Lecture 12 - CHO Analysis (Phys, Chrom, Enz) Flashcards

1
Q

what are physical methods of CHO analysis? (4)

A
  • refractometry
  • hydrometry
  • pycnometry
  • plolarimetry
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2
Q

what are instrumental methods of CHO analysis? (4)

A
  • chromatography
  • NMR
  • Electrophoresis
  • IR
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3
Q

describe the use of refractometry

A
  • based on refractive index
  • relies on Snell’s law (n1sina=n2sinb)
  • refractive index is related to density of solution
  • depends on concentration, temperature, and wavelength
  • inc of [sugar] changes water density, and therefore a increases refractive index
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4
Q

where can refractometers be used?

A
  • on processing line

- lab bench

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5
Q

what kind of products are commonly assessed with a refractometer?

A
  • carbonated soft drinks
  • orange juice (dissolved solids)
  • milke (to assess % solids)
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6
Q

how is hydrometry used?

A
  • based on Archimedes principle:

- object displaces weight of liquid = own weight

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7
Q

what kinds of hydrometers exist?

A
  • lactometer (milk density)
  • Baume (salt)
  • Brix (saccharometer)
  • alcoholometer
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8
Q

which hydrometer measures sugar (sucrose) content?

A

brix hydrometer

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9
Q

one degree brix equates to how many grams of sucrose per grams of solution?

A

1 g sucrose/100 g solution

or % sucrose

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10
Q

how is pycnometry used?

A

based on measuring specific gravity

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11
Q

list the 3 steps of pyncometry

A

1) weigh empty pycnometer
2) fill with water and reweigh
3) fill with sample liquid

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12
Q

how is polarimetry used?

A
  • molecules (like sugars) w/asymmetric C atom can rotate plane polarized light
  • polarimeter is used to measure optical activity to obtain specific rotation of a solution
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13
Q

what’s it called when light is rotate in a clockwise direction when viewed through a polarimeter?

A

dextrorotatory

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14
Q

what’s it called when plane polarized light is rotated in a counterclockwise direction and viewed through a polarimeter?

A

levorotatory

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15
Q

what is specific rotation?

A

angle of rotation of plane polarized light by 1.00 gram per cm^-3 sample in a 1 dm tube

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16
Q

what is rotation related to?

A

molecules in solution (aka concentration in g solute/ 1 cc solution)

17
Q

what methods can be used for the specific analysis of mono and oligosaccharides?

A
  • enzymatic methods

- chromatographic methods (HPLC, GC)

18
Q

what’s the name of the treatment used to prepare samples for enzymatic analysis?

19
Q

what are the steps of the Carrez treatment?

A

1) add potassium ferrocyanide
2) add zinc sulfate
3) add NaOH
4) filter suspension
5) use clear suspension for enzyme-catalyzed assays

20
Q

what does the Carrez treatment accomplish?

A

breaks emulsions, precipitates proteins, & absorbs colors from food products prior to enzymatic determination of CHO

21
Q

how can glucose be analyzed?

A

Glucose oxidase/peroxidase/dye (GOPOD) method

22
Q

how does the GOPOD method work?

A
  • Glucose oxidase oxidizes d-glucose to d-glucono-1,5-lactone and hydrogen peroxide
  • peroxidase is added to react with H2O2, turning a colorless dye into a colored compound
  • colored compound measured w/spec
23
Q

what’s an example of a dye used for the GOPOD method?

A

4 aminoantipyrine. produces red quinoneimine

24
Q

how do you analyze for starch?

A
  • prepare sample by first gelatinizing in hot DMSO
  • digest result with a-amylase (makes linear & branched fragments of amylose and amylopectin)
  • digest this with glucoamylase (makes glucose)
  • use GOPOD reagent on d-glucose (makes color)
  • measure with spec
25
true or false: enzyme purity does not have significant influence on results
false - purity of enzyme is critical
26
presence of which enzymes can lead to overestimation for starch determination?
ones that release glucose not from starch - cellulase - invertase - sucrase - B-glucanase
27
presence of which enzyme can lead to underestimation for starch determination?
- catalase (destroys H2O2)
28
what kind of starch can't be detected by enzymatic methods?
enzyme-resistant starch
29
pros of enzymatic methods? (6)
- HIGH specificity - doesn't require high purity of sample - very low detection limits - do not require expensive equipment - can be easily automated - commercially available kits
30
cons of enzymatic methods?
- need clear solution - must maintain optimal conditions (buffer, pH, temp, etc) - possible interference from other components
31
how is HPLC used?
- pumps sample mixture in a solvent at high pressure through a column with chromatographic packing material - column: anion exchanger (AE) - detector: electrochemical detector (ECD)
32
what is AE-HPLC used for?
detection and quantification of CHO from complex mixtures
33
identification of the CHO is _____ analysis
qualitative
34
how do you perform quantitative analysis using HPLC?
peak integration
35
pros of HPLC?
- relatively fast - can undertake a wide range of sample concentrations - high degree of precision and accuracy
36
in what form should sugars be for GC?
derivatized (volatile derivatives)
37
how do you turn sugars into volatile derivatives?
- reduce aldehyde groups to primary OH groups | - convert reduced sugars to volatile peracetate esters
38
what kind of detectors are used for GC?
- flame ionization detector (FID) | - mass spec (MS)