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FN 2232 > Lecture 7 > Flashcards

Lecture 7 Flashcards

1
Q

What is starch?

A

A Carb

-polysaccharide made up of glucose molecules

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2
Q

How do plants store energy?

A

As starch

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3
Q

What are the 2 major categories of starch?

A

Native Starch: Pure starch isolated from original plant material

Modified Starch: Native starch that has undergone chemical or physical processing to change its properties

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4
Q

What is the difference between amylose and amylopectin?

A

Amylose: Linear molecule of glucoses

Amylopectin: Branched molecule of glucoses stuck together

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5
Q

How are glucose molecules joined together in starch?

A

No. 1 carbon atom of one glucose molecule and the no.4 carbon atom of the next one

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6
Q

How does amylopectin join the branching glucose molecules?

A

Joined between No. 1 atom of one glucose unit and the No. 6 carbon atom

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7
Q

How is starch broken down?

A

Amylase beaks down the glucoside bond of maltose to form glucose

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8
Q

What are sources of starch?

A

Cereal grains (corn, wheat, rice, oats)

Legumes

Roots and tubers

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9
Q

What are the steps in the wet milling process?

A
  1. Cleaning
  2. Grinding or Grating
  3. Slurry
  4. Separation/Refining
  5. Drying
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10
Q

What is refined starch?

A

Refined to remove other components of the food such as fat, protein vitamins and minerals

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11
Q

What is refined starch added too?

A

Added to other foods to act as a thickener, stabilizer, bulking agent and anti caking agent
-little nutritive value

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12
Q

What is a gel?

A

Colloidal dispersion that holds shape

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13
Q

What is a colloid?

A

Intermediate between small particles in solution and large particles in suspension

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14
Q

What is a starch granule?

A

Starch is deposited in plants in organized units

-seeds, roots and tubers

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15
Q

What is Birefringence?

A

When he starch molecules are observed microscopically under polarized light

  • light is rotated so that the cross pattern on each granite is observed
  • This pattern disappears once. the starch is heateed
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16
Q

What is native starch?

A

No physical or chemical modification of the starch

-Developed through traditional plant breeding or genetic engineering

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17
Q

What is modified starch?

A

Chemical or physical modifications may be used to change function in food preparation

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18
Q

What are the steps to modify starch?

A

Hydrolysis or acid converted–> used in the confecitionary industry

Cross-linked or cross-bonded–> improved viscosity and texture

Substitution or stabilization–> Prevents retrogradation

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19
Q

In step one of modifying starch what is the result?

A

Low viscosity paste
Produces stiff gel
Useful in confectionary industry

20
Q

In step 2 of modifying starch, what is the result?

A
  • Increased temp for hydration therefore greater tolerance to heat
  • Resistant to shear or stirring
  • Useful for canned soup, spaghetti sauces and pie fillings
21
Q

In step 3 of modifying starch what is the result?

A
  • Prevents retrogradation
  • Reduces syneresis
  • Useful for frozen or refrigerated starch-thickened foods
22
Q

What is the function of modified starch?

A

Chemical or physical modifications may be used to change function in food preparation

23
Q

What are the ways in which starch is physically modified?

A

Instant or pregelatinized–> instant dry mixes, gravies, sauces

Cold water swelling–> pregelatiniized

Heat treated–> greeter viscosity and stability

24
Q

What is resistant starch?

A

Not digested by the human body

25
Q

What are the 4 main types of resistant starch?

A

RS1- Resistant to digestion (whole grains, seeds)
RS2- Resists digestion due to compact structure (green bananas)
RS3-Retrograded (cooked and cooled potatoes)
RS4- Only one chemically modified (modified starches)

26
Q

What can modified starch be used in food for?

A

Increase fibre content

27
Q

What effect does dry heat have on starch?

A

Starch becomes more soluble
Reduced thickening ability
Dextrinization: when starch Is broken down into dextrins
Brown, nutty, toasted flavour develops

28
Q

What effect does moist heat have on starch?

A

Starch granules insoluble in cold water
Colloidal dispersion produced with heating
Starch paste

29
Q

What happens during gelatinization?

A

With heat, starch granules absorb water and swell

Increased viscosity and increased translucency

30
Q

What happens during get formation/gelation?

A

Occurs with cooling

31
Q

What occurs during retrogradation?

A

Occurs with standing after gel formation
Amylose molecules associate more closely
Gel network (syneresis)

32
Q

What are the factors affecting starch pastes?

A

Temperature and time of heating

Agitation and stirring

Acidity

Addition of other ingredients

33
Q

How is starch pastes affected by temperature and time of heating?

A

Thicker if cooked quickly

If undercooked

  • raw starch flavour
  • less smooth and silky
34
Q

How is starch pastes affected by agitation or stirring?

A

Stirring is desirable to disperse starch

If excessive- starch granules may rupture
-Slick and pasty mouthful

35
Q

How is starch pastes affected by acidity?

A

May cause fragmentation and hydrolysis

Decrease of thickening powder

Add acid late in cooking process (lemon pie)

36
Q

How is starch pastes affected by the addition of other ingredients?

A

Sugar: raises temperature of gelatinization and may decrease sicosity

Fat & Protein: delay hydration of starch and lowers rate of viscosity development

37
Q

What are the methods of cooking with starch?

A

Combining starch with hot liquids

Roux: Prepared by blending melted fat with flour

Slurry: Mixing flour or starch with some of the cold liquid which is then added to a hot liquid while stirring

38
Q

How do you thicken a liquid with a roux?

A

Add cold liquid or stock to a hot roux
OR
Add cold roux to a hot liquid or stock

39
Q

What do you need to avoid doing when making a roux?

A

Blending a hot roux into a hot liquid is not recommended because it is very hard to smoothly blend the roux into the liquid before lumps are formed due to the rapid gelatinization of the starch

40
Q

What are the 5 basic bother sauces?

A

Bechamel (fat, flour, milk, seasoning)
Veloute ( fat, flour, veal/chicken/fish stock, seasoning)
Espagnole (fat, flour, beef stock, seasoning)
Tomato
Hollandaise

41
Q

Which of the sauces are thickened with starch or emulsion?

A 
Starch:
Bechamel
Veloute
Espagnol 
Tomato (sometimes)

Emulsion:
Hollandaise

42
Q

What do cream soups usually have?

A

Mirepoix for flavouring

Thickened with

  • starch (roux or slurry)
  • Pureed starchy vegetables (potatoes)
43
Q

What is the thing you dont want to happen with cream soups?

A

Curdling

  • acid (tomatoes)
  • Freshness of milk/cream
  • Higher fat milk/cream is more stable than low or nonfat
44
Q

How do you thicken desserts with starch?

A

Corn starch (clear & glossy)
Flour
Tapioca

Cook starch mixture before adding eggs
-temper eggs

45
Q

Can starch be microwaved?

A

Yes, best for small batched

Stop microwave and stir in about every 1 minute

FN 2232 (20 decks)

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