Chilli - is this one really hot?
In 2011 I wrote a series of articles on this variable plant that excites the passions of gardeners, foodies and heat fanatics. To recap, they are in the genus Capsicum and refer to the fruits of five species and their hybrids although the genus has in excess of 25 species. They come from the Americas where several species have been in cultivation for over 5000 years. The genus Capsicum is a member of the family Solanaceae (the Nightshade family) which includes many staple food plants like capsicum, potato, tomato, egg plant and a couple of drugs; tobacco and Daytura. It also includes Petunia and the Belladonna.
The main difference between a capsicum and a chilli is the presence of the chemical capsaicin which is what gives Chillies their heat. This is the key ingredient of the anti personal ‘Capsicum Spray’. It generally occurs in the septa in the fruit and in the white pith around the seeds. It does not occur in the seeds themselves and is present in smaller quantities in the flesh of the fruit. It is believed that the production of capsaicin (and a couple of closely related compounds) is a deterrent to herbivores and fungal infection. They react to certain receptors that are only present in mammals.
The heat has evolved as a way of controlling harmful soil born fungi and deterring mammals from eating the fruit and destroying the seeds. It matches up with specific receptors on nerve cells in the mammalian body. They trick the brain in to thinking there is a strong 'heat' stimulus affecting the nerve ends.
Capsaicin is the ‘hot’ part of the chilli which is what so many fans are chasing. Many of us like both the heat and the flavour so it is wise to know how hot each cultivar is. This is really a subjective characteristic and what is hot for one person maybe mild for another. In 1912 Wilbur Scoville an American pharmacist devised a system for rating the heat. His rating system was originally called "The Scoville Organoleptic Test" but was eventually shortened to the ‘Scoville Scale’ and chillies are given a Scoville Heat Unit (SHU). It related the level of sugar syrup needed to negate the chilli heat to give the SHU.
This was done by five experts tasting the chilli mixture. As such this is still slightly subjective so a ratio of capsaicin levels to SHU levels was developed. It seems that the SHU rating is 16 times the concentration of capsaicin. A form of chromatography is used to determine the level of capsaicin present in a sample and this is then multiplied by 16 to give the SHU rating.
There is still some level of variation in this method but it is generally accepted around the world as the official method of detailing the heat of a particular chilli. It is the rating system recognised by the Guinness Book of World Records. In 2006 it noted that the Chilli Bhut Jolokai was the world's hottest chilli at 1.1million SHU. In March 2011 an Australian plant was given this honour at 1.4 million SHU. This was plant of the cultivar Trinidad Scorpion Butch T.
There are five species cultivated around the world are: C. annum, C. frutescens, C.pubescens, C. chinense and C. baccatum. All species come from north, central or southern America but the plant has been so widely spread that many plants are thought to be native to other regions. Bhut Jolokai and Butch T are hybrids of C. chinense and C. frutescens. Between the Bhut Jolokai and Butch T have been several other cultivars that have been the 'world's hottest' for short periods.
As with most plant types that are predominantly grown by seed and have so many cultivars there can be a lot of variation in seed grown plants. Bhut Jolokai comes relatively true from seed where as the is still a lot of variation in seed grown plants of Butch T. There also seems to be a strong relationship to the nutrient source and levels of ground moisture and humidity to the heat of the fruit produced on a particular plant. This means there is a fair level of heat variation between fruit from a single plant, between individual plants and within a particular cultivar depending on where and when the plant is grown and the fruit is harvested.
With the complexity of the rating system and the fact that at the top end it is very hard for the human body to differentiate between 1.1 and 1.2 million units it is very hard to determine how true to form a particular plant is. Unlike the 'colour', 'shape' or 'size' of a plant it is hard for a grower to determine how hot their plants are. Even so, like with most commercial plants that have a lot of internal variability, I suspect that plants like Butch T will need to be grown by cutting.
For most of the old fashioned Jalapeno (around 3000 SHU) is hot enough and these extreme heat fruit are for those who enjoy the endorphin rush released when we eat them. I love the taste and health benefits of this magical fruit and find it a great ingredient to so many different food styles.