MEDICINE&SCIENCE
More at on a microscopic level, he explained. It’s too dry an environment for bacteria to grow.
A process that involves adding citric acid and leaving milk at room temperature for 12 or 16 hours produces both buttermilk and sour cream, depending on whether the cream is separated out.
Heating milk to about 185 degrees and then leaving it around 110 degrees for several hours is all it takes to start turning it into yogurt. The lactic acid produced during that process gives yogurt its sour taste, while a chemical compound known as acetaldehyde is responsible for the signature tart flavor.
Yogurt’s acidity is not just for its flavor, though — it also prevents pathogenic bacteria from growing, instead leaving only the gut-healthy probiotics for which the product is touted.
There is even a scientific term for what happens when the liquid whey separates out of yogurt — syneresis — but Crane explained that there’s nothing wrong with it. Some types of yogurt are better than others at maintaining stability as gels — particularly nonfat varieties, many of which have starchy flavors because stabilizers have been added.
In classroom experiments, the students learned how to at least start the process of fermenting grapes into wine, and how to (and not to) make sauerkraut. One proper batch was made by sealing salted cabbage in a jar, leaving it submerged in the brining liquid that is naturally produced, while another showed that mold and malodorous bacteria can appear if the cabbage is left exposed to the air.
Lessons about wine explained how different compounds create different “notes” of scent. A chemical reaction with natural cork can spoil as much as 10 percent of wines, Crane explained, and that is why, traditionally, restaurants give diners a taste from a bottle before they commit to it.
In final projects, students explored everything from the Australian spread known as Vegemite to unique varieties of beer and cheese to sourdough bread.
The “starters” — fermented mixes of water and flour — that give sourdough bread its trademark flavor are like pets, explained Willoughby and Laura Nugent, a sophomore cognitive science major.
“There are sourdough hotels,” Nugent said, where someone will mind and feed your starter to keep it alive. The starter used by the famous Boudin Bakery in California has been alive for more than 150 years and contains a strain of bacteria named Lactobacillus sanfranciscensis in honor of its hometown.
Brao and classmate Turner Schwartz explained that there isn’t anything unusual about the brewing process behind Trappist beers — they can vary from 4 percent to 12 percent alcohol content by volume and come in many varieties.
What makes them so sought after is instead their rarity. The Roman Catholic monks who brew them abide by a strict prohibition on profiting from the endeavor, only making enough in sales to keep their monasteries running.
Though much of the class is devoted to alcohol, it’s not an excuse for students to get buzzed. Included in a slide from Crane’s presentation one Friday was this disclaimer: “A random subsample of wines are heavily salted and very, very not tasty.”