Science and Cooking: From Haute Cuisine to Soft Matter Science - Fermentation

As I posted way back when, I enrolled in an on-line course about the relationship between science and cooking. Here's what went on during Week 10.

• The star power is upped this week with guest lecturers Wylie Dufresne of wd~50 and David Chang of Momofuku making appearances. Ted Russin of The Culinary Institute of America also makes an appearance. 
• Harold McGee informs us that food fermentations are the work of living microbes; they're essentially invisibly small cooks that change foods for the better.
• Foods that owe their popularity to fermentation include dry cured sausages, pickles, breads, the vinegar in vinaigrette, cheeses, chocolates, wine and beer and ciders and the distilled beverages made from them. These are all thanks to bacteria and fungi like Saccharomyces cerevisiae and Leuconostoc mesenteroides.
• The most common food fermentations develop spontaneously. They're spontaneous because the microbes that are responsible are all over the place, in the air and in the soil and on surfaces of everything. And they thrive on the sugars in nutrient-rich materials like plant tissues and animal secretions like milk. 
• The second big group of food fermentations is produced by yeasts, usually Saccharomyces cerevisiae, but also others. They produce alcohols and carbon dioxide from fruit juices and other liquids that are rich in sugars. 
• There's a third group of fermentations is based on an Asian method for fermenting starchy foods, like the seeds of grains and legumes. Yeasts and lactic acid bacteria can't deal with starch directly. Sometime before the second century BC, Chinese brewers domesticated a species of mold, a kind of Aspergillus, which prepares starchy foods for the yeasts and the lactic acid bacteria by converting the starch into fermentable sugars. At the same time that it does that, the mold generates its own distinctive aromas. With the help of this Aspergillus, called koji in Japan, sake and other alcohols are made from rice in Asia. It's also how soy and tamari sauces and miso pastes are made. 
• We are told that the fermentation reactions in yeast, or in bacteria, are due to enzymes. An enzyme is a protein that is a type of catalyst; a catalyst is a molecule that increases the speed of a favourable reaction either by helping to break bonds, or by helping to make bonds form, without being used up.
• An example of a catalyst is baking soda or lye, which speeds up Maillard reactions that contribute to browning and flavour. 
• As magical as catalysts appear, they cannot make unfavorable reactions become favorable. 
• For more on fermentation, here's David Chang and one of his minions:
• In terms of the bond breaking, enzymes do this by either rearranging the molecule, or by affecting the atoms in the molecules in some way. In terms of making bonds form, enzymes do this by bonding to two molecules, or bringing them closer in proximity. The bond can then form more easily, because the molecules are positioned in a way that makes the bond happen more easily. Enzymes need to be very specially designed to fit the particular molecules they work on, so for each type of chemical reaction that an enzyme catalyzes, it is designed to help that reaction.
• The enzymes bromelain and papain are enzymes from pineapple and papaya. Because these are often found in meat tenderizers, they are used a lot in recipes because they break down the proteins in meats, making it tenderer.
• The browning of fruit or vegetables is also due to enzymes. Biting or cutting releases enzymes in special compartments of the cell, and they react with other compounds in the fruit or vegetable. 
• Thanks to one of Dufresne and Russin's collaborations, we can now glue one piece of meat or one protein to another, thanks to meat glue, an enzyme also known as transglutaminase.