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Food Technology > Food Tech: Chapter 8 > Flashcards

Food Tech: Chapter 8 Flashcards

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1
Q

Why is food preserved?

A
  • extension of shelf life
  • prevention of waste when there is a surplus
  • increase range of food choices year around
  • transportation of food over long distances
  • trading of products between countries
  • maintenance of the nutritional value of food
  • easier and more convenient meal preparation
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2
Q

How can food be preserved?

A
  • reduced moisture levels
  • temperature heating
  • reduction in temperature
  • pH levels
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3
Q

How does the addition of salt preserve food?

A

The salt draws out the moisture from the food cells. The salt dissolves in this moisture and raises the salinity levels, making it unsuitable for micro-organisms to grow.

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4
Q

What is dry salting?

A

Dry salting is food layered or coated with salt and sometimes other flavourings are added. The salt draws out the moisture from the food, creating a brine of its own juices.
e.g. sardines, capers

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5
Q

What is a brine solution?

A

A solution of salt and water.

e.g. corned beef, ham, olives, cabbage and lemons.

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6
Q

How does the addition of sugar preserve food?

A

In strong concentrations, sugar inhibits the growth of micro-organisms because it has a dehydrating effect similar to that of salt.

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7
Q

What is pectin?

A

Pectin is a natural component in fruits. It has the ability to form a gel in the presence of sugar and acid. It is a vital part when making jam. Slightly under-ripe fruits have more pectin.

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8
Q

Name fruits with high pectin levels

A
  • apples
  • grapefruit
  • lemon
  • limes
  • oranges
  • plums
  • quinces
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9
Q

Name fruits with medium pectin levels

A
  • apricots
  • blackberries
  • blueberries
  • raspberries
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10
Q

Name fruits with low pectin levels

A
  • kiwi fruit
  • mangoes
  • nectarines
  • passionfruit
  • pineapple
  • strawberries
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11
Q

Factors influences the formation of a gel in jam

A
  • fruit quality, including seeds, flesh, peel
  • boiling time to form a gel
  • amount of acid and pectin
  • ratio of sugar to fruit
  • boiling time to develop pectin
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12
Q

What is colour retention?

A

Sugar helps retain the colour of fruit by its ability to attract and hold water. When making jam, the sugar prevents the fruit from absorbing water, which would cause its colour to fade.

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13
Q

What is a jam?

A

James are whole fruit or fruit pulp boiled with sugar until the mixture sets or gel. It holds its shape, but is less firm than jelly.

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14
Q

What are conserves?

A

Conserves have whole or large pieces of fruit preserve in a sweet syrup of light jelly

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15
Q

What is a marmalade?

A

A marmalade is a preserve of a citrus fruit. The cut peel of the fruit is embedded in a jelly which is flavoured with the juice.

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16
Q

What is a jelly?

A

A jelly is like a jam, however is made from the strained juice of the fruit. They are clear and firm enough to hold their shape. Fruits with high pectin levels are best for this.

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17
Q

How is the pectin levels determined?

A
  • a tablespoon of methlylated spirits are added to a teaspoon of cook fruit juice and swirled for 1-2 minutes.
  • high pectin levels= large clotted mass
  • medium pectin levels= two or three small clots
  • low pectin levels= small scattered lumps
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18
Q

What does a gel test determine?

A

A gel test determines whether a jam or jelly has set and therefore ready to place into jars.

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19
Q

What are the two types of gel tests?

A
  • on the spoon or fork test

- on the cold plate test

20
Q

How do you sterilise a jar?

A
  • wash well in hot soapy water
  • place in the oven at 100 degrees for about 30minutes
  • place on a wooden board or tea towel once removed
  • lids can be boiled
21
Q

Is it better to cook the jam for longer of shorter time?

A

Shorter, cooking the jam too long can damage the pectin and decrease its ability to form a gel

22
Q

How is a vacuum seal created?

A

The heat of the jam will help create a vacuum seal.

23
Q

How does dehydration preserve food?

A

Dehydration reduces the water content down to between 5%-25% so that the bacteria that causes decay cannot survive.

24
Q

Reasons for dehydrating foods?

A
  • They take up less space
  • The weight is significantly less
  • Creates a new texture and flavour
25
Q

Why are vegetables blanched before dehydrating?

A

Blanching the vegetables prevents any further enzyme action and deterioration in colour and texture of the vegetable.

26
Q

How is the enzymatic browning prevented in fruits?

A

Dipping the fruit slices in undiluted pineapple juices

27
Q

What is a honey dip?

A

-1/2 cup of sugar
-1 1/2 cups of warm water
-1/2 cup of honey
It is used for sour or tart fruit.

28
Q

Name 4 dehydrating techniques

A
  • sun drying
  • air drying (hung in a dry shady place)
  • oven drying
  • using a dehydrator (35-60 degrees)
29
Q

How does increasing the temperature preserve food?

A

Food is heated to temperatures above 60-70 degrees to kill micro-organisms.

30
Q

What is bottling?

A
  • a jar of food is heated to kill micro-organisms and create a partial vacuum
  • a controlled environment is created
  • the natural acidity of the fruit helps the growth of micro-organisms and ensure safe preservation
31
Q

What foods are best for bottling?

A

Food with a high acid level

vegetables are not suited as they have low acid levels

32
Q

Reasons why fruit is preserved using bottling

A
  • stop the action of enzymes
  • destroy micro-organisms
  • prevent further entry of harmful organisms by creating a vacuum or airtight seal
33
Q

How should bottled fruit be stored?

A

In a cool, dark, dry place

34
Q

How does decreasing the temperature preserve foods?

A

Freezing food at a very low temperature (around -18degrees) extends the storage life. The life of the microbes is stopped, however not killed. The chemical and enzymatic changes are slowed.

35
Q

How does freezing damage the cell structure?

A
  • Large crystals form inside the cell wall and the cell wall is ruptured or broken
  • When thawed the ice crystals melt and the structure collapses.
  • The appearance, flavour and texture is changed
36
Q

Why is ice-cream churned?

A

To produce small crystals, making the ice-cream smoother

37
Q

What happens to meats when it is frozen?

A

The spaces between the muscle cells freeze first and then draw water out of the cells by osmosis. This causes dry patches of freezer burns and can be seen on frozen meat.

38
Q

How long can meat be frozen for?

A

3-6 months if packaged properly and kept at -18 degrees or lower

39
Q

How should meat be packaged for freezing?

A
  • when freezing steaks, insert freezer wrap between each steak
  • for cubes, strips and mince, divide into individual meal serves and wrap in a freezer bag, pack as flat as possible
  • seal tightly
  • label each bag with serving portion, type of meat and date of packing
40
Q

What must be done to vegetables before freezing?

A

Vegetables must be blanched or plunged into boiling before freezing for 1-2 minutes and then refreshed in iced water and drained. This inhibits the enzyme activity, that otherwise would cause the vegetables to deteriorate.

41
Q

How does the addition of acids preserve food?

A

Acids preserve foods by creating a low pH level, which inhibit the growth of micro-organisms and subsequent deterioration of the food.

42
Q

What pH level can micro-organisms not survive?

A

below 4.5

43
Q

What is the pH of citric acid and vinegar?

A

around 2

44
Q

What are preserves made with vinegar?

A

Relish, chutney, pickle

45
Q

What is a relish?

A

Contains a fruit and vegetables, vinegar, sugar and spices. Chunky texture and sharper flavour.

46
Q

What is a chutney?

A

Contains fruit and vegetables, vinegar, sugar and spices; smooth texture and rounded flavour; cooked for a long time

47
Q

What is a pickle?

A

Fruit and/or vegetables are soaked in brine, then covered in flavoured vinegar; sweet; sour; hot spice flavour.

Food Technology (7 decks)

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