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Food Chemistry > (3,4) Carbohydrates > Flashcards

(3,4) Carbohydrates Flashcards

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1
Q

what are the 3 component of carbohydrates and its examples?

A

monomer: glucose
oligomer: collagen
polymer: starch, fibers, pectin, gum

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2
Q

what is oligomer?

A

substance contain few or one species of atom linked to each other

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3
Q

what are dimers, trimers, and tetramers?

A

all is the example of oligomers stated two, three, and four monomers

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4
Q

2 examples of natural gum

A

a. xantham gum (bacterial) - very stable in acid, expensive
b. arabic gum (acacia tree exodate) - not very stable, cheaper

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5
Q

2 examples of starch

A
  • cassava starch (tapioca)
  • maize starch (maizena)

*both contain 99% starch

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6
Q

3 types of flour

A

wheat, rice, and oat flour

  • all contain starch +fibers. wheat flour also contain gluten
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7
Q

function of carbohydrates in human

A

comprising 40-75% or energy intake ( the rest is protein and lipids)

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8
Q

essential structural component of carbohydrates

A

simple sugar: monosaccharides
complex carbohydrate: polysaccharides (mostly polymers)

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9
Q

what is the energy value of carbohydrate?

A

4 kcal/g (same like sucrose, glucose, starch)

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10
Q

role of carbohydrates in foods

A

1.) taste: xylitol - cooling effect due to energy in mouth being absorbed
2.) color: reaction between carbo with amino acids or protein to give brown color (BBQ)
3. texture: polysaccharides - jelly texture in jam due to pectin

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11
Q

what is the main source of carbohydrates?

A

plant produce and animals as glycogen

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12
Q

application of carbohydrates in foods

A

product: syrup, starch, edible film, etc
industry: sweetener, texture, coloring agent, gelling agent stabilizer, etc

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13
Q

what does coloring agent formed?

A

brown - mailard (CH + amino acid) and caramelization (from sugars only)

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14
Q

application in non-food

A

pharmacy, wood (cellulose), paper (pulp), chemical (shampoo thickener by modified starch), etc

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15
Q

molecular structure of carbohydrates

A

simple sugar containing from 3 - 7 carbon atoms to very complex polymers

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16
Q

main compound of carbohydrates

A
  • aldehyde group (CHO)
  • ketone group (CO)
  • carboxyl group (COOH)
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17
Q

define polyhydroxy aldehydes in carbohydrates

A

monomer: glucose
polymer: glycan

*monomer contain hydroxyl & aldehyde (triose, tetrose, pentose, nexose)

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18
Q

define ketones in carbohydrates

A

contain (-OH) and (C–O) e.g fructose as polymer (gum)

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19
Q

define alcohols in carbohydrates

A

contains (-OH) e.g polyols

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20
Q

define acids in carbohydrates

A

polyhydroxyl acids contain hydroxyl and acid groups (-COOH)

e.g gluconic acid as polymer (pectin)

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21
Q

define glycosamines

A

hydroxyl, aldehyde, amine

e.g mushrooms, chitin

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22
Q

what is degree of polymerization (DP)

A

the average number of monomer units in the molecule

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23
Q

3 principle of carbohydrates based on DP

A

sugars, oligosaccharides, polysaccharides

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24
Q

what is digestible carbohydrates

A

can be digested by amylase/ carbohydrates

e.g alpha amylase, alpha glucosides (human), beta glucosides (animal)

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25
Q

define raffinose and stachiose

A

can be digested by bacteria fermentation in large intestine

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26
Q

define modified starch

A

modified by physical or chemical or enzymatic reaction

present in cheese or chips

can be digested by body

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27
Q

parent of monosaccharides

A

polyhydroxyl aldehydes or polyhydroxyl ketones with 3 or more C atoms

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28
Q

define monosaccharides

A

single unit without glycosidic connection to such units

cannot be converted hydrolytically into smaller molecules

plays as sweetener and instant energy source

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29
Q

some of examples of monosaccharides

A
  • triose (3C) : glyceraldehide
  • tetrose (4C) : erythrose
  • pentose (5C) : arabinose, ribose, xylose
  • hexose (6C) : galactose, glucose, fructose
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30
Q

what is the difference between aldoses and ketoses

A

aldoses is monosaccharides contain aldehydic carbonyl (-CHO) at C1 while ketoses contain ketonic carbonyl (-C–O) at C2

aldose has pyranoid structure while ketose has furanoid structure

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31
Q

define nomenclature

A
  • functional group: ketose, aldose
  • number of carbon atoms attached: triose, tetrose, pentose, hexose
  • position of OH group: D-glucose, L-glucose, D-fructose, L-fructose
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32
Q

what is reducing sugar?

A

sugar with aldehydic carbonyl group and determined by the presence of free OH in C1 which involved in maillard reaction

e.g glucose and lactose

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33
Q

define structural representation in Haworth Projection

A

in 6C glucose, a covalent bond form reaction between aldehyde at C1 and the (-OH) at C5 which produces glucopyranose ring structure

ketone at C2 (in fructose) react with (-OH) at C5 which produce a glucofuranose ring

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34
Q

pyranose vs furanose

A

pyranose: aldose
furanose: ketose

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35
Q

what is D and L configuration?

A

D and L specifies configuration at C5 (chiral center far from reference group)

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36
Q

alpha vs beta configuration

A

alpha: (-OH) group points downward in alpha form of sugar

beta: (-OH) group points upward from the ring in beta of sugar

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37
Q

amylose vs cellulose

A
  • cellulose is synthesized from beta glucose units, insoluble, and cannot be digested as food source by most animals
  • amylose assembles from alpha glucose units, soluble, and easily digested
38
Q

what is disaccharides?

A

a two monosaccharides link together contain O that forms bridge between couple units. O must be part of acetal or ketal group. it can be ruptured by enzymes at specific sites in the amylose and amylopectin polymers

e.g maltose, lactose, sucrose

39
Q

what is glycosidic bond?

A

a covalent bond that bind alpha or beta (1,4) between unhydroglucose unit in starch chains

40
Q

what are the physical properties of sugar?

A
  1. sweetness: contribute 4 kcal/g and relative sweetness around 1.0
  2. hygroscopicity: ability to attract and hold water, maintaining the freshness of some baked products, source of problem in texture if RH (relative humidity) is high, temperature increases the absorption of moisture in atm
  3. solubility: sugar soluble in water caused by numerous (-OH) groups and they have different solubility range
41
Q

what is invert sugar?

A

sugar formed by hydrolysis of sucrose (a mixture equal amount of fructose and glucose)

42
Q

define hydrolysis

A

a breakdown of covalent bond by water and inserting H+ across bond. disaccharides undergo hydrolysis when heated

43
Q

define caramelization

A
  • only occurs ot mono/ disaccharides with water content almost 0
  • create pleasing color and flavor changes
  • require high temperature (sugar heated > reach above melting point > dehydration causing furfural derivatives which undergo reaction polymerization to brown pigments)
  • caramel color can be used as colorant in food processing
44
Q

overview of hydrolysis and caramelization

A

sucrose > invert sugar (hydrolysis)

invert sugar > caramel/ colloids (caramelization)

The first reaction step in the caramelization process is sucrose hydrolysis leading to glucose and fructose production (7,8)

45
Q

define maillard reaction

A
  • an non-enzymatic reaction between amino acids and reducing sugars (not all sugar) that results in food browning and producing fresh aromas and flavours
  • affecting color, flavour, taste, and decrease nutritional quality
  • involves aldehyde (reducing sugar) and amine (amino acid)
46
Q

who is Louis-Camille Maillard?

A

a founder of maillard reaction of mixing amino acid and sugar from 8 paper he has published (1878-1936)

47
Q

who is John Hodge?

A

a chemist from CSDA who proposed mechanism of non-enzymatic reaction after 60 years (1941-1980)

48
Q

what is Maillard-Hodge reaction?

A

First, the carbonyl group (C–O) of a sugar reacts with an amino group on a protein or amino acid to produce water and an unstable glycosylamine (sugar derivatives).

Then, the glycosylamine undergoes Amadori rearrangements to produce a series of aminoketose compounds

49
Q

mention steps of maillard reaction

A
  1. aldose (reducing sugar) react with amino acid or amine to form Schiff Base (N-Substitute Glycosylamine)
  2. N-Glycosylamine forms carbonyl compound through amadori re-arrangement
  3. carbonyl compound forms melanoidin (brown) with different reaction pathway depends on reaction condition and temperature - forming brown colour and flavour
50
Q

examples of amine

A

ammonia, phospolipids, amino acids, protein

51
Q

examples of carbonyl

A

aldehydes, ketones, reducing sugar, polysaccharides, oxidised lipids

52
Q

amadori (amino carbonyl interaction) product

A

furans, pyrroles, thiopenes, thaizoles, oxazoles, imidazoles, pyridines, pyrazines

53
Q

how water activity and temperature affect maillard reaction?

A

water will lower the temperature of the system and greatly minimizes the reaction.

Using high heat may not guarantee flavorful Maillard reaction products if too much water is released from food.

54
Q

what is oligosaccharides?

A

small linear or branched fragments consisted of original starch (3 &10 unhydroglucose units) which formed acid, enzyme, or other starch degradative.

e.g raffinose, stachyose, fructo-oligosaccharides (FOS), maltodextrin

55
Q

why some oligosaccharides considered as prebiotics?

A

The large majority of oligosaccharides cannot be broken down by the human digestive tract. Instead, they travel through your gut all the way to the colon, where they feed and support the growth of beneficial bacteria ( 2 , 3 ).

56
Q

what is maltodextrin and its function?

A

white and starchy powder polysaccharides used as thickener or filler of processed food, increase shelf life, cheap, and easy to produce

e.g puddings, salad dressing, etc

57
Q

what is starch

A

a primary stored energy sources in plant act as water-insoluble granules with unlimited quantities.

58
Q

where does the common starch used in food industry extracted from?

A

cereals (roots), tubers

59
Q

functions of starch

A

gelling, thickening, adhesion, moisture-retention, stabilising, film forming, texturising

60
Q

what are the composition of starch?

A
  • consist of amylose (20-30%) and amylopectin (70-80%)
  • linked to alpha (1,4) amylose and alpha (1,6) amylopectin

*the proportion of of amylose and amylopectin depends on the source of starch

61
Q

mention some of the starch sources

A

Potatoes, rice, tapioca, wheat

62
Q

amylose vs amylopectin

A
  • amylose: linear, form blue color with iodine
  • amylopectin: branched, form reddish brown color with iodine
63
Q

characteristics of starch granules

A

Smaller starch granules have a larger superficial area, surface pores, and channels that enhance water uptake.

High hydration increases the swelling, viscosity, and gelatinization ability of starch granules.

64
Q

amylose and amylopectin ratio

A

starches has its own proportion of amylose and amylopectin, this ration depends on the types of starch.

amylose length of molecules can vary (DP) and amylopectin length and branches are just as variable

65
Q

explain more about starch sources: potato and rice

A

potato: 20% amylose, its starch granule are large, smooth, round oval shape. plays as the largest granules

rice: the ratio of amylopectin and amylose is 20:80 respectively, while waxy rice only has 2% amylose - small granule

66
Q

explain more about starch sources: tapioca and wheat

A

tapioca: has 15-18% amylose, its granules are smooth, irregular shape with 5-25 microns

wheat: has 25% amylose, relatively thick to 5-15 microns, smooth and round shape up to 22-36 microns diameter

67
Q

define starch hydrolysis

A

a reaction in the eznyme or acid catalyzed conversion of starch into maltodextrin and glucose syrup

the degree of hydrolysis determine the final molecular weight and properties of product

68
Q

what is starch granules?

A

small-grain like particle in which amylose and amylopectin molecules are deposited and stored by plant ( 3- 100microns)

in case of corn: located in the endosperm of seed or kernel

69
Q

how does granules form its shape and size

A

some starches contained both large and small granules (ex: wheat starch), smooth and polyhedrons surface

70
Q

what are the specific characteristics to differ among starch?

A
  • granule size and shape
  • amylose content
  • gelatinization temperature
  • viscosity and pasting properties
  • setback or cold viscosity
  • gel strength
  • paste clarity
71
Q

what is birefrigence?

A

maltose cross pattern happen when ungelatinized starch viewed under microscope with polarized light and this disappearance in starch suspension heating will determine gelatinization temperature

72
Q

characteristics of birefrigence?

A
  • granules like semi-crystal
  • fraction light under microscope produce “maltose cross”
  • if its disappeared it will gelatinized
73
Q

what is starch gelatinization?

A

the process where starch and water are subjected to heat, causing the starch granules to swell

when starch suspension is heated, granules absorb water > swell irreversibly

74
Q

parameter of measuring starch gelatinization

A
  • swelling of granules
  • increased viscosity
  • increased translucency
  • increase solubility
75
Q

what are the properties of irreversible changes of starch gelatinization?

A
  • granular swelling
  • native crystalline melting
  • loss of birefrigence
  • starch solubilization
  • increased suspension viscosity
76
Q

parameter of gelatinization temperature

A
  • starch concentration
  • method of observation
  • granule types
  • heterogeneities within granule population under observation
77
Q

what happen if the temperature of gelatinization going high?

A

starch rapidly swells and absorbs water to become viscous dispersion

78
Q

gelatinization process

A
  1. granule swelling: granules heated and absorb water that will swell irreversibly
  2. double-helical melting: water enter crystalline structure by continue heating increase which absorb more water, then it will bump each other and rupture. water break bonds, and crystalline regions diffuse resulting dissolution of amylose chains
  3. amylose leaching: amylose chain separate and reach maximum viscosity causing the mixture thick
  4. retrogradation: water molecules trapped, starch granules leak out allowing amylose and amylopectin recrystallize (high amylose starch)
79
Q

what is retrogradation

A

recrystallization of starch in which amylose and amylopectin chains realign into more crystalline structure

80
Q

starch gelatinization process: temperature

A

forming starch paste - depends on starch types, environment, etc

81
Q

starch gelatinization process: starch paste

A

contain swollen granules, dissolved amylose, and intermediate species. the stability depends on starch types, concentration, and storage temperature

82
Q

starch gelatinization process: peak viscosity

A

high viscosity -> swollen granules at maximum levels

83
Q

starch gelatinization process: end viscosity

A

end viscosity means final viscosity value produced in brabender viscograph which denotized fully gelatinization after cooling paste to a specific temperature

84
Q

starch gelatinization process: set back, heat and shear stability, clarity

A
  • set back: rise in paste viscosity as starch paste cools
  • heat stability: stability of product when exposed to storage hot conditions
  • shear stability: resistance to viscosity
  • clarity: degree of transparency in starch pastes measured by methods on light transmission
85
Q

starch gelation

A

formation of gel from a cooled paste that is rigid, thick, water mixture.

starches with high amylose can form gel more easily than starch high in amylopectin

86
Q

define pastes

A

derived from high amylopectin starch that has gummy and cohesive texture

useful as thickening agent due to their ability in increasing viscosity

87
Q

what is retrogradation

A

a process when polymers gelatinized starch begin to re-associate in ordered structure

87
Q

how retrogradation process occurs?

A
  • in initial phase, 2 or more amylose or amylopectin form simple juncture point which then develop into extensively ordered regions
  • linear amylose attracted to each other forming polysaccharides chain by hydrogen and hydroxyl groups
  • happens clearly when amylose containing cool starch resulting in water release (syneresis)
  • amylose has higher chance to retrograde rather than amylopectin
88
Q

examples of retrogradation

A

dried rice after bing cooled in refrigirator

89
Q

what is native starch?

A

Native starches are basically pure forms of starch.

90
Q

disadvantages of native starches

A
  • inconsistent viscosity: due to physiological and climate condition
  • solubility: due to limit amount that can be dissolved (high dissolved solid content)
  • susceptibility to shear: reduction in viscosity due to how well it has been stirred
  • susceptibility to acid attack: acid food caused by degradation of unmodified starch
  • set back and syneresis: if left for longer period, water molecules expressed from the gel to solid by expressed water

Food Chemistry (4 decks)

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