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[LEC] Food Chemistry > Midterms [Carbohydrates] > Flashcards

Midterms [Carbohydrates] Flashcards

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1
Q

Food Chemistry definition

A
  • the study of the composition of food, the interaction between these components, and changes that occur during harvesting, transportation, handling, storage, and packaging until the food gets to the table of the consumers
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2
Q

Macronutrients

A
  • Require in large amounts for the body
  • Carbohydrates, lipids, water, proteins
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3
Q

Micronutrients

A
  • Require in small amounts for the body
  • Vitamins and minerals
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4
Q

How many kcal/g in

  1. Carbohydrates
  2. Protein
  3. Lipids
  4. Alcohol
A
  1. 4 kcal/g
  2. 4 kcal/g
  3. 9 kcal/g
  4. 7 kcal/g
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5
Q

Carbon - hydrates

A
  • hydrates of carbon
  • carbon to which water has been added
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6
Q

General formula for carbohydrates

A

Cx(H2O)Y

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7
Q

Carbohydrates definition

A
  • compounds that have carbon, hydrogen, and oxygen with hydrogen and oxygen in the same ratio as found in water (2:1)
  • polyhydroxy aldehyde (CHO) or polyhydroxy ketones
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8
Q

Alkanal

A
  • third carbon position of the carbonyl group
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9
Q

Alkanone

A
  • second/middle carbon position of the carbonyl group
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10
Q

Group of Carbohydrates

A
  1. Monosaccharides
  2. Oligosaccharides
  3. Polysaccharides
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11
Q

Monosaccharides

A
  • one sugar unit
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12
Q

Oligosaccharides

A
  • 1 < x < 10
  • Disaccharide, trisaccharide
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13
Q

Polysaccharide

A
  • > 10
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14
Q

Nomenclature for carbohydrates

A
  1. according to the functional group
  2. according to the number of carbon atoms
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15
Q

Aldose

A
  • CHO
  • sugar with aldehyde
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16
Q

Ketose

A
  • CH2OH
  • sugar with ketones
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17
Q

Three carbon atom sugar

A
  • triose
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18
Q

Four carbon atom sugar

A
  • tetrose
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19
Q

Five carbon atom sugar

A
  • pentose
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20
Q

Six carbon atom sugar

A
  • hexose
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21
Q

Sucrose

A
  • contains glucose and fructose
  • table sugar
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22
Q

Maltose

A
  • contains two molecules of glucose
  • malt sugar
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23
Q

Lactose

A
  • milk sugar
  • one molecule of glucose and galactose
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24
Q

Monosaccharide (in-depth)

A
  • simple sugars
  • smallest units that make up any carbohydrate
  • glucose, galactose
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25
Q

Sugar can be drawn into two forms

A
  1. Fischer projection
  2. Haworth projection
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26
Q

Fishcer projection

A
  • line form
  • Left = top
  • Right = bottom
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27
Q

Haworth projection

A
  • ring form
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28
Q

Furan

A
  • Five membered ring cyclic
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29
Q

Pyran

A
  • six membered ring cyclic
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30
Q

Configuration of sugar

A
  • determined on the Fischer projection
  • determined by the position of the carbonyl group
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31
Q

Penultimate

A
  • carbon before the last (C5)
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32
Q

D-sugar

A
  • hydroxy group (OH) is in the 5th on the right (Fischer projection)
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33
Q

L-sugar

A
  • hydroxy group (OH) is in the 5th on the left (Fischer projection)
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34
Q

Conformation of sugar

A
  • found at C1
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35
Q

Alpha (conformation)

A
  • OH at the botton (at C1)
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36
Q

Beta (conformation)

A
  • OH at the top (at C1)
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37
Q

Epimers

A
  • sugar differ in one carbon atom
  • Cx epimers (x = which carbon they differed)
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38
Q

Galactose epimer

A

C4 epimer of glucose

39
Q

Mannose

A
  • C2 epimer of glucose
40
Q

Disaccharide

A
  • sugars that contain 2 sugar units
41
Q

Alpha 1-4 glycosidic bond

A
  • bonds two glucose molecules
  • C1 and C4 joins up
42
Q

Condensation in disaccharide

A
  • linking monosaccharides by removing water
43
Q

Hydrolysis at disaccharide

A
  • add water to split the disaccharide
44
Q

Lactose

A
  • milk sugar
  • galactose and glucose
45
Q

Sucrose

A
  • glucose and fructose
  • linked with alpha-1-glucose and beta-2-fructose bond
46
Q

Fructose

A
  • fruit sugar
  • 5 membered ring
47
Q

Isomers

A
  • same chemical formula but different structure
48
Q

Optical activity

A
  • whether it can rotate plane polarized light
  • have chiral center
49
Q

Chiral center

A
  • has four different atoms attached to it
50
Q

Vant hoffs rule

A
  • Number of chiral centers can estimate the number of possible isomers that such compound can have
  • Isomers = 2n, n = chiral center
51
Q

Disaccharide examples

A
  • Maltose
  • Lactose
  • Sucrose
52
Q

Oligosaccharides

A
  • typically less than 10 monsaccharides linked together
  • 2 < x < 10
53
Q

Maltotriose

A
  • maltose and glucose
  • linked by alpha 1-4 glycosidic bond
54
Q

Polysaccharide

A
  • more than 10 monosaccharide combined
  • more than 10 bonds
  • glycans
55
Q

Homopolysaccharides

A
  • contains a single type of monosaccharide
  • Storage form of monosaccharides
  • Ex. only contains glucose
56
Q

Heteropolysaccharides

A
  • contains 2 or more different types of monosaccharide
  • branched or unbranched
  • Ex. contains fructose and glucose
57
Q

Starch

A
  • storage form of monosaccharides in plants
  • main carbohydrate in human diet
  • found in bread, cereal, and rice
  • homopolysaccharide
58
Q

Functions of carbohydrates

A
  1. Provides energy through oxidation
  2. Storage in the form of glycogen
  3. Supply carbons for synthesis of reactions
  4. Form part of the structural framework of DNA and RNA
  5. Structural components of cell membranes when linked to lipids
  6. Cell to cell and cell to molecule recoginition processes when linked to proteins
59
Q

Solubility of sugars

A
  • sugars are soluble
  • highly branched polysaccharides like starches are not soluble
60
Q

Viscosity and surface activity of sugar

A
  • polysaccharides are viscous
  • it thickens up when added water
61
Q

Crystallinity of sugar

A
  • have a wide range of crystallinity
  • sucrose is readily crystallized
62
Q

Hygroscopicity of sugar

A
  • can absorb water easily even after drying
63
Q

Stability of sugar

A
  • fairly stable molecules
  • reducing sugars are sensitive to oxidation
64
Q

Optical properties of sugar

A
  • absorb light in the UV and spectral regions
65
Q

Hydrolysis of sugar

A
  • sugars can be hydrolyzed
66
Q

Oxidation/reduction of sugar

A
  • highly oxidized; resistant to oxidation
67
Q

Uronic acid

A
  • COOH is at C6
68
Q

Onic acid

A
  • COOH at C1
69
Q

Aric acid

A
  • oxidation of both C1 and C6
70
Q

Functional groups

A
  • in addition to aldehydes and ketones, have primary and secondary hydroxy groups
71
Q

Chelation and complexation

A
  • display affinity towards various classes of iron ions
72
Q

Reactions that can take place during processing

A
  1. Hydrolysis
  2. Enolization
  3. Dehydration
  4. Caramelization
73
Q

Enolization

A
  • changing from a keto- to an -enol form
  • at higher temperatures, acyclic sugars undergo enolization
74
Q

Dehydration

A
  • in an acidic environment (pH < 3) enolization is followed by dehydration
  • formation of unwanted 2-furaldehydes
75
Q

Caramelization

A
  • degradation reaction can also occur during melting of dry sugars and during heating of syrups above 100C
76
Q

Caramelisation occurs during food processing

A
  • heated strongly
  • jams and certain fruit juices
  • wine preparation
  • traditional sucrose syrups
77
Q

Caramelization involves 4 stages

A
  1. Enolisation
  2. Dehydration
  3. Fragmentation
  4. Polymerisation
78
Q

Functional properties of sugar in foods

A
  • can act as sweeteners
  • can contribute to the viscosity
  • food preservative (at high concentration)
79
Q

Pectin

A
  • located in the middle of lamella
  • useful for fruit preserves
  • gellling agents
80
Q

Process of pectin

A
  • As fruit ripen, hydrolysis of the glycosidic bonds by polygalacturonases and hydrolysis of their methoxyl groups by pectin methyl esterases leads to conversion of protopectin to pectinic acids (which are more soluble)
81
Q

Formation of pectinic acids =

A
  • softening and improvement in sensory quality
82
Q

If continued, polygalacturonic acids forms, then turned to monomeric galacturonic acid

A
  • fruit is too soft and susceptible to microbial spoilage
83
Q

Starch

A
  • present in cereals, root parts, tuberous plants, and legumes
  • made up of amylose (linear) and amylopectin (branched)
84
Q

Waxy starch

A
  • contains little or no amylose
  • waxy maize
85
Q

Starch granule properties

A
  • occurs in different sizes and shapes
  • extract starch from different plants
86
Q

Functions of starch

A
  • Adhesion
  • Binding
  • Clouding
87
Q

Gelatinization and pasting

A
  • used to describe changes starch undergoes heating
  • Powder + water = pasting
  • Cools down = gelatinization
88
Q

In the native form of starch

A
  • not stable
  • less application in the food industry
  • must be modified to enhance their use
89
Q

Cross-linking

A
  • forms bond between the cross-linking agent and hydroxy group
  • to strengthening the starch and make it more stable
90
Q

Substitution

A
  • substitute some functional groups to a new chemical agent
91
Q

Acid hydrolysis and dextrinization

A
  • acidification of starches under stringent control
  • makes it dispersible without thickening
92
Q

Dextrins formation

A
  • starch are heated dry under agitation
  • used in the coating of foods
93
Q

Maltodextrin

A
  • controlled enzymatic hydrolysis with amylase
94
Q

Pregelatinization

A
  • starches are gelatinized and then dehydrated to dry powder form

[LEC] Food Chemistry (2 decks)

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