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Food Chem analysis > Non- volatile analysis > Flashcards

Non- volatile analysis Flashcards

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1
Q

Properties of non volatile compounds (4)

A
  • taste compounds
  • Soluble in water
  • MW in range 50 –1000
  • Threshold range 1 –10,000 (mg/kg)
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2
Q

Ex of Water-soluble compounds

A
  • Amino acids
  • Organic acids
  • Peptides
  • Ribonucleotides and their metabolites
  • Sugars
  • Sugar-phosphates
  • Thiamine
  • Other N-compounds
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3
Q

Taste precursors analysis

A

Water or acidified water

  • -> Concentrate
  • -> Analyse extract by GC, LC, CE
  • -> Identify compounds LC/GC/CE-MS (+ other methods)
  • -> Comparison with authentic compounds
  • -> Assess taste of separated components
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4
Q

High Performance Liquid Chromatography (HPLC)

process

A

Solvent reservoir

  • -> pump solvent manager & solvent delivery system
  • -> [Sample –> injector/ AutoSampler]
  • -> HPLC column
  • -> Detector
  • -> [Chromatogram & pc data station] & [Waste]
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5
Q

Separation - Column (2)

A
  • Normal phase (alumina or silica)

- Reverse phase (alkyl, aliphatic or phenyl bonded phases)

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6
Q

Separation - Elution (2)

A

-Isocratic (constant eluent composition)
1 solvent or 1 mixture of solvent of constant composition
during elution of compounds

-Gradient (variant eluent composition)
2 or more solvents programmed to change composition of polarity during elution of compounds

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7
Q

Detectors

A
  • UV
  • Fluorescence
  • Electrochemical
  • Refractive Index
  • Radiochemical
  • Mass Spectroscopy
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8
Q

LC-MS

A

•Molecules can be ionised via a number of different methods, meaning they are either positively or negatively charged
•Charged particles can be manipulated by the presence of an electric or magnetic field
• This effect is dependent on several parameters including the mass (m) and the charge(z) of the particle
•Mass spectrometers give information about
the molecular mass and more!

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9
Q

High Performance Capillary Electrophoresis

measurement & formula

A

Separation of components from mixtures by differential migration through a buffered medium when electric field is applied

  • Electrophoretic velocity
  • formula on slide 12
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10
Q

High Performance Capillary Electrophoresis

diagram

A

Two buffer reservoirs

  • Very small diameter capillary tube (<0.5 m in length and <0.1mm i.d.)
  • High voltage power supply (10-60kV)
  • Detector:UV,Fluorescence,MS
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11
Q

High Performance Capillary Electrophoresis can use to analysis?

A
  • Organic acids,amino acids & sugars
  • Nucleotides and related compounds
  • Amino acids, peptides & other amino groups
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12
Q

in CE analysis, the order of possible elution of Organic acids,amino acids & sugars

A

1: citric acid
2: malic acid
3: aspartic acid
4: glutamic acid
5: fructose
6: glucose
7: sucrose

[What is the relationship between 1-7? ]

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13
Q

in CE analysis, the order of possible elution of Nucleotides and related compounds

A

ATP →ADP →AMP →IMP →Inosine → Hypoxanthine →xanthine →uric acid

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14
Q

Analysis of amino acids & small peptides

A
  • [EZ:Faast] followed by GC-MS or LC-MS
  • SPE procedure followed by two-step derivatization at room temperature
  • Analysis by GC-MS
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15
Q

Advantage of using [EZ:Faast] for analysing amino acids & small peptides
(2)

A
  • Precise, accurate, sensitive, and reproducible results

* can be use for variety of complex matrices including foodstuffs, fermentation broths, etc

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16
Q

Derivatization

A

slide 17

17
Q

Ex of Bioactive compounds

A
  • Plantsterols
  • Carotenoids
  • ω-3-fattyacids
  • Indoles (benzopyrroles)
  • Phenols
18
Q

Classification of phenolic compounds
(4)

(These compounds can occur in…?)

A
  • Phenolic acids
  • Polyphenols (tannins or flavonoids)
  • Miscellaneous (Coumarins, stilbenes, lignans)

•These compounds can occur in free form (aglycon) or conjugated form with sugar or acid units

19
Q

Phenolic acids

A

slides 21

20
Q

flavonoid belongs to which chem group?

basic flavonoid structure

A

group name: Polyphenols

basic flavonoid structure is the flavan nucleus: 15 carbon atoms arranged in three rings (C6-C3-C6)

21
Q

Ex of Flavonoids (6)

structures?

A 
anthocyanidin
flavanone
flavanol
flavone
flavonol
isoflavone

slide 22

22
Q

forms of tannins: (2)

Ex

A

hydrolysable tannins or condensed tannins

H = Ellagitannin
C = Proanthocyanidin
23
Q

Approach to bioactive analysis (5 & Ex)

A

Extraction-
Solvent extraction, microwave or ultrasound extraction

Purification -
TLC, Column Chromatography, HPLC

Pure Compound

Structure elucidation (LCMS, GCMS, FTIR, H-NMR, C-NMR)
—- OR —-
Biochemical characterization —>
Toxicity Assay / In vivo Evaluation / Clinical Study

24
Q

Extraction of Bioactive compounds

A

•Solvent extraction -selection of solvent
–Hydrophilic compounds: methanol, ethanol or ethyl-acetate
–Lipophilic compounds: Dichloromethane, dichloromethane:methanol(1:1), Hexane

  • Sonification, heating under reflux, soxhletextraction, maceration or percolation
  • SPME, supercritical-fluid extraction, pressurized-liquid extraction, microwave-assisted extraction, SPE and surfactant-mediated techniques
25
Q

Purification of Bioactive compounds

A
  • THIN LAYER CHROMATOGRAPHY (TLC)
  • These paration of a mixture will depend on the polarity of the compounds present. These paration takes place on a planar bed (TLC plate–stationary phase) as the mobile phase flows due to capillary forces.
26
Q

TLC Stationary phase

A

A variety of finely-divided particulate sorbents including silica-gel, cellulose powder, ion-exchange resins.

27
Q

TLC Mobile phase:

A

Single solvents or blend of two or more solvents having the appropriate overall polarity to achieve the required separation. They range from non-polar hydrocarbons to polar alcohols, water and acidic or basic solvents.

28
Q

TLC Solute detection

A

Spraying the surface of the thin layer plate with a chromogenic reagent, or viewing it under a UV lamp if the sorbent has been treated with a fluorescent indicator

29
Q

Calculation of TLC

factor & relationship between results

A

𝑅𝑓= 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 𝑏𝑦 𝑠𝑝𝑜𝑡 /
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 𝑏𝑦 𝑠𝑜𝑙𝑣𝑒𝑛𝑡

Rf depends on polarity
Rf polar compound < Rf non-polar compound

30
Q

Purification using COLUMN CHROMATOGRAPHY

A

Components within a mixture are separated in a column based on each component’s affinity for the mobile phase.

•Stationary phase is held in a narrow tube through which the mobile phase is forced under pressure or under the effect of gravity

31
Q

Purification using ION EXCHANGE CHROMATOGRAPHY

A

Components (ions and polar molecules) within a mixture are separated in a column based on each component’s affinity to the ion exchanger.

•Stationary phase displays ionic functional groups (R-X) that interact with the analyteions of opposite charge.

  • Cation exchange chromatography –separate cations
  • Anion exchange chromatography –separate anions
32
Q

Identification using Fourier-Transformed Infrared Spectroscopy

A

IR radiation is passed through a sample where some of the infrared radiation is absorbed by the sample and some of it is passed through (transmitted).

  • The resulting spectrum represents the molecular absorption and transmission, creating a molecular fingerprint of the sample
  • Like a fingerprint no two unique molecular structures produce the same infrared spectrum
33
Q

Identification using Nuclear Magnetic Resonance

A
  • It identifies the carbon-hydrogen framework of an organic compound
  • Determine the entire structure of a molecule
  • H-NMR; C-NMR; N-NMR (hydrogen)
34
Q

How to analysis Phenolic compounds in lettuce

A
  • Extraction: freeze-dried material dissolved in 90% methanol, sonication, centrifugation, filtration
  • Separation of the compounds in HPLC (Reverse phase column; gradient elution)
  • Detection: Photodiode array detector and mass spectrometer

Food Chem analysis (3 decks)

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