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Food Analysis > Analysis of Carbs > Flashcards

Analysis of Carbs Flashcards

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1
Q

Carbs importance

A

Source of NRG
Textural properties
Physiological properties
A large % of the diet

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2
Q

Carbohydrates by difference

A

Easiest way to measure carbs

(100 - protein - fat - water - ash) / 100 g of food

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3
Q

Qualitative methods

A

Color reaction in strong acids
Yields furan derivatives (furfurals)

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4
Q

Alpha naphthol

A

For all carbs (mono, di, and polysaccharides)
Purple color

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5
Q

Resorcinol

A

Test for ketoses
Fructose, allulose
Red color

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6
Q

Orcinol

A

Test for pentoses
Aribonse, xylose, ribose
Yellow –> blue

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7
Q

Tollens

A

Test for aldoses
React with silver
Create a precipitate

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8
Q

Reducing sugar tests

A

Somogyi Nelson
DNS
Tollens
Fehling’s

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9
Q

Somogyi Nelson

A

Reduction of Cu ions
Cu ions reduce an arsenomolybdate complex
Create a blue color

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10
Q

Quantative analysis

A

Cuprous oxide measured gravimetrically

Titration

Calibration curves

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11
Q

DNS test

A

3,5-dinitrosalycilate is reduced to 3 amino 5 nitrosalicylic acid

Absorbs in UV range

Reducing sugar test

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12
Q

Analysis of mono and oligosaccharides

A

Chromatography (paper, thin layer, GC, HPLC)

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13
Q

Paper + thin layer chromatogrphy

A

Polar solvents
Develop with heat, acid, chromogen

TLC densitometry

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14
Q

Specific analysis of mono and oligosaccharides

A

Electrophoresis

Capillary electrophoresis

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15
Q

HPLC

A

Quantative and qualitative
Analyze complex mixtures
Anion/cation exchange colums

Sugars might hydrolyze, be careful with temp and pH

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16
Q

GC

A

Sugars converted into volatile derivatives

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17
Q

Fehling’s

A

Copper sulfate, potassium tartrate

Distinguish between functional groups of ketones and carbohydrates that are water-soluble

18
Q

Enzymatic pros

A

Cheap
Simple to use
Any sugar
Convenient
Specific to substrate

19
Q

Enzymatic reaction types

A

Measuring reaction

Indicating reaction

20
Q

Measuring reaction

A

Molecule we want to quantify is used by the specific enzyme to create products

Useless on its own

21
Q

Indicating reaction

A

One of the products from the 1st reaction is used as the substrate

Reduce Nad+

Need a dehydrogenase enzyme

Measure NADH with an absorbance change

22
Q

Only reliable starch method

A

Complete conversion of starch into D glucose w/ a specfic enzyme

23
Q

Dietary fiber

A

Sum of non digestable components of food

24
Q

Soluble fiber

A

Pectin
Hydrocolloids
Gums

25
Q

Insoluble fiber

A

Cellulose
Lignin
Hemicellulose

26
Q

Crude fiber method

A

Fat extracted with a solvent
Digestion w/ H2SO4 and NaOH
Insoluble residue collected, dried, weighed, ashed

27
Q

Crude fiber cons

A

Hemicellulose and pectin are solubilized

28
Q

Crude fiber foods

A

Grains, soybeans, pet food

29
Q

Detergent methods measure

A

Lignin
Cellulose
(Acid detergent fiber)

Hemicellulose
(Natural detergent fiber)

30
Q

Detergent methods cons

A

Doesn’t include pectin and gums

31
Q

Fiber methods

A

Often measured gravimetrically

Gelatinization and hydrolysis of starch

Inulin and oligosaccharides can be lost in extract

Best when samples are low fat, dry, ground

32
Q

Microscopy

A

Examine starchy fooods
Granule size, shape, form

Polarized light microscope
Can see biofringence

33
Q

Microscopy uses

A

Eval gelatinzation
Look at mechanical damage
Extent of starch hydolysis

34
Q

Specific gravity

A

Ratio of density of a substance compared to refernece substance (water)

35
Q

Refractive index varies with

A

Concentration
Temp
Wavelength

36
Q

Polarimetry

A

A way to measure the optical activity of compounds

Optically active = rotates polarized light

Different sign/values based
on the direction of light rotation

37
Q

Rotating capacity/angle is proportional to

A

concentration and length of column

38
Q

Polarimetry pros

A

Nondestructive and fast

39
Q

Polarimetry cons

A

Need a clean and colorless solution

Make standards to calculate unknown concentration

40
Q

Polarimetry uses

A

analysis of invert sugar, purity of sucrose

41
Q

Optical rotation

A

Sample rotates the plane of a polarized light beam

42
Q

How does polarimetry work

A

Polarized light oscillating in 1 plane –> tube with solution –> plane of light rotates

Food Analysis (19 decks)

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