Food Production

(crop plants and fish farming are in Human Influences/Ecology)

Microorganisms

The processes and properties of some microorganism have been used to produce many types of food and drink:

• Bread - yeast respires anaerobically to produce CO₂ to make the dough light and fluffy, when it’s baked the yeast is killed and ethanol evaporates

• Cheese - lactic acid bacteria is added to milk creating curds which are separated and dried into cheese

• Vinegar - Acetobacter bacteria is added to convert ethanol into vinegar

• Soy sauce - Fungus, yeast, and lactic acid are used

Yoghurt production

Yoghurt is milk that’s fertilised lactic acid bacteria (Lactobacillus Bulgaricus), the lactic acid causes the pH to fall to 4.4 causing the milk proteins to coagulate, thickening the mixture.

Investigating anaerobic respiration by yeast

The conditions in which yeast respires more effectively can be investigated by measuring the volume of CO₂ produced.

1. set up a series of closed tubes with a solution of yeast and sugar

2. place in water baths of ranging temperature e.g. 10,20,30,40,50

3. connect each tube to a gas syringe to measure CO₂ volume

Industrial Fermenter

what are they?

A fermenter is any vessel that is used to grow microorganisms used for fermentation. Industrial fermenters are large tanks that can hold up to 200000dm³ of liquid. They enable the environmental conditions like temperature, oxygen, CO₂ concentration, pH, and nutrient supply. This ensures the microorganisms yield their products most efficiently.

conditions

Before the fermenter is filled with new nutrients the inside are cleaned and sterilised with high pressure hot steam, this is to prevent growth of unwanted fungi and bacteria and to prevent the product from being contaminated with other things.

Aseptic precautions are used to prevent the contamination by unwanted microorganisms which could affect the growth of microorganisms, this is done by filtering air and sterilising the fermenter. All solutions added must be sterilised.

diagram

pH recorder - keeps the pH to the desirable constant by adding acid or alkali

air inlet - filtered air is added when the microorganisms need oxygen

stirring paddles - stop the nutrients from sinking to the bottom, evenly distributes temperature

water jacket - has cold water running through it to control the temperature