food tech- food safety- chapter 5 (food spoilage and contamination)

jan-feb

3 types of micro-organisms that can spoil foods

bacteria

mould

yeast

how do microorganisms make food unsafe to eat

contaminates the product with waste,toxins and their presence

microorganisms

tiny forms of life, only visable under a microscope

contaminate

making a food unsafe to eat by allowing it to come in contact with micro-organisms that will grow and multiply in it

food poisining

an illness caused by microorganisms contaminating food

high risk food

food containing a lot of moisture and nutrients and can easily support the growth of pathogenic micro organisms.

also called perishable items

enzyme

name given to natural substances in living things that speed up chemical reactions

catalyst

a substance that speeds up the rate of chemical reactions

6 main types of bacteria (pathogens) that cause food poisoning

-Bacillus cerus

-Campylobacter

-E.coli

-Listeria

-Salmonella

-Staphylococcus aureus

campylobacter

sources, incubation time, typical symptoms

sources

-raw poultry/meat

-milk

-untreated (dirty) water

incubation time

-48-60 hrs

typical symptoms

-diarrhoea (often with blood)

-abdominal pain

-nausea/fever

E.coli

sources,incubation time, typical symptoms

sources

beef (minced) + other meat

milk not heat treated

untreated (dirty) water

incubation time

12-24hrs sometimes longer

typical symptoms

diarrhoea / abdominal pain

vomiting

fever

kidney damage/failure

salmonella

sources,incubation time, typical symptoms

sources

raw/undercooked poultry/eggs/meat

incubation time

12-36 hrs

typical symptoms

diarrhoea/abdominal pain

vomiting

fever

Listeria

sources,incubation time, typical symptoms

sources

soft cheese/cheese with unpasteurised milk

salad veg

pates

incubation time

1-70 days (why people don’t know what caused their illness)

typical symptoms

flu-like symptoms

miscarriage in pregnancy/infect unborn baby

staphylococcus aureus

sources,incubation time, typical symptoms

sources

people-on hands/nose/mouth

skin infections

raw milk

cold cooked meat

dairy

incubation time

1-6hrs

typical symptoms

abdominal pain

vomiting

low body temp

bacillus cereus

sources,incubation time, typical symptoms

sources

COOKED rice

milk

meats

veg

incubation time

diarrhoeal-8-16hrs after eating

emetic-1-6hrs after eating

typical symptoms

diarrhoeal-nausea,abdominal pains

emetic-nausea, vomiting

what bacterial reactions happens at

8°C

5-63°C

<63°C

<75°C

100°C

8°C - bacteria multiply slowly

5-63°C - danger zone (bacteria multiply rapidly)

<63°C - keep cooked food above this otherwise danger zone

<75°C - cook from raw to at least 75°C

100°C - water boils- bacteria cells are dead

what temp should your fridge and freezer be at

what happens to the food in the freezer

fridge - 0-5°C

freezer - -18 - -24

when food is in freezer the cells become dormant

what happens to the bacteria in a food when stored in a refrigerator

-they will grow very slowly

danger zone

the range of temp (5°-63°)that are just right for bacteria to multiply rapidly

spore

a special protective coating some types of bacteria grow if the conditions are not right for them to multiply

germinate

when the conditions become right,the protective spore breaks open and the bacteria becomes active again

contamination

making a food unsafe to eat by allowing it to come into contact with micro-organisms that will grow and multiply in it

cross-contsminate

how bacteria are spread from one source onto some food

how often should food waste in a kitchen be thrown away into a waste bin outside

regularly throughout the day

why do bacteria produce spores where they stay for a while Why?

the conditions are not t right for them to grow

in ideal conditions pathofenic bacterial multiply every

20 mins

how do pathogenic micro-organisms spoil food/cause food poisoning

they contaminate it with their waste products, toxins and their presence

what 5 conditions do micro-organisms need to be in to grow and multiply

-temp

-moisture

-food

-time

-pH

why do micro-organisms need the temp to be right to be able to grow and multiply (3)

-37°C is their optimum temp- grow most rapidly when its warm

-if too hot it will destroy them

-if too cold their growth and multiplication will become dormant

how can you control micro-organisms growth and multiplication-temperarure (3)

-cook food thoroughly + long enough so it reaches high enough temp (75) to kill the unwanted micro-organisms

-don’t leave food out in a warm room for a long enough time

-cool left over cooked food quickly and refrigerate or freeze it

why do micro-organisms need the moisture to be right to be able to grow and multiply (2)

-micro-organisms need water for all biological processes

-if theres not enough moisture in the food to supply water-can’t grow/multiply

how can you control micro-organisms growth and multiplication-moisture (2)

-preserve the food-dry it

-preserve the food with high concentrations of sugar or salt- removes water from micro-organisms cells-process of osmosis

why do micro-organisms need the food to be right to be able to grow and multiply (1)

-micro-organisms need nutrients and energy from food to grow + multiply

why do micro-organisms need the time to be right to be able to grow and multiply (2)

-takes time for micro-organisms to grow and multiply-the more suitable conditions the quicker they’ll grow + multiply

-most micro-organisms multiply every 10-20 mins

how can you control micro-organisms growth and multiplication-time (2)

-store,cook and cool foods thoroughly to avoid giving micro-organisms the time to grow + multiply

-use foods by its ‘use by’ date

why do micro-organisms need the pH to be right to be able to grow and multiply (1)

-if conditions are too acidic/alkaline it will affect whether they can grow/multiply

how can you control micro-organisms growth and multiplication-pH (1)

-preserve food in acid (e.g vinegar) to prevent micro-organisms from growing + multiplying

what are enzymes and what do they do (4)

-biological catalysts made from proteins

-natural substances in food

-speed up chemical reactions

-make fruits and veg ripen

-cause bodies tissues in meat and fish to break down after they are killed

ripening

process of a fruit or veg maturing so that its ready to eat

how to control enzymic action (3)

-blanching of veg before freezing

-adding acid- denatures the enzyme protein

-cooking food-heat denatures the enzyme protein

enzymic browning

the discolouration of a fruit or veg due to the reaction of enzymes with plant cell substances and oxygen from the air

why do fruit + veg go brown

• plant cells contain storage vacuoles -contain a variety of natural substances, outside the vacuole is cytoplasm-contains enzymes

• the cells break open the enzyme and oxygen in air mix (oxidation)

• this makes substances join together and change colour

how does mould multiply

-they send out tiny airborne spores that land on food and germinate

-the germinated spores send down roots into the food and send up thousands of ‘shoots’ with a fruiting body at the top- called mould

how does yeast affect foods

settle on foods and start to grow

the ferment the sugar to produce CO2 and alchalol

How micro-organisms are used to make cheese (9)

• Non-pathogenic bacteria and moulds are used in cheese making.

• Bacteria culture turns lactose in the milk into lactic acid.

• Lactic acid adds flavour, texture and preserves cheese.

• Rennet added – turns milk to curds (solid) and whey (liquid)

• Whey drained off.

• Curds cut up, salt added, then curds are pressed.

• Bacteria ripen the cheese to develop flavour.

• Cheese left to mature for a few weeks.

• Blue cheeses have a safe mould added to produce blue veins and flavour.

How micro-organisms are used to make bread (1)

• Yeast used to produce carbon dioxide gas to make the bread rise by fermentation.

How micro-organisms are used to make yoghurt

• Special bacteria culture added to milk.

• Milk held at 42°C – bacteria ferment the lactose sugar to lactic acid.

• The milk becomes semi-solid due to coagulation of protein by lactic acid.

• Milk cooled – flavouring may be added.

how does contamination happen with other contaminated foods (raw meat,poultry,fush ect) (5)

-storing raw foods next to cooked foods

-allowing these foods drip onto other foods

-storing unwashed veg with soil still on them next to HRF

-adding contaminated foods to other foods in a meal

-using same chopping boards/knives ect for different foods without washing between

how to control/prevent bacterial contamination with other contaminated foods (raw meat,fish,poultry ect) (5)

-separate raw + cooked foods

-store HRF in sealed containers (so they don’t drip)

-wash hands after handling HRF

-store HRF and cook them thoroughly at correct temp

-use separate equipment for diff foods or was them thoroughly in between

how does contamination happen with work surfaces and equipment (5)

-not cleaning WS or E properly

-using the same WS or E for diff preparations + cooking cooking processes

-using dirty dishcloths to clean WS

-not using hot water when washing

-allowing animals to walk on WS

how to control/prevent bacterial contamination with work surfaces and equipment (4)

-was WS + E as you go/frequently

-use hot water when washing up/dishwashers

-use disposable cloths/wipes

-let E air dry/use a regularly replaces,clean drying up cloth

how does contamination happen with people (preparing,handling,cooking,serving food)(2(4 in 1))

• people failing to wash hands properly

  -before/during/after dealing with food

  -after using toilet

  -after disposing of food in waste bin

  -after touching their face while dealing with food/licking fingers,equiptment then touching the food

  -coughing/sneezing near food

• wearing dirty clothing/not following the rules of food safety + hygene

how to control/prevent bacterial contamination with people (preparing,handling,cooking,serving food) (4)

-wash hands regularly/thoroughly-scrub nails

-tie hair back +wear clean clothes (apron)

-cover cuts on skin with a blue waterproof plaster

don’t lick fingers

-remove jewlry on hands,wrists/remove false nails or wear disposable gloves4

how does contamination happen with pests (flies,rats,birds,pets)(3)

-pets carry bacteria + other microorganisms in/on their bodies and their waste

-urinating on food, landing by the food,walking over food and eating the food

-flies lay eggs in food which hatch into maggots-contaminating the food

how to control/prevent bacterial contamination with pests (4)

-cover food to protect it from flies

-make sure pests can’t get into the kitchen by using deterrents

-keep animal feeding bowls/utensils seperate from those used by people

-don’t allow pets onto kitchen work surfaces

how does contamination happen with waste food/rubbish(3)

-food + rubbish will decompose quicker in a warm kitchen-bacteria + other micro organisms will grow in it

-waste bins attract pests

-waste bins have been allowed to become dirty with food spills will quickly become contaminated with bacteria

how to control/prevent bacterial contamination with waste foood/rubbish (5)

-empty kitchen food waste bins regularly throughout the day

-keep main food waste bin away from food preperation areas-outside

-wash waste bin regularly

-wash hands after throwing rubbish away

-try to avoid wasting food

how does contamination happen with food packaging (4)

-FP not stored correctly may become contaminated with pests

-canned foods become damaged if dropped/badly stored and develop splits-allows bacteria into canned foods

-cans that have gone rusty may develop tiny holes-allowing bacteria in them

-if plastic packaging gets damaged air can get in and micro-organisms will contaminate the food

how to control/prevent bacterial contamination with food packaging (5)

-store FP in a cool/dry place

-check FP for “use by“ and “best before” dates

-check the FP you buy to make sure it isnt damaged

-don’t buy food if you think the P is damaged-esp with HRF

-remember to store HRF properly once opened1

different factors causing bacterial contamination (6)

-other contaminated foods

-work surfaces+ equipment

-people

-pests

-waste food/rubbish

-food packaging

what is ambient storage

where the product is required to be stored at room temperature (15-25C)

why is storing food at 10C a bad idea (6marks)

-it is in the danger zone (5-63C)

-cells multiply rapidly at this temp

-you should store the food below 5C once the food is cooked above 75C so the cells don’t grow rapidly anymore.Ensure that the cells/ bacteria grow slower, or become dormant if food is in freezer (-18- -24C)