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Advice on Publications Available.Timothy Lester
14 Spencer St
Gatton, Queensland, 4343
Email: s344585@student.uq.edu.au
Stevia rebaudiana is a herbaceous perennial, which is normally used as a natural herbal sweetener.
It is native to Brazil, Venezuela, Colombia and Paraguay where the native Guarani have used caa-ehe (stevia) for over 1500 years to sweeten otherwise unpalatable medicinal drinks.
Other uses for the plant and its extracts are in weight-loss programs because of its ability to reduce the cravings for sweet and fatty foods. The plant has also been used to treat the diseases diabetes, hypoglycemia, candidiasis, high blood pressure, skin abrasions and inhibiting growth and reproduction of bacteria-like plaque.
Stevia's greatest economic potential is as a natural alternative to artificial sweeteners (such as aspartame or sodium saccharin). Dry stevia leaf is up to 30 times sweeter than sucrose.
The sweetness in stevia is mainly attributed to two compounds viz stevioside (3-10% of dry leaf weight) and rebaudioside A (1-3%) which can be up to 250 times sweeter than sucrose.
Stevioside has a few advantages over artificial sweeteners in that it is stable at high temperatures (100 C) and a pH range of 3-9 and does not darken with cooking.
In the 70's and 80's stevia was developed as a sweetener/flavour enhancer which has since been used widely for this purpose in Japan, China, Korea, Israel, Brazil and Paraguay.
The products in which stevia has been used include soft drink, ice cream, cookies, pickles, chewing gum, tea and skin care products.
In Japan about 40% of the sweetener market is stevia-based.
The main producers of stevia are Japan, China, Taiwan, Thailand, Korea, Brazil, Malaysia and Paraguay.
The main current commercial constraint on the stevia industry is a ban on its use in food products in the US. This is based on the suspicion that a derivative of stevioside may be harmful to humans.
Until further research is conducted, stevia can only be sold as a dietary supplement and a skin care product but not as a sweetener in the US.
Stevia rebaudiana from the Asteraceae family was re-discovered by MS Bertoni in 1888.
It is a short day plant, growing up to 0.6 meters in the wild and flowering from January to March in the southern hemisphere. Flowering under short day conditions should occur 54-104 days following transplanting, depending on the daylength sensitivity of the cultivar.
Stevia grows naturally on infertile, sandy acid soils with shallow water tables. This is normally in areas like the edge of mashes and grassland communities.
The natural climate is semi-humid subtropical with temperature extremes from 21 to 43 C, averaging 24 C.
Stevia grows in areas with up to 1375mm of rain a year.
Large areas on the coastal strip from Sydney to Brisbane have a high probability of being able to establish Stevia (as shown in the map on this page which was prepared by S Connell of the Western Australian Department of Agriculture and included in Technical Report 42 (1992): Frances C Hoyle 'A review of four potential new crops for Australian agriculture: Amaranthus caudatus, Chenopodium quinoa, Grindelia camporum and Stevia rebaudiana'. WA Department of Agriculture, Division of Plant Industries).
The sweet stevia compounds vary in concentration with the method of propagation, daylength and agronomic practices.
Reproduction in the wild is mainly by seed, but seed viability is very poor and highly variable. Stevia can be produced by cuttings or in vitro but once good varieties have been created, a seed/transplant production system is more economic.
Some of the biggest production constraints in Australia are extreme radiation, low water availability, Australian landrace stock and general agronomic information to suit the local environment.
Under cultivation, stevia plants can achieve a height of one metre. In agronomic conditions, the plant is normally treated as an annual. Seeds are germinated in the glasshouse and in spring and the plants are transplanted into the field (usually at 6-7 weeks old).
The whole plant is harvested once, just before flowering to obtain maximum glycoside content.
The plant is dried and threshed to remove the stem material which has little sweetener content. Leaves can be sold in this condition or are further processed.
Leaf yields of 2850 kg/ha with a stevioside concentration of 105 mg/g have been achieved in Canada.
This is equivalent to 66.2 tonnes per hectare of sugar.
The average cost of production is $CAN8,500/ha and an estimated 2,200 kg/ha of dried leaves is required to break-even.
The major cost in stevia production is the cost of transplants.
Production seed yields of up to 8.1 kg/ha have been recorded but it is common to have under 50% germination.
One hectare of seed production would be enough to produce 200 hectares of leaf production.
Breeding programs in stevia would aim to optimise:
Stevia is highly self-incompatible and studies of heritabilities of leaf yield (75%), leaf to stem ratio (86%) and stevioside content (83%) are high enough to warrant selection.
At the moment there is no commercial production of stevia but a few health food and tea companies are looking for a cheaper local product than that currently available from Paraguay.
Products that are available in Australia now are stevia tea from Fitness 2000, stevia leaf extract and dried stevia leaf from Shipard's Herb Farm, Nambour, QLD.
Shipard's Herb Farm also sells stevia seeds and plants.
In Australia, especially in Queensland and northern NSW we have a long growing season, enough water, high humidity and high altitudes.
The plant should perform to its optimum.
Problems with successful cultivation would be the lack of information available of weed, insect and pest control.
Further research and development needs to be carried out to find optimum growing conditions, seed germination, cultural practices and a landrace suited to our Australian conditions.
Sources of information from the Internet:
http://www.riverhouse.com.au/
http://res.agr.ca/lond/pmrc/faq/menu.html
http://res.agr.ca/lond/pmrc/herbs/stevia.html
http://www.healthfree.com/herbgarden/stevia.html
Reading
Brandle, JE and Rosa, N (1992) Heritability for yield, leaf-stem ratio and stevioside content estimated from a landrace cultivar of Stevia rebaudiana. Canadian Journal of Plant Science 72: 1263-1266
Crammer, B, and Ikan, R (1986) Sweet glycosides from the stevia plant. Chemistry in Britain 22: 915-916
Kinghorn, AD, and Soejarto, DD (1985) Current status of stevioside as a sweetening agent for human use. In 'Economic and medical plant research'. Academic Press. London
Metivier, J, and Viana, AM (1979) The effect of long and short day length upon the growth of whole plants and the level of soluble proteins, sugars and stevioside in leaves of Stevia rebaudiana Bert. Journal of Experimental Botany 30: 1211-1222
Soejarto, DD, Compadre, CM, Medon, PJ, Kamath, SK and Kinghorn, AD (1983) Potential sweetening agents of plant origin. II. Field search for sweet-tasting Stevia species. Economic Botany 37: 71-79.
Any claims made by authors in the Australian New Crops Newsletter are presented by the Editors in good faith. Readers would be wise to critically examine the circumstances associated with any claims to determine the applicability of such claims to their specific set of circumstances. This material can be reproduced, with the provision that the source and the author (or editors, if applicable) are acknowledged and the use is for information or educational purposes. Contact with the original author is probably wise since the material may require updating or amendment if used in other publications. Material sourced from the Australian New Crops Newsletter cannot be used out of context or for commercial purposes not related to its original purpose in the newsletter
Contact: Dr Rob Fletcher, School of Land and Food, The University of Queensland Gatton College, 4345; Telephone: 07 5460 1311 or 07 5460 1301; Facsimile: 07 5460 1112; International facsimile: 61 7 5460 1112; Email:
r.fletcher@mailbox.uq.edu.au[
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