Here’s a new crop to sweeten your harvest

What you need to know:

  • In Kericho, over 2,000 rural farmers are growing it for export market. It has a ready market in the US, Asia, Australia and Europe.
  • Stevia does not have major pests and diseases challenges hence farmers don’t incur extra costs on agrochemicals and crop protection.
  • Depending on different climatic conditions, stevia is cultivable throughout the year except for times when it is extremely hot or cold.

The stevia plant (stevia rebaudiana bertoni) is a natural sweetener.

Stevia leaves are used as sweeteners due to the presence of sweet crystalline glycosides called steviosides, which are 200 to 300 times sweeter than sucrose.

Stevioside is non-caloric, non-fermentable, non-discolouring, heat stable at 95 degres Celcius and has an excellent lengthy shelf-life.

It can be added to cooked, baked or processed foods and beverages. With its steviol glycoside extracts having up to 300 times the sweetness of sugar, stevia has garnered attention because of the rise in demand for low-carbohydrate, low-calorie and low-sugar food alternatives.

Stevia does not raise blood glucose, meaning that the steviol glycosides responsible for stevia’s sweet taste do not induce a glycaemic response when consumed, which makes it an appealing sweetener for individuals diagnosed with metabolic syndrome who have been advised to strictly adhere to a strict, carbohydrate-controlled diet.

Fermentation-derived steviol glycosides are individually produced and highly pure forms of the stevia sweetener. They are produced through fermentation rather than by refining of extracts from cultivated stevia leaves.

As a natural sweetener, it is very healthy because it contains no calories. Hence recommended for diabetics and is used in preventing lifestyle diseases and controlling obesity because one gets the sweetness without gaining calories.

Stevia is an emerging crop in Kenya. The crop under very good management yields up to eight metric tonnes per hectare (MT/ha) per year.

OVER 2000 FARMERS

In Kericho, over 2,000 rural farmers are growing it for export market. It has a ready market in the US, Asia, Australia and Europe.

Stevia is propagated from seeds planted in trays placed in nurseries or greenhouses for a period of seven to eight weeks then transplanted to the main field.

The plant grows well in altitude 1,200m above sea level and in soils rich in organic matter. It grows well in infertile, acidic sandy loamy soils, but can also be cultivated on more neutral soils (pH 6.5 to 7.5).

A high plant density of 60 crops per acre planted with well-decomposed manure gives the best yields of up to 8MT/ha per annum. Optimum rainfall of between 1,500mm to 2,000mm per annum well spread throughout the year and average temperatures of 10 to 30 degrees Celcius gives the best performance of stevia.

CULTIVATED THROUGHOUT THE YEAR

Depending on different climatic conditions, stevia is cultivable throughout the year except for times when it is extremely hot or cold.

Stevia does not have major pests and diseases challenges hence farmers don’t incur extra costs on agrochemicals and crop protection.

Drying is done in the field before transportation. After pruning, the leaves are dried in shade and then immediately sent to market for selling. Harvesting can generally be scheduled when plants are 40 to 60cm tall. Optimum yield (biomass) and stevioside quality and quantity is best just prior to flowering.

In large-scale industrial production, drying of the woody stems plus the soft green leaf material is completed immediately after harvesting, utilising a drying wagon or a kiln.

Depending on weather conditions and density of loading, it generally takes 24 to 48 hours to dry stevia at 40 to 50 degrees Celcius. An estimated 10,000kg per acre of green weight is dried down to 2,000kg.

Immediately following drying, a specially designed thresher/separator is necessary to separate dry stevia leaves from its stem. The leaves are stored in gunnysacks in shade or in open in a room where there is no sunlight.

Lilian Jeptanui and Prof. Paul Kimurto, Egerton University, Crops, Horticulture and Soils Department