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Food Fundamentals > Lab 6 > Flashcards

Lab 6 Flashcards

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1
Q

What is Gelatin?

A

Protein derived from beef and pork bones and pork skin. Used in powder form in food prep to set a liquid or to turn a liquid into a solid as it is chilled.

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2
Q

What is a plant alternative of gelatin?

A

Agar flakes and Carrageenan -> from algae and seaweed

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3
Q

How do you prep gelatin?

A

Soften unflavored gelatin in cold water before it is dispersed in another liquid

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4
Q

What will happen to gelatin if it is not softened?

A

It will clump if boiling water is added

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5
Q

What can reduce the clumping of gelatin?

A

Sugar

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6
Q

What factors affect the setting of gelatin?

A

1) Gelatin concentration
2) Sugar
3) Acid
4) Salts
5) Physical Interference
6) Enzymes
7) Temperature

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7
Q

How does concentration affect gelatin?

A

There is minimum concentration necessary for gelling. 15ml for 500ml liquid

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8
Q

How does sugar affect gelatinization?

A

Sugar decreases gelatinization by competing with water for binding site on the gelatin molecule.

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9
Q

How does Acid affect gelatinization?

A

More tender when acidic. Most rigid between pH5-10

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10
Q

How does Salt affect gelatinization?

A

Gives a firmer gel.. like milk or hard water

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11
Q

How does physical interference affect gelatinization?

A

Presence of fruit/veg in gelatin product and mechanical agitation interfere with bond formation. Amount of liquid should be adjusted if solids are added. Solids should be added after some thickening so that gel structure can keep it well distributed and prevent sinking to the bottom

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12
Q

How do Enzymes affect gelatinization?

A

Proteolytic enzymes in raw fruits prevent gelling by denaturing gelatin.
-Bromelin in pineapple
-Actinidin in Kiwi
Easily destroyed by blanching the fruit or using canned versions

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13
Q

How does temperature and time affect gelatinization?

A

When boiled, gelatin loses its setting ability. Gel network is formed slowly but under cool temperatures. BUT if it is cooled very quickly, a weak gel will form due to the weak bonds and at room temp, it will re-liquify

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14
Q

What is an emulsion

A

Dispersion of one liquid in another. Mutually antagonistic or immiscible.

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15
Q

What are the classes of emulsions?

A

1) temporary emulsion
2) Semi-Permanent emulsion
3) Permanent emulsion

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16
Q

How are emulsions classified?

A

Degree of stability

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17
Q

What is a temporary emulsion?

A

thin viscosity and stability ex Italian dressing

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18
Q

What is a semi-permanent emulsion?

A

have a viscosity similar to thick cream and a higher degree of stability ex commercial dressings

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19
Q

What is a permanent emulsion?

A

Have a very thick viscosity (semi-solid) and are very stable ex. mayo

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20
Q

What are starches used for in food prep?

A

Thickening purposes

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21
Q

What are some starches that thicken?

A

wheat flour, cornstarch, tapioca, arrowroot, sage starch, rice starch, modified starch, sorghum starch and potato starch.

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22
Q

The ratio of the polysaccharide composition (amylopectin vs. amylose) determines…?

A

The starch’s characteristics

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23
Q

What are some problems with mixing liquid and starch?

A

Starch tends to form lumps that are very difficult to dissolve. Starch granules on the outside of the lump can absorb water and gelatinize during cooking, forming a water-proof gel coating while granules on the inside remain dry.

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24
Q

How do you prevent lumps in liquid and starch mixes?

A

Separating or dispersing granules before liquid is added by coating in fat, surrounding it in sugar, or dispersing in a small amount of cold liquid.

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25
Q

What is Reversible swelling?

A

Water is absorbed in the starch granules

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26
Q

Does swelling increase with heat or cold?

A

Heat.

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27
Q

What is BIREFRINGENCE?

A

Molecular order

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28
Q

What is gelatinization?

A

Irreversible breakdown of starch structure-> translucent

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29
Q

What happens with further heating of the starch and liquid?

A

gelatinizes and thicken the mix. Each has a gleatinization temperature range.

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30
Q

What happens with continued heating?

A

Pasting -> this is due to starch granules swelling enormously, starch leaking from the granule (amylose especially) and the water evaporation

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31
Q

When does pasting happen?

A

Approximately 5 minutes of cooking beyond gelatinization point

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32
Q

What happens with over-cooking and over-stirring?

A

Causes swollen starch granules and thinning of sauce

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33
Q

What happens when the starch paste cools?

A

A gell forms due to the formation of various bonds.

34
Q

Which starches cloud when heated and gel quickly when cooled?

A

High content of amylose

-cornstarch, rice, maize

35
Q

Which starches will remain more translucent and not gell as well?

A

Lower Amylose content (more amylopectin)
-tapioca, potato, arrowroot, waxy cornstarch
BUT they will thicken due to the amylopectin

36
Q

Which paste is preferable for a glaze?

A

Lower amylose-> translucent

37
Q

Which starches result in better freezing?

A

Tapioca and Arrowroot

38
Q

What is syneresis?

A

Leakage or seperation of liquid from the gel. If a cooled starch is left standing for some time.

39
Q

Why does syneresis happen?

A

Amylose molecules continue to form bonds, forcing out water

Accelerated if the gel is frozen- water is unable to rebind to fragile mass.

40
Q

What happens to the thickening power when starch is not stored in an airtight container?

A

LOWERS

41
Q

How dies sugar effect gelatinization of starches?

A

Competes with starch for water. IF in small amounts, it can tenderize starch gels and prevent mechanical damage from over stirring. Large amounts will decrease gel strength (can turn into a thick mass)
Can be added after gelatinized and thickened

42
Q

How does Dextrized starch or acids effect gelatinization of starches?

A

Decreases the thickening power

43
Q

How are white sauce made?

A

Milk, thickened with flour, dispersed in fat (roux) and cooked together and removed the starchy taste. Consistency is dependant on the proportions of the thickening agent (flour) to liquid (milk).

44
Q

A veloute uses ..

A

white stock as liquid

45
Q

Creamy veloute uses ..

A

cream in addition to stock

46
Q

Mornay sauce contains ..

A

Cheese

47
Q

Brown sauces are made with ..

A

brown roux (fat) and brown stock, most flavourful when made with meat drippings.

48
Q

Reduction sauces contain no ..

A

flour, develop from simmering until the liquid has evaporated, achieving a thickened consistency.

49
Q

Thin bechemal sauce ..

A

used in cream soup.

50
Q

Medium bechemal sauce ..

A

pasts dishes, over fish and poultry.

51
Q

Thick bechemal sauce ..

A

in soufflés

52
Q

What does bechemal sauce consist of ?

A

Milk, flour, margarine/butter

53
Q

Instant/canned pudding contain a high amount of :

A

modified starch, pre gelatinized.

54
Q

Instant thickening agents are useful for ..

A

people with dysphagia.

55
Q

Thickening of beverage reduces ___

A

the speed of transport of volts to oral cavity thus preventing choking.

56
Q

What is a consistometer used for ?

A

Setting recommended concentrations required to obtain the consistency categories.

57
Q

what are the consistency categories ?

A

Nectar, Honey, Pudding

58
Q

What are modified textured diets?

A

Pureed or blended, modified to accommodate chewing or swallowing difficulties.

59
Q

define pureed

A

thick paste similar to consistency of applesauce or mashed potatoes. May need to be strained, to obtain smooth product.

60
Q

Define blenderized

A

foods with consistency that will pass through a straw. gelatine slurry may be incorporated to soften dry and crumbly foods.

61
Q

Define dysphagia

A

swallowing disorder that requires liquids to be thickens, easier to swallow.

62
Q

Examples of thickeners for dysphagia

A 
Resource Thicken Up
Quick Thick
Starches
Potato Falkes
Infant/instant cereal
Bread crumbs
Skim milk powder
Pureed veg and fruit
63
Q

Eg white foams are used for what __

A

meringues, souffles, omelettes and sponge cakes. Due to their light and porous texture.

64
Q

Advantage of using egg white foams

A

Reducing caloric content while increasing volume

65
Q

Factors that affect formation and stability of egg white foams:

A

1) Copper bowl
2) Temp
3) Concentration
4) Acid
5) Sigar
6) Fat
7) over beating

66
Q

Explain copper bowl

A

volume and firmness of egg white increases bc of RXN with COPPER and CONALBUMIN (protein) in egg.

67
Q

Explain temp

A

room temp = greater volume vs refrig. eggs.

WHY? lowered surface tensions of warmer egg whites BUT stability of foam is not as great at room temp.

68
Q

Explain concentration

A

Dilution w/ water increases volume BUT decreases stability of egg white foam.

69
Q

Explain acid

A

Denatures pH to near isoelectric pt. Proteins are now more sensitive to denaturation.
Pinch of tartar at beginning will INCREASE beating time to produce foam, but INCREASES foam stability.

70
Q

Explain sugar

A

increase the time req. for development of foam but foam is stable. Sugar should be added little at a time, beating after each addition.

71
Q

What happens if sugar is added to egg white before beating?

A

extensive beating req.

foam = stable but reduced in volume.

72
Q

What happened if foam is beaten to stiff stage after each sugar addition?

A

Foam will have a dull surface after baking.

73
Q

Explain fat

A

the addition of even small amount of fat will INTERFERE w/ formation of foam. Egg yolks =contamination!!

74
Q

Explain over beating

A

peak stability of foam occurs BEFORE max volume occurs. THUS .. overbearing produces an unstable foam, tendency to collapse and become coarse.

75
Q

Egg yolks ___

A

have a GREATER thickening ability than egg whites

76
Q

Custards, sauces + certain pie fillings depend on ..

A

egg protein coagulation and or starch gelatinization for thickening.

77
Q

Explain bain marie ?

A

When baked custards are placed in water bath (like in lab) this allows to reach equal temp. to obtain homogenous temperature UNLESS they include starch, which will prevent curdling by limiting the rejoining of proteins after they denature and unwind.

78
Q

what is synersis ?

A

When an overbooked custard curdles and weeps.

79
Q

How can we prevent coagulation and undesirable texture ? (pudding)

A

Gradual increase in temp, by adding small amount of hot liquid into egg yolk slowly.

80
Q

How can we prevent skin forming at surface of pudding?

A

Dotting w/ butter or covered with plastic wrap.

Food Fundamentals (7 decks)

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