Microbes and Biotechnology F.4 Objectives
|F.4.1 Explain the use of Saccharomyces in the production of beer, wine and bread.||• Beer|
• Sweet liquid wort is made from malt
• Hops are added and liquid is boiled and cooled
• Wetted barley allowed to germinate: amlyase is formed.
• Amylase catalyses starch into maltose.
• Fermentation by yeast produces beer containing ethanol and CO2
• Crushed grapes and yeast are put into a tank
• Yeasts respirate aerobically until oxygen is depleted
• The yeasts then switch to fermentation (anaerobic)
• Ethanol stays in the tank, while CO2 escapes
• Process ends when ethanol concentration reaches ax. 15%, killing the yeast, or when substrates have been used up.
• Fermentation of sugars in the dough by yeast
• CO2 makes the dough rise
• Baking in the oven kills the yeast, stops fermentation and evaporates the ethanol
|F.4.2 Outline the production of soy sauce using Aspergillus oryzae.||• Soak soy beans, boil and drain|
• Mix a mash of soy beans with toasted wheat
• Add a culture Aspergillus oryzae
• Incubate for 3 days at 30°C
• Add salt and water and fermentation of starch and proteins to alcohol, organic acids, sugars and amino acids occurs for 3-6 months.
• Filter and pasteurize; liquid produced is the soy sauce product.
|F.4.3 Explain the use of acids and high salt or sugar concentrations in food preservation.||• Food preservation with acid:|
• Microbes cannot live in low pH levels
• Common examples include vinegar and production of yoghurt.
• Food preservation with high sugar/salt concentrations:
• high concentrations of either will kill any microbes in food samples, since the high concentration draws out water through osmosis.
• Common examples include honey, jam, salted meat.
|F.4.4 Outline the symptoms, method of transmissions and treatment of one named example of food poisoning.||• Transmission of Salmonella food poisoning|
• Lives in the intestinal tract and is transmitted after ineffective hand washing
• Can be found in the feces of some pets and be transferred to food
• Eating contaminated foods not properly cooked
• Uncooked meat cut on a cutting board which if not washed can cause transfer of Salmonella
• Raw eggs
• Treatment of Salmonella food poisoning
• Treat the dehydration by drinking lots of water
• Serious dehydration is treated with intravenous
• Antibiotics can be given if the infection is serious and has spread from intestine to the blood