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2) Food Chemistry I > Carbohydrates I > Flashcards

Carbohydrates I Flashcards

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1
Q

The fundamental units of carbohydrates are __________

A

monosaccharides

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2
Q

What is the general formula of monosaccharides?

A

Cx(H2O)x

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3
Q

Monosaccharides are the fundamental units because they are not _______ by ________ to form a smaller unit.

A

hydrolyzed

acid

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4
Q

The most common monosaccharides have the molecular formula: ________

A

C6H12O6

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5
Q

Monosaccharides exist primarily in the ________ form

A

cyclized

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6
Q

What are the three monosaccharides?

A
  • Glucose
  • Galactose
  • Fructose
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7
Q

Disaccharides consist of two sugars linked by a covalent _________

A

glycosidic bond

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8
Q

_______ is the common enzymatic hydrolysis product of starch

A

Maltose

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9
Q

________ is the common table sugar

A

Sucrose

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10
Q

_______ is the major sugar in cow’s milk

A

Lactose

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11
Q

________ consist of 3 to 10 monosaccharides linked together by glycosidic bonds

A

Oligosaccharides

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12
Q

_________ is a trisaccharide formed of galactose, glucose, and fructose

A

Raffinose

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13
Q

_________ is a tetrasaccharide, formed of glucose, fructose, and two galactose

A

Stachyose
glucose
fructose
two galactose

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14
Q

When the chain length of an oligosaccharide exceeds __ units, the polymers are termed _________

A

10

polysaccharides

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15
Q

________ is an energy source in seeds

A

Starch for germination

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16
Q

_______ and ________ are structural carbohydrate components

A

Cellulose

hemicellulose

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17
Q

______ and ________ are a ready supply of energy

A

Monosaccharides

disaccharides

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18
Q

_________ are a short-term energy supply for muscles

A

Glycogen

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19
Q

_______ and ________ act as sweetening agents, coloring agents, and produce flavors

A

Monosaccharides

disaccharides

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20
Q

_______ act as thickening agents, gelling agents, emulsion stabilizers, water-holding agents and anticaking agents

A

Polysaccharides

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21
Q

Monosaccharides range from __ carbons to __ carbons

A

3

7

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22
Q

Monosaccharides have either a ______ or an _____ functional group in their linear form

A

ketone

aldehyde

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23
Q

The carbon chain of a monosaccharide is numbered from the aldehyde (C-__) or the ketone (C-__) functional group down.

A

1

2

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24
Q

__________ exhibit optical isomerism (D- and L-isomers)

A

Monosaccharides

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25
Q

The smallest monosaccharide is _________, which has ___ carbons

A

glyceraldehyde

3

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26
Q

Glyceraldehyde has ____ asymmetric carbon(s)

A

1

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27
Q

_______ is used as a reference compound to determine D-L isomerism

A

Glyceraldehyde

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28
Q

In the Fischer projections, OH group on the asymmetric carbon is on the _____ in the D-isomer and on the ____ in the L-isomer.

A

right

left

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29
Q

Apart from glyceraldehyde, D or L isomerism for other sugars refers ONLY to the n-___ carbon (___ from the bottom) and not any of the other asymmetric carbons that may be in the chain.

A

1

2nd

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30
Q

Optical isomers involving asymmetric carbons other than the carbon at the n-1 position are considered different sugars or _______.

A

epimers

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31
Q

All C6 aldehyde monosaccharaides are ______ of glucose.

A

epimers

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32
Q

Monosaccharides can be classified on the basis of ______ and __________

A

carbon number

functional group

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33
Q

The actual conformation of simple sugars is _____ in their crystalline state and in solution, but they are illustrated as ______ for simplicity

A

cyclic

linear

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34
Q

Cyclization is due to the formation of internal _______ and _______

A

hemiacetals

hemiketals

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35
Q

A hemiacetal is formed from an ______ and an _______

A

alcohol

aldehyde

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36
Q

A hemiketal is formed from a ______ and an _______

A

ketone

alcohol

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37
Q

In the cyclization of monosaccharides, these reactions are (intermolecular/intramolecular)

A

intramolecular

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38
Q

Hemiacetal formation in glucose (an aldohexose) forms a ________ ring

A

pyranose

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39
Q

Hemiketal formation in fructose (a ketohexose) forms a ________ ring

A

furanose

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40
Q

Glucose is an ________

A

aldohexose

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41
Q

Fructose is a _________

A

ketohexose

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42
Q

Cyclization results in an additional ________________ at the ___ position

A

asymmetric carbon

C1

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43
Q

The additional asymmetric carbon at the C1 position from cyclization is termed _________ carbon, and leads to ___ optical isomers, termed ________

A

anomeric
2
anomers

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44
Q

The cyclic form in which the OH group at the anomeric carbon is on the same side of the ring as C6 is termed ___

A

B

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45
Q

The cyclic form in which the OH group at the anomeric carbon is on the opposite side of the ring is termed ___

A

alpha

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46
Q

The crystalline form of the simple sugars is always _____.

A

cyclical

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47
Q

In solution, there is a dynamic equilibrium between the three
forms: ______, _____, and _______

A

alpha
beta
open chain

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48
Q

The dynamic equilibrium between a, B, and open-chain simple sugars is observed by following the ________ of _______ by a solution of the sugar

A

optical rotation

plane-polarized light

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49
Q

When pure ___-D-glucopyranose is dissolved in water, the optical rotation starts at 112o and gradually changes to 53o.

A

alpha

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50
Q

When pure ___-D-glucopyranose is dissolved in water, the optical rotation starts at 19o and gradually changes to 53o.

A

beta

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51
Q

______ is the phenomenon that causes the change in optical rotation

A

mutarotation

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52
Q

_______ is the result of the cyclic form opening up and re- cyclizing, coming to equilibrium with its _____.

A

Mutarotation

anomer

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53
Q

For _____, the equilibrium is roughly 62% α-D-glucopyranose and 37% β-D-glucopyranose, with only 1% in the open-chain form with the active ______ group.

A

glucose

aldehyde

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54
Q

The equilibrium of (glucose/fructose) is more complex than (glucose/fructose) since it is a ______

A

fructose
glucose
hemiketal

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55
Q

Cyclization via the formation of a _______ can produce either a five-membered ____ ring or a six-membered _____ ring

A

hemiketal
furanose
pyranose

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56
Q

The formation of furanose (five-membered) ring by attack of OH group at C-__ on C-__ keto group.

A

5

2

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57
Q

Formation of pyranose (six-membered) ring by attack of OH group at C-__ on C-__ keto group.

A

6

2

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58
Q

The aldehyde group present on ALDOSES has strong _________

A

reducing power

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59
Q

________ are capable of reducing metal ions (in an oxidation- reduction reaction that converts the _____ to a _________).

A

Aldehydes
aldehyde
carboxylic acid

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60
Q

As a group, ________ are generally termed “reducing sugars” and can be tested for and quantified by specific __________ reactions

A

monosaccharides

oxidation/reduction

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61
Q

The most common test for reducing sugars is _________, which involves the reduction of Cu(__) in the form of __________ to Cu(__) oxide.

A

Fehling’s test
II
copper tartrate
I

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62
Q

Fehling’s reagent only reacts with free ________ groups in the ________ form

A

aldehyde groups

open-chain

63
Q

Only 1% of sugar is in the _____ form

A

open-chain

64
Q

When

the ________ form is depleted, it is replenished by the opening of the ring forms (with which it is in equilibrium).

A

open-chain

65
Q

Is fructose a reducing sugar? Does it have an aldehyde group?

A
  • It is a reducing sugar

- It does not have an aldehyde group

66
Q

Fructose is a reducing sugar since in a ____ medium, _________ takes place and fructose is converted to ______, which then is capable of reacting with the Fehling’s solution

A

basic
enolization
glucose

67
Q

The reducing power of a sugar is lost when the ____ at the ______ carbon of the cyclic form is covalently bonded to another group because this prevents the ring from opening

A

OH

anomeric

68
Q

Conversion to the open-chain form requires that an __ group bound to the ____ carbon reverts back to an _____ group

A

OH
anomeric
aldehyde

69
Q

Is maltose a reducing sugar? What about sucrose?

A

Maltose: reducing
Sucrose: non-reducing

70
Q

Maltose is composed of ______ and ______ linked by a ______ linkage

A

glucose
glucose
a-1-4

71
Q

The anomeric carbon of the __nd glucose of _____ is not involved in the glycosidic bond, ring opening can occur at one end of the molecule, rendering it a reducing sugar

A

2

maltose

72
Q

_____ is a reducing sugar but has half the reducing power of glucose because _______________________________

A

Maltose

one of the two anomeric carbons is used in the glycosidic bond

73
Q

Sucrose is composed of _______ and ______ linked by a ____ glycosidic linkage

A

glucose
fructose
a-1-2

74
Q

______ is a non-reducing disaccharide because both ______ carbons are tied up in the glycosidic bond, so the ring opening cannot occur

A

Sucrose

anomeric

75
Q

______ reactions of sugars are the basis for _______ and the Maillard reaction

A

Dehydration

caramelization

76
Q

Dehydration reactions can take place at temperatures below ____oC, and in ____ solutions, but they occur very slowly

A

100

dilute

77
Q

Dehydration reactions are prevalent in concentrated sugar solutions at temperatures above 130oC, or in _____ pH

A

acidic

78
Q

As water evaporates from the solution, ______ dehydration and oxidative _____ can take place, leading to the breakdown of the carbon chain into smaller units, which produce ____ compounds

A

molecular (internal)
fission
flavor

79
Q

What are the two ways that water can be eliminated from a sugar molecule? Which one is predominant?

A

1) The loss of water from two sugar molecules by reaction of their hydroxyl groups
2) Elimination of water from within a sugar molecule, leading to the formation of highly unsaturated ring structures (predominant)

80
Q

What does the loss of water from two sugar molecules by reaction of their hydroxyl groups lead to?

A

Random polymerization

81
Q

What does the elimination of water from within a sugar molecule lead to?

A

The formation of highly unsaturated ring structures

82
Q

A common intermediate formed during caramelization reactions by dehydration is _____________________

A

hydroxymethylfurfural (HMF)

83
Q

Hydroxymethylfurfural (HMF) is formed from the loss of __ water molecules

A

3

84
Q

HMF is formed from _______, which is converted to ______, and HMF once it loses 3 water molecules

A

fructopyranose

fructofuranose

85
Q

Fragmentation reactions of highly unsaturated ring structures produce various (high/low)-molecular-weight, (saturated/unsaturated) and reactive compounds, which can ________

A

low
unsaturated
polymerize

86
Q

Fragmentation of highly unsaturated ring structures produces _____, _____, and _____ under (acidic/alkaline) conditions

A

acetol
acetoin
diacetyl
alkaline

87
Q

Extensive dehydration reactions eventually lead to the formation of an amorphous, charged brown pigment commonly called _______.

A

caramel

88
Q

What are the two categories of browning reactions?

A

1) Oxidative (enzymatic)

2) Non-oxidative (non-enzymatic)

89
Q

Oxidative browning is associated with browning of _______, and not related to carbohydrates

A

plant tissues

90
Q

Oxidative browning is instigated by ___________, which oxidizes _______ into ________

A 
polyphenol oxidase (PPO)
mono- or dihydroxy phenols
quinones
91
Q

________ are quite reactive and can react non-enzymatically to polymerize into a brown pigment.

A

Quinones

92
Q

Other enzymes are indirectly associated with browning, including oxidative enzymes such as ________ and _______, which can produce reactive ______ compounds that can undergo non-enzymatic browning

A

ascorbic acid oxidase
lipoxygenase
carbonyl

93
Q

_________ reaction occurs when any concentrated sugar solution is heated.

A

Caramelization

94
Q

Caramelization is used to produce _______ and _______

A

caramel syrup

caramel color

95
Q

Caramel flavors are generally made from ___________

A

concentrated sucrose solutions

96
Q

Caramel color are generally made from ________

A

glucose syrup

97
Q

The two main reactions in caramelization are _______ and ________, producing (high/low) molecular weight (fat/water) soluble polymers that are very dark in color

A

dehydration
polymerization
high
water

98
Q

__________ produces compounds that have a high tinctorial power

A

Caramelization

99
Q

The Maillard reaction involves the reaction of ______ sugars with primary _______, generally amino acids and protein

A

reducing

amines

100
Q

In the _____ reactions, color, flavor, and volatinle compounds are produced

A

Maillard

101
Q

The _______ reaction is at the root of coffee aroma, popcorn aroma, roasted peanut flavor, and baked bread aroma

A

Maillard

102
Q

In the Maillard reaction, the first reaction is the _________ of a primary amine and a reducing sugar to form a _______ followed by the formation of an __________

A

condensation
Schiff base
Amadori compound

103
Q

The ______ compound in the Maillard reaction is comparable to HMF in caramelization

A

Amadori compound

104
Q

What is the key intermediate in the Maillard reaction?

A

Amadori compound

105
Q

The overall process of converting from the initial Schiff base to
an Amadori compound is termed _________________

A

Amadori rearrangement

106
Q

The Amadori compound can lose _____ from within the molecule

A

water

107
Q

Following the formation of the Amadori compound in the Maillard reaction, what are the major reactions at higher temperatures?

A

Dehydration and fragmentation

108
Q

What is the difference between the Maillard reaction at high temperatures and caramelization?

A

An amine group attached to the sugar in the Maillard reaction and hence the end products tend to contain nitrogen in their structure.

109
Q

In the Maillard reaction, fragmentation produces short-chain highly unsaturated ______ and _____ compounds that can polymerize and/or be released as ______ into the environment

A

carbonyl
amino
volatile

110
Q

The net result of the Maillard reaction is that ____ pigments and volatile compounds containing ______ are formed.

A

brown

nitrogen

111
Q

___________ is a subcomponent of the Maillard reaction.

A

Strecker degradation

112
Q

The Strecker degradation involves the reaction of free ___________ with the ____________ intermediates produced by either the Maillard reaction or caramelization reactions

A

amino acids

dicarbonyl

113
Q

The products formed from the Strecker degradation are ____, ______, ______, and _______, which are compounds that contribute to the characteristic aroma of roasted foods

A

CO2
ammonia
formaldehyde
pyrazines

114
Q

The Strecker aldehyde and _______ give rise to strong _____

A

aminoketone

odors

115
Q

Ethanal, methylpropanal, and 2-phenylethanal are common _________

A

Strecker aldehydes

116
Q

_______ is a Strecker aldehyde with a fruity, sweet aroma

A

Etanal

117
Q

_________ is a Strecker aldehyde with a malty aroma

A

Methylpropanal

118
Q

_________ is a Strecker aldehyde with a flowery/honey like aroma

A

2-phenylethanal

119
Q

Condensation of two __________ may yield pyrazine derivatives that are also powerful aroma compounds

A

aminoketones

120
Q

______________ reactions are used commercially to produce artificial flavor compounds

A

Strecker degradation

121
Q

By reacting _____ and selected ________ or mixtures thereof under the proper conditions, one can produce a wide variety of flavors such as chocolate, bread, caramel, almond, and many other flavors.

A

sugars

amino acids

122
Q

Can sweetness be measured?

A

No, it is a subjective response

123
Q

______ is considered the least sweet sugar, while _______ is considered the most sweet

A

Lactose

fructose

124
Q

_________ is sucrose that is hydrolyzed to a mixture of glucose and fructose

A

Invert sugar

125
Q

Is invert sugar sweeter than sucrose?

A

No: invert (65) and sucrose (100)

126
Q

Sweetness (increases/decreases) with increasing temperature

A

decreases

127
Q

What attributes the decrease in sweetness with increasing temperature?

A

The change in the relative concentrations of the open-

chain, α, and β forms, which differ in sweetness.

128
Q

Is sweetness perceived the same way by different people?

A

No

129
Q

The relative sweetness of sugar is changed in the presence of other components such as ____, ____, other ____, and a host of other components.

A

salts
acids
sugars

130
Q

Alcohol (increases/decreases) sweetness

A

increases

131
Q

Sugars are (sweeter/less sweet) when mixed together than when tasted separately, thus giving a ______ effect

A

sweeter

synergistic

132
Q

What is the only way to determine suitability for sugars?

A

Run taste panels and evaluate the overall response

133
Q

Sweetening power is related to sugar ______

A

solubility

134
Q

_______ has the highest saturation point (85%), while ______ has the lowest (20%)

A

Fructose

lactose

135
Q

________ is a very important criterion when high sugar concentrations are required to inhibit microbial growth

A

Solubility

136
Q

If the solubility of the sugar is too low, it can _______, making the product texture ______.

A

crystallize

grainy

137
Q

Limitations in _______ may be encountered in sweetened condensed or evaporated milk and ice cream

A

solubility

since lactose has low solubility

138
Q

A common method used to avoid sugar crystallization is to __________________, which inhibits their crystallization.

A

mix two sugars together

139
Q

Sugars effectively bind _____, making it unavailable for microorganisms due to the lowering of the ________ of the system, acting as a preservative

A

water

water activity

140
Q

If browning is not desired, it can be minimized by using _______

A

sucrose

141
Q

_________ prevent the ______ of meat pigments

A

Reducing sugars

oxidation

142
Q

_______ act as humectants, flavor binding agents, and viscosity enhancers

A

Humectants

143
Q

Sugars alcohols are produced by reducing the ______ group to a ______ group by _______

A

aldehyde
hydroxyl
hydrogenation

144
Q

Sugar alcohols are only absorbed by ___________, thereby contributing fewer calories than sugars.

A

passive diffusion

145
Q

__________ are poorly metabolized by the microbial flora of the mouth – do not contribute to dental caries

A

Sugar alcohols

146
Q

Dental caries are caused by ____ produced by the microflora from the ________ of sugars

A

acids

fermentation

147
Q

Most sugar alcohols are (more/less) sweet than sugars

A

less

148
Q

The most common sugar alcohols are _____ and ______

A

glucitol

mannitol

149
Q

______ is a sugar alcohol which has comparable sweetness to sucrose

A

Xylitol

150
Q

Xylitol is produced from _____, a polymer of ______

A

xylan

xylose

151
Q

Xylan is _____ to xylose and _______ using a nickel catalyst to produce xylitol

A

hydrolyzed

hydrogenated

152
Q

Xylitol can be produced from xylose by ______ fermentation, or from glucose by _________

A

yeast

enzymatic conversion

153
Q

________ are used as bulking agents and viscosity enhancers in artificially sweetened products to provide “body“.

A

Sugar alcohols

154
Q

________ are used as water-binding agents to plasticize intermediate-moisture foods and reduce the water activity of the food system without adding excessive sweetness

A

Sugar alcohols

2) Food Chemistry I (31 decks)

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