Food Tech: Chapter 4

Question 0

Describe the physical and sensory properties of goats milk

Answer 0

Goat’s milk is sweeter and whiter in colour than cow’s milk. Its nutritional composition is similar to cow’s milk

Question 1

Describe the physical and sensory properties of cow’s milk

Answer 1

Cow’s milk is a white, opaque liquid which contains almost three times more protein than human milk

Question 2

Describe the physical and sensory properties of sheep’s milk

Answer 2

Sheep’s milk has a much higher fat content than cow’s milk, providing almost twice the fat content. This high fat content gives it a sweeter and richer flavour and much whiter colour.

Question 3

Name the nutrients found in milk

Answer 3

• protein
• fat
• carbohydrates (sugars, lactose)
• vitamins (vitamin A and D)
• minerals (calcium, phosphorus)
• water (87% water)

Question 4

Name the dairy products made from milk

Answer 4

Liquid milk, concentrated (condensed) milk, powdered milk, buttermilk, milk proteins, yoghurt, cream, butter, ice-cream, cheese.

Question 5

Describe pasteurisation

Answer 5

Pasteurisation destroys pathogenic or disease-causing bacteria and also extends the shelf life of milk. The milk is heated to 72 degrees for 15 seconds and the is cooled rapidly to 2 degrees.

Question 6

Describe UHT (ultra high temperature)

Answer 6

UHT refers to processing milk at higher temperatures than for pasteurisation, but for a much shorter time, killing all bacteria in milk, including those that turn milk sour. The milk is heater to 135 degrees for 2-3 seconds. UHT milk can be stored for 3-6 months without refrigeration.

Question 7

Describe homogenisation

Answer 7

The milk is forced through small nozzle-like openings or between closely position plates to break down fat globules and evenly distribute cream to create a smooth, creamy texture

Question 9

What are the advantages of homogenising milk?

Answer 9

• uniform distribution of fat, so there is no cream layer
• more full-bodied flavour
• white, more appealing colour
• faster coagulation in the manufacture of cheese

Question 10

Describe membrane technology

Answer 10

Membrane technology involves using a porous membrane or filter to separate the particles in a fluid. Two of the most commonly used forms or membrane technology in food production are ultrafiltration and reverse osmosis.

Question 11

Describe ultrafiltration

Answer 11

Ultrafiltration is a form of membrane technology in which milk is pumped across a membrane to collect the protein and fat and some of the calcium molecules, but the water and lactose are allowed to pass through.

Question 12

Describe reverse osmosis

Answer 12

Reverse osmosis is a form of membrane technology similar to ultrafiltration but the pores in the membrane are smaller and allow only water to pass through, leaving behind concentrated milk solids

Question 13

Describe the primary processing of milk

Answer 13

• milking of cows
• collection of milk
• analysis
• membrane technology filtration
• pasteurisation
• homogenisation
• packaging or secondary processing

Question 14

Describe the secondary processing of milk (production of cheese)

Answer 14

• curd formation
• syneresis (the curd is gently heated so it shrinks and toughens)
• milling (curd is cut into small, even sized pieces)
• salting
• moulding (cheese is pressed into shape)
• maturation (cheese is stored Ina cool environment to develop flavour and texture, the longer the sharper the flavour and crumblier texture)
• packaging and labelling

Question 15

Define coagulation

Answer 15

Coagulation is a form of denaturation and occurs when there is a permanent change in the protein from a liquid into a thick mass as a result of heat, or the addition of acids.

Question 16

Define denaturation

Answer 16

Denaturation describes a permanent structural change of the protein molecules in food. This can occur with the application of heat, mechanical action or the addition of acids.

Question 17

What happens when you heat milk to 100degrees?

Answer 17

• Milk starts to boil at 100 degrees.
• The proteins present on the surface of the milk combine with the fat to form a skin.
• Milk boils over as a result of pressure of steam forcing its way through the skin.

Question 18

What happens when you combines egg with milk?

Answer 18

• A custard mixture is formed.
• The consistency of custard depends on the proportion go eggs to milk. The more eggs than milk, the thicker it will be.
• The smooth texture is due to the gentle cooking, making sure the eggs coagulates or sets evenly within the milk at a temperature between 65-70 degrees.
• custards can be baked or cooked on a stove top

Question 19

Why is a double boiler used to prepare a custard?

Answer 19

Cooking a custard in a water bath helps prevent the delicate mixtures from curdling or separating.
-If the custard is overheated, the proteins from the egg and milk begin to over-coagulate to form small limos and separate from the whelmed and the smooth, rich texture is lost.

Question 20

What happens when you combine acid with milk?

Answer 20

• Adding lemon juice to fresh milk will cause the milk to curdle.
• The flavour of the milk becomes sour to taste
• Some products rely on this reaction to create a unique texture

Question 21

What is curdling?

Answer 21

Curdling is when the milk protein, casein, joins together or coagulates to form tiny lumps or clots

Question 22

What nutrients are found in eggs?

Answer 22

• protein
• B vitamins (B12)
• vitamin A and D
• iron
• phosphorous

Question 23

How is a high level of Omega-3 egg formed?

Answer 23

Polyunsaturated fatty acid Omega-3 would be added to the hens’ feed.

Question 24

What does sugar contribute to denaturing eggs?

Answer 24

It increases coagulation temperature.

Question 25

What does acid contribute to denaturing eggs?

Answer 25

It lowers coagulation temperature

Question 26

At what temperature do egg whites and egg yolks coagulate?

Answer 26

62-65 degrees (egg whites) | 65-70 degrees (egg yolks)

Question 27

What are the factors contributing to the coagulation of eggs?

Answer 27

- concentration - acid - sugar

Question 28

What does adding Salt do when beating egg whites?

Answer 28

- adding salt will help create a more stable, stiff foam without influencing the flavour as if helps bring the proteins together. - the salt and beating contribute to the denaturation of the egg protein

Question 29

What does adding acid to water when poaching eggs do?

Answer 29

Adding acid can assist in the denaturation process. Combining heat and an acid helps to denature the egg protein so it coagulates and holds it's shape at a lower temperature, making the end product more appealing.

Question 30

Describe the physical and sensory properties of meat

Answer 30

Lean meat is composed of bundles or long muscle fibres. Each fibre has a wall of elastin and is filled with water carrying dissolved protein, mineral and extractives. These fibres create the grain of the meat. The bundles of fibres are held together with collagen, which dissolves into gelatine during wet cooking.

Question 31

What makes meat tender?

Answer 31

The tenderness of a cut of meat depends on the age of the animal and the part of the body from which it comes.

Question 32

Describe the properties of the animals legs and neck

Answer 32

The animals legs and neck are hard-working muscles and highly developed, so their is a greater build-up of hard connective tissue-the resulting cute if meat are tougher, darker in colour and have a stronger flavour

Question 33

Describe the properties of meat around the ribs, back and rear.

Answer 33

The meat around the ribs, the back and the rear move less when the animal is in the pasture and produces the most tender cuts of meat.

Question 34

What other factors contribute to the tenderness of the meat?

Answer 34

- methods of preparation - methods of cooking - cut selected - meat can be partially tenderised by scoring or pounding or cutting across the grain - marinating

Question 35

What is the nutrient content of meat?

Answer 35

- protein - iron - zinc - vitamin B12 - fats (saturated fats, fat-soluble vitamins)

Question 36

How much of raw lean meat is made of water?

Answer 36

70%, which reduces after cooking

Question 37

Why is a dry method of cooking used for some meats?

Answer 37

The cuts of meat have enough water present in the tissue to enable the conversion of the protein, collagen, to gelatin.

Question 38

Why is a wet method of cooking used for some meats?

Answer 38

This is a slow way of cooking meat that is suitable for less tender cuts of meat. These cuts do not have enough water present in their tissues to convert collagen to gelatin. Therefore, the long, slow, wet cooking softens the connective tissue that makes meat tough.

Question 39

Changes that occur when meat is cooking: muscle fibre

Answer 39

The proteins in the muscle fibre begin to change shape (denature). As the proteins change, there is contraction in the direction of the muscle fibre, resulting in the piece of meat shrinking and becoming hard. -the longer the meat is heated, the tougher it becomes.

Question 40

Changes that occur when meat is cooking: connective tissue

Answer 40

The tough collagen, which makes up connective tissue, must be cookies sufficiently to convert it to water-soluble gelatine so that is becomes tender enough for us to bite through

Question 41

Changes that occur when meat is cooking: fat

Answer 41

During cooking the fat melts and acts as a lubricant so that the muscle fibre appears less tough. Fat also contributes to the flavour and aroma of cooked meat.

Question 42

Changes that occur when meat is cooking: water

Answer 42

When the meat is heated, a little water will flow out of the meat as the proteins begin to denature. Most of the water remains locked within the proteins. Meat cooked for too long will become dry because the water has been lost

Question 43

Nutrient content of poultry

Answer 43

Poultry has the American amount of protein as red and other white meats, less saturated fat and more polyunsaturated fat.

Question 44

Describe the thigh and leg meat of poultry

Answer 44

They are the active muscles of the bird so they are the tough cuts. They are a darker in colour because they require more oxygen to move about and are higher in fat -best for wet method of cooking

Question 45

Describe the breast of poultry

Answer 45

Domestic checked do not fly, so their breast meat is white and tender because there is less connective tissue. -best for dry method of cooking

Question 46

Describe the physical and sensory properties of seafood

Answer 46

The muscles are arranged in layer or short fibres. These bundles of short fibres are surrounded by very thin sheet ps of delicate connective tissue. Fish doesn't contain much connective tissue (3% only) which makes it fragile and easily converted to gelatine

Question 47

Describe the sensory properties of oily fish

Answer 47

The oil is dispersed throughout a darker coloured flesh and they have a strong flavour. e.g. Salmon, tuna, trout, sardines, mackerel and gem fish

Question 48

Describe the sensory properties of fish in the white classification

Answer 48

These fish have a white flesh and a delicate flavour. The oil is contain in a small sac near the liver. E.g. Whiting, flathead, flake, garfish and bream

Question 49

Describe the sensory properties of raw fish

Answer 49

- translucent - firm to touch - juices are clear and watery

Question 50

Describe the sensory properties of fully cooked fish

Answer 50

- flesh is opaque - flakes just begin to separate - juices are milky white

Question 51

Describe the chemical properties of seafood

Answer 51

- fish has a high water content (70% of flesh is water) - 20% of flesh is protein - fat in fish is a good source of omega 3 (especially oily fish)