for an estimated 32.9% of the market stock in hydroponics cultivation. Total lettuce exports amounted to US $ 2.4 billion in 2016, an increase of 2.6% over the five-year period from 2012. But in recent years, it is declining because more and more countries are producing lettuce.
Below are the 15 countries that exported the most lettuce in 2016:
Spain: US $ 790.9 million (32.7% of total lettuce exports)
United States: $ 479.1 million (19.8%)
Italy: $ 217.4 million (9%)
The Netherlands: $ 205.7 million (8.5%) The production of processed cabbage lettuce varies between 120 and 125 million kg. (1981)
Malaysia: $ 20 million (0.8%)
Mexico: $ 157.8 million (6.5%)
Belgium: $ 88.7 million (3.7%)
China: $ 81.2 million (3.4%)

Leaf vegetables generate the most profit in addition to cannabis. That is about $ 64 per square foot or about $ 2,800,000 per acre. This, of course, is because the average yield of conventional lettuce production is about £ 30,000 per hectare, while indoor cultivation produces an average of £ 340,000 per hectare annually. That is 11 times the yield compared to conventionally grown lettuce.

When you merge this story and the article about nitrate you can conclude that the production of lettuce is a commercially unhealthy product. And a product that will give the hydroponics a negative image. Lettuce is no vegetable, so use hydroponics for real healthy vegetables

© Ed van der Post