| FOOD CHAIN No. 3 - July 1991 |
'Bixin is used in margarine, salad dressings and edible oils, while norbixin is used in some cheeses, breakfast cereals and snackfoods.'
Annatto colourant - the product resulting from processing achiote
This article draws on work carried out by Appropriate Technology International (ATI) on processing annatto - a reddish-orange colouring used in foods - which took place in Peru and Kenya. ATI suggests that a producers' organization or co-operative processing 8 to 10 tons of annatto per year can be a viable concern. Decentralized processing near the source of the raw material can reduce production costs by about 15 per cent: this brings increased benefits to people living in rural areas, compared with processing in a major city which involves long distance transfer and storage.
The seeds of the achiote tree (Bixa orellana) are the source of annatto: a reddish-orange colourant widely used in foods, cosmetics and textiles. The tree, native to the Amazon basin, is now found throughot Latin America, the Caribbean, East Africa and Asia. It reaches a height of 5 to 10 metres and bears clusters of brown spiney seed pods for about 12 years.
The carotenoid pigment found in the seed coat can be produced in two forms; oil soluble bixin and water soluble norbixin. Crude annatto contains a mixture of the two pigments; in Peru typical norbixin levels resulting from small-scale processing range between 25 and 32 per cent.
Bixin is used in margarine, salad dressings and edible oils, while norbixin is used in some cheeses, breakfast cereals and snackfoods. Bixin can be converted to norbixin but the reverse process is difficult. The colour in the product depends on the concentration used, for example 1 oz of a 1 per cent norbixin solution is sufficient to colour lOOOlbs of milk for cheese.
While Kenya and Peru are the largest suppliers of annatto, producing 60 per cent of the world's demand, there is increasing competition from other countries such as Costa Rica.
Until ten years ago, most international trade was in unprocessed achiote seeds, but now most producing countries have set up processing facilities to capture more of the added value. Processing in-country also lowers transport costs since the annatto powder weighs less than 10 per cent of the whole seed. World demand, which rose rapidly in 1980 to roughly 7000 tons of seed, has continued to grow, in part due to concerns over the safety of synthetic colourings.
The yield and pigment content of the seeds vary with the variety of the tree. Average yields of wild trees in Pert, are only 400-600 kg/ha while in Costa Rica managed plantations are obtaining 1500-2000kg/ha. Pigment levels in the seeds range from 1.5 - 5 per cent.
The seed pods are harvested when they are woody, dry and about to split open. Drying on mats in the sun for two to four days causes the pods to burst open. Controlled drying is essential. If the seeds are underdried, they risk becoming mouldy; if overdried, they may loose pigment from over-exposure to the sun. After drying, the seeds are threshed traditionally by hand, in a very labour intensive way. It can take up to six person days to thresh and clean 100 kg of seed. The seeds may then require further drying to 7-10 per cent moisture, but this should not be attempted in direct sunlight.
In an ATI assisted project in Peru, a small hand operated dehusker/winnower was developed to open the posts, separate the seeds from the husks and winnow off chaff. A team of five people taking turns can produce 50 kg of seed/hr with a 95 per cent recovery rate. The dehusker costs approximately $300 and is produced locally in Peru.
There are three main types of methods for extracting annatto from achiote seeds. The one most common in developing countries involves chemical precipitation in which pigment is made soluble in aqueous alkaline solutions and then precipitated out by the addition of acid. Other methods involve extraction into oil and solvent extraction.
The first step in the precipitation process is to place 200 kg of seed in a stainless steel batch tank containing 400 litres of water. Then 2.5 litres of caustic soda solution made up of 3 litres of 98 per cent sodium hydroxide pellets and 39 litres of water is added. The contents are then stirred with a powered agitator for 10 minutes. The pH of the solution should be near 11 for optimum dye extraction. The liquid is then drawn off from the tank through a mesh screen at the bottom of the tank's outlet. Then 300 litres of water are added to another litre of the caustic soda solution. After 10 minutes of agitation, the liquid is drawn off as before. The washing procedure is repeated two more times with only 200-250 litres of water and without the addition of caustic soda. All the wash solutions are then combined in a large precipitation tank.
The next step is to add three litres of a prepared acid solution (eight litres of 98 per cent sulphuric acid solution mixed with 40 litres of water) to the stabilized pigment to give a final pH of about 3. After four or five hours, the supernatent liquid is drawn off, leaving the precipitated annatto paste at the bottom of the tank. The watery annatto paste is then passed through a filter press where it is washed with water to reduce the acidity.
The final step is to dry the filter press cake in a hot air drier starting with temperatures of up to 90°C, gradually reducing it to 60-70°C. When the moisture content of the paste is down to 20 per cent or so, the paste is removed from the drier and ground in a hammer mill to a particle size of 1.0-1.5 cm. The coarse powder is then dried further to a moisture of 4-5 per cent. It is milled again to a particle size of 2-5mm. The final product should be stored in a cool place, preferably in plastic bags inside drums or boxes, where they will be protected from the light.
Annatto processing can be made more profitable by better use of its by-products. The spent seeds after dye extraction can be used in poultry feed. Trials have shown that the spent seeds can replace up to 60 per cent of commercial feed. The sodium sulphate solution can be sold to detergent, paper, or textile plants, thus generating profits while reducing pollution.
In 1986-87, the demand for and price of annatto powder and seed increased because: many importing countries banned or severely restricted use of synthetic food colours; new uses for bixa colourings evolved; droughts in Kenya (1983/84) and Peru (1984/85) reduced production and; several producing countries exported annatto-derived powders rather than seed. Low and/or inconsistent quality of norbixin water soluble powder, coupled with buyers' inability to control the quality of seed processing to give them the quality and functional properties desired in powder increased demand for seed over norbixin powder. All of these factors prompted many producing countries to greatly increase production, causing an over supply of both seed and powder.
Potential for increased exports exists if producers take a strong market driven approach. This means taking annatto products (seeds or powder) out of the world commodity category and customizing them to more closely meet buyers' needs. Market research on buyers and products, services, and incentives must be offered to encourage the purchase of annatto products.
Buyers desire a consistently high percentage of bixin in norbixin powder and/or other products meeting more sophisticated consumer expectations.
The potential to expand seed production and export is very good if the main objective is to produce high quality, not just large quantities of seed.
Credit: ATI. Separating the seeds from the husks.
'Annatto processing can be made more profitable by better use of its by-products. The spent seeds after dye extraction can be used in poultry feed. The sodium sulphate solution can be sold to detergent, paper, or textile plants, thus generating profits while reducing pollution.'