Fermentation

Fermentation This is a biological reaction that slowly splits complex organic compounds into simpler substances. It is the conversion of carbohydrates into alcohols and carbon dioxide, or organic acids using yeasts, bacteria (or a combination) under anaerobic (no oxygen) conditions. Lots of foods rely on fermentation at some point in their production: sourdough bread, beer, wine, mead, cider, miso, soy sauce, chocolate, tea, cheese, sour cream, yogurt, cured meats, vanilla extract, vinegar, hot sauce, dill pickles, and more!

Louis Pasteur He discovered that the fermentation of fruit by yeast produced alcohol in wine-making He also discovered that certain bacteria in the wine were causing the wine to spoil, as they were producing vinegar instead as they fermented. Discovery of Pasteurization - a process of using heat to kill bacteria in liquids.

Fermentation caused by micro-organisms - bacteria, yeast, and mould. can be damaging - causes food to spoil or become rancid can be beneficial - preserves food for long-term storage improves flavour and enjoyment of food makes some food usable - coffee and chocolate would not be enjoyable without fermentation produces alcohol

Bacterial Fermentation a form of anaerobic respiration - this is a cellular process that occurs in the ABSENCE of oxygen. converts glucose (sugar) into various acids or gases lactic-acid bacteria acetic-acid bacteria carbon-dioxide bacteria

Lactic-Acid Bacteria (LAB) produce lactic acid through fermentation used in making yogurt, sour cream, cottage cheese, cheddar cheese, dill pickles, bottled olives, sauerkraut glucose is converted into lactic acid bacteria C6H12O6 ---------> HC3H5O3 + Energy glucose lactic acid There are many kinds of lactic acid bacteria, each with their characteristic flavours.

Vegetables that Ferment! Vegetables are covered in lactic-acid bacteria (LAB) When you submerge vegetables in a liquid (i.e. water), the LAB eat the sugars and produce lactic acid, which preserves the food and makes it tangy (think dill pickles!) LAB is the dominate culture, crowding out the bad bacteria

Acetic Acid Bacteria produce acetic acid through fermentation used in making vinegar from fruit glucose is first converted into alcohol by yeast (just like in wine making) acetic acid bacteria then convert the alcohol into acetic acid there are many different types of acetic-acid producing bacteria, each with their characteristic flavours Step 1: glucose + yeast = ethanol Step 2: ethanol + acetic acid bacteria = acetic acid

Carbon-dioxide bacteria produces carbon-dioxide through fermentation pockets of carbon dioxide gas are trapped, producing the characteristic holes in products like Swiss cheese

Yeast Fermentation a microscopic fungus that convert glucose into ethanol (alcohol) and carbon dioxide used in wine and beer making, and in bread making (leavening agent) requires critical temperature control (27oC is perfect) wine-making - CO2 is allowed to escape, ethanol is kept to produce the beverage bread-making - CO2 is trapped in the dough and causes it to rise salt contents in bread are critical too much salt prevents or slows fermentation too little salt and the dough is not strong enough to trap CO2 and rise Process: glucose (with yeast) = ethanol + carbon dioxide C6H12O6 = C2H5OH + CO2

Mold Fermentation molds are microorganisms that break down cellulose (fibre) in foods our bodies cannot digest cellulose, molds break down the coatings of many grains so that the body can use the nutrients. alter the flavour and texture of foods, making them palatable and enjoyable (old cheese, blue cheese)

Popular Fermentation Coffee: coffee trees grow cherry-like berries. The coffee beans are on the inside. The berries are fermented using bacteria and enzymes after harvesting to prepare the beans Tea: after drying, the tea leaves are rolled repeatedly for 2 hours and then allowed to ferment for a few hours, gaining their characteristic colours and flavours Chocolate: Cacao beans are allowed to sit in the sun for several days and ferment with bacteria and enzymes, allowing the structure of the beans to break down and develop flavours