Chillis - A red hot export?

Dr Andreas Klieber inspects a chilli crop.

Dr Andreas Klieber inspects a chilli crop.
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Ripe chillis ready to harvest.

Ripe chillis ready to harvest.
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Powdered chilli is an ingredient of many spices.

Powdered chilli is an ingredient of many spices.
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Friday, 11 August 2000

South Australia's climate is more Mediterranean than South American, but an Adelaide University researcher has been developing horticultural techniques to grow chillis there. As well as its economic importance, the research has health implications, as eighty per cent of samples of chilli-based spices imported to Australia have been found to be contaminated with the potent cancer-causing agent, aflatoxin.

Adelaide may be the capital of South Australia, but its Mediterranean climate lends itself to a Mediterranean cuisine. Most gardens can boast a good crop of tomatoes, grape vines prosper, while olives do so well that they have gone feral, invading the Adelaide Hills as a serious environmental pest. With a touch of global warming, they might yet be replaced by feral chillies.

Chillies are the fruit of various Capsicum species, a diverse group which produces not only capsicums, which are eaten raw or cooked, but spices such as chilli, prepared by drying the fruit and grinding it to a powder. These spices provide the characteristic 'hotness' of Asian and South American foods.

Chillies originated in South America. While they now grow worldwide, the warmer sub-tropical regions produce the hottest chillies. Habanero is the hottest; three times more powerful than Thai chillies, and far more so than the green and red capsicums that decorate many salads.

The main quality characteristics of chillies are the colour and heat level, or pungency, but there is much more to the fruit than just their eye-watering power. Dr Andreas Klieber is studying chillies at Adelaide University's Waite Campus. His research involves determining the best conditions for growing and harvesting chillies, preparing them for spice manufacture and preventing the resultant spice from spoiling.

Chillies have traditionally been used in warm countries to cover the taste of spoiled food and also to prevent it from going bad as quickly. It is surprising, then, to discover that chilli powder is itself susceptible to mould that can produce aflatoxin, thought to be a potent carcinogen.

Currently virtually all chilli spice is imported into Australia, but a survey of 90 products showed extensive contamination with aflatoxins. "Overall only 9% of samples complied with Australian standards, with another 12% marginal," said Dr Klieber. "This survey shows that considerable improvements need to be made to produce a safe food for consumers," he said. "Importers need to insist on better quality assurance and testing by producers, but a significant opportunity exists for local producers to develop a safe product that will replace imported products of unknown safety," said Dr Klieber.

"We set out to examine the whole chilli spice production system to maximise yields and quality of the final product," said Dr Klieber. " The need for this arose from the lack of detailed information for Australian conditions, as most previous work had been carried out overseas, and recommendations were not always clear."

Growing chillies under cool conditions, reduces their hotness. The final colour is influenced by the stage of ripeness at which the fruit is harvested, and the processing and storage of the final spice powder.

In Australia, from Mediterranean South Australia to sub-tropical Queensland, the best fruit grows from around September to March. Cooler months or climates produce slower growth rates of plants and fruit, in which the heat levels are also dramatically reduced.

The perceived hotness of chillies occurs because the nervous receptors in the mouth that send pain signals when burnt are also stimulated by the chemicals termed capsaicins that are found in chillies. "When you eat a lot of chillies, some nerve cells in the mouth die, " said Dr Klieber. "You then need more spice to get the same effect, which explains why some people can tolerate more and more chilli in their food," he said.

"Researchers are now looking at capsaicins to control chronic pain by using the chemicals to overstimulate and deaden nerve cells," said Dr Klieber.

Chilli-based cuisine often includes other foods, such as yoghurt, which help to overcome the burning sensation of hot chillies, and cool the mouth. It is a perception that Dr Klieber likes to test on school students when they visit the Waite Institute.

"We had a school visit and I got the students to taste chillies, including Habaneros, and then see whether yoghurt is good for cooling the mouth," said Dr Klieber. "I cut one chilli into very small pieces and kept one half of the chilli to show what it looked like. One student wasn't listening and promptly ate this half Habanero," said Dr Klieber. "It took him half a litre of yoghurt to recover, but I think he will now listen to what people say in class."

The research has been published as a 20-page RIRDC report which details the best methods for growing, harvesting and processing chillies in Australia, how to store chilli products and assess their quality, and make chilli spice production competitive. The report can be found at:

Photos available at: /pr/media/photos/2000/


Contact Details

Dr Andreas Klieber
The University of Adelaide
Business: +61 8 8313 6653

Mr David Ellis
Deputy Director, Media and Corporate Relations
External Relations
The University of Adelaide
Business: +61 8 8313 5414
Mobile: +61 (0)421 612 762