Carbohydrates - Summary Flashcards
(152 cards)
1
Q
_________ is a trisaccharide formed of galactose, glucose, and fructose
A
Raffinose
2
Q
_________ is a tetrasaccharide, formed of glucose, fructose, and two galactose
A
Stachyose
3
Q
Monosaccharides range from __ carbons to __ carbons
A
3
7
4
Q
The carbon chain of a monosaccharide is numbered from the aldehyde (C-__) or the ketone (C-__) functional group down.
A
1
2
5
Q
The smallest monosaccharide is _________, which has ___ carbons
A
glyceraldehyde
3
6
Q
Optical isomers involving asymmetric carbons other than the carbon at the n-1 position are considered different sugars or _______.
A
epimers
7
Q
Hemiacetal formation in glucose (an aldohexose) forms a ________ ring
A
pyranose
8
Q
Hemiketal formation in fructose (a ketohexose) forms a ________ ring
A
furanose
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
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
11
Q
When pure ___-D-glucopyranose is dissolved in water, the optical rotation starts at 112o and gradually changes to 53o.
A
alpha
12
Q
When pure ___-D-glucopyranose is dissolved in water, the optical rotation starts at 19o and gradually changes to 53o.
A
beta
13
Q
______ is the phenomenon that causes the change in optical rotation
A
Mutarotation
14
Q
The formation of furanose (five-membered) ring by attack of OH group at C-__ on C-__ keto group.
A
5
2
15
Q
Formation of pyranose (six-membered) ring by attack of OH group at C-__ on C-__ keto group.
A
6
2
16
Q
________ are capable of reducing metal ions (in an oxidation- reduction reaction that converts the _____ to a _________).
A
Aldehydes
aldehyde
carboxylic acid
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
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
19
Q
Maltose is composed of ______ and ______ linked by a ______ linkage
A
glucose
glucose
a-1-4
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
21
Q
Sucrose is composed of _______ and ______ linked by a ____ glycosidic linkage
A
glucose
fructose
a-1-2
22
Q
What does the elimination of water from within a sugar molecule lead to?
A
The formation of highly unsaturated ring structures
23
Q
A common intermediate formed during caramelization reactions by dehydration is _____________________
A
hydroxymethylfurfural (HMF)
24
Q
Hydroxymethylfurfural (HMF) is formed from the loss of __ water molecules
A
3
25
HMF is formed from _______, which is converted to ______, and HMF once it loses 3 water molecules
fructopyranose
| fructofuranose
26
Oxidative browning is instigated by ___________, which oxidizes _______ into ________
```
polyphenol oxidase (PPO)
mono- or dihydroxy phenols
quinones
```
27
________ are quite reactive and can react non-enzymatically to polymerize into a brown pigment.
Quinones
28
The two main reactions in caramelization are _______ and ________, producing (high/low) molecular weight (fat/water) soluble polymers that are very dark in color
dehydration
polymerization
high
water
29
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 __________
condensation
Schiff base
Amadori compound
30
The ______ compound in the Maillard reaction is comparable to HMF in caramelization
Amadori compound
31
In the Maillard reaction, fragmentation produces short-chain highly unsaturated ______ and _____ compounds that can polymerize and/or be released as ______ into the environment
carbonyl
amino
volatile
32
___________ is a subcomponent of the Maillard reaction.
Strecker degradation
33
The Strecker degradation involves the reaction of free ___________ with the ____________ intermediates produced by either the Maillard reaction or caramelization reactions
amino acids
| dicarbonyl
34
The products formed from the Strecker degradation are ____, ______, ______, and _______, which are compounds that contribute to the characteristic aroma of roasted foods
CO2
ammonia
formaldehyde
pyrazines
35
The Strecker aldehyde and _______ give rise to strong _____
aminoketone
| odors
36
Ethanal, methylpropanal, and 2-phenylethanal are common _________
Strecker aldehydes
37
_______ is a Strecker aldehyde with a fruity, sweet aroma
Etanal
38
_________ is a Strecker aldehyde with a malty aroma
Methylpropanol
39
_________ is a Strecker aldehyde with a flowery/honey like aroma
2-phenylethanal
40
Condensation of two __________ may yield pyrazine derivatives that are also powerful aroma compounds
aminoketones
41
______ is considered the least sweet sugar, while _______ is considered the most sweet
Lactose
| fructose
42
Sweetness (increases/decreases) with increasing temperature
decreases
43
Alcohol (increases/decreases) sweetness
increases
44
Sweetening power is related to sugar ______
solubility
45
_______ has the highest saturation point (85%), while ______ has the lowest (20%)
Fructose
| lactose
46
If browning is not desired, it can be minimized by using _______
sucrose
47
_________ prevent the ______ of meat pigments
Reducing sugars
| oxidation
48
Sugars alcohols are produced by reducing the ______ group to a ______ group by _______
aldehyde
hydroxyl
hydrogenation
49
Most sugar alcohols are (more/less) sweet than sugars
less
50
______ is a sugar alcohol which has comparable sweetness to sucrose
Xylitol
51
Starch is made up exclusively of _______
D-glucose
52
When the granules have swollen extensively, the viscosity of the solution (increases/decreases) drastically, which is called ________
increases
| pasting
53
If the concentration of starch is high during gelatinization, it will form a ____, and not a _____
viscous solution
| gel
54
______ has very low solubility as it readily hydrogen bonds to neighbouring polymers to form large aggregates that precipitate out of solution.
Amylose
55
__________ forms a viscous solution; branching produces a tangled net-like web in solution.
Amylopectin
56
Starch gels become _______ with time - a generally undesirable aspect of starch behavior in food systems
firmer
57
________ commonly causes starch gels to become more opaque with time.
Retrogradation
58
Starch from ________, which is a genetically modified low- amylose corn (almost devoid of amylose), will not form a gel at all.
waxy maize
59
______ tend to retard gel formation and retrogradation
Sugars
60
__________________ tend to inhibit retrogradation and gelation by forming complexes with starch
Surfactants
61
Surfactants are most noticeable with ___________ starch systems
high-amylose
62
Pre-gelatinized starches are dispersible in _________ and requires less ___ or ____ to develop viscosity
cold water
heat
time
63
A higher amount of ___________ starch is required to attain similar viscosity effects as with an untreated starch.
pre-gelatinized
64
_________ are commonly termed thin-boiling starches.
Acid-modified starches
65
Why is acid used in acid-modified starch?
To partially and randomly hydrolyze the glycosidic linkages in the starch granule without breaking up the INTEGRITY of the granule
66
Acid-modified starches are used in _________ manufacture
candy
67
Swollen granules normally break down, but _________ starches are held together chemically so that the swollen granule retains its integrity
cross-linked
68
What compounds are used as cross-linking agents?
- Acetic anhydride
- Citric anhydride
- Adipic anhydride
69
________ compounds can bridge two _______ groups from adjoining polymers, and hold the swollen granule structure together
Anydride
| hydroxyl
70
The granules swell (more/less) in cross-linked starch
less
71
The maximum viscosity is (higher/lower) in cross-linked starch
lower
72
_________ are less susceptible to acid hydrolysis
Cross-linked starches
73
Starch derivatives are formed by introducing _________ or ________ into the granules
hydroxypropyl
| acetyl
74
________ can be added to produce starch derivatives, which increase stability against retrogradation because of their _______
```
Orthophosphate
charge (like charges repel)
```
75
_____ is used to oxidize a portion of the _______ groups to _______ groups in starches
Sodium hypochlorite (NaOCl)
hydroxyl
carboxyl
76
The solubility of oxidized starches is _____ dependent
pH
77
What are the two basic types of starch conversions?
1) Dry pyroconversion
| 2) Acid hydrolysis
78
_________ is used for the production of cold-water-soluble starches
Dry pyroconversion
79
___________ is used for wet conversion
Acid hydrolysis
80
In pyroconversion, starch granules are sprayed with dilute ______ and subjected to relatively (high/low) temperatures
HCl
| high
81
Which four reactions may take place in pyroconversion?
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
__________ is the breaking of 1,4-linkages and the formation of other linkages, generally random in nature (1,3 or 1,5)
Transglucosidation
83
What are the three products formed by pyroconversion?
1) White dextrins
2) Yellow dextrins
3) British gums
84
_________ dextrins are soluble in cold water
White
85
In pyroconversion, under conditions of high moisture, high acid, and relatively low temperature, hydrolysis predominates, and _________ are formed
white dextrins
86
In pyroconversion, under low moisture, moderate acid, and higher temperatures, _______ are formed
yellow dextrins
87
In pyroconversion, _______________ are produced under conditions with little or no acid used, and higher temperatures
British gums
88
The pyroconversion products ___________ are dark in color with little hydrolysis and much ore transglucosidation
British gums
89
The pyroconversion product _________ is much more viscous and capable of forming a stiff gel; used extensively in candy manufacture
British gums
90
Starch breakdown can be followed by measuring the ___________ content of the hydrolysate.
reducing sugar
91
Reducing sugar content is expressed in terms of ______________
dextrose equivalents (D.E)
92
What is the equation for D.E?
D.E. = [(RP/g of syrup)/(RP/g of dextrose)](100)
93
__________ is not the best means of producing very sweet, high D.E syrups
Acid hydrolysis
94
To obtain syrups that have high D.E., ____________ of gelatinized starch is carried out.
enzymatic conversion
95
_________ is also known as liquefying enzyme
a-amylase
96
_________ is a trisaccharide containing the α- 1,6 branching linkage
Pannose
97
_________ is commonly known as a saccharifying enzyme
B-amylase
98
__________ develops sweetness rapidly, but viscosity does not change significantly
B-amylase
99
_________ attacks the branch points so that the trisaccharide pannose can be broken down to _______ and ________
Pullulanase
glucose
maltose
100
Why is sucrose inverted?
Glycosidic link in sucrose is acid labile, and readily hydrolyzed by heat or acid
101
By controlled hydrolysis, the more amorphous regions of cellulose can be hydrolyzed, leaving behind _______________
microcrystalline cellulose
102
What is CMC?
Carboxymethyl cellulose
103
CMC is formed by hydrating cellulose in a strongly (acidic/basic) solution, and then reacting it with ___________
basic
| sodium chloroacetate
104
_______ is a more soluble cellulose polymer that is capable of contributing to the _______ of a solution as well as forming ________
CMC
viscosity
weak gels
105
The presence of ________ groups means that CMC is susceptible to _____ changes
carboxyl
| pH
106
The presence of ionized carboxyl groups in CMC allows _____ ions to be used to cross-link the polymers to form a _____
divalent
| gels
107
_____________ and _____________ cellulose derivatives are quite soluble and their viscosities are not affected by pH or salts since these derivatives are __________
hydroxypropyl cellulose
methyl cellulose
non-ionic
108
Hydroxypropyl cellulose and methyl cellulose are formed in (acidic/basic) solutions
basic
109
A pectic substance is a complex carbohydrate largely made up of ______________, which can be extracted from plant material
polygalacturonic acid
110
What are the three categories of pectic substances?
1) Pectic acids
2) Pectinic acids
3) Pectin
111
_________ are polymers of predominantly polygalacturonic acid free of methyl ester groups.
Pectic acids
112
_________ are polymers of polygalacturonic acid with some degree of methylation (low methoxy pectin).
Pectinic acids
113
__________ are polymers of polygalacturonic acid with >50% of the carboxyl groups methylated.
Pectin
114
The categories of pectic substances are based on their degree of the ________ of the ________ groups
methylation
| carboxyl
115
Most pectin is obtained as a by-product of the ______ industry, form which pectin is extracted using dilute ______
citrus
| acid
116
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
without
| with
117
Rapid setting pectin has a (higher/lower) DM
higher
118
High-DM pectin requires special extraction procedures and will set at (higher/lower) temperatures
higher
119
_________ pectins, such as _____ and ______, are useful in the manufacture of diet jams and jellies
Low-methoxy
pectic
pectinic acids
120
Low-methoxy pectins are produced by controlled hydrolysis of the ______ groups using (acid/alkaline) conditions
methyl
| alkaline
121
______ and _________ are capable of producing a gel with divalent ions to cross-link the polymers at the carboxyl groups
CMC
| low-methoxy pectins
122
The pH range for gel formation is much broader in ________ pectins
low-methoxy
123
Guar gum and locust bean gums are both ____________
galactomannans
124
Galactomannans consist of a ______ backbone (_____ linkages) with ______ side groups (______ linkages)
mannose
B-1,4
galactose
a-1,6
125
The most important property of guar gum is its ability to hydrate very rapidly in ________ and form a very _______ solution.
cold water
| viscous
126
In _______ there is a D-galactose branch on the mannose backbone every other mannose unit
guar gum
127
In ________ there is a D-galactose branch on the mannose backbone every fourth or fifth mannose unit
locust bean gum
128
________ gum requires more heating to go into solution than _______ gum
Locust bean
| guar
129
________ are all charged heteropolysaccharides
Plant exudate gums
130
________ is a polysaccharide consisting of D-galactose, L-arabinose, L-rhamnose and D-glucuronic acid
Gum arabic
131
A number of _____ are said to be present in the side chain portions of _________
sugars
| plant exudate gums
132
Plant exudate gums are charged due to the presence of ________
glucoronic acid
133
The distinguishing feature of gum arabic is that it is _____________
extremely soluble in water
134
________ is commonly used to convert citrus essential oil flavor emulsions to a water-dispersible powder by spray drying.
Gum arabic
135
Giant kelp (brown algae) is a source of _________
alginates
136
_________ is a polysaccharide composed of D- and L-galactose and 3,6- anhydro-D-galactose units
Carrageenan
137
Some of the galactose moieties in _______ are sulfonated
carrageenan
138
________, like starch, is made up of two fractions (linear and branched)
Carrageenan
139
__________ has the UNIQUE ability to complex with milk proteins to form a very light gel
Carrageenan
140
_______ are made up of largely linear polymers of D-mannuronic and L-glucuronic acids.
Alginates
141
Presence of ______ groups makes _______ sensitive to pH and ionic strength of a food system.
carboxyl
| alginates
142
_______ is extracted in the form of their sodium salts, so that they will be readily soluble.
Alginates
143
Similarly to the behavior of carboxymethyl cellulose and low-methoxy pectin, ________ gels can be produced by cross-linking using divalent ions such as ______.
alginates
| calcium
144
Many microorganisms produce "______" which are extracellular polysaccharides.
slimes
145
How do dextrans differ from starch?
Glucose units are linked by a-1,6 rather than a-1,4
146
Where are the branch points of dextrans?
a-1,3
147
____________ is the most common organism used to produce dextran by fermentation of _______.
Leuconostoc mesenteroides
| sucrose
148
Xanthan gum is made up of D-______, D-______, and D-___________, present in approximately a _____ ratio
glucose
mannose
galacturonic acid
3:3:2
149
What is the viscosity of xanthan gum affected by? What happens when it is removed?
- Affected by shear
| - Viscosity returns after shear is removed (pseudoplastic)
150
_______ gum is very useful in highly acidic foods
Xanthan
151
________ will form a gel with locust bean gum in very low concentrations
Xanthan gum
152
_______ is very useful in production of instant puddings or gels without the need for heat.
Xanthan gum
