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GCSE Food Preparation and Nutrition > 3.1.1 Micro-organisms and Enzymes > Flashcards

3.1.1 Micro-organisms and Enzymes Flashcards

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1
Q

What are micro-organisms?

A

tiny organisms found in many places that can spoil foods. also known as microbes. yeast, moulds and bacteria are types of this

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2
Q

How is food spoilt?

A

contamination of yeasts, moulds or bacteria and contaminates with their waste products (toxins they produce)
enzymic activity can spoil food + ripen fruit and veg

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3
Q

What conditions do micro-organisms need for growth?

A

yeast, moulds and bacteria require:
food, moisture, warmth, time and correct pH

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4
Q

Why is food a condition for micro-organism growth?

A

nutrients are needed for growth

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5
Q

How can you prevent growth and multiplication of micro-organisms in food?

A

prevent contact with food and keep it covered

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6
Q

Why is moisture a condition for the growth of micro-organisms?

A

water is needed for all biological processes. if water is removed they cannot grow/multiply

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7
Q

How and why might you remove moisture from a food?

A

drying: adding high concentrations of sugar/salt - the water from cells are removed by osmosis

in order to prevent micro-organisms to grow/multiply

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8
Q

Why is warmth a condition for the growth of micro-organisms?

A

if too hot the micro-organisms will be destroyed, if too cold their multiplication slows down until it stops (become dormant)

the ideal temp is 37 degrees celcius

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9
Q

How to control micro-organism growth/multiplication by temperature?

A

cook food thoroughly at high enough temperature. cook at least to 75 degrees celcius to kill most microbes.

don’t leave food out in warm places. cool cooked and left over food must be refrigerated quickly and not left out. refrigerate between 0-5 degrees celcius or freeze -18 degrees celsius or below.

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10
Q

Why is time a condition for the growth of micro-organisms?

A

bacteria multiply every 10-12 minutes in the right conditions by binary fission

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11
Q

How to control the growth/multiplication of micro-organisms through time?

A

cook and cool foods thoroughly and use within “use by date”/ expiry date

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12
Q

Why is pH level a condition for the growth of micro-organisms?

A

right amount of acidity/alkalinity (pH) needed. if too much of one they cannot grow.

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13
Q

How can you prevent the growth of micro-organisms through pH level?

A

preserving food in vinegar is a method of preventing multiplication

vinegar is pH 2-3 (strongly acidic)

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14
Q

What are yeasts?

A

single celled fungi that reproduce by “budding”

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15
Q

What is ‘budding’?

A

the yeast cells grows a bud that becomes bigger, until it it breaks off and becomes a new yeast cell

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16
Q

How can yeasts grow?

A

with oxygen (aerobic yeast) or without oxygen (anaerobic yeasts)
in high concentrations of sugar + salt (jam, honey, chutney)
grown best in warm conditions (25-29 degrees)
can grow at refrigerator temps (0- below 5 degrees)

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17
Q

What kind of foods do yeasts prefer?

A

most, acidic foods (eg. oranges)

18
Q

What temperature are yeasts destroyed at?

A

55 degrees celcius

19
Q

What are moulds?

A

tiny fungi that produce thread like filaments that help the mould spread around the food

20
Q

In which foods do moulds grow in?

A

foods with high sugar and salt concentrations
fairly dry food (like hard cheese)
often breads and bakery products

21
Q

In which temperatures do moulds grow in?

A

grow best between 20-30 degrees
can grow at refrigerator temps (0 - below 5 degrees)

22
Q

How can mold growth be sped up?

A

high humidity and fluctuating temperatures

23
Q

What must you not do with foods with moulds?

A

eat them. even if scraped off, they can spread harmful substances deep into the food

24
Q

What is bacteria?

A

single-celled micro-organisms

25
Q

What groups can bacteria be divided into?

A

harmless bacteria, pathogenic bacteria and food spoilage bacteria

26
Q

Where can bacteria be found?

A

everwhere around you - skin, food, water, soil, air etc

27
Q

What do pathogenic bacteria do?

A

these are harmful and can cause food poisoning

28
Q

What do food spoilage bacteria do?

A

they cause food to decay - to smell and lose its texture + flavour

29
Q

What are the conditions for growth of bacteria?

A

warmth (body temp 37 degrees)
moist conditions on neutral foods with protein

30
Q

How do bacterias reproduce?

A

binary fission: when one bacterium divides into two cells

31
Q

How can bacterial growth be slowed/prevented?

A

storing food in fridge
cooking perishable food quickly (90 minutes before refrigerating)
reheating leftovers to 75 degrees only once
high concentration of salt/sugar/acid

32
Q

What are the ideal conditions for bacterial growth and what are these types of food?

A

foods with moisture, high protein content, neutral pH, in warm environment

foods with these conditions that you can eat without cooking are known as high risk foods

33
Q

What are some high risk foods?

A

cooked meat and poultry
cooked meat products like gravy, soup, stock
milk and eggs + their dishes
shellfish like mussels, crabs, lobsters
cooked rice

34
Q

What are enzymes?

A

biological catalysts made from proteins to speed up chemical reactions

35
Q

What do enzymes do?

A

cause browning in foods that are bruised/cut open - known as enzymic browning
they cause meat + fish tissues to break down once animal is killed

36
Q

How is enzymic action controlled?

A

by causing them to denature through heat or acids

37
Q

What is blanching?

A

heating food in boiling water for a short time to destroy enzymes before plunging it in iced water to stop the cooking process

38
Q

When can enzymes still be active?

A

at freezer temperatures of -18 degrees of below

39
Q

What can be used to prevent enzymic browning?

A

acids such as lemon juice. the acid denatures the enzymes so they become inactive (due to acidic pH)

40
Q

What is sterlisation?

A

the complete destruction of all microbes in food processing

GCSE Food Preparation and Nutrition (4 decks)

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