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Home Ec > Food Preservation > Flashcards

Food Preservation Flashcards

1
Q

What are the principals of food preservation

A

Inhibits microbial activity that causes food spoilage and food poisoning
Inactivates enzymes that cause food spoilage
Prevents microorganisms re entering food by sealing it
Maintains colour taste texture flavour and nutritional value of food

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2
Q

Advantages of food preservation

A

Avoids waste as they can be preserved before spoil eg apples made into chutney
Preserved out of season food eg frozen strawberries
Add variety as it allows new foods to be produced eg pickles
Saves money as food last longer consumers can stock up

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3
Q

Name 4 methods of home preservation

A

Freezing
Heat treatements eg jam making
Chemical preservation eg pickling
Dehydration eg drying herbs

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4
Q

What are the underlying principals of freezing

A

Using low temperatures below 0 degrees to inactivate microorganism growth snd slow down enzyme activity
Converts water into ice making it unavailable to microorganisms
Before freezing foods should be wrapped well

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5
Q

What are the two methods of home freezinf

A

Quick freezing and slow freezing

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6
Q

What is the method of quick freezing

A

Food quickly frozen at -25degrees in the fast freeze section
Small ice crystals are formed causing little damage to cell walls
Texture colour and flavour are retained on thawing

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7
Q

What is the method of slow freezing

A

Food is frozen between 0-18 degrees in the ice box in a fridge or freezer
Large crystals are formed causing damage
Low of nutritional value, texture, colour and flavour on thawing

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8
Q

What are foods that are not suitable for home freezing

A

Mayonnaise - emulsion separates
Whole eggs - crack due to white expanding
Foods with high water content eg cucumber
Soft cheese - dry and crumbly on thaw

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9
Q

What are the advantages if freezing

A

Retains sensory characteristics and nutritional value
Saves time as you can bulk buy and freeze
Saves money as individuals can bulk freeze meals for busy days instead of takeaway
Avoids food waste
Makes out of season food available

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10
Q

What are disadvantages of freezing

A

Initial cost of the freezer can be costly
Bulk freezing can be time consuming
Packaging is needed which can be costly
Defrosting can be time consuming

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11
Q

Guidelines for home freezing

A

Turn on fast freeze button 3-4 hrs before to reduce temperature from -18 to -25
Cool food beofre freezing
Avoid freezing more then one tenth of the freezer within 24 hrs as it puts pressure on the motar
Freeze foods in usable quantities
Blanch veg before

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12
Q

How to blanch veg

A

Bring one litre to the boil
Wash peel and chop 100g carrots
Place carrots in boiling water for 3-5 mins
Immedietly place in cold water with ice for 5 mins
Place in freezer bags in usable portions and label with food and date of freezing
Fast freeze section of the freezer

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13
Q

What packaging to use for freezing

A

Good quality that is strong and airtight and moisture proof
Seal packaging well otherwise freezer burn will occur
If freezing liquids leave room for expansion
Label the name of food quantity and date of freezing

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14
Q

What are guidelines for storing

A

Store similar foods together to avoid unnecessary searching
First in first out
Foods should only be stored for recommended storing time g beef and chicken 12 mths
Keep freezer full to capacity as majority of energy is used to cool between foods
Avoid keeping door open for long periods of time

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15
Q

How to thaw food

A

Read instructions as some retain their nutritional value and sensory characteristics if cooked from frozen
Thaw food in fridge as room temo is optimum temp for bacterial growth
Never refreeze thawed food unless cooked

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16
Q

What are the underlying principals of jam making

A

Boiling fruit at 100 degrees to destroy microorganisms and inactivate enzymes
It also softens food by breaking down cell walls
Adding sugar acts as a preservative the sugar solution draws water out of microbial cells
Presence of pectin and acid allows fruit to set

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17
Q

What are the ingredients of jam

A

Fruit
Sugar
Pectin
Acid

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18
Q

How to add extra pectin

A

Commerical pectin eg certo
Use sure set sugar
Mix with pectin fruit eg apples

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19
Q

What does acid prevent

A

Crystallisation

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20
Q

How to make jam

A

Weigh our ingredients
Wash jars un hot soapy water and dry and place on baking tray to sterilise in the oven at 140 for 20 mins to remove microbes
Fruit prep remove bruises wash peel and remove stalks
Cook fruit in a greased saucepan and simmer gently to release pectin
Warm sugar at 140 degrees for 5 mins
Add sugar and stir till dissolved
Bring to boil and stir occasionally
If jam is set skim scum from thr top using a ladle and spoon into sterilized jars leaving 1.5 cm at the top
Cover with a wax disk and apply a cellophane cover
Label
Store in a cool dry place

21
Q

How to set test

A

Wrinkle - spoon jam into a refrigerated plate and push with finger
Flake - dip a spoon into the jam and allow it to cool flr a minute tilt the spoon and allow jam to run off if set the jam will fall in one large flake
Thermometer test - place sugar thermometr into a pot of jam when it reads 105 jam is set

22
Q

What are the problems that can occur when making jam

A

Crystallisation- when too much sugar is added, if jam isnt boiled for long enough, sugar not stirred continuously
Unset jam- insufficient pectin or acid, jam not boiled for long enough as not enough pectin released , jam poured before setting point
Fermentation - insufficient sugar, poor quality fruit, jam not boiled for long enough

23
Q

What are the underlying principals of chutney making

A

Boil fruit and veg @100 then simmer to destroy microorganisms
Add sugar
Add vinegar - preservative as it lowers PH

24
Q

Why use plastic funnel and wooden spoon when making chutney

And plastic lids

A

Metal can react with the acid in vinegar

25
Q

Why use brown sugar for chutney

A

Brown sugar gives richer colour

26
Q

What are the underlying principals of chemical preservation

A

Concentrated solution causing water being drawn out of microbial cells by osmosis
Acids lower ph inhibiting microbial growth and inactivation enzymes

27
Q

What are types of home chemical preservation

A

Jam making
Chutney making
Pickling

28
Q

What are the underlying principals of dehydration

A

Removing moisture and inhibiting microbial growth and inactivating enzymes

29
Q

What foods are suitable for dehydration

A

Herbs
Fruit
Veg

30
Q

Name the 4 types of commercial preservation

A

Blast freezing
Contact freezing
Cryogenic freezing
fluidised bed freezing

31
Q

Explain blast freezing

A

Most common
Food subjected to a blast if cold air -30–40 that circulates food as it travels through a tunnel on a conveyor belt
Takes approx 2.5 hrs

32
Q

Explain plate freezing

A

Food placed on or between cold metal pkates by direct contact that have been cooled by circulation of a refrigerant eg ammonia at -30–40
Takes 60-90 mins

33
Q

Explain cryogenic freezing

A

Most expensive but produces most superior product
Food placed on a conveyor belt and moved into an insulated chamber and cooled spraying liquid notrogen (-196 degrees)
Freezes within minutes

34
Q

Explain fluidised bed freezing

A

Food blasted with cold air from underneath a conveyor belt so food separates separately

35
Q

What are the underlying principals of canning and bottling

A

High temps destroy microorganisms and inactivate enzymes

Sealing food in airtight containers prevent re entry

36
Q

What are the stages in canning process

A

Food is preped eg veg washed, bones removed, meat ir fish cooked and veg blanched
Cans are lacquered to prevent reaction between food and metal
Either syrup or brine added
Air removed
Cans are hermetically sealed in sterile environment
Cans and food are sterilised snd cooled
Cans are labelled

37
Q

What are the 3 methods of canning

A

Aseptic
High acid
Low acid

38
Q

Describe aseptic canning

A

Cans and food are sterilised separately at high temps
Food to 120 degrees
Food placed into cans and hermetically sealed and cooled and labelled
Short process

39
Q

Describe high acid food

A

Hugh acid food eg fruit require short processing time due to low ph
Heated to 100 degrees for less then 30 mins

40
Q

Describe low acid canning

A

Heated to 115 for more then 30 mins

41
Q

What are the commercial dehydration methods

A 
Fluidised bed drying 
Acceleration freeze drying 
Sun drying 
Fermentation 
Irradiation
42
Q

Whats fluidised bed drying

A

Food subjected to blast of hot air
Food continuously moved to prevent sticking together
20-40 mins

43
Q

Whats acceleration freeze drying

A 
Food initially frozen at low temps 
Small ice crystals are formed 
Ice crystals are then evaporated inna vaccuum chamber by sublimation 
Takes 9-24 hrs  
Used for coffee fruit veg ect
44
Q

What is sun drying

A

Exposed to direct sunlight in hot climates eg california

Water is evaporated

45
Q

What is fermentation

A

Breakdown of carbohydrate by microorganisms to produce carbon dioxide, alcohol and energy

46
Q

What is irradiation

A

Exposure to low levels of radiation which passes throigh foods destroying microorganisms, pests and prevents sprouting

47
Q

What is irradiation legislation

A

Any irradiation products on sale in Ireland as ther are no irradiation facilities
Any imported food must have RADURA SYMBOL
must contain words irradiated or ionising radiation

48
Q

What are the disadvantages of irradiation

A

Vitamin can be eliminated or reduced
Can cause chemical composition of high fat foods to change
May mislead customers into thinking foods are fresh
Can cause large numbers of free radicals to occur

Home Ec (31 decks)

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