The story

Britain is home to a new world-record breaker.

The Infinity chilli developed by Fire Foods in Lincolnshire is the world’s hottest chilli having beaten the Bhut Jolokia chilli into second place. The Bhut Jolokia hails from India where their army use its powerful heat in tear-gas grenades to immobilise the enemy. And what use have the Brits come up with for the infinity chilli? You guessed it – it has been made into a chilli sauce for dousing kebabs.

You would have to be pretty mad to eat this condiment as it tops the chart at an eye-watering 1 176 182 Scoville units. To get a sense of just how hot this is, the hottest chillies that I dare to use in my kitchen are bird’s eye chillies which are a trifling 100 000 SHU but still hot enough to be used with extreme care. For a further comparison of chilli heat see the chilli Scoville scale in the weblink below.

Teaching ideas

The science of chillies is a really interesting subject.

For example, did you know that chillies produce their burning sensation because the active substance in them, capsaicin, binds with receptors known as TRPV1 which reside on the membranes of pain and heat sensing neurons?

TRPV1 is a heat activated calcium channel, which normally only opens and triggers an impulse when a temperature above 37°C is reached. However, when capsaicin binds with it a signal is generated below this temperature – hense the sensation of a burning sensation when there is no heat.  The TRPV1 receptor is only found in mammals and is also activated by tarantula venom.

The mechanisms of the receptor and the impulses it sets up could be used as an example when teaching about the nervous system with KS4/5 students.
The reason why chilli plants produce capsaicin is because it stops mammals from eating their fruit. The molars of mammals crush the seeds which stop them from germinating when they emerge from the digestive tract. Birds do not have crushing teeth nor do they have the receptor so can therefore freely eat the chillies and disperse the seeds. A nice example of natural selection – only the hottest chillies are able to reproduce.

How the chilli was produced is another example of selective breeding of plants.The growers bred together plants with the hottest chillies until they reached the pinnacle of hotness in the Infinity chilli.

Teaching resource

I thought that this story would link in well with a bonustop chemistry lesson on molecular structure and molarity.

The Scoville rating of chillies is calculated by measuring the concentration of capsaicin. This is done using HPLC (high performance liquid chromatography) and it is a nice example to use when teaching this to KS5 chemistry students.

One part per million (ppm) of capsaicin is the equivalent of 15 Scoville units. A quick calculation led me to the conclusion that the infinity chilli contains an unbelievable 78g/l of capsaicin!

The PowerPoint presentation asks KS4 and KS5 students to this calculation backwards.

There are two different starters (one for KS4 and one for KS5) which asks them to work out the RMM of capsaicin (answer: 305) and then an activity where they are told the molarity of the infinity chilli and they calculate its Scoville units to see if it beats the Bhut Jolokia into second place (it does – if they do it right)

Weblinks

Firefoods – home of the Infinity chilli (if you buy some of that sauce let us know what it’s like!)

Nice graphic that shows the Scoville rating of different chillies

Some interesting information on the chemistry of chillies

Want to inspire your students to become chilli breeding scientists? Show them this video

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