5.5: Understand the Role of Yeast in the Production of Food Including Bread

YEAST IN BREAD PRODUCTION:

USE OF YEAST IN BREAD

Picture showing the Effect of Yeast on Bread

EQUATION FOR ANAEROBIC RESPIRATION (YEAST):

EXPLANATION: Yeast is used in baking bread and is mixed into dough prior to baking While baking, Yeast rapidly uses up all Oxygen present in the dough via aerobic respiration As a result, anaerobic respiration will occur to produce Carbon Dioxide, which forms bubbles that make the dough rise, and Ethanol, which evaporates into the atmosphere

YEAST IN THE PRODUCTION OF BEER:

PRODUCTION OF BEER

Diagram showing the Process to Produce Beer

EQUATION FOR ANAEROBIC RESPIRATION (YEAST):

EXPLANATION: Yeast can be used to produce Ethanol via fermentation Yeast is cultured in a liquid containing sugar and other Nutrients, except for Oxygen to ensure anaerobic respiration occurs to produce Carbon Dioxide, which bubbles into the atmosphere, and Ethanol, which gives Alcoholic content to drinks Beer, wine, and other Alcoholic drinks are brewed using this method

5.6: Practical: Investigate the Role of Anaerobic Respiration by Yeast in Different Conditions

EQUATION FOR ANAEROBIC RESPIRATION (YEAST):

EXPERIMENT:

CARBON DIOXIDE PRODUCTION BY YEAST

Diagram showing Carbon Dioxide Production by Yeast

METHOD: Mix boiling tube of Sugar solution with Yeast, covering it with a layer of Oil to prevent the entry of Oxygen; hence, ensuring aerobic respiration Boiling tube is connected to a test tube of Limewater via capillary tube that is kept airtight by a bung Boiling tube of Sugar solution with Yeast is placed in a Water bath of set temperature Rate of Carbon Dioxide production is measured by number of bubbles produced in a fixed time in test tube of Limewater Compare results obtained at different temperatures

RESULTS: As temperature increases towards optimum, the rate of Carbon Dioxide production will increase This is because the increase in temperature towards optimum will allow optimum enzyme activity for Yeast enzymes, hence increasing the rate of Anaerobic respiration to produce Carbon Dioxide (and Ethanol) However, as temperature increases above optimum, enzymes involved in Anaerobic respiration will denature, therefore causing the rate of Carbon Dioxide production to decrease

5.8: Understand the Use of an Industrial Fermenter and Explain the Need to Provide Suitable Conditions in the Fermenter, Including Aseptic Precautions, Nutrients, Optimum Temperature and pH, Oxygenation and Agitation, for the Growth of Micro-Organisms

INDUSTRIAL FERMENTATION: Anaerobic process involving the use of microorganisms - Yeast, Bacteria etc, to commercially produce food products in a controlled environment

Diagram:

Diagram showing an Industrial fermenter

SUITABLE CONDITIONS:

CONDITION	EXPLANATION
ASEPTIC PRECAUTIONS	Fermenter is steamed to kill Bacteria and prevent chemical contamination, only allowing desired microorganisms to thrive and carry out metabolic processes to produce desired product
NUTRIENTS	Nutrients are needed for organisms to release energy via respiration for growth, allowing metabolic reactions to occur to produce desired product
OPTIMUM TEMPERATURE AND pH	Temperature and pH probes are used to maintain an optimum environment for enzymes that carry out metabolic process in organisms, allowing organisms to thrive and produce desired product
OXYGENATION	Oxygen is needed organisms to release energy via aerobic respiration for growth, allowing metabolic reactions to occur to produce desired product
AGITATION	Agitation by stirring paddles ensure that microorganisms, Nutrients, Oxygen, temperature and pH is evenly distributed

5.7: Understand the Role of Bacteria (Lactobacillus) in the Production of Yoghurt

FERMENTATION: Anaerobic process involving the use of microorganisms - Yeast, Bacteria etc, to commercially produce food products

LACTOBACILLUS IN THE PRODUCTION OF YOGHURT:

PRODUCTION OF YOGHURT

Diagram showing the Production of Yoghurt

EXPLANATION: All equipment is sterilised to kill Bacteria and prevent chemical contamination Milk is firstly pasteurised (at 85 - 95°C) to kill harmful Bacteria, and then homogenised to emulsify fat droplets Homogenised Milk is left to cool (at 40 - 45°C), allowing cultured Bacteria Lactobacillus to be added at optimum temperature Mixture is incubated at this temperature for several hours in an anaerobic environment (Oxygen free), ensuring Bacteria anaerobically respires to break down fat droplets (Glucose) into Lactic acid Lactic acid produced by Bacteria via anaerobic respiration lowers the pH of Milk to give the thick texture of Yoghurt, additionally preserving Yoghurt until consumption Lastly, flavourings, colourants, and fruits are added prior to packaging