Improving Food productionImproving Food production

ObjectivesObjectives• Describe how the use of fertilisers and

pesticides with plants and the use of antibiotics with animals can increase food production

• Describe the advantages and disadvantages of using microorganisms to make food for human consumption

• Outline methods used to prevent food spoilage by microbes

• in many countries farming has become more intensive (since world war 2)

• fertilisers/pesticides used• animals fed supplements and antibiotics

• recent backlash• people prepared to pay more for organic food

fertilisers• ammonium nitrate• plants need ammonium ( NH4

+ ) and nitrate (NO3-)

ions• expensive • soil tested using GPS to see if needed – can be

applied in exact quantities• too much fertiliser not only damages environment

and is costly but actually reduces yield by reducing water potential in soil

• http://www.youtube.com/watch?v=k-5gNgegCB8• precision not possible using manure

Classwork/Homework questions

• saq 8, 9, 10 p158-159 cambridge

pesticides

• insecticides/fungicides• DDT – accumulates in food chain. broad

spectrum . banned. malaria• several applications a year needed• resistance can develop• traces left on food

antibiotics

• intensively farmed animals• more susceptible to disease• treatment increases growth rates• may destroy bacteria in gut that would slow

growth• widely used with pigs and chickens• risk of resistance to antibiotics evolving in

bacteria if used too widely,

How can microbes spoil our food?

• Visible growth on bread, cheese etc - Grows for a few days before it is noticible – Mucor – black, Penicillium- blue green

• Sweet smell (bananas) – indicates enzymes are releasing sugars from carbohydrate – food will become mushy

• Can cause infection – Salmonella, in chicken – also Clostridium botulinum and E.Coli

preventing food spoilage by microbes

• Refrigeration – slows enzyme activity of microbes• Salting/sugaring/drying- dries the food by osmosis• Pickling- acid denatures microbe enzymes• freezing – lack of water prevents growth of microbes• pasteurisation/UHT- kills harmful microbes• Irradiation- disrupts DNA of microbes• vacuum sealing/canning- prevents air reaching food

(needed for microbial aerobic respiration)• Name a different foodstuff that is preserved by

each method

Using microbes to make food

• Yogurt- milk turned sour by Lactobacillus bacteria- uses lactose sugar in milk to make lactic acid. This also thickens the milk proteins

• Cheese - from curdled milk. Lactobacillus

• Bread- uses yeast ( Saccharomyces) to rise. The carbon dioxide produced provides the bubbles

• Alcohol- a by product of anaerobic respiration- uses strain of yeast called Saccharomyces Carlsbergensis. This respires (ferments) on sugars in grapes( glucose /fructose) to make wine or malted barley ( maltose sugar) to make beer

mycoprotein (QUORN)• myco – fungus• Fusarium venenatum /graminearum• Single cell protein (SCP)• http://www.mycoprotein.org/what_is_mycoprotein/

product_process.html • Advantages

– Similar texture to meat– Faster growth than meat– All essential amino acids, lower in fat, no cholesterol– Production can easily be changed with demand– Can be grown all year round

• Disadvantages– taste– Can be grown using waste as a substrate material such as paper and

whey( curdled milk from which curds are removed)– Protein needs to be purified to avoid contamination– Care needs to be taken to avoid microbial infection of product

Homework Questions

1. Why should frozen food never be thawed and then refrozen?

2. Describe the effects of these temperatures on bacterial growth and activity (all degrees celsius): -12, 4, 25, 37, 50, 65, 100, 120

3. Explain how osmosis can help keep food fresh

4. What is the difference between milk that is pasteurised and UHT?