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The Fermentation of Food Chapter 22 The good, the bad, and the smelly What food or beverage comes to mind when you hear the word fermentation? Fermentation in History Louis Pasteur: Page 341 Hypothesised that certain bacteria was spoiling wine. Suggested that wine be heated to kill bacteria. Pasteurization of milk. Making Use of Fermentation Extended shelf life of food (ex. Cheese) Eases Digestion (ex. Wild rice) New [better] flavours (ex. Chocolate) The Fermentation Process Cell Respiration – cells of your body need energy they get it through this process. Oxygen is required during the last stage of respiration. Respiration Processes Aerobic respiration VS Anaerobic respiration What is the difference? Fermentation is sometimes called anaerobic respiration. Early stages of respiration can occur without oxygen. Without oxygen respiration cannot continue. Fermentation splits complex organic compounds into simpler substances. Sugar is changed to carbon dioxide and alcohol. What causes this process to occur in foods and beverages? Page 343 Sources of Bacteria Occur naturally in plants – cucumbers and cabbage have bacteria on them when they are harvested. Microorganisms found on these are called native or indigenous microorganisms. Added to food products – lactic-acid bacteria. – – Streptococcus thermophilus Lactobacillus bulgaroicus Produced commercially. – Preserved through drying, freeze drying, or concentrating and freezing. Bacterial Fermentation Four types 1. Lactic-acid 2. Acetic-Acid 3. Carbon-dioxide 4. Proteolytic (least common) bacteria 1. Lactic-Acid Bacteria Used in production of yogurt, sour cream, cottage cheese, cheddar cheese, dill pickles, olives, sauerkraut, and vanilla Glucose is converted into lactic acid and energy Formula: bacteria C6H12O6 → 2HC3H5O3 + Energy Glucose Lactic Acid 2. Acetic-Acid Bacteria Produces Vinegar Two steps involved First step – sugar from the fruit is fermented to ethyl alcohol (yeast makes this happen). Second step – acetic-acid bacteria attack the alcohol that was produced. – Ethyl alcohol combines with oxygen, oxidation occurs. 3. Carbon-dioxide Yeast Fermentation – process converts glucose into ethyl alcohol and carbon dioxide. During fermentation – yeast grows and produces carbon dioxide at different rates. – Temperature is critical Too cool fermentation will not take place. Too hot will kill the yeast. Yeast needs sugar to produce carbon dioxide (Feeds the yeast) Salt will cause the fermentation to slow down.