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5) FDSC 300 > Lecture 10- Carbohydrates > Flashcards

Lecture 10- Carbohydrates Flashcards

1
Q

What are the functions of digestible Carbohydrates?

A

Metabolic energy

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2
Q

What is the function of non-digestible carbohydrate?

A

bulkiness, water holding, stability, browning, textures, lower water content

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3
Q

What is classification based on with the WHO/FAO?

A

Sugar (1-2 Degree of Polymerizatoin)
Oligosaccharides (DP 3-9)
Polysaccharides (DP >9)

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4
Q

What is the the international nomenclature rule classificaiton of carbohydrates?

A

Oligosccharide (2-10 sugar units)

Polysaccharides (30 +)

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5
Q

Examples of Monosaccharides

A

fructose, glucose, galactose, arabinose and xylose

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6
Q

Examples of Oligosccharides (2-10 monomers)

A

disaccharides: sucrose and lactose
Trisaccharides: raffinose

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7
Q

Examples if polysccharides

A

Polymer of monomers >10

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8
Q

Examples of Homopolysaccharides

A

starch, cellulose, glycogen,

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9
Q

Examples of Heteropolysaccharides

A

PEctin, hemicellulose and gums

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10
Q

Three monosaccharides

A

Glucose
Fructose
Galactose

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11
Q

In what form are carbohydrates present as in foods?

A

Unbound molecuoles
Physically associated to otherr moleclues (Starch, granules)
Chemically bound to other molecules ( glycolipids, glycoproteins)

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12
Q

What is the relevance of determining food carbohydrates? (4)

A

Nutrition Labeling
Detection of adulteration
Food Quality
Food Processing

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13
Q

What is the old method of carbohydrate analysis

A

calculating the percent remaining after all the other components have been measured
%carbs= 100-(%H2O+ % protein + %lipid + %Ash + %Fiber)

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14
Q

What are the disadvantages of determination of carbohydrates through difference from proximate analysis?

A

Experimental errors, better to directly measure the carbohydrate content for accurate measurements

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15
Q

Sample Preparation (3 main steps)

A

** INSERT image slide 12 in carbohydrates)
Dry raw material, grind the dehydrates material & extract with CHCl3-MeOH to remove lipids & lipid soluble components, extract residue with ethanol, ion exchange to get mono and disaccharides

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16
Q

What are the methods of Analysis? (5)

A 
Chemical
Physical
Enzymatic
Instrumental
Immunoassays
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17
Q

What are the chemical methods?

A

Colorimetric, titration , gravimetric

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18
Q

What are the physical methods?

A

Polarimetry, refractometery

Density

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19
Q

What are the instrumental methods?

A

Polarimtery, Refractometery,

Density

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20
Q

What are the instrumental methods?

A

Chromatography, NMR, Electrophoresis and IR

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21
Q

What are the three colorimeteric methods?

A

Pheno-sulfuric acid, Anthrone Method, Somogyi-Nelson Method

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22
Q

What is the name of the titration method

A

Lane-Enon Method

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23
Q

What is the name of gravimetric method?

A

Munson-Walker Method

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24
Q

What does the phenol-sulfuric method determine?

A

Total Carbohydrates

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25
Q

What is the Phenol sulfuric acid method?

A

samples that conttain mono, oligo, poly, glucose, fructose, matlose, sucrose, starch, cellulose
–>(heat, H2SO4) –> Furan Components –> (condensation with Phenol) Colored compounds (yellow-gold color)
Measured with spectrophotometer at 490nm

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26
Q

Advantages of Phenol Sulfuric method

A

simple, sensitive, accurate, specific for carbohydrates

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27
Q

Disadvatages of the Phenol Sulfuric method

A

Does not involve stoichiometric reactios and the extent of rxn is a function of the structure
If different sugars found in sample, glucose is used to prepare the standard curve
Sorbitol or other sugar alcohol does not produce positive result
Results are expressed in terms of 1 carb because absorption only at one wavelength

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28
Q

What is the basic princople of the Anthrone Method?

A

Carbohydrates are dehydrated by strong acids to produce furan components

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29
Q

What is the Anthrone method?

A

Furan components react with Anthrone reagent to yield a blue- green color solution
Absorbance is meausred at 620nm

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30
Q

What does the Anthrone method measure? (2)

A

reducing and non reducing carbohydrates

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31
Q

What are the reagents in the Anthrone test? What color yields a positive result?

A

H2SO4
Dehydrated

Bluish green complex

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32
Q

What is Fehling’s test

A

Tests the presence of aldehydes via the reduction of deep blue solution of copper(2) to a red precipitate of onsoluble copper oxide
Used for reducing sugars

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33
Q

What two solutions are required for the Fehling’s solution?

A

Fehlings A –> 7 g CuSO4. 5H2O dissolved in distilled water containing 2 drops of dilute sulfuric acid
Fehling’s B –> 35g of potassium tartrate and 12 g of NaOH in 100ml of distilled water

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34
Q

What bonds are detected with the Fehling’s test?

A

Aldose and Ketose groups

–> Cu2O

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35
Q

What is the Somogyi-Nelson Method?

A

improvment of fehling’s method
Used to determin reducing sugars
For the determination of oligo- and poly saccharides, enzymes are used before the addition of reagent

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36
Q

What is the principle of Somogyi-Nelson Method?

A

Aldehyde group of reducing sugar reduces the Cu2+–> Cu+ in basic solution

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37
Q

What happens to ketoses in the Somogyi-Nelson Method?

A

enolize to aldoses in bsic solution so that they are also reducing sugars

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38
Q

What is the reagent for Somogyi-Nelson Method

A

arsenomolybdate complex produced from ammonium molybdate (NH4)6Mo7O24 with sodium arsenate

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39
Q

What product is the Cu+ reduced to? (Somogyi-Nelson Method)

A

arsenomolybdate is reduced to a stable blue product

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40
Q

How is the colour read with the Somogyi-Nelson Method

A

520nm and quantified against a standard curve of glucose

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41
Q

What are the Somogyi-Nelson Method steps?

A
  1. Solution of CuSO4 and NaOH is added to solution of reducing sugars
  2. The mixture is heated in a boiling water bath ** reducing sugars reduce Cu2+ to Cu+
  3. Add aresennomolybdate complex reagent from ammonium molybdate and sodium arsenate
  4. Cu+ reduces arsenomolybdate complex reduction of the arsenomolybdate complex produces a stable blue color that is measured
42
Q

What is the Lane and Enynon Titration method?

A

based on reducing action of carbohydrates toward certain metallic salts
Reducing sugars in the sample reduce copper sulfate (CuSO 4) from Cu(II) to Cu (I) in alkaline tartrate system Potassium sodium tartrate KNaC4H4O6 with NaOH

43
Q

What are the steps of the titration method?

A

Titrate carbohydrate against known concentration of CuSO4 in alkaline condition
Methylene blue is used as the indicator
Once all CuSO4 is used up, reducing sugar will reduce MB to form colorless solution

44
Q

What are the disadvantages of method

A

results depend on the precise reaction times, temperatures and reagent concentrations used and so these paramters must be carefully controlled
Cannot distinguish betwenn different types of reducing sugar
Susceptible to interference from toehr types of molecules that act as reducing agents

45
Q

What is the titration method based on?

A

reducing action of carbohydrates toward certain metallic salts
Reducing sugars in the sample reduce copper sulfate from C2+ to C+ in alkaline tartrate system with NaOH

46
Q

Whta is the gravimetric method called?

A

Munson and Walker Method

47
Q

What is the Munson and Walker Method?

A

Carbohydrates are oxidized in the presence of heat and excess of copper sulfate in alkaline tartrate
–> leads to the formation of copper oxide precipitate

48
Q

What is the equation of the gravimetric method?

A

Redicing sugar + Cu2+ + base–> Oxidized sugar + CuO2 (precipitate)

49
Q

What is the precipitate formed related to? (gravimetric method)

A

concentration of reducing sugars in the sample

50
Q

How is the precipitate present determined? (gravimetric method)

A

Gravimetrically.

By filtration, drying and weighing

51
Q

What are the disadvantages of the gravimetric method

A

Same disadvantages of Lane-Eynon method

BUT more more reproducible and accurate

52
Q

What is the oxidation

A

Loss of electrons

53
Q

What is the reduction? (sugars)

A

sugars give up electrons

54
Q

What are the physical methods?

A

Refractory, hydrometry, polarimetry

55
Q

What is refractory based on?

A

refractive index: absolute refractive index of a medium is the ratio of speed of light in a vacuum relative to the speed in the medium

56
Q

What does refraction mean?

A

beam of light is passed from one medium to another and the density of the two differ therefore bending the light

57
Q

What is Snell’s Law?

A

ratio of the sine of the angles of incidence and refreaction is equivalent to the ratio of phase velocities in two media
n1* sinα= n2* sin β

58
Q

What is total reflection?

A

No refraction

59
Q

Where is the critical angle taken from?

A

90* “line” form the horizontal between the two mediums

60
Q

What is the refractive index related to?

A

density of the solution

61
Q

What does the refractive index depend on?

A

concentration of the solution, temp and wavelength

62
Q

What is the refractive index of water?

A

η20= 1.33299

63
Q

What happens to a sugar solutions refractive index

A

addition of sugar changes the density of water which leads to change in refractive index ( η) of the solution

64
Q

What is another used of the refractometer?

A

liquid processing line to monitor the Brix of products such as carbonated soft drink, dissolved solids in orange juice etc

65
Q

What is Hydrometry

A

based on Archimede;s principle, which states that a solid suspended in a liquid will be buoyed by a force equal to the weight of the liquid displaced
○ Object displaces a weight of liquid equal to its own weight
○ Based on displacement of a liquid by floating body

66
Q

What is the specific gravity?

A

Constant weight for the liquid

Density of a liquid compared to that of water

67
Q

How do you calculate the specific gravity?

A

Wt. of an object = Wt. of the displaced liquid.
-Wt.= Volume (V) x density (D)
-So, V x D (object) = V x D (displaced liquid)
= density of a liquid/ density of water

68
Q

What is a lactometer?

A

measure the density of milk

69
Q

What is a Baume hydrometer

A

density of salt solution

70
Q

What is a Brix hydrometer(sacchrometer)

A

Measure the density of the sugar solution

71
Q

What are the steps to determin the brix solution?

A

a. Wt. measurement system calibrated using sucrose solution concentration
b. Percentage of sucrose by wt in a solution –> Brix = % sucrose
c. On degree brix= 1 gram of sucrose in 100 g of solution. Represents the strength of the solution as percentage by mass

72
Q

What is alcoholmeter

A

Alcohol content in beverages is measured

73
Q

What is Pycnometry

A

Measuring specific gravity –> measure the weight

74
Q

What is the concept of pycnometry?

A
  • Have a glass container with a level, weight of the liquid vs. weight of water
    ○ s.g. = density of liq/density of H2O
    s.g.= W/V (liquid0/ W/V (H2O)
75
Q

What are the steps of Pycnometry?

A

1-Wt. empty pycnometer(W1).
2-Fill it with water and reweight (W2).
3-Fill it with the liquid (W3).
SG= W3-W1/ W2-W1

76
Q

What is polarimtery based on?

A

molecules that contain an asymetric carbon atom (chiral) have the ability to rotate plane polarized light

77
Q

Why can we measure polarimtery with sugars?

A

opticlaly active because they are chiral

78
Q

What does plane polarized mean?

A

○ Polarized light is a where all the the light is changed so that there is only one plane of light–> NO rotation

79
Q

What do polarizers absorb?

A

one component of polarization but not the other.

80
Q

What are some things with light that could lead to error

A

Input is natural light, the output is polarized light–> dichroism, reflection, scattering

81
Q

What is dextrototary

A

when the plane of polarized light is rotated in a clockwise direction when viewed through a polarimeter.
(+) or (d) do not confuse with D

82
Q

What is levorotary?

A

when the plane of polarized light is rotated in a counter-clockwise direction when viewed through a polarimeter.
(-) or (l) do not confuse with L

83
Q

What is specific rotation?

A

angle of rotation of plane polarized light by a 1.00 gram per cm_3 sample in a 1dm tube

84
Q

How do you determine specific rotation?

A 
[α ]T(T= temperature, D = sodium lamp).
		[α]_d=α /l * d
		D= where α = observed rotation
		 l = length (dm)
		d = concentration (g/cc)
85
Q

What is specific rotation related to?

A

number of moleules in the solution, which is concentration in g substance/1cc solution

86
Q

What are some advantages of enzymatic method?

A

○ Sensitive

Can determine specific levels of a sugar

87
Q

What is the Carrez tretment?

A

breaks emulsision, precipitates, proteisn, and absrobs colors from food products prror to enzymatic determination of carbohydrates

88
Q

What are the steps of the Carrez method?

A
  1. Addition of potassium ferrocyanide
    2. Addition of zinc sulfate (ZnSO4)
    3. Addition of sodium hydroxide
    4. Filtration of the suspension
    5. Use the clear suspension for enzyme-catalyzed assays.
89
Q

What does glucose ozidase oxidize?

A

d-glucose quantitatively to d-glucono-1,5-lactone (glucono-delta-lactone) and hydrogen peroxide

90
Q

What is measured with the CArrez method?

A
  • D-glucose is measured from H2O2generated using peroxidase that turnsa colorless compound (a leucodye) to a colored compound
    • Coloured compound is measure spectrometerically
91
Q

How is Starch determinined enzymatically?

A

gelatinization in hot DMSO –> Digest with a-amylase–> digest with glucoamylase–> GOPOD reagent –> color is determined

92
Q

Why is the purity of enzymes important with determination of starch enzymatically?

A

Presence of cellulase, invertase, sucrase, β-glucanasereleaeD-glucose from other than starch (false high value)
Catalase destroy the hydrogen peroxide (false low value)
Enzyme resistant starch is not destroyed
Trapped in a cell wall
Crystaline strah is not digestible

93
Q

What are the PROS of enzymatic carbohydrate determination?

A

Enzymatic methods have HIGHER specificity
Does not require high purity of the sample being analyzed
Have very low detection limits,
Do not require expensive equipment,
Can be easily automated
Commercially available kits

94
Q

What are the CONs of enzymatic starch determination

A

Need clear solution
Optimum condition-buffer, pH, temperature etc
Possible interference from other components

95
Q

What is dependent on the chromatography sugar?

A
  • Selection of mobile phase, column (usual one as anion
    exchange (AE)) and detector (pulsed electro chemical
    detector (ECD)) may depend on the specific carbohydrate
    Analyzed
96
Q

What happens with a higher pH?

A

they get charged into hydronium ions, can add alkaline, the solution needs to be charged

97
Q

What is HPAEC

A

chromatograpy for carbohydrates

98
Q

What is the Column?

A

stationary phase of the chromatography
○ Carbohydrate column–> anion exchange
○ Positive change sugars

99
Q

What is the pulse electron detector?

A

charged molecules , detec the the charge and create a dchromatogram

100
Q

What is used for detection with chromatography?

A
  • AE-HPLC coupled to an ECD is used for detection and

quantification of carbohydrate from complex mixtures

101
Q

What types of analysis are determined with chromatography?

A 
- Qualitative analysis (identification of the carbohydrate)
 Quantitative analysis (peak integration)
102
Q

What is Gas chromatography?

A

○ Qualitative and quantitativ analysis fof carbohydrates
○ Sugars must be converted into volatile derivatives (derivitization
§ Reduction of aldehydic groups to primary hydroxyl groups and conversion of reduce sugars into volatile preacetate esters
○ Detector- flame ionization detector (FID) or mass spectrometric (MS)

5) FDSC 300 (14 decks)

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