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

Midterms [Carbohydrates] Flashcards

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
Sugar can be drawn into two forms
1. Fischer projection 2. Haworth projection
26
Fishcer projection
- line form - Left = top - Right = bottom
27
Haworth projection
- ring form
28
Furan
- Five membered ring cyclic
29
Pyran
- six membered ring cyclic
30
Configuration of sugar
- determined on the Fischer projection - determined by the position of the carbonyl group
31
Penultimate
- carbon before the last (C5)
32
D-sugar
- hydroxy group (OH) is in the 5th on the right (Fischer projection)
33
L-sugar
- hydroxy group (OH) is in the 5th on the left (Fischer projection)
34
Conformation of sugar
- found at C1
35
Alpha (conformation)
- OH at the botton (at C1)
36
Beta (conformation)
- OH at the top (at C1)
37
Epimers
- sugar differ in one carbon atom - Cx epimers (x = which carbon they differed)
38
Galactose epimer
C4 epimer of glucose
39
Mannose
- C2 epimer of glucose
40
Disaccharide
- sugars that contain 2 sugar units
41
Alpha 1-4 glycosidic bond
- bonds two glucose molecules - C1 and C4 joins up
42
Condensation in disaccharide
- linking monosaccharides by removing water
43
Hydrolysis at disaccharide
- add water to split the disaccharide
44
Lactose
- milk sugar - galactose and glucose
45
Sucrose
- glucose and fructose - linked with alpha-1-glucose and beta-2-fructose bond
46
Fructose
- fruit sugar - 5 membered ring
47
Isomers
- same chemical formula but different structure
48
Optical activity
- whether it can rotate plane polarized light - have chiral center
49
Chiral center
- has four different atoms attached to it
50
Vant hoffs rule
- Number of chiral centers can estimate the number of possible isomers that such compound can have - Isomers = 2n, n = chiral center
51
Disaccharide examples
- Maltose - Lactose - Sucrose
52
Oligosaccharides
- typically less than 10 monsaccharides linked together - 2 < x < 10
53
Maltotriose
- maltose and glucose - linked by alpha 1-4 glycosidic bond
54
Polysaccharide
- more than 10 monosaccharide combined - more than 10 bonds - glycans
55
Homopolysaccharides
- contains a single type of monosaccharide - Storage form of monosaccharides - Ex. only contains glucose
56
Heteropolysaccharides
- contains 2 or more different types of monosaccharide - branched or unbranched - Ex. contains fructose and glucose
57
Starch
- storage form of monosaccharides in plants - main carbohydrate in human diet - found in bread, cereal, and rice - homopolysaccharide
58
Functions of carbohydrates
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
Solubility of sugars
- sugars are soluble - highly branched polysaccharides like starches are not soluble
60
Viscosity and surface activity of sugar
- polysaccharides are viscous - it thickens up when added water
61
Crystallinity of sugar
- have a wide range of crystallinity - sucrose is readily crystallized
62
Hygroscopicity of sugar
- can absorb water easily even after drying
63
Stability of sugar
- fairly stable molecules - reducing sugars are sensitive to oxidation
64
Optical properties of sugar
- absorb light in the UV and spectral regions
65
Hydrolysis of sugar
- sugars can be hydrolyzed
66
Oxidation/reduction of sugar
- highly oxidized; resistant to oxidation
67
Uronic acid
- COOH is at C6
68
Onic acid
- COOH at C1
69
Aric acid
- oxidation of both C1 and C6
70
Functional groups
- in addition to aldehydes and ketones, have primary and secondary hydroxy groups
71
Chelation and complexation
- display affinity towards various classes of iron ions
72
Reactions that can take place during processing
1. Hydrolysis 2. Enolization 3. Dehydration 4. Caramelization
73
Enolization
- changing from a keto- to an -enol form - at higher temperatures, acyclic sugars undergo enolization
74
Dehydration
- in an acidic environment (pH < 3) enolization is followed by dehydration - formation of unwanted 2-furaldehydes
75
Caramelization
- degradation reaction can also occur during melting of dry sugars and during heating of syrups above 100C
76
Caramelisation occurs during food processing
- heated strongly - jams and certain fruit juices - wine preparation - traditional sucrose syrups
77
Caramelization involves 4 stages
1. Enolisation 2. Dehydration 3. Fragmentation 4. Polymerisation
78
Functional properties of sugar in foods
- can act as sweeteners - can contribute to the viscosity - food preservative (at high concentration)
79
Pectin
- located in the middle of lamella - useful for fruit preserves - gellling agents
80
Process of pectin
- 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
Formation of pectinic acids =
- softening and improvement in sensory quality
82
If continued, polygalacturonic acids forms, then turned to monomeric galacturonic acid
- fruit is too soft and susceptible to microbial spoilage
83
Starch
- present in cereals, root parts, tuberous plants, and legumes - made up of amylose (linear) and amylopectin (branched)
84
Waxy starch
- contains little or no amylose - waxy maize
85
Starch granule properties
- occurs in different sizes and shapes - extract starch from different plants
86
Functions of starch
- Adhesion - Binding - Clouding
87
Gelatinization and pasting
- used to describe changes starch undergoes heating - Powder + water = pasting - Cools down = gelatinization
88
In the native form of starch
- not stable - less application in the food industry - must be modified to enhance their use
89
Cross-linking
- forms bond between the cross-linking agent and hydroxy group - to strengthening the starch and make it more stable
90
Substitution
- substitute some functional groups to a new chemical agent
91
Acid hydrolysis and dextrinization
- acidification of starches under stringent control - makes it dispersible without thickening
92
Dextrins formation
- starch are heated dry under agitation - used in the coating of foods
93
Maltodextrin
- controlled enzymatic hydrolysis with amylase
94
Pregelatinization
- starches are gelatinized and then dehydrated to dry powder form

[LEC] Food Chemistry (2 decks)

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