Microbiology of Alcohol Fermentation (Ex. 65)
- Some products of fermentation are generally foods and beverages that are produced by different strains of yeasts or bacteria. Yeasts such as Saccharomyces and bacteria like Lactobacillus and Acetobacter. Some examples of fermented products include beer, wine, vinegar, buttermilk, cottage cheese, sauerkraut, pickles, yogurt.
- Fermentation is a means of food preservation because the acids formed help to create a reduced environment that prevents the growth of spoilage microbes. It is an anaerobic process where we degrade a substance without an external electron acceptor. It is an energy yielding process that returns NADH to NAD+
- Wine is considered fermented fruit juice where alcoholic fermentation is carried out by Saccharomyces cerevisiae (a yeast).
o Three components are necessary:
1. simple sugar
3. anaerobic conditions
Equation: sugar fermentation to alcohol
|C6H1206 â' |2CH3CH2OH |+ |2CO2 |
|in the presence of yeast |Acetaldehyde | | |
End product of alcohol fermentation is alcohol (ethanol)
Where pyruvate is converted to acetaldehyde then into ethanol.
Microbiology of Yogurt Production
Yogurt production has been carried out for centuries as a process of fermenting milks. In this process lactobacilli act together with some other microorganisms to curdle and thicken milk thus producing a distinctive flavor.
Equation C6H12O6Â â'Â pyruvateÂ â'Â lactic acidÂ
The presence of lactic acid, produced during the lactic acid fermentation is responsible for the sour taste and for the improved microbiological stability and safety of the food.
End product of yogurt production is lactic acid.