Stevia, or "honey leaves"
In time immemorial, when America was not yet discovered by Columbus, the Guarani Indians invented a wonderful drink - mate, which is also called Paraguayan tea. In order to give the mate a sweet taste and an unusually pleasant aroma, guarani added the leaves of a mysterious plant, which they called “kaa-ehe”, which means “sweet grass” or “honey leaves”. Two or three small leaflets were enough to make a sweet cup of mate or another drink.
The name of the mysterious plant sounds like the name of the overseas princess - Stevia rebaudiana. This is a small shrub from northeastern Paraguay and related areas of Brazil. Stevia leaves are 10-15 times sweeter than regular sugar. The Indians zealously kept the secret of the plant. Stevia became known to scientists only in 1887, when it was "discovered" by South American naturalist Antonio Bertoni. As the director of the College of Agronomy in the capital of Paraguay, Asuncion, he became interested in stories about an extraordinary plant, sweet in taste.
Having obtained a bunch of twigs, Bertoni started to work, but he could finally determine and describe the species only after 12 years, having received in 1903 a living specimen as a gift from the priest. It turned out that this is a new representative of the Stevia genus; the pioneer named it after his chemist friend Dr. Ovid Rebaudi, who helped make the extract, so that in the end it turned out Stevia rebaudiana Bertoni. Later it turned out that almost 300 species of stevia are growing in America. But only one - Stevia rebaudiana - has a sweet taste, this is its hallmark.
The secret of the sweetness of this plant is that it contains a complex substance - stevioside, which is a glycoside. In 1931, it was distinguished by the French chemists M. Bridel and R. Lyavey. Its composition includes glucose, sucrose, steviol and other related compounds. Stevioside is the sweetest natural product found so far. In its pure form, it is 300 times sweeter than sugar. Without calorie content and other negative properties of sugar, stevioside is its ideal substitute for both healthy people and those suffering from diabetes, obesity and other metabolic disorders.
Studies have also shown that this plant does not cause fermentation, does not contribute to the formation of plaque on the teeth or bacteria that cause dental caries, and also did not adversely affect animals that were used in experiments during laboratory studies. The beneficial substances of the plant do not break down during heating, which is important for people who use mainly heat-treated and sublimated products, etc.
In mid-2004, WHO experts also temporarily approved stevia as a dietary supplement with a daily allowable glucoside intake of up to 2 mg / kg. In terms of sugar, this is far from a bag - for the average person 40 g per day.
Stevia is a perennial plant from the Astrov family. In nature, it reaches a height of 60-80 cm, while cultivars - 90 cm. The stevia bush is highly branched, leaves are simple with a pair arrangement. The flowers are white, small. The root system is fibrous, well developed. Currently, the amount of stevia in nature has slightly decreased due to increased collection of leaves, grazing, and also due to the export of some plants for cultivation on cultivated plantations.
Stevia grows mainly on barren acid sands or on silt, which lies in a strip along the edge of swamps. This suggests that it can adapt to various soil conditions. Stevia is found in areas with a moderately humid subtropical climate in the temperature range from -6 to 43 ° C. The optimum temperature for the growth of stevia is 22-28 ° C. The local rainfall is quite high, so the soil is constantly moist, but without prolonged flooding.
In nature, stevia is propagated by seeds, by separating leaf rosettes, or by rooting broken branches that accidentally stuck into the soil or were trampled into it by cattle. Stevia shoots appear in early spring, and at the end of summer it reaches full development and quickly fades. It was found that the duration of daylight affects the growth and development of stevia. Short days promote flowering and seed formation. The flowering season in Paraguay is from January to March, which corresponds to the period from July to September in our hemisphere. Longer days favor the growth of new branches and leaves and, accordingly, increase the yield of sweet glycosides.
Due to its plasticity, stevia is successfully cultivated in many parts of the world - in South America, Japan (since 1970), China (since 1984), Korea, Great Britain, Israel and others. The commercial use of stevia in Japan has been ongoing since 1977, it is used in food products, soft drinks and in table form, 40% of the entire stevia market falls on Japan - more than anywhere else. Stevia appeared in Russia thanks to academician N.I. Vavilov, who brought it to Russia from an expedition to Latin America in 1934.
Samples of plant species brought by him are stored at the All-Russian Institute of Plant Production. In culture, stevia plants cannot develop well in the presence of weeds and need regular weeding. A dense landing is also preferred to avoid damage by rain and wind in unprotected areas. Close-planted plants support and protect each other. Stevia needs constantly moistened soil, it does not tolerate drought, but moisture stagnation is harmful to it.
Crops are harvested at the beginning of flowering, when the largest mass of leaves and the maximum content of stevioside. The yield of stevioside from the leaves of cultivated stevia is usually 6-12%. Under optimal conditions, a stevia crop from one hundredths can replace 700 kg of table sugar!
In the middle band, stevia does not winter and is grown as an annual, by seedling. Seeds are sown for seedlings in March-April (earlier, if you use the backlight) in light soil, without sowing. Top cover with glass. Seedlings are planted in open ground when the threat of spring frost passes (in late May - early June). The distance between the plants is 25-30 cm. The location for planting stevia should be selected solar, protected from cold northern winds. The soil is preferably light, loose, nutritious, liming is contraindicated.
Flowering occurs 16-18 weeks after sowing. The use of greenhouses and greenhouses increases the yield. If desired, stevia can be grown as a perennial. In this case, the rhizome is dug up for the winter and stored in a cool room, covered with soil. In spring, the plant is planted in the open ground entirely or used for cuttings. Numerous studies have proven that stevia is a safe natural product. Currently, its sale is permitted in almost all countries. The use of stevia by the Guarani Indians for centuries is also a strong argument in favor of its safety.
In addition, the last forty years, stevia and stevioside are widely consumed in large quantities throughout the world. However, during this time not a single case of its adverse effects on humans has been noted. In this way, stevia compares favorably with artificial sweeteners, the use of which often leads to dangerous side effects.
The properties of stevia do not deteriorate when heated, so it can be present in all dishes that are subjected to heat treatment. In cooking, both fresh stevia leaves and products of its processing (industrial production or made at home) are used.
Fresh leaves. The shoots are cut at the beginning of flowering. However, a small number of leaves for fresh use can be plucked throughout the growing season. They are used, for example, to sweeten drinks or to decorate desserts.
Dried leaves. Stevia leaves are separated from the branches and dried in the usual way. If you grind the dried leaves in a mortar or in a coffee grinder, you get a green stevia powder, which is about 10 times sweeter than sugar. 1.5-2 tbsp. l powder replace 1 cup (glass) of regular sugar.
Stevia extract. It goes on sale in the form of a white powder, 85-95% consisting of stevioside. It is 200-300 times sweeter than sugar. 0.25 parts of the extract replaces 1 cup of sugar. The extract is obtained by water extraction, decolorization and purification using ion-exchange resins or precipitating agents. Stevia extract can be prepared on its own, but it will be less concentrated and should be added more when preparing dishes than industrial extract. At the same time, orient yourself to your taste.
Extract preparation. Pour whole stevia leaves or green powder with pure edible alcohol (you can also use vodka or brandy) and leave for 24 hours. Then filter the liquid from leaves or powder. The alcohol content can be reduced by heating the extract over very low heat (do not boil), allowing the wine vapor to evaporate. A full extract can be prepared in this way, but sweet glycosides are not extracted as completely as alcohol. The liquid extract, both aqueous and alcoholic, can be evaporated and concentrated in syrup.