All over the world there is an increasing tendency towards consuming natural products and thus living a more natural life. At the same time our lifestyles have changed so much over the last four to five decades that sweeteners (either high-calorie natural or processed sugars or high potency and low-calorie synthetic sweeteners such as aspartame) have become an integral part of our natural daily diet. Due largely to the sedentary lifestyles that we all tend to lead these days, the incidences of obesity and diabetes are increasing dramatically. In India, for example, the number of diabetics in the age group of 25-45 is now about 15 percent and is increasing at an alarming pace. The USA is the largest consumer of sugar in the world, which has contributed substantially to a dramatic increase in its diabetic population.
Stevia, botanically known as Stevia rebaudiana Bertoni (Family: Asteraceae) is a sweet herb that has grown significantly in popularity among those in search of a healthier lifestyle. A perennial, Stevia is a member of the daisy family. The leaves are intensely sweet due to the presence of glycosides, two compounds called stevioside and rebaudioside (there are also several others) which can be more than 200 times sweeter than sugar. The plant bears white flowers in the fall.
Although Stevia has been in use in South America and Asia for years, and has been gaining acceptance in Eastern countries such as Japan and Korea, it was only in the past couple of years that it has really started to capture the attention of the U.S. market as a healthy , noncaloric alternative to sugar. It is safe for diabetics, as it does not adversely affect blood-sugar levels and does not have the side effects associated with artificial sweeteners such as aspartame.
There are many advantages of using Stevia over conventional sweeteners, the main one being that Stevia leaves are 20-30 times sweeter than sugar. Stevia leaves can be dried and stored, and can be used in the raw . Stevia is a short-duration crop that is harvested three to four times a year in tropical areas and once a year in temperate regions. The yearly yields can be in the range of six to eight tons per acre. The commercial grower will sell bulk Stevia at $5 to $7. per pound of dried leaves and is thus economically beneficial to grow.
The many uses of Stevia leaves
Now that the Food and Drug Administration has relaxed previous restrictions on Stevia’s use as a sweetener, it has the potential to replace other sweetening agents in products like ice creams, baked goods, soft drinks and candies that are targeted particularly to diabetics and health-conscious consumers.
All cooked and baked food items and desserts can be sweetened with much smaller quantities of Stevia leaf powder or extract than comparable amounts of table sugar. Just two tablespoons of Stevia leaf or ¼ teaspoon of the white Stevia extract can replace one cup of cane sugar. The sweetness of stevioside is non-fermenting and it does not display browning when cooked. This further widens its area of application in baking. Breads made with Stevia as an ingredient (for diabetics patients) have been found to display improved texture, softness and an increased shelf life. The confectionery industry is yet to reap the benefit of Stevia, which has the potential to replace sugar.
The leaves and extract can be used in chocolates and candies not only to meet the requirement of diabetic and health-conscious consumers, but also to provide the added advantage that it does not encourage tooth decay, since it possesses antimicrobial properties. A mere fragment of the leaf is enough to sweeten the mouth for an hour, permitting it to also be used in the manufacture of chewing gums, mints, mouth refreshers and even in soft drinks.
Medicinal Properties of Stevia
Several health drinks and supplementary beverages, especially for diabetic patients, now contain Stevia, which is rich in nutrients, containing substantial amounts of protein, calcium and phosphorus, and is thought to contribute to pancreatic health.
In addition to its anti-fungal and anti-bacterial property, mild Stevia leaf tea offers excellent relief for an upset stomach. A wet Stevia leaf teabag provides a cooling effect on eyes (similar to using cucumber). The leaves effectively tighten the skin and are good for wrinkles. Stevia has proved to give exceptional benefits when used regularly in skin care. It also has a healing effect on blemishes, wounds, cuts and scratches. Stevia is helpful in weight and blood pressure management. It has also been reported that Stevia lowers incident of colds and flu.
You need not be a South American farmer to be a successful Stevia grower. A short day plant, it researches a height of 36 inches in three months. The concentration of Stevioside in the leaves of Stevia increases when the plants are grown under long day conditions. Stevia grows best in upland areas in sub-tropical climate. In other places it can be grown as an annual. The plant prefers a lightly textured, well-drained soil to which organic matter has been added. It needs ample water so that the soil is consistently moist, but not wet. In hot, sunny climates it will do best in semi-shade. Propagation is from cuttings in the spring and summer.
Tthe young plants can be put out out once all danger of frost is over and soil temperatures reach 65 degrees F. Leaves are best harvested just before flowering in the fall. The next year’s crop will grow from cuttings best taken in the late summer. The concentration of stevioside in the leaves of Stevia increases when the plants are grown under long day conditions. Cultivating Stevia on a large scale should be grown in well-drained sandy loam soil. The soil should be in the pH range of 6.5-7.5. Saline soils should be avoided to cultivate this plant. The high summer temperatures do not affect this plant as much as low (below 65 deg F) night time temperatures. Though stem cuttings are normally used, vegetative tissue culture plants have proven to be good as well. Tissue culture plants of Stevia are genetically pure, free from pathogens and have excellent vigor. The Stevia plants can be planted throughout the year except during peak summer months. An ideal planting density is 30,000 plants per acre with spacing of 12 x 18 inches in a raised bed system.
Land should be plowed initially with a disc plow or harrowed to break down the clods. Fine tilth is required. Plowing has to be done one or two times after harrowing. Often raised beds are formed at this time. The width of the bed will depend upon the type and size of equipment available. Some operations may have a bed with a single row of plants while others may use a bed with 3 staggered rows.
Stevia requires very good drainage. Any soils that retain moisture for very long periods of time are unsuitable for Stevia cultivation and should be religiously avoided. Similarly black soils with very heavy clay content should also be avoided. It is mandatory that before planting, each and every soil sample should be properly tested and analyzed by an expert. A sandy loam soil with a 6-7 pH is best for the cultivation of Stevia.
Raised bed preparation
Forming raised beds is the most economical way to grow Stevia. The raised bed should be of 4 to 6 inches in height and 12 inches in width, with 12 inches between plants. The raised beds are often covered with black plastic and the Stevia is planted through it. This would give a plant population of around 30,000 per acre.
Stevia can be planted in many ways. The types of agronomic practices generally depend on type of soil and climate conditions. Generally it is advisable to plant a minimum of 30,000 plants per acre. There are basically two types of planting material recommended: tissue culture and stem cuttings. Tissue culture is the best option, stem cuttings tending to be more expensive in very large operations.
There have been many selections of Stevia rebaudiana developed all around the world. Basically all these selections have been developed for different climatic requirements. At the end of the day it is the stevioside and rebaudioside content in the Stevia leaves that determine the price and marketability of Stevia leaves. Hence it becomes imperative that the grower selects proper varieties from the planting material suppliers.
Stevia requires ample supply of good water all year around. As the plant cannot tolerate drought, frequent irrigation is required. Micro drippers are the best means of providing plants with the required amount of water at the right time, allowing the water to be sprinkled once a day in winter and two to four times in a day in summer depending upon the heat and relative humidity in the air. Watering frequency should be scheduled so that the plants do no wilt for want of water yet are never waterlogged. Irrigation pipe with drippers is best installed under the black plastic mulch.
The recommended dose of fertilizer is 10:10:10 NPK.
Organic gardeners in particular should find Stevia an ideal addition to their crops. Though nontoxic, Stevia plants have been found to have insect-repelling tendencies. Their very sweetness, in fact, may be a kind of natural defense mechanism against aphids and other bugs that find it not to their taste. Perhaps that is why crop devouring grasshoppers have been reported to bypass Stevia under cultivation. In case any disease symptoms are noticed, spraying of agricultural oil diluted in water is the best organic method.
Removal of weeds can be done manually, since the crop is grown in raised beds. If black plastic mulch is used weeding will be minimal.
Stevia plants do best in a rich, loamy soil, the same kind in which common garden-variety plants thrive. Since the feeder roots tend to be quite near the surface, it is good idea to add compost for extra nutrients if the soil in your area is sandy. Besides being sensitive to cold during their development stage, the roots can be also be adversely affected by excessive levels of moisture. So take care not to over-water them and to make sure the soil in which they are planted drains easily and isn’t soggy or subject to flooding. Frequent light watering is recommended during the summer months. Adding a layer of compost or black plastic mulch around each Stevia plant will help keep the shallow feeder roots from drying out. Stevia plants respond well to fertilizers with lower nitrogen content than the phosphoric acid or potash content. Most organic fertilizers would work well since they release nitrogen slowly. Since Stevia has a significant apical dominance, the plant tends to grow tall and lanky. Pinching of the terminal bud can enhance bushy growth of the plant with side branches.
Depending on climate conditions one can achieve yields of 6 to 8 tons per acre in harvests annually. Another important aspect of harvesting is timing. The best quality Stevia leaf is the one that is harvested in the fall just before the blossoms open. It should be noted that Stevia leaves should not be harvested after flowering since the stevioside percentage goes down rapidly and leaves are rendered unmarketable. It is normal for the plants to flower in the fall during the short days. Leaves are harvested by plucking in small quantity or the entire plant with the side branches is cut leaving four to six inches from the base. The first harvesting can be done four to five months after planting. Subsequent harvesting can be done every three months, for three consecutive years. The sweetener in the leaf is at maximum levels just before the plant flowers. Just before flowering, the plant should be cut completely leaving 4 inches from the ground. The new flush of leaves will sprout from there, with the new plant ready for harvest again in three months. The plant yields around six tons of dried leaves per acre every year. Harvesting should be done as late as possible, since cool autumn temperatures and shorter days tend to intensify the sweetness of the plants as they evolve into a reproductive state.
Once all leaves have been harvested it is necessary to dry them. This can be accomplished on a net. The drying process is not one that requires excessive heat and not more than 110 degrees F. More important is good air circulation. On a moderately warm fall day, Stevia crop can be quick dried in the full sun in about 12 hours. If the leaves are not completely dry by the end of the first day they must be brought indoors before sundown and brought back out the next day. Drying times longer than that will lower the stevioside content of the final product. Crushing the dried leaves is the final step in releasing Stevia’s sweetening power. The dried leaves are powdered, sieved and the fine powder is stored in containers. This can be done either by hand or, for greater effect, in a grinder or in a special blender for herbs.
Fresh Stevia leaves
This form of Stevia is the herb in its most natural, unrefined state. A leaf picked from a Stevia plant and chewed will impart a sweet taste, a dried leaf will taste much sweeter. For Stevia to have a more practical application as a tea or sweetener, the leaves must be dried or put through an extraction process, which makes the sweet taste even more potent.
For more of the flavor and sweet constituents of the Stevia leaf to be released, drying and crushing is necessary. A dried leaf is considerably sweetener than a fresh one, and is the form of Stevia used in brewing herbal tea or in cooking.
The form in which Stevia is primarily used as a sweetener in Japan is that of a white powdered extract. In this form it is approximately 200 to 300 times sweeter than sugar (by weight). This white powder is an extract of the sweet glycosides (natural sweetening agents) in the Stevia leaf. Not all Stevia extract powders are the same. The taste, sweetness and cost of the various white Stevia powders will likely depend on their degree of refinement and the quality of the Stevia plant used. Since extracted Stevia powder is so intensely sweet, it is always recommend that it be used by the pinch or drop if diluted in water. Once mixed, this solution should be stored in the refrigerator.
These come in several forms. There is a black syrup liquid that is the result of boiling the leaves in water. This was used as a face mask or for skin healing. Steeping Stevia leaves in distilled water or a mix of water and grain alcohol makes another type of liquid sweetener.
The market potential for this natural sweetener is still untapped. It is estimated that about 30 million people are presently suffering from diabetes and it is estimated that by 2025 our contribution to the diabetic global population would be a whopping 89 million. With such a huge share of the population being diabetic, new ventures in the food industry are focused entirely on them. American soft drink manufacturers have yet to exploit the natural sweetness and health benefits of this herb. Though many soft drinks are described as “sugar free,” the usage of Stevia in such products could create a far greater demand than for the ones with artificial sweeteners. The beverage industry has just started introducing new products for diabetic patients, realizing the major share held by them in the consumer market. But all those sugar-free products in the market at present are sweetened with artificial sweeteners that can produce adverse health effects. Stevia can thus be used to replace the artificial sweeteners completely. As Stevia leaf powder with no processing is safe to use, calorie-free and around 20-30 times sweeter than cane sugar. The process of manufacturing Stevia leaf powder is quite simple, when compared to the tedious steps involved in cane sugar manufacture.
America being largest consumer of cane sugar along with largest diabetic population in the world, Stevia is ideally poised to play a major role in satisfying the U.S. and world demand for a natural low-calorie sweetener. Today Stevia rebaudiana extract accounts for 40% of the sweetener market in countries such as Japan, Korea and Malaysia. Because Stevia is relatively new to the American market, however, there is still considerable confusion in the U.S. in regard to the marketing of this unique herb.
The demand for high potency sweeteners is expected to increase worldwide. The increase in the number of diabetic patients and health-conscious individuals is pushing forward the need for natural, noncaloric alternatives to sugar. Stevia represents the best potential replacement for artificial sweeteners like saccharin and aspartame. Unlike many low-calorie sweeteners, stevioside is stable at high temperature and over a pH range of 3 -9.
Steps therefore need to be taken to exploit the natural sweetness of Stevia, such as the launching of new products containing it.. This would obviously promote the need to grow more, resulting in more areas under Stevia cultivation. Large scale development of cuttings suitable for field planting would be the first requirement. A crop production system, providing information on optimized crop inputs, weed and disease control, harvesting and handling methods also needs to be developed.
In short, initiatives need to be undertaken to promote this natural sweetener and create greater awareness of how Stevia can actually improve our health while sweetening our food and beverages.