Getting volatile! The detectives test their knowledge of analytes in beer.

Chapter 48
📂 Case overview: Things get volatile as the detectives discuss whose country makes the best beer. They argue over what factors make the best beer and why; this leads to Shallot Holmes putting their chemistry knowledge to the test. The various analytes of interest and their effect on the flavor and qualities of the beer are discussed, along with the various methods of determination. Should beer be warm and flat, as the British detectives suggest, or cold and fresh, as the Detectives from the US suggest, or is strength the deciding factor, as the Belgian in the group suggest? Read on to find out.

The detectives reconvene after their successful trip to Italy, where they learned all there is to know about semolina. Each of the detectives has taken the client’s advice, made a semolina pudding, and put their own spin on the recipe. “I remembered the client’s comments about the Lebanese pudding and made mine with whipping cream and pistachios,” says Holmes. Nancy Beef tells the detectives that she put her baking skills to the test and baked hers. Cornlumbo had done as he said he would and covered his pudding in chocolate, and Miss Mapple made hers with a dash of rosewater. “How do you eat yours, Eggcule?” asked Nancy Beef. “I made my semolina pudding with Dubbel,” says Eggcule. The detectives all look confused, apart from Shallot Holmes, who nodded approvingly. Eggcule went on to explain that Dubbel was a dark brown Belgian beer with a strong flavor of dark fruits and a mildly spiced flavor profile. “Oh! I’m not sure I’d like that, I’m not a big fan of beer, but if I do drink beer, I like a nice cold refreshing bubbly light beer,” says Nancy. Miss Mapple immediately responds, saying, “I agree that beer should be light, Belgian beer is far too strong, but beer should not be cold; a good ale should be at room temperature and certainly not fizzy”. Cornlumbo looks horrified at the idea of room-temperature beer and says he agrees with Nancy that beer should be cold, fizzy, and light. “No, no, no, Light beer has no flavor, I agree it should be cold and fizzy, but beer must be dark and strong,” says Eggcule.

Seeing that the detectives are getting worked up, Shallot Homes thinks he has a way of reducing the volatility amongst the group. “Well, I can see we have found a topic that you all seem very opinionated on,” says Homes. “How about we test your knowledge and see who knows the most about beer? As we are not solving a case for a client this week, I shall pose a series of questions, and the winner shall receive a case of beer of their choice, be it flat, fizzy, warm, cold, light, dark, whatever you like, sound good?” says Holmes. The detectives are very happy with his suggestion, “May the best detective win!”

Holmes begins the test of the detective’s knowledge and asks what factors influence flavor in beer. Eggcule begins by explaining how dark Belgian beer gets its unique flavor. “Dubbels dark color and flavor is a result of the addition of caramelized beet sugar, which ferments into alcohol, contributing to the high alcohol level and dry finish,” says Eggcule. For extra brownie points, he continues, “The brown coloration comes from the Maillard reaction that occurs as the sugar is caramelized; as temperature increases, the reactive carbonyl group of the sugars reacts with the nucleophilic amino group. The chemical reaction between the amino acids and reducing sugars gives browned food its distinctive flavor, such as biscuits, bread, baked goods, and Belgian beer. It is this reaction that makes Belgian beer taste so delicious, and the reason why pale lager beer from the USA is so tasteless.” Cornlumbo immediately takes offense at this attack on his nation’s beer and immediately tries to get Holmes on his side. “Clearly, all that strong Belgian beer has deteriorated Eggcule’s tastebuds, and he can no longer appreciate the subtleties of a good American Pale Ale. The distinct, delicious, and delicate flavor comes from the pronounced hop character and flavor. Several alpha acids and essential oils contribute to the characteristic citrusy and floral aromas that remain undetectable to Eggcule’s leathery tongue. The yeast can also influence taste; byproducts of fermentation, such as diacetyl, can add a buttery flavor.” Shallot Holmes is impressed and turns to his British colleague, Miss Mapple, and says, “It looks as though we need to make a case for our nation’s beer; what do you think?” Miss Mapple, keen to make a good impression, makes her case. “Cornlumbo mentioned the influence of yeast on the flavor of beer, and I feel that this is one thing that distinguishes good British Ale from the fizzy, cold, lager beers that Nancy seems to prefer. Lager yeasts produce sulfur dioxide during fermentation, which affects the flavor intensity of many beer aldehydes, imparting a sulfury character to the beer. Sulfur dioxide is also added as an antioxidant in some markets, and I, for one, do not like the taste it imparts, which is not present in ales or wheat beers.”

Before the Belgian and American detectives have a chance to make further arguments, Holmes decides to push the detective’s knowledge a bit further. “Well done detectives! you have all made some good points about the factors that influence the flavor of beer, but I would like to know how you would measure these influencing factors. Eggcule, what do you think?” Eggcule explains that the alcohol level in Belgian beer that the other detectives seemed so hung up on could be measured through steam distillation. He describes how steam distillation can be used for the analysis of alcohol as it has a lower boiling point than water and can be vaporized and separated from the non-volatile components. After steam distillation, the alcohol is determined via a density meter. Nancy Beef jumped in to say that stream distillation can also be used to measure the diacetyl Cornlumbo had mentioned, which gives beer its buttery taste. She explains that diacetyl is one of several Vicinal Diketones, a group of flavor components in beer. “For the type of beer that I prefer, with a light, clean, and fresh taste, vicinal diketones are undesirable, and excessive levels can indicate either a bacterial infection or improper fermentation,” says Nancy Beef. Miss Mapple pointed out that she had solved a case for a client that involved vicinal diketone determination and that steam distillation was also a fantastic way of determining sulfites in beer. In fact, like alcohol, SO₂ had to be monitored for compliance and labeling requirements. For SO₂ determination, the optimized Monier-Williams method was the best analytical technique. This method involves the liberation of SO₂ gas from the sample by aeration and acidification, followed by the absorption of SO₂ in hydrogen peroxide, resulting in sulfuric acid. The concentration of SO₂ is then determined with potentiometric titration in a diluted H₂O₂ solution, using a pH electrode to detect the endpoint, which is more accurate than a colorimetric indicator.

“Finally, you’re all in agreement,” says Holmes. “After all your arguing about what makes the best beer, you at least agree that steam distillation is the best method for the determination of a vast number of analytes in beer. Just as steam distillation removes the volatile compounds in a solution, it has also managed to remove the volatility among the detectives! And as I dare not reintroduce any volatility to the group, and because I think you have done a great job, I declare you all winners. You may each choose a case of your favorite beer to take home – a case I am certain you detectives will relish getting to the bottom of!”