Carbohydrates II Flashcards
1
Q
What are the three common polysaccharides?
A
- Starch
- Cellulose
- Pectin
2
Q
Guar gum and locust bean gum are _____ gums
A
seed
3
Q
Gum arabic and gum tragacanth are _________ gums
A
plant exudate
4
Q
Agar and carrageenan are _______ gums
A
seaweed
5
Q
Dextran and xanthan gum are _______ gums
A
microbial
6
Q
Other than cellulose, the most abundant form of stored carbohydrate is ______
A
starch
7
Q
______ is the main source of dietary carbohydrate
A
Starch
8
Q
_____ is used extensively in the food industry due to its unique properties as a thickening/texture-modifying agent and as a source of sugars and dextrin
A
Starch
9
Q
Starch is a source of _____ and _____
A
sugars
dextrins
10
Q
Starch is made up exclusively of _______
A
D-glucose
11
Q
The two fractions of starch are ______ and ______
A
amylose
amylopectin
12
Q
________ is a long-chain linear polymer composed of D-glucose linked by _____ glycosidic bonds
A
Amylose
a-1-4
13
Q
_______ is a branched polymer, composed of D-glycose linked by _____ glycosidic bonds in the linear position, and _____ bonds at its branch points
A
Amylopectin
a-1-4
a-1-6
14
Q
Starch is found in most plant sources as hard, water-(soluble/insoluble) ______
A
insoluble
granules
15
Q
______ contains almost 100% amylopectin
A
Waxy maize
16
Q
________ contains 28% amylose and 62% amylopectin
A
Regular corn starch
17
Q
Starch is readily isolated from the plant source by ______, then centrifuged out of solution and dried
A
wet milling
18
Q
Isolated starch produces a _________ composed of discrete starch granules
A
dry white powder
19
Q
Each starch granule is made up of ______ amylose and amylopectin tightly bound and held together by _____ bonding between the polymers
A
anhydrous
hydrogen
20
Q
Heating in the presence of moisture breaks the ________ bonds,
leading to ________.
A
hydrogen
gelatinization
21
Q
Swelling of the granule is due to the adsorption of ______, which is facilitated by _____
A
water
heat
22
Q
The swelling of starch granules increases ________, and breaks________
A
kinetic energy
hydrogen bonds
23
Q
During gelatinization, starch granules are ______ as ____ molecules access the __ groups on the polymer
A
hydrated
water
OH
24
Q
Gelatinization temperature is a function of the _______
A
starch source
25
_________ occurs between 60-70oC
Loss of granular integrity (gelatinization)
26
When the granules have swollen extensively, the viscosity of the solution (increases/decreases) drastically, which is called ________
increases
| pasting
27
If the swollen granule solution is stirred, the granules will break up and disperse to form __________
a colloidal solution
28
If the concentration of starch is high during gelatinization, it will form a ____ upon _____
gel
| cooling
29
If the concentration of starch is high during gelatinization, it will form a ____, and not a _____
viscous solution
| gel
30
What are the factors that influence the gelatinization of starch?
- Concentration
- Amylose/amylopectin
- Average molecular weight of the starch
- Rate of cooling
- Presence of other components
31
________ is a linear polymer that tends to form a long thin helical filament-like structure in solution.
Amylose
32
______ has very low solubility as it readily hydrogen bonds to neighboring polymers to form large aggregates that precipitate out of solution.
Amylose
33
On its own, _______ is useless functionally in food systems as it is effectively insoluble.
amylose
34
________ is a highly branched water-dispersible macromolecule.
Amylopectin
35
_________
| forms a viscous solution; branching produces a tangled net-like web in solution.
Amylopectin
36
In the presence of ________, which acts like a cross-linking agent, a three- dimensional gel can form, entrapping ______.
amylose
| water
37
A gel forms when the kinetic energy of the system is (increased/reduced) sufficiently to allow random _________ to re-form
reduced
| hydrogen bonds
38
The extensively hydrogen bonded starch molecules trap ______ within the matrix formed, producing a _____.
water
| gel
39
Starch gels become _______ with time - a generally undesirable aspect of starch behavior in food systems
firmer
40
What is the cause of retrogradation?
Continued hydrogen bond formation between starch molecules
41
What are the two problems caused by retrogradation?
1) Texture changes
| 2) Syneresis
42
What is syneresis?
When a gel tightens up so much that it starts to exude water
43
________ commonly causes starch gels to become more opaque with time.
Retrogradation
44
___________ is one of the key processes responsible for the staling of bread and stiffening of pie fillings.
Retrogradation
45
Normal ____ starch (about 28% amylose) will set to a rigid (transparent/opaque) gel.
corn
| opaque
46
Starch from ________, which is a genetically modified low- amylose corn (almost devoid of amylose), will not form a gel at all.
waxy maize
47
_______ does not contain amylose
waxy maize
48
______ starch (~23% amylose) and ______ starch (~28% amylose) form reasonably stable gels that tend to maintain their clarity and do not stiffen appreciably with time
Potato
| tapioca
49
The stability of potato and tapioca starch is due to the high ___________ of the starches, making them less mobile, which decreases the rate of hydrogen bond formation
molecular weight
50
______ tend to retard gel formation and retrogradation
Sugars
51
__________________ tend to inhibit retrogradation and gelation by forming complexes with starch
Surface-active agents (surfactants)
52
Surfactants are most noticeable with ___________ starch systems
high-amylose
53
_______ compete for available water and interfere with starch- to -starch hydrogen bonding.
Sugars
54
The pH of most foods lies in the range of ______.
4-7
55
In highly ______ foods, particularly when heated or stored for extensive periods, there is the possibility of a reduction of the _______ due to the _______ of starch
acidic
viscosity
hydrolysis
56
_________ processing can affect the final viscosity of starch
Thermal
57
Why does ionic strength have minor effects in starches?
Since starches have no ionizable groups
58
Which two factors have minor effects on starches?
- pH
| - Ionic strength
59
______ are capable of dramatically changing how a starch behaves in terms of gelation and viscosity.
Proteins
60
The interaction with starch and _______ produces a smooth gel known as _______
milk proteins
| pudding
61
In North America, most of our starch is derived from ______
corn
62
In pre-gelatinized starches, granules are ____________________, which causes them to swell, and are then _______
heated below the gelatinization temperature of the starch
| drum-dried
63
Pre-gelatinized starches are dispersible in _________ and requires less ___ or ____ to develop viscosity
cold water
heat
time
64
A higher amount of ___________ starch is required to attain similar viscosity effects as with an untreated starch.
pre-gelatinized
65
_________ starches are convenient for food processors and are used extensively in the food industry .
Pre-gelatinized
66
_________ are commonly termed thin-boiling starches.
Acid-modified starches
67
Acid-modified starches are produced by holding starch just below its gelatinization temperature in an ______ medium, then it is ______ and ____
acidic
neutralized
dried
68
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
69
Acid-modified starches are used in _________ manufacture
candy
70
__________ produce easy-to-handle low-viscosity fluids that can be poured into molds and will set into a firm gel upon cooling
Acid-modified starches
71
Maximum viscosity is normally reached when the granules are ________ extensively but still intact
swollen
72
Swollen granules normally break down, but _________ starches are held together chemically so that the swollen granule retains its integrity
cross-linked
73
What compounds are used as cross-linking agents?
- Acetic anhydride
- Citric anhydride
- Adipic anhydride
74
________ compounds are used as cross-linking agents
Anhydride
75
________ compounds can bridge two _______ groups from adjoining polymers, and hold the swollen granule structure together
Anydride
| hydroxyl
76
The granules swell (more/less) in cross-linked starch
less
77
The maximum viscosity is (higher/lower) in cross-linked starch
lower
78
_________ are less susceptible to acid hydrolysis
Cross-linked starches
79
What is the overall objective of starch derivatives?
To reduce polymer-polymer hydrogen bonding via steric hindrance or the introduction of charged groups
80
What are starch derivatives used to?
- Control retrogradation and staling
- Improve freeze/thaw stability
- Reduce textural and opacity changes
81
Starch derivatives are formed by introducing _________ or ________ into the granules
hydroxypropyl
| acetyl
82
In starch derivatives, _________ prevents the polymers from associating as readily as in natural starch
steric hindrance
83
________ can be added to produce starch derivatives, which increase stability against retrogradation because of their _______
```
Orthophosphate
charge (like charges repel)
```
84
What other types of new groups can be introduced in a starch?
- Ester
- Ether
- Acetyl
85
Give an example of a specialty derivative?
Introduction of hydrophobic side chains enables starches to be used as emulsifiers and emulsion stabilizers
86
_____ is used to oxidize a portion of the _______ groups to _______ groups in starches
Sodium hypochlorite (NaOCl)
hydroxyl
carboxyl
87
Which groups may be introduced in oxidized starches?
Aldehyde and ketone groups
88
The solubility of oxidized starches is _____ dependent
pH
89
What is the advantage and the disadvantages of oxidized starch?
Advantage: stabilized against retrogradation
Disadvantage: more susceptible to variations in pH and ionic strength in a food product
90
What are the two basic types of starch conversions?
1) Dry pyroconversion
| 2) Acid hydrolysis
91
_________ is used for the production of cold-water-soluble starches
Dry pyroconversion
92
___________ is used for wet conversion
Acid hydrolysis
93
Acid hydrolysis may be used for the production of _______ or as a preliminary step in the production of ______ from ______
dextrins
sugars
starch
94
In pyroconversion, starch granules are sprayed with dilute ______ and subjected to relatively (high/low) temperatures
HCl
| high
95
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)
96
__________ is the breaking of 1,4-linkages and the formation of other linkages, generally random in nature (1,3 or 1,5)
Transglucosidation
97
What are the three products formed by pyroconversion?
1) White dextrins
2) Yellow dextrins
3) British gums
98
_________ dextrins are soluble in cold water
White
99
_________ from pyroconversion can be controlled to produce desired ranges of viscosity
White dextrins
100
In pyroconversion, under conditions of high moisture, high acid, and relatively low temperature, hydrolysis predominates, and _________ are formed
white dextrins
101
In pyroconversion, under low moisture, moderate acid, and higher temperatures, _______ are formed
yellow dextrins
102
The color of yellow dextrins is due to the ______________ reaction
non-enzymatic browning (caramelization)
103
In pyroconversion, the viscosity and degree of polymerization of __________ can be controlled
yellow dextrins
104
In pyroconversion, _______________ are produced under conditions with little or no acid used, and higher temperatures
British gums
105
The pyroconversion products ___________ are dark in color with little hydrolysis and much ore transglucosidation
British gums
106
The pyroconversion product _________ is much more viscous and capable of forming a stiff gel; used extensively in candy manufacture
British gums
107
Over half of the isolated starch produced is converted to ______ and ______.
syrups
| sugars
108
___________ is commonly a preliminary step in the conversion of starch to syrups and sugars.
Acid hydrolysis
109
In acid hydrolysis, starch is ________ and hydrolyzed in the presence of ______ and pressurized steam
gelatinized
| HCl
110
Acid hydrolysis is extensive and random, producing ______ and ______
dextrins
| sugars
111
By controlling acid hydrolysis, the degree of ____________ can be manipulated to a degree to produce glucose syrups of various viscosities and sweetness.
dextrinization
112
Starch breakdown can be followed by measuring the ___________ content of the hydrolysate.
reducing sugar
113
Reducing sugar content (increases/decreases) with hydrolysis as mono-, di- and oligosaccharides are produced.
increases
114
Reducing sugar content is expressed in terms of ______________
dextrose equivalents (D.E)
115
If the hydrolysis of starch is 100% complete, then D.E. = ______
100
116
What is the equation for D.E?
D.E. = [(RP/g of syrup)/(RP/g of dextrose)](100)
117
Acid hydrolysis cannot yield dextrose equivalents much beyond ____ since an equilibrium is reached between ________ and ___________.
50
hydrolysis
repolymerization
118
__________ is not the best means of producing very sweet, high D.E syrups
Acid hydrolysis
119
To obtain syrups that have high D.E., ____________ of gelatinized starch is carried out.
enzymatic conversion
120
The enzymes that are capable of hydrolyzing starch are commonly termed _________ - these enzymes are found in most living systems.
amylases
121
Commercially, the sources of _____________ are microorganisms because relatively large quantities of selective enzymes can be obtained through genetic manipulation and the enzymes are simple to isolate.
amylases
122
_________ is an endoenzyme - can attack anywhere within the starch
molecule other than the α-1,6 branch point.
a-amylase
123
_________ is also known as liquefying enzyme
a-amylase
124
__________ causes viscosity of a starch solution to drop rapidly
a-amylase
125
Random internal bond breakage (increases/reduces) the overall molecular weight of starch, which is done by _________
reduces
| a-amylase
126
The end-products of the __________ enzyme are mainly oligosaccharides together with some glucose, maltose, and pannose
a-amylase
127
_________ is a trisaccharide containing the α- 1,6 branching linkage
Pannose
128
________ is an exoenzyme that attacks the non-reducing end of the starch
chain.
B-amylase
129
__________ produces _________ by hydrolyzing the a-1,4 bond every two glucose units over
B-amylase
| maltose
130
_________ is commonly known as a saccharifying enzyme
B-amylase
131
__________ develops sweetness rapidly, but viscosity does not change significantly
B-amylase
132
__________ are capable of removing single glucose units from the non-reducing end of starch and to split ________ into two glucose units
Glucoamylases
| maltose
133
Glucoamylases act from the __________ end of the starch, to split __________ into two glucose units
non-reducing end
| maltose
134
Combined action of α- and β-amylase and glucoamylase leaves 'limit _______" - largely the trisaccharide ________.
dextrins
| pannose
135
___________ hydrolyzes a-1,6 glycosidic linkages
Pullulanase
136
_________ attacks the branch points so that the trisaccharide pannose can be broken down to _______ and ________
Pullulanase
glucose
maltose
137
a-amylase, B-amylase, glucoamylase, pullulanase brovide a means of converting starch to predominantly __________ (______), which produces syrups with a (high/low) D.E.
D-glucose
dextrose
high
138
At D.E. > 90, _________ can be crystallized out of solution and obtained in pure form in a manner very similar to sucrose refining.
glucose
139
________ is a useful sweetener, but not as sweet as sucrose.
Glucose
140
D-glucose is isomerized to D-
| fructose using _____________.
glucose isomerase
141
________ has about 1.3 times the sweetening power of glucose
| and is somewhat sweeter than sucrose.
D-Fructose
142
Glucose isomerase is capable of converting about ____% of D- glucose into D-fructose.
45
143
High-fructose corn syrups are similar to ________ and are in direct competition with ________.
invert sugars
| sucrose
144
Sucrose is commonly inverted using the enzyme __________ to stabilize its sweetness in _________ environments
invertase
| acidic
145
Why is sucrose inverted?
Glycosidic link in sucrose is acid labile, and readily hydrolyzed by heat or acid
146
For acidic beverages, sweetness can be stabilized by ________
inversion
147
The term ‘”inverted” refers to the change in the specific rotation of ________________ by a sucrose solution
plane-polarized light
148
In a fully converted solution, the direction of rotation is _________
inverted (from +66.5o to -39o)
149
Why does high-fructose corn syrup have great value?
1) Sweeter than glucose
2) More soluble
3) Does not crystallize readily
150
High-Fructose Corn Syrup becomes sweeter with (increasing/decreasing) temperature
decreasing
151
Why does HFCS not crystallize readily? What is this good for?
- Because it is a mixture of sugars
| - Good for frozen products
152
____________ have made large inroads into the sucrose market and made the sweetener industry more competitive.
High-fructose corn syrups
