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2) Food Chemistry I > Carbohydrates - Summary > Flashcards

Carbohydrates - Summary Flashcards

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1
Q

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

A

Raffinose

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2
Q

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

A

Stachyose

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3
Q

Monosaccharides range from __ carbons to __ carbons

A

3

7

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4
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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5
Q

The smallest monosaccharide is _________, which has ___ carbons

A

glyceraldehyde

3

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6
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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7
Q

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

A

pyranose

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8
Q

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

A

furanose

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9
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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10
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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11
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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12
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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13
Q

______ is the phenomenon that causes the change in optical rotation

A

Mutarotation

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14
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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15
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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16
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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17
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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18
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

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19
Q

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

A

glucose
glucose
a-1-4

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20
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

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21
Q

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

A

glucose
fructose
a-1-2

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22
Q

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

A

The formation of highly unsaturated ring structures

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23
Q

A common intermediate formed during caramelization reactions by dehydration is _____________________

A

hydroxymethylfurfural (HMF)

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24
Q

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

A

3

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25
Q

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

A

fructopyranose

fructofuranose

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26
Q

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

A 
polyphenol oxidase (PPO)
mono- or dihydroxy phenols
quinones
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27
Q

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

A

Quinones

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28
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

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29
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

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30
Q

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

A

Amadori compound

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31
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

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32
Q

___________ is a subcomponent of the Maillard reaction.

A

Strecker degradation

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33
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

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34
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

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35
Q

The Strecker aldehyde and _______ give rise to strong _____

A

aminoketone

odors

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36
Q

Ethanal, methylpropanal, and 2-phenylethanal are common _________

A

Strecker aldehydes

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37
Q

_______ is a Strecker aldehyde with a fruity, sweet aroma

A

Etanal

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38
Q

_________ is a Strecker aldehyde with a malty aroma

A

Methylpropanol

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39
Q

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

A

2-phenylethanal

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40
Q

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

A

aminoketones

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41
Q

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

A

Lactose

fructose

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42
Q

Sweetness (increases/decreases) with increasing temperature

A

decreases

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43
Q

Alcohol (increases/decreases) sweetness

A

increases

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44
Q

Sweetening power is related to sugar ______

A

solubility

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45
Q

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

A

Fructose

lactose

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46
Q

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

A

sucrose

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47
Q

_________ prevent the ______ of meat pigments

A

Reducing sugars

oxidation

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48
Q

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

A

aldehyde
hydroxyl
hydrogenation

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49
Q

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

A

less

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50
Q

______ is a sugar alcohol which has comparable sweetness to sucrose

A

Xylitol

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51
Q

Starch is made up exclusively of _______

A

D-glucose

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52
Q

When the granules have swollen extensively, the viscosity of the solution (increases/decreases) drastically, which is called ________

A

increases

pasting

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53
Q

If the concentration of starch is high during gelatinization, it will form a ____, and not a _____

A

viscous solution

gel

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54
Q

______ has very low solubility as it readily hydrogen bonds to neighbouring polymers to form large aggregates that precipitate out of solution.

A

Amylose

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55
Q

__________ forms a viscous solution; branching produces a tangled net-like web in solution.

A

Amylopectin

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56
Q

Starch gels become _______ with time - a generally undesirable aspect of starch behavior in food systems

A

firmer

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57
Q

________ commonly causes starch gels to become more opaque with time.

A

Retrogradation

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58
Q

Starch from ________, which is a genetically modified low- amylose corn (almost devoid of amylose), will not form a gel at all.

A

waxy maize

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59
Q

______ tend to retard gel formation and retrogradation

A

Sugars

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60
Q

__________________ tend to inhibit retrogradation and gelation by forming complexes with starch

A

Surfactants

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61
Q

Surfactants are most noticeable with ___________ starch systems

A

high-amylose

62
Q

Pre-gelatinized starches are dispersible in _________ and requires less ___ or ____ to develop viscosity

A

cold water
heat
time

63
Q

A higher amount of ___________ starch is required to attain similar viscosity effects as with an untreated starch.

A

pre-gelatinized

64
Q

_________ are commonly termed thin-boiling starches.

A

Acid-modified starches

65
Q

Why is acid used in acid-modified starch?

A

To partially and randomly hydrolyze the glycosidic linkages in the starch granule without breaking up the INTEGRITY of the granule

66
Q

Acid-modified starches are used in _________ manufacture

A

candy

67
Q

Swollen granules normally break down, but _________ starches are held together chemically so that the swollen granule retains its integrity

A

cross-linked

68
Q

What compounds are used as cross-linking agents?

A
  • Acetic anhydride
  • Citric anhydride
  • Adipic anhydride
69
Q

________ compounds can bridge two _______ groups from adjoining polymers, and hold the swollen granule structure together

A

Anydride

hydroxyl

70
Q

The granules swell (more/less) in cross-linked starch

A

less

71
Q

The maximum viscosity is (higher/lower) in cross-linked starch

A

lower

72
Q

_________ are less susceptible to acid hydrolysis

A

Cross-linked starches

73
Q

Starch derivatives are formed by introducing _________ or ________ into the granules

A

hydroxypropyl

acetyl

74
Q

________ can be added to produce starch derivatives, which increase stability against retrogradation because of their _______

A 
Orthophosphate
charge (like charges repel)
75
Q

_____ is used to oxidize a portion of the _______ groups to _______ groups in starches

A

Sodium hypochlorite (NaOCl)
hydroxyl
carboxyl

76
Q

The solubility of oxidized starches is _____ dependent

A

pH

77
Q

What are the two basic types of starch conversions?

A

1) Dry pyroconversion

2) Acid hydrolysis

78
Q

_________ is used for the production of cold-water-soluble starches

A

Dry pyroconversion

79
Q

___________ is used for wet conversion

A

Acid hydrolysis

80
Q

In pyroconversion, starch granules are sprayed with dilute ______ and subjected to relatively (high/low) temperatures

A

HCl

high

81
Q

Which four reactions may take place in pyroconversion?

A

1) Hydrolysis of a-1-4 and a-1-6 linkages
2) Transglucosidation
3) Repolymerization (free sugars undergo caramelization)
4) Caramelization (free sugars undergo caramelization)

82
Q

__________ is the breaking of 1,4-linkages and the formation of other linkages, generally random in nature (1,3 or 1,5)

A

Transglucosidation

83
Q

What are the three products formed by pyroconversion?

A

1) White dextrins
2) Yellow dextrins
3) British gums

84
Q

_________ dextrins are soluble in cold water

A

White

85
Q

In pyroconversion, under conditions of high moisture, high acid, and relatively low temperature, hydrolysis predominates, and _________ are formed

A

white dextrins

86
Q

In pyroconversion, under low moisture, moderate acid, and higher temperatures, _______ are formed

A

yellow dextrins

87
Q

In pyroconversion, _______________ are produced under conditions with little or no acid used, and higher temperatures

A

British gums

88
Q

The pyroconversion products ___________ are dark in color with little hydrolysis and much ore transglucosidation

A

British gums

89
Q

The pyroconversion product _________ is much more viscous and capable of forming a stiff gel; used extensively in candy manufacture

A

British gums

90
Q

Starch breakdown can be followed by measuring the ___________ content of the hydrolysate.

A

reducing sugar

91
Q

Reducing sugar content is expressed in terms of ______________

A

dextrose equivalents (D.E)

92
Q

What is the equation for D.E?

93
Q

__________ is not the best means of producing very sweet, high D.E syrups

A

Acid hydrolysis

94
Q

To obtain syrups that have high D.E., ____________ of gelatinized starch is carried out.

A

enzymatic conversion

95
Q

_________ is also known as liquefying enzyme

A

a-amylase

96
Q

_________ is a trisaccharide containing the α- 1,6 branching linkage

A

Pannose

97
Q

_________ is commonly known as a saccharifying enzyme

A

B-amylase

98
Q

__________ develops sweetness rapidly, but viscosity does not change significantly

A

B-amylase

99
Q

_________ attacks the branch points so that the trisaccharide pannose can be broken down to _______ and ________

A

Pullulanase
glucose
maltose

100
Q

Why is sucrose inverted?

A

Glycosidic link in sucrose is acid labile, and readily hydrolyzed by heat or acid

101
Q

By controlled hydrolysis, the more amorphous regions of cellulose can be hydrolyzed, leaving behind _______________

A

microcrystalline cellulose

102
Q

What is CMC?

A

Carboxymethyl cellulose

103
Q

CMC is formed by hydrating cellulose in a strongly (acidic/basic) solution, and then reacting it with ___________

A

basic

sodium chloroacetate

104
Q

_______ is a more soluble cellulose polymer that is capable of contributing to the _______ of a solution as well as forming ________

A

CMC
viscosity
weak gels

105
Q

The presence of ________ groups means that CMC is susceptible to _____ changes

A

carboxyl

pH

106
Q

The presence of ionized carboxyl groups in CMC allows _____ ions to be used to cross-link the polymers to form a _____

A

divalent

gels

107
Q

_____________ and _____________ cellulose derivatives are quite soluble and their viscosities are not affected by pH or salts since these derivatives are __________

A

hydroxypropyl cellulose
methyl cellulose
non-ionic

108
Q

Hydroxypropyl cellulose and methyl cellulose are formed in (acidic/basic) solutions

A

basic

109
Q

A pectic substance is a complex carbohydrate largely made up of ______________, which can be extracted from plant material

A

polygalacturonic acid

110
Q

What are the three categories of pectic substances?

A

1) Pectic acids
2) Pectinic acids
3) Pectin

111
Q

_________ are polymers of predominantly polygalacturonic acid free of methyl ester groups.

A

Pectic acids

112
Q

_________ are polymers of polygalacturonic acid with some degree of methylation (low methoxy pectin).

A

Pectinic acids

113
Q

__________ are polymers of polygalacturonic acid with >50% of the carboxyl groups methylated.

A

Pectin

114
Q

The categories of pectic substances are based on their degree of the ________ of the ________ groups

A

methylation

carboxyl

115
Q

Most pectin is obtained as a by-product of the ______ industry, form which pectin is extracted using dilute ______

A

citrus

acid

116
Q

Pectin with a DM of 50 serves well for jellies (with/without) suspended material, while for jams (with/without) particles, a DM > 75 is required

A

without

with

117
Q

Rapid setting pectin has a (higher/lower) DM

A

higher

118
Q

High-DM pectin requires special extraction procedures and will set at (higher/lower) temperatures

A

higher

119
Q

_________ pectins, such as _____ and ______, are useful in the manufacture of diet jams and jellies

A

Low-methoxy
pectic
pectinic acids

120
Q

Low-methoxy pectins are produced by controlled hydrolysis of the ______ groups using (acid/alkaline) conditions

A

methyl

alkaline

121
Q

______ and _________ are capable of producing a gel with divalent ions to cross-link the polymers at the carboxyl groups

A

CMC

low-methoxy pectins

122
Q

The pH range for gel formation is much broader in ________ pectins

A

low-methoxy

123
Q

Guar gum and locust bean gums are both ____________

A

galactomannans

124
Q

Galactomannans consist of a ______ backbone (_____ linkages) with ______ side groups (______ linkages)

A

mannose
B-1,4
galactose
a-1,6

125
Q

The most important property of guar gum is its ability to hydrate very rapidly in ________ and form a very _______ solution.

A

cold water

viscous

126
Q

In _______ there is a D-galactose branch on the mannose backbone every other mannose unit

A

guar gum

127
Q

In ________ there is a D-galactose branch on the mannose backbone every fourth or fifth mannose unit

A

locust bean gum

128
Q

________ gum requires more heating to go into solution than _______ gum

A

Locust bean

guar

129
Q

________ are all charged heteropolysaccharides

A

Plant exudate gums

130
Q

________ is a polysaccharide consisting of D-galactose, L-arabinose, L-rhamnose and D-glucuronic acid

A

Gum arabic

131
Q

A number of _____ are said to be present in the side chain portions of _________

A

sugars

plant exudate gums

132
Q

Plant exudate gums are charged due to the presence of ________

A

glucoronic acid

133
Q

The distinguishing feature of gum arabic is that it is _____________

A

extremely soluble in water

134
Q

________ is commonly used to convert citrus essential oil flavor emulsions to a water-dispersible powder by spray drying.

A

Gum arabic

135
Q

Giant kelp (brown algae) is a source of _________

A

alginates

136
Q

_________ is a polysaccharide composed of D- and L-galactose and 3,6- anhydro-D-galactose units

A

Carrageenan

137
Q

Some of the galactose moieties in _______ are sulfonated

A

carrageenan

138
Q

________, like starch, is made up of two fractions (linear and branched)

A

Carrageenan

139
Q

__________ has the UNIQUE ability to complex with milk proteins to form a very light gel

A

Carrageenan

140
Q

_______ are made up of largely linear polymers of D-mannuronic and L-glucuronic acids.

A

Alginates

141
Q

Presence of ______ groups makes _______ sensitive to pH and ionic strength of a food system.

A

carboxyl

alginates

142
Q

_______ is extracted in the form of their sodium salts, so that they will be readily soluble.

A

Alginates

143
Q

Similarly to the behavior of carboxymethyl cellulose and low-methoxy pectin, ________ gels can be produced by cross-linking using divalent ions such as ______.

A

alginates

calcium

144
Q

Many microorganisms produce “______” which are extracellular polysaccharides.

A

slimes

145
Q

How do dextrans differ from starch?

A

Glucose units are linked by a-1,6 rather than a-1,4

146
Q

Where are the branch points of dextrans?

A

a-1,3

147
Q

____________ is the most common organism used to produce dextran by fermentation of _______.

A

Leuconostoc mesenteroides

sucrose

148
Q

Xanthan gum is made up of D-______, D-______, and D-___________, present in approximately a _____ ratio

A

glucose
mannose
galacturonic acid
3:3:2

149
Q

What is the viscosity of xanthan gum affected by? What happens when it is removed?

A
  • Affected by shear

- Viscosity returns after shear is removed (pseudoplastic)

150
Q

_______ gum is very useful in highly acidic foods

A

Xanthan

151
Q

________ will form a gel with locust bean gum in very low concentrations

A

Xanthan gum

152
Q

_______ is very useful in production of instant puddings or gels without the need for heat.

A

Xanthan gum

2) Food Chemistry I (31 decks)

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