Useful microorganisms Flashcards
uses of bacteria
- yoghurt making
- cheese production
- vinegar production
- silage production
- composting
describe fermentation
the production of alcohol, including wine and beer, by the breakdown of sugars
by yeast in the absence of oxygen
what gas is produced during fermentation?
carbon dioxide
what can some products of fermentation be used for?
it can be further treated to increase the alcohol concentration to produce spirits
Describe the action of Lactobacillus bacteria in yogurt
making
- the breakdown of lactose in milk
* the production of lactic acid
Describe the main stages in making yoghur
- sterilisation of equipment
- pasteurisation of milk
- incubation of culture
- sampling
- addition of flavours, colours and packaging
word equation for fermentation
anaerobic respiration in yeast
glucose (sugar) → ethanol (alcohol) + carbon dioxide
Describe the main stages in brewing beer or wine
extracting sugar from source material
• adding yeast, keeping it warm
• preventing entry of air and other microorganisms
• clarifying/clearing, drawing off the wine/beer
• pasteurising, casking or bottling
balanced chemical equation for
fermentation (anaerobic respiration)
C6H12O6 → 2C2H5OH + 2CO2
Explain the implications for the fermentation process of yeast being able to undergo aerobic or anaerobicrespiration
when yeast is used in fermentation it must be grown without oxygen, because if oxygen is available, the yeast will respire aerobically and make only carbon dioxide and water.
Describe the process of distillation to increase the alcohol concentration
it involves heating the liquid to evaporate the alcohol and then trapping and cooling the concentrated alcohol back into a liquid.
where can distillation only take place?
on a licensed premises
Describe what is meant by the term pasteurisation
heat treatment of milk which prolongs shelf-life by limiting bacteria growth
Understand that different strains of yeast can tolerate different levels of alcohol
some varieties or strains of yeast have a greater tolerance to higher concentrations of alcohol and can be used to brew stronger beers
