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Food Chemistry > carbs > Flashcards

carbs Flashcards

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1
Q

monosaccharide

A

Monosaccharides are the fundamental units because they are not hydrolyzed by acid to form a smaller unit.

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2
Q

disaccharide

A

consist of two simple sugarslinked by a covalent

glycosidic bond

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3
Q

oligosaccharide

A

consist of 3 to 10 monosaccharides linked together by glycosidic bonds

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4
Q

what is the functionality of monosaccharides

A 
Coloring agents (caramel color)
Production of flavors (caramelization)
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5
Q

what is the functionality of a polysach.

A 
Thickening agents 
Gelling agents
Emulsion stabilizers
Water holding/ binding agents
Anticaking agents
Edible films
Encapsulate flavors
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6
Q

complete

Their actual conformation is … in their crystalline state and
predominantly cyclic in solution

A

cyclic

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7
Q

Cyclization is due to the formation of internal … and

…

A

hemiacetals and hemiketals

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8
Q

hemeacetal formation in glucose forms a

A

pyranose ring

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9
Q

hemiketal formation in fructose form a

A

furanose ring

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10
Q

mutaotation

A

is the result of the cyclic form opening up and recyclizing, coming to equilibrium with its anomer.

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11
Q

which is the most comon test for reducing sugars

A

fehling’s test

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12
Q

The disaccharide maltose a reducing sugar while the

disaccharide sucrose is a non-reducing sugar - why?

A

Because even when 2 molecules of maltose are bind together they can open up however fructose cannot do this and so it is not a reducing sugar

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13
Q

which are the 2 ways that water can be elimiated from sugar

A
  1. by reaction of tehir hydroxyl groups

2. elimination of water grom within a sugar molecule, leading to the formation of higly unstaurated ring structure

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14
Q

A common intermediate formed during caramelization reactions by
dehydration is

A

hydroxymethylfurfural (HMF)

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15
Q

what are the 2 categories of browning reactions

A

(1) oxidative browning

(2) non-oxidative browning

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16
Q

caramelization reaction used to producde

A

flavor, color

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17
Q

carame flavor and color are made of

A

flavors - sucrose

color- glucose

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18
Q

what is an amadori rearrangement

A

schiff base to amadori compound

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19
Q

at higher temperature in the maillard reacion , the major reactions will be

A

dehydration and fragmentation

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20
Q

strecker degration

A

subcomponent of maillard reaction. Involves free amino acids produced by meaillard reacion or caramelization

21
Q

which is the most sweet of the sugars and the less

A

most- fructose

less- lactose

22
Q

true or false

The least sweet the less soluble

A

true

23
Q

which sugar is an exception int he sence of sweetnes of the sugar alcohols

A

xylitol

24
Q

the properties of polysaccharide are a fucntion of

A

their sugar/chemical makeup
• the presence of unique functional groups
• their molecular weight and degree of branching
• a combination thereo

25
Q

wha are the unique porperties of starch

A

thickening, texture

26
Q

starch is made up of

A

D glucose which are divided in amylose (alpha 1-4 linkages) and amylopectin (alpha 1-6)

27
Q

explain starch granules

A

granyles are characterisic of the starch source. The starch is isolated and it is white. It contains granules that are made of amylose and amylopectin

28
Q

what happens in gelatinization

A

starch and water are heated and it causes teh granules to swell. The viscocity increases

29
Q

what are the variables that occur in the starch

A

concentration of starch
• The amylose:amylopectin ratio of the starch
• The average molecular weight (chain length) of the starch
• The rate of cooling
• The presence of other components in solution

30
Q

true or false
Amylopectin is a highly branched water-dispersible
macromolecule

A

true

31
Q

retrogration

A

continued Hbonds formation between starch molecules

32
Q

what are the 2 problems with retrogration

A
  1. texture changes

2. syneresis may occur = the gel tightens up that it starts to exude water

33
Q

factors affecting behaviours of starches in complex food system

A

pH, ionic strengh, proteins,

34
Q

pre gelatinized strach

A

Starches granules are heated below the gelatinization temperature of the starch, causing them to swell
Causes some disorganization of the starch granule- making it dispersible in cold water and requires less heat or time to develop viscosity

35
Q

acid modified starches

A

Produced by holding starch just below its gelatinization temperature in an acidic medium

Acid is used to partially and randomly hydrolyze the glycosidic linkage in the starch granule without breaking up the INTEGRITY of the granule per se.

36
Q

cross linked starches explain

A

Maximum viscosity is normally reached when the granules are swollen
extensively but still intact - however, swollen granules normally break
down with subsequent shear.
Can hold starch granules together by cross-linking starch chemically so
that the swollen granule retains its integrity

37
Q

what are the 2 types of starch conversion

A

dry pyroconversion and acid hydrolysis

38
Q

what is pyroconversion

A

Starch granules are sprayed with dilute HCl and subjected to relatively high temperatures

39
Q

what are the 3 products that are produced by pyroconversion

A

white dextrins, yellow dextrins, british gums

40
Q

white dextrins

A

can be Under conditions of high moisture, high acid, and relatively low
temperature, hydrolysis predominates.

41
Q

yellow dextrins

A

Lower moisture, moderate acid, higher temperature. Color due to caramelizatio

42
Q

british gums

A

Little or no acid used - high temp. Dark color. Viscous and capable of forming a stiff gel

43
Q

what are the 4 available enzymes to broke starch

A

alpha amylase
beta amylase
glycoamylase
pullulanase

44
Q

what does alpha amylase does

A

attack the starch everywhere except the alpha 1- 6 branch. produce oligosaccharide

45
Q

what does beta amylase does

A

attacks the non reducing end of the starch. Produces maltose! Also develop sweetness rapidly

46
Q

what does the glucoamylase does

A

remove single glucose units form the non reducing end of starch and to split maltose into 2 glucose units

47
Q

what pullulanase does

A

Take care of the branch

48
Q

High-fructose corn syrups are similar to … and are in direct competition with sucrose, which is commonly inverted
(e.g., using the enzyme invertase) to stabilize its sweetness in
acidic environments )

A

invert syrups

49
Q

Cellulose is often accompanied by other carbohydrates
(hemicelluloses and pectic substances) and … to form the
structural components of most plant tissues

A

lignin

Food Chemistry (11 decks)

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