About chilli peppers
Allen Hibberd, Department of Primary Industries and Fisheries, Queensland
What are chilli peppers?
Chillies are simply capsicums that are hot to taste. There is only a single
gene marking the difference between sweet capsicum and chilli fruit; it produces
the chemical known as capsaicin that causes the sensation of heat. In all
other respects the two types of fruit can be identical. For example, there
are varieties of 'hot' bell capsicums, and there are chilli types
that are not 'hot'.
Capsaicin is the family name of a group of eight alkaloids that are produced in the fruit by the single genetic locus. These alkaloids differ slightly in their chemistry. The main difference is the speed with which they react with moisture in the mouth to cause the heat sensation: it can be instantaneous or delayed for a short while, but the net result is much the same.
Most of the capsaicin is in small 'glands' around the placental tissue that holds the seed. Small fruit have more placental tissue relative to the red 'flesh' than do large fruit. That is why small-fruited types of chilli are generally hotter than types with large fruit. Varieties differ in the concentration and principal type of capsaicin present.
How is heat measured?
Experienced tasters can accurately determine different levels of heat. This is important for exploiting niche markets, for example sauces labelled mild, medium or extreme heat. The taste test is, of course, very rapid.
Various chemical tests also are used. The most common is the Scoville test first developed in 1912. It measures 'heat' as Scoville units in a given weight of fruit tissue. Chillies with a slight bite such as the mild bell type may have 100 to 500 Scoville units, but the blistering habeneros have between 200 000 and 300 000 Scoville units.
How many different types of chilli are there?
There are many. They are generally grouped according to fruit size and shape, and range from the tiny piquin chilli, about 8 mm long, to the large, bell type weighing 150 to 300 grams. There are usually many different varieties in each type of chilli. Varieties of any desired type are easily obtainable.
Heat levels
Different types of chilli have their own reputations for heat levels. Birdseyes are regarded as very hot but the large, hot bells are mild. Different varieties within a particular type of chilli may have different heat levels, for example, one variety of birdseye type may be milder than another.
Types of chillies
The following is a list of the main types of chilli peppers grown in Queensland. There are other types not listed here.
Bells
These are identical to the sweet bell capsicum except they are mildly hot. There may be as few as five or six fruit to as many as 20 fruit per bush. Each fruit has three or four locules (lobes) and the 'flesh' is thick.
Birdseye
Fruit are short, about 40 to 50 mm long, thin, two lobed, sharply pointed, with flesh about 1.5 mm thick. Colour of immature fruit may be dark green or light green depending on the variety. Fruit are held erect on the bush, and there are many fruit per bush. The most recent varieties have short bushes with fruit clearly displayed at the top. This feature makes them suited for trying once over mechanical harvesting. They are, however, continuous bearers. Very high yields have been reported with hand harvesting over a nine month period. Heat level may be in the range of 30 000 to 50 000 Scoville units, making them very hot. They are usually sold on the fresh market.
Cayenne
These are long, thin, sharply pointed fruit that may be either held erect on the bush or hang pendant depending on variety. Length of fruit also varies with variety and there are usually many fruit per bush. Flesh thickness is about 2 mm. Heat level varies with variety in the range of 5 000 to 25 000 Scoville units, making them medium heat. They usually are fresh market fruit.
Habanero
Actually a different species from all other chillies mentioned here, the habanero is blistering hot. Fruit are thin fleshed, and shaped similar to a Scotch bonnet or Christmas bell decoration. Mature colour may be orange or red depending on variety. They are suited for niche markets.
Horn
These have the length of cayennes but are broader, about 25 mm, and usually are slightly curved. They are of an ideal size to fit, whole, on the side of a dinner plate, and often are consumed in that way. Flesh is 2 to 3 mm thick. They are not large enough for processing and so are a fresh market type. Heat level varies greatly with variety: about 1 000 to 10 000 Scoville units, making them mild to medium heat. This is a popular type in Taiwan and Korea from where many varieties originate.
Jalapeno
Pronounced "hal-uh-pen-yah", this type is a great favourite in Mexico and USA where the industry is very valuable and has grown rapidly. Fruit are about 9 cm long and 30 to 40 mm wide. Flesh is exceptionally thick, about 4 to 5 mm, making these fruit very heavy for their size (approximately 30 g). Jalapenos have excellent flavour and are ideal for fresh or processed products. The US market normally consumes green fruit of mature size because surface 'netting' similar to netting of rockmelons develops as the fruit matures. Netting is preferred in Mexico, because flavour is best in red/ripe fruit. Heat level varies widely with different varieties from very mild to medium heat (1 000 to 15 000 Scoville units). Netting has made the jalapeno less attractive to Australian consumers.
Large processing types
Fifteen to 20 cm long, 3 to 5 cm wide, two lobed, 3 to 5 mm thick flesh, and weighing 35 to 70 grams, this type is the mainstay of the US processing industry. Heat level varies widely with variety from mild to medium heat (1 000 to 15 000 Scoville units).
Large processing types (and large fresh market types) have fewer fruit per bush than the smaller fruited types. Fruit may be so long that the basal ends of the first fruit set on the bush may rest on the soil or plastic mulch. Contact with the soil makes them more prone to rot. Losing even a small number of these fruit to decay may mean a substantial loss of yield. Growers may need to adjust their fertiliser rates to produce taller bushes before fruit set.The risk that comes from tall bushes, however, is that fruit setting may be later than expected, and branches may break more easily.
Large fresh market types
This is a type similar to the large processing type except that fruit are about one/third smaller.
Dried fruit types
Any chilli can be dried and sold either whole or ground into powder or pieces for specific niche markets. Small pieces, sometimes known as 'sprinkles', are often used in restaurants. A desirable colour combination for sprinkles is yellow from the seeds with red from the flesh, therefore small fruit with thin flesh are preferred.
Where can chillies best be grown?
Chillies can be grown on a wide variety of soil types provided it is well drained and a minimum of 30 cm deep, with pH in the range of 6 to 7. Irrigation is necessary in most growing areas.
Temperatures are critical. Like all capsicums, chillies grow very slowly below 15°C, and are frost sensitive. Temperatures exceeding 30°C interfere with fruit setting.
Bushes are brittle and can be damaged by strong wind. Sunburn damage to fruit can be aggravated by wind. Windbreaks are necessary in some areas.
Summer production can be from all areas not subject to extremes of high temperature, and winter/spring production in those areas not limited by cool temperatures. Any region growing bell capsicums and tomatoes can produce chillies.
There are many factors that influence heat level. The most important factor is the variety of chilli. As a general rule, the more luxurious the growth of the bushes, the milder the heat level; that is, a variety with mildly hot fruit will produce very mild fruit if grown luxuriously with no limiting factors but have moderately hot fruit when grown in harsh conditions. Poorer soil types and hard growing conditions will generally produce lower yields of hotter fruit.
Processors require a heat level that is uniform between fruit from different bushes of the same variety. Variation can be quite large and unpredictable. It is a real problem when mild varieties are grown. It is better to produce varieties of medium or greater heat so that the average heat level compensates for variation between bushes. Processors can vary the heat level of chilli products by mixing with other components.
Yields
Fruit yields of 1 to 1.5 kg per bush have been obtained from trial work with different varieties grown at a population of 34 000 plants per planted hectare in south east coastal Queensland. Fruit were picked once each week for four or five weeks during summer or early autumn. Much higher yields have been reported e.g. up to 5 kg per bush over 9 months continuous cropping from the birdseye variety Inferno. Yields will be lower with once-over machine harvests.
Pests and diseases
Small fruited chillies generally suffer less from the foliar disease bacterial spot than do large fruited types, jalapenos and sweet bell capsicums. Bacterial spot is likely to be a problem in warm areas where rainfall is common. Powdery mildew can be common on all variety types in dry production areas such as the dry tropics. Sudden wilt, probably caused by Pythium and Fusarium, often causes the loss of a small proportion of plants during summer months. Potato virus Y (PVY) may result in stunting and reduced yields of affected plants and is spread by aphids. Few varieties of chilli are resistant to foliar viruses but PVY has not been a significant problem in south eastern Queensland in the authors experience. There is also a range of other minor diseases that may affect plants and fruit at pre or post-harvest.
Varieties of the large processing type grown widely in New Mexico are not well adapted to the more moist and humid climate of south eastern Queensland. Plants suffer from bacterial spot to a greater degree than most other varieties but this is less likely to be a problem in drier areas.
The same insect pests that attack sweet capsicums also attack chillies except that fruit fly damage appears to be less frequent in Queensland.
Machine harvesting
Growers have imported machine harvester technology into Queensland and improved it to suit local conditions.
In 1992, a machine harvester that had been originally designed for fresh beans was tested on several different types of chilli. Thin or small fruit such as the thin cayennes and birdseyes were not injured and there were few breakages. Broader fruit, such as the jalapenos were damaged by the revolving metal fingers.
Once-over harvesting of jalapenos can easily be achieved: cut the bush at ground level with secateurs, up-end it and simply shake the fruit off. The fruit are so heavy relative to their size that they fall off easily. Fruit can then be graded to size and colour.
Further information
The Capsicum and chilli home page has a wide range of information about chillies and capsicums.
DPI&F Notes:
DPI&F information and services
- To access DPI&F's information and services, Queensland residents can contact the DPI&F Business Information Centre on 13 25 23 for the cost of a local call, from 8 am to 6 pm Monday to Friday (excluding public holidays). E-mail callweb@dpi.qld.gov.au. Non-Queensland residents phone (07) 3404 6999.
- Current national information on agricultural chemicals registered for use on all crops is available on the Infopest CD-ROM. Write to DPI&F, GPO Box 46, Brisbane, Qld 4001, E-mail infopest@dpi.qld.gov.au, visit the Infopest web page, or phone (07) 3239 3967 for further information.
Industry links
- Industry links is a page of links to various sites of interest to horticultural growers.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries, Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last updated 27 September 2007
