Food Production Flashcards
What are greenhouses?
A greenhouse (or glasshouse) is a structure with transparent walls and roof, usually made of glass or clear plastic, that’s designed to grow and protect plants
What are polytunnels?
A polytunnel is a tunnel-shaped structure made of strong plastic (polythene) stretched over hoops or frames.
How do polytunnels and greenhouses work?
they provide controlled conditions for plants to grow and increase yeild
the transparent walls allow natural light for photosynthesis during summer, and additional lighting can be added to give a ‘longer day’ during winter
the greenhouse effect also occurs
heaters release CO2 and water vapour for photosynthesis and gives moist atmosphere reducing water lost by transpiration
hydroponic culture balances mineral ions for the crop
Describe the greenhouse effect in glasshouses
short wavelength infrared radiation enters the glasshouse and is absorbed and re-radiated as longer wavelength infrared radiation and cannot escape through the glass. this heats up the glasshouse and reduces convection currents that would normally cause cooling.
What are the types of fertilisers?
organic fertilisers and inorganic fertilisers
What are organic fertilisers?
Organic fertilizers are natural materials derived from living things (plants or animals) that add nutrients to soil and increase growth.
For example manure made from the faeces of farm animals as their waste products contain excess nutrients they consumed which can help the growth of plants.
What are inorganic fertilisers?
inorganic/chemical compounds that are used to add nutrients to soil and increase growth by replacing lost ions
For example, potassium nitrate, ammonium nitrate
What are the drawbacks of inorganic fertilisers?
can lead to pollution problems and don’t improve soil structure like organic fertilisers do.
What are the advantages of organic fertilisers?
improves soil structure as they contain decaying matter which is an essential part of soil
Describe the process of nitrogen fixation in legumes
legumes have nitrogen-fixing bacteria in nodules in their roots and convert nitrogen gas in the soil into ammonium ions used to make proteins when passed to the plants. at the end of the season, decomposers convert nitrogen in proteins to ammonia and is oxidised to make nitrate by nitrifying bacteria for next years crop
What are pests?
organisms that reduce the yeild of crop plants/stock animals
How do pests reduce yeild?
they can reduce growth by consuming the crops, can affect the appearance/quality so unsuitable to sell
What are pesticides?
chemicals used to kill pests
What is biological control?
releasing other organisms to reduce numbers of a pest
What are the type of pestcides?
herbicides (plant pests)
insecticides (insects)
fungicides (fungi)
molluscicides (snails/slugs)
What are the drawbacks of pesticides?
pests may develop resistance to the pesticide through natural selection, can cause environmental damage, slow to decompose (persist in environment), build up in tissues of organisms (bioaccumalation), kill harmless insects that help the species
What should the idea pesticide do?
control the pest effectively, biodegradable, kill only the specific pest, not accumulate, safe to transport/store/supply, easy to apply
How does biological control work?
introduces parasites that kill the pest but doesn’t fully get rid of it. because if the parasite kills all of the pests they would die out too because they wont have food left. therefore only reduces the number of pests to a level where its not making any significant economical damage anymore
What are the methods of biological control?
natural predator, herbivore, parasite, pathogenic organism (makes disease), sterile males, pheromones
What do sterile males do in biological control?
mates with females but doesn’t produce offspring therefore overtime the population decreases
What do pheromones do in biological control?
insects that produce natural chemicals to attract mates and then destroy them
What are microorganisms?
living things that you can only see under a microscope, they are single celled
What do microorganisms do?
they form colonies with millions of them together which can be visible to the human eye. they regulate waste products and themselves when they die. useful for producing food, drink and medicines
What are some examples of microorganisms?
protoctists, fungi and bacteria
What happens when yeast is deprived of oxygen?
it respires anaerobically
glucose -> ethanol + carbon dioxide
How is bread produced with yeast?
- wheat flour, water and yeast combined to form dough
- enzymes from the cereal grains in the wheat flour break down starch into sugars which are respired by the yeast. (extra sugar can be added this stage)
- yeast respires aerobically producing water and carbon dioxide. the carbon dioxide helps the dough rise.
- when dough is baked the gas bubbles expand giving the bread a light and cellular structure as well as killing the yeast cells and evaporating the ethanol produced from fermentation
What is yoghurt?
fermented milk by lactic acid bacteria which turns the liquid into a semi-solid food with a sour taste
Describe the process to produce yoghurt`
- milk pasteurised to 72 degrees celsius for 15-30 minutes to kill natural bacteria
- milk is homgenised to disperse fat globules and even out the liquid
- milk is then cooled to 40-45 degrees celsius and inoculated with starter culture (lactobacillus)
- kept at this temperature for several hours until the pH falls to 4.4
- the mixture coagulates as the milk proteins denature and form semi solids
- fermentation completed and yoghurt stirred and cooled to 5 degrees
- flavourings, colours, mix-ins added before packaged for sale
What is lactobacillus?
the bacteria that produces lactic acid and digests the milk proteins
What does the drop in pH do to yoghurt?
reduces the reproduction of lactic acid bacteria. doesn’t fully kill them though, just prevents growth of other microorganisms and preserves nutrients in the milk
What is a fermenter?
vessel used to grow microorganisms used for fermentation
What is an industrial fermenter?
large tanks holding up to 200000dm^3 of a liquid culture that control the environmental conditions
What are the aseptic precautions in industrial fermenters?
prevent contamination of unwanted organisms by filtering the air or sterilising the fermenter with very hot steam and pressure
What is the purpose of industrial fermenters?
to use microorganisms to transform raw materials into valuable products
What would happen if the industrial fermenter is not sterilised?
bacteria/fungi would compete with the organism in the culture reducing the yield of the product and would be contaminated with waste products of the foreign organism
