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Food Science > Pectins and Gums > Flashcards

Pectins and Gums Flashcards

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1
Q

What is dietary fiber?

A

Dietary fiber is the edible parts of plants or carbs that are resistant to digestion and absorption.

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2
Q

What are the important polysaccharides in foods?

A

Pectins and gums

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3
Q

Why are pectins and gums important polysaccharides in foods?

A

Pectins and gums are important because of their functional properties.

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4
Q

What are uses for pectins and gums?

A

Thickeners, stabilizers and gelling agents.

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5
Q

What are pectic substances?

A

Important constituents of plant tissue

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6
Q

What are different types of pectic substances?

A

Protopectin, pectinic acids, pectins and pectic acid.

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7
Q

What is considered as a linear polymer of D-galacturonic acid joined by α-1,4 glycosidic linkages?

A

Pectic substances

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8
Q

Each glycosidic linkage is a _________ bond.

A

Cross-planar

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9
Q

How are pectic substances classified?

A

Based on the number of methyl ester groups attached to the polymer.

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10
Q

Which derivative of pectic substances does not have a methyl group?

A

Pectic acid

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11
Q

Where is protopectin formed?

A

Protopectin forms in immature fruits

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12
Q

Where is pectinic acid formed?

A

Pectinic acid forms in ripened fruits

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13
Q

Where is pectic acid formed?

A

Over-ripe fruits

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14
Q

Which pectic substance forms a gel?

A

Pectinic Acid

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15
Q

Which pectic substnace is insoluble in water?

A

Protopectin

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16
Q

True or False. The degree of esterification varies for pectins.

A

True

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17
Q

What compound needs to be present for low-methoxyl pectins to form a gel?

A

Calcium

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18
Q

What needs to be added to high-methoxyl pectins for a gel to form?

A

Sugar and acid

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19
Q

What is commonly used to form pectin jellies?

A

High-methoxyl pectins

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20
Q

Why is pectin hydrophillic?

A

Due to the large number of polar hydroxyl groups and charged carboxyl groups

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21
Q

True or False. The positive charge on the pectin molecule, coupled with their attraction to water, keeps them apart, so they form a sol.

A

False. The negative charge does this.

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22
Q

How does pectin gel formation occur?

A

Decrease the forces that attract the pectin molecules for water or increase the forces that attract the pectin molecules to each other.

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23
Q

How does sugar help with gel formation?

A

Sugar competes with water, making water less available to bond with pectin molecules

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24
Q

How doe acid help with gel formatin?

A

Acid reduces the pH and the charge on the pectin molecules. Making the pectin molecules no longer repel each other.

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25
Q

What are junction zones?

A

Attractive forces between molecules that help form the 3D network.

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26
Q

What is the purpose of junction zones?

A

To form pockets that trap water.

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27
Q

What was formed when the following occurs: 1) water binds to ionic polar groups on pectin
2) pectin molecules are negatively charged and hydrated
3) they do not react to each other

A

Pectin sol

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28
Q

What was formed when the following occurs:
1) Sugar is added
2) Acid is added

A

Pectin gel

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29
Q

What is something that decrease pectin interaction with water?

A

Sugar

30
Q

What is something that increases pectin molecules interaction with each other?

A

Acid, water trapped in network and pectin interacting with junction zones

31
Q

Pectin content of fruit depends on what factors?

A

The type of fruit and the maturity or ripeness

32
Q

How ca you obtain low-methoxyl pectin?

A

By demthylating pectin with enzymes, acid or alkaline.

33
Q

What is the critical control point of making jelly?

A

Boiling time

34
Q

What is a gum?

A

A group of complex hydrophilic carbohydrates containing thousands of monosaccharides units?

35
Q

What is the most common monosaccharide unit in a gum?

A

Galactose

36
Q

True or false. Gums are also referred to as hydrocolloids.

A

True

37
Q

What are characteristics of hydrocolloids?

A

Highly branched, cannot form gels, form stable aqueous colloidal dispersions or sols, and very viscous

38
Q

True or false. Gum is an insoluble fiber.

A

False. Gum is a soluble fiber

39
Q

What are 2 examples of seed gums?

A

Guar bean and locust bean gums?

40
Q

What are seed gums?

A

Branched polymers containing only mannose and galactose

41
Q

Which seed gum has a higher galactose ratio guar bean or locust bean?

A

Neither

42
Q

Which seed gum has a higher mannose ratio guar bean or locust bean?

A

Locust

43
Q

What seed gum stabilizes ice cream?

A

Guar bean

44
Q

What seed gum is a stabilizer in dairy and processed meat products?

A

Locust bean

45
Q

What are plant exudates?

A

Complex, highly branched polysaccharides

46
Q

What are two examples of plant exudates?

A

Two examples of plant exudates would be gum arabic and gum tragacanth.

47
Q

What plant exudate is highly soluble in water?

A

Gum arabic

48
Q

What plant exudate forms very viscous sols?

A

Gum tragacanth

49
Q

What is an application of gum arabic?

A

Stabilize emulsions and control ice crystallization

50
Q

What is an application of gum tragacanth?

A

Stabilizer in salad dressings, ice ream and confections. To give a creamy texture to food.

51
Q

How are microbial exudates produced?

A

Using fermentation by microorganisms

52
Q

What is the most common microbial exudates?

A

Xanthan

53
Q

What gum forms viscous sols that are stable over a wide pH and temperature?

A

Xanthan

54
Q

True or false. Seaweed polysaccharides are able to form gels under certain conditions.

A

True

55
Q

What is agar noted for?

A

Its strong, transparent, heat-reversible gels

56
Q

Agar contains what?

A

Agarose and agaropectin

57
Q

Agarose and agaropectin are polymers of what?

A

β-D- and α-L-galactose

58
Q

Where can you obtain agar?

A

Red seaweed

59
Q

Where can you obtain alginates?

A

Brown seaweed

60
Q

Alginates form gel in the presence of what ions?

A

Calcium

61
Q

True or False. Alginates contain mainly D-mannuronic acid and L-guluronic acid.

A

True

62
Q

What are 2 forms of cellulose that intend to increase viscosity of foods?

A

CMC and MC

63
Q
A
64
Q

What is a sol?

A

A fluid colloidal system of two or more components

65
Q

What is a gel?

A

A non fluid colloidal network or polymer network that is expanded throughout its whole volume by a fluid.

66
Q

In sol formation what promotes gel?

A

Attraction! Specifically pectin molecules attraction

67
Q

In sol formation what prevents gel formation?

A

Repulsion! Hydrophilic interactions and water hydration

68
Q

In gel formation how do you decrease repulsion?

A

Adding sugar or acid

69
Q

What factors affect pectin gel formation?

A

Degree of methylation, sugar content, pH, Calcium ion, endpoint temperature, boiling time

70
Q

What is the salt form of alginic acid and gum mainly extracted from cell walls of brown algae?

A

Sodium alginate

71
Q

True or false.Alginate-based hydrogel can be used for encapsulation and biomaterials.

A

True

72
Q

Alkaline pH produces what color?

A

Violet-blue or turquoise

Food Science (14 decks)

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