Nano-whatever is all the rage. They're a big deal because they can make a blacker version of black and lots of other things but what does that even mean?

Richard Compton and his team at Oxford University are here to help make carbon nanotubes understandable to everyone - namely, by making it relevant to food. They have developed a sensitivity technique to measure the levels of capsaicinoids, the substances that make chilis hot, in samples of hot sauce. They report their findings in The Analyst.

The current industry procedure is to use a panel of taste-testers, which is highly subjective. Compton’s new method unambiguously determines the precise amount of capsaicinoids and is not only quicker and cheaper than taste-testers but more reliable for purposes of food standards; tests could be rapidly carried out on the production line.

They tested a range of chili sauces, from the mild “Tabasco Green Pepper” sauce to “Mad Dog’s Revenge”, which sports an extensive health warning and liability disclaimer.

The well-established Scoville method – currently the industry standard – involves diluting a sample until five trained taste testers cannot detect any heat from the chilli. The number of dilutions is called the Scoville rating; the relatively mild Jalapeño ranges from around 2500-8000, whereas the hottest chilli in the world, the “Naga Jolokia”, has a rating of 1000000.

High performance liquid chromatography (HPLC) can also be used, but this requires bulky, expensive equipment and detailed analysis of the capsaicinoids.

In Compton’s method, the capsaicinoids are adsorbed onto multi-walled carbon nanotube (MWCNT) electrodes. The team measures the current change as the capsaicinoids are oxidised by an electrochemical reaction, and this reading can be translated into Scoville units.

The technique is called adsorptive stripping voltammetry (ASV), and is a relatively simple electrochemical method. Compton says, “ASV is a fantastic detection technique for capsaicinoids because it’s so simple - it integrates over all of the heat creating constituents because all of the capsaicinoids have essentially the same electrochemical response.”

Compton has applied for a patent on the technology, and Oxford University’s technology transfer subsidiary ISIS Innovation is actively seeking backers to commercialise the technique.

Citation: Roohollah Torabi Kachoosangi, Gregory G. Wildgoose and Richard G. Compton, 'Carbon nanotube-based electrochemical sensors for quantifying the heat of chilli peppers: the adsorptive stripping voltammetric determination of capsaicin',Analyst, 2008, DOI: 10.1039/b803588a