Spicing Things Up: The detectives pit themselves against modern chemical analysis

Chapter 54
📂 Workshop overview: Riding on the back of their recent success solving the case of the haunted hounds, the detectives decide to have some fun, all while putting their chemistry knowledge to the test. Cornlumbos’ love of chilies leads the detectives to hunt for the hottest habanero, the tangiest tabasco, and the most sizzling scotch bonnets. To determine the heat, the detectives discuss various extraction methods and put their tongues to the test against modern laboratory equipment to see which method of determination works best.

Eggcule and Cornlumbo are sitting in the corner giggling, which prompts Miss Mapple to ask why. “We’re watching a chili-eating competition online; they’re really struggling and haven’t even had the really hot ones yet; that last chili was only 500,000 SHU,” says Eggcule. Nancy Beef asks what SHU stands for, and immediately Cornlumbo explains that SHU stands for Scoville Heat Unit. “I’ve never heard of a Scoville; it doesn’t sound very technical to me,” says Miss Mapple. Cornlumbo tells her that Wilbur Scoville, a pharmacist, developed a test in 1912 to determine the heat level of peppers by dilution. A pepper with a rating of 500,000 SHU must be diluted 500,0000 times before the heat becomes undetectable. This led to a debate between Eggcule and Cornlumbo about how they would have no problems eating such hot chilis. Their debate finally ends as Shallot Holmes enters the room and congratulates the detectives on their hard work and determination in solving the case of the haunted hounds.

“SHU stands for Scoville Heat Unit – A pepper with a rating of 500,000 SHU must be diluted 500,0000 times before the heat becomes undetectable.”

Holmes thinks about how to treat the detectives and realizes it’s been a while since their last workshop. “Ok, detectives. I think we should prepare a workshop. Does anyone have any fun suggestions?” Miss Mapple immediately has an idea “How about we do a workshop on the different methods of extraction and compare the subsequent means of analysis,” she says. Holmes is enthusiastic as the extraction process is central to several other laboratory processes. “What did you have in mind?” asks Holmes. “Well, extraction is used to isolate and purify specific components as a preparation step for subsequent analysis. Why don’t we discuss the different methods of extraction, perform an extraction, then send our extracts for different types of analysis and compare the results?” says Miss Mapple. “That sounds great; did you have anything in mind for the extraction and types of analysis?” asks Holmes. “Well, as a matter of fact, I do… Because Eggcule and Cornlumbo are SO keen on hot chilis, I thought we could extract capsaicin from a selection of chilis to determine how hot each chili is,” says Miss Mapple.

Holmes seems very pleased with the suggestion and asks what methods of determination they should use. Miss Mapple says, “Oh, I’ve already thought about that. Nancy and I shall use traditional wet chemical analysis, such as HPLC and SFC, and ONLY because Eggcule and Cornlumbo keep saying how much they LOVE hot chilis, I thought they would be willing to conduct an organoleptic analysis for us,” she says. “Ummm, errrrrrr, you mean…. You want us to taste test the chilis?” says Eggcule looking nervous. “Well, yes, I thought you said you love hot chilis – unless you’re too scared? Asks Miss Mapple. “Of course not; we’ll happily eat them, won’t we, Eggcule?” said Cornlumbo nervously. “Umm, yes, of course,” replied Eggcule. “Perfect,” shouts Holmes, who sets about acquiring some chilis for the detectives to analyze.

Holmes begins the workshop with an introduction to capsaicin.

“Rather than the Scoville taste test, chemical analysis is now used to determine capsaicin content, and a conversion factor is used to gain a SHU value. Capsaicin is a chemical irritant and neurotoxin – which means it is destructive to nerve tissue, causing neurotoxicity.” Cornlumbo and Eggcule look at each other nervously, then back at Holmes and the selection of chilis. “Capsaicin activates the same pathway of pain as the vanillotoxin-containing venom of a certain tarantula and is a fascinating example of a shared pathway in plant and mammalian defense.” Eggcule and Cornlumbo begin to sweat profusely, while Nancy and Miss Mapple can hardly hold back their laughter, thinking of the inevitable schadenfreude about to ensue.

“The hot extraction method called Randall extraction uses higher temperatures than Soxhlet extraction increasing efficiency.”

Miss Mapple recalled having previously extracted piperine in pepper, the compound that gives pepper its characteristic spiciness. The extraction was performed using the hot extraction method called Randall extraction, which uses higher temperatures than Soxhlet extraction increasing efficiency. Nancy Beef had also previously extracted pesticides from spices; extracting capsaicin would be a similar process. She recalled the efficiency of using a pressurized solvent extractor. The temperature can be increased above a solvent’s boiling point by performing the extraction at elevated pressures. Also, solvents absorb more at elevated pressure with each cycle as the solubility of components and the solvent’s viscosity increase, further increasing efficiency. Eggcule explains that Economic Continuous Extraction (ECE), known as Twisselmann extraction, could also be used. Like Soxhlet extraction, the sample is separated from the solvent; however, unlike Soxhlet, the solvent is not collected in the extraction chamber. During ECE, the sample is kept in the hot solvent and rinsed with freshly distilled solvent to increase the extraction efficiency.

Nancy and Miss Mapple decide to use pressurized solvent extraction, as the method was both fast and efficient, which meant the detectives could get their samples sent off for analysis and get the results as soon as possible – Then they could watch Eggcule and Cornlumbo perform their organoleptic tests!

During ECE, the sample is kept in the hot solvent and rinsed with freshly distilled solvent to increase the extraction efficiency

The first step was to prepare a standard solution of known capsaicin concentration in ethanol. This solution would be used to create calibrations for the UV/Vis spectrophotometer, which would later be used to determine the concentrations present in the chili pepper samples. Next was sample preparation, which involved cleaning and weighing the samples before placing them in cellulose thimbles and into the pressurized extraction instrument. Once the extraction was complete, Nancy sent her sample for HPLC analysis, and Miss Mapple sent her sample to be analyzed with a modern SFC instrument.

Using a pressurized solvent extractor – the temperature can be increased above a solvent’s boiling point by performing the extraction at elevated pressures.

It was now the moment that Nancy and Miss Mapple had been waiting for and Eggcule and Cornlumbo had been dreading. The organoleptic test! Holmes weighs a thin slice of each chili and tells them to eat each chili in turn and rate the heat on a scale of 1 to 2,000,000. Only Holmes, Nancy, and Miss Mapple knew that the three chilis lined up got progressively and exponentially hotter. Eggcule and Cornlumbo grabbed the first chili, closed their eyes, and, expecting the worst, tried to eat it as quickly as possible. They both opened their eyes and breathed a sigh of relief; the chili seemed mild and caused little discomfort. It was time for the verdict. “I’d say that was about 50,000 SHU,” says, Eggcule. “Oh no, that was nothing; I’d say 25,000 SHU,” says Cornlumbo. Holmes revealed that it was a shishito pepper and only 200 SHU. Onto the second chili, Eggcule and Cornlumbo felt confident after the first round and dived straight in. For a brief moment, everything seemed ok. Until… Eggcule’s eyes opened wide as sweat began to pour down his face; Cornlumbo looked as if he had emerged from a sauna, and Nancy and Miss Mapple could barely hold in their laughter. “What’s the verdict?” asks Holmes. “2 million, there can’t be anything hotter than that,” shouted Eggcule. “Well, it’s quite hot, but not 2 million; it must be at least a million,” says Cornlumbo. They awaited Holmes with the actual number. “That chili was the devil’s tongue pepper, and it’s rated as 250,000 SHU,” says Holmes.

It was time for the last chili. Eggcule and Cornlumbo both hoped for something milder than the last one as they realized they had overestimated their ability to handle the heat. They anxiously reach forward and grab the final chili. Nancy and Miss Mapple lean in with a sense of anticipation, and Holmes holds a straight face to not give anything away. And then the inevitable happened. Eggcule’s eyes darted around the room, and he looked as if he was going to crack. Cornlumbo didn’t fare much better as he turned red and began sweating profusely. His kernels looked as if they might pop. Nancy and Miss Mapple were also crying, but not because of the heat; they could hardly hold back their tears of laughter. Shallot Holmes rolls his eyes, “They say that genius is an infinite capacity for taking pains,” he remarks with a smile. “It’s a very bad definition, but it does apply to detective work.”

Eggcule starts running in circles, banging into things and searching for a towel as his own sweat is blinding him, Cornlumbo runs straight to the tap and starts drinking water, but as soon as he drinks the water, he screams even louder. Holmes points out that capsaicin is oil soluble, meaning it will not dissolve in water, and the water will only spread the heat around the mouth more. At this point, Miss Mapple is in fits of laughter, and Nancy almost falls off her chair. Holmes feeling sorry and somewhat guilty for the detective’s fate, hands Eggcule and Cornlumbo some milk “Here, this contains a protein called casein, which can bind to capsaicin and help wash it away”. Once the detectives regained their composure, Holmes revealed the strength of the final chili. “That last one was the Trinidad Moruga Scorpion, a chili almost 200 x hotter than a Jalapeno. It is just over 2 million SHU, so it’s no wonder you are both struggling.”

Holmes then compared the declared results with the results from HPLC and SFC analysis and revealed that both methods gave extremely accurate results with very low relative standard deviation, unlike the Eggcule and Cornlumbo analysis, which was wrong by orders of magnitude. For a brief moment, Holmes, Nancy, and Miss Mapple felt guilty for the trick they had pulled on Eggcule and Cornlumbo; however, as soon as they had gotten over the heat, they were so proud that they had eaten and survived one of the hottest chilis in the world and they could not stop talking about it.