Filed by Steve Ritter
Before coming to Brazil, I was inundated by suggestions that I had to try a caipirinha, Brazilians’ favorite alcoholic mixed drink. The caipirinha is a simple cocktail made from sugar, limes, and cachaça, which is a type of rough-tasting brandy made from—what else—sugarcane. It’s similar to rum.
On Sunday afternoon, the U.S.-Brazilian biofuels delegation was invited to attend a barbeque hosted by chemists from the Federal University of São Carlos. There was plenty of succulent grilled beef and chicken, manioc (cassava), fresh oranges and limes picked straight off the tree, and of course, caipirinhas.
Being a group of chemists, the discussion naturally turned to the chemistry behind the potent caipirinhas. I learned quite a bit from our Brazilian hosts and then ventured on my own to learn more.
Cachaça is made just like ethanol, as we saw earlier at the Santa Elisa plant we visited. The sugarcane is crushed to remove the juice, some water is evaporated to concentrate the sugar, and yeasts ferment the sugar to ethanol. A single distillation leads to cachaça containing 40–45% alcohol.
Distillers have a variety of ways of preparing cachaça, several of our Brazilian friends related. Stainless steel vessels are used by some processors to make clear, unaged liquor, which is typically used to make caipirinhas. Copper pots are also used to make cachaça, with the copper reportedly imparting subtle differences in the flavor.
Some types of cachaça have a golden color, which comes from aging in wooden barrels (many types of native wood are used) or by adding herbs, such as orange tree leaves. Someone mentioned that distillers sometimes bury the barrels in the ground for aging, but no one seems to know what enhancement that might provide. The golden cachaça typically is drunk straight up in a small glass, like brandy.
Anyway, with a bottle of cachaça at hand, making caipirinhas is easy: To a pitcher or glass full of ice, add cachaça, lots of lime slices, and lots of sugar. The sugar should settle out thickly on the bottom of your glass, then with a stirrer or straw, you mix in as much sugar as you like with the lime and cachaça.
But nothing is so simple in Brazil, as João Batista and Paulo C. Vieira, natural products chemists at São Carlos, explained. Some people prefer leaving the peel on the lime slices that go into the drink, whereas others insist on removing the peel or just squeezing in juice and pulp. The outer peel of citrus fruits such as limes contains limonene, a terpene. And the inner part of the peel contains flavonoids, which are a little bitter. These compounds add flavor to the drink, which some people like, and others don’t.
And there are about a half-dozen varieties of limes that grow in Brazil, Batista added. For example, one type we tried looks more like an orange (shown right), which, in typical Brazilian fashion, makes things complicated but more interesting when it comes to doing something like making caipirinhas.
Although there are many ways to make caipirinhas, there is only one good way to enjoy them—relaxing with friends and colleagues, as demonstrated by graduate student Daniel A. Bortoleto (opening photo) of the University of São Paulo, Ribeirão Preto, after a long day on our biofuels tour.