Analysis of Carbs

Question 1

Carbs importance

Answer 1

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

Question 2

Carbohydrates by difference

Answer 2

Easiest way to measure carbs

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

Question 3

Qualitative methods

Answer 3

Color reaction in strong acids
Yields furan derivatives (furfurals)

Question 4

Alpha naphthol

Answer 4

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

Question 5

Resorcinol

Answer 5

Test for ketoses
Fructose, allulose
Red color

Question 6

Orcinol

Answer 6

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

Question 7

Tollens

Answer 7

Test for aldoses
React with silver
Create a precipitate

Question 8

Reducing sugar tests

Answer 8

Somogyi Nelson
DNS
Tollens
Fehling’s

Question 9

Somogyi Nelson

Answer 9

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

Question 10

Quantative analysis

Answer 10

Cuprous oxide measured gravimetrically

Titration

Calibration curves

Question 11

DNS test

Answer 11

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

Absorbs in UV range

Reducing sugar test

Question 12

Analysis of mono and oligosaccharides

Answer 12

Chromatography (paper, thin layer, GC, HPLC)

Question 13

Paper + thin layer chromatogrphy

Answer 13

Polar solvents
Develop with heat, acid, chromogen

TLC densitometry

Question 14

Specific analysis of mono and oligosaccharides

Answer 14

Electrophoresis

Capillary electrophoresis

Question 15

HPLC

Answer 15

Quantative and qualitative
Analyze complex mixtures
Anion/cation exchange colums

Sugars might hydrolyze, be careful with temp and pH

Question 16

GC

Answer 16

Sugars converted into volatile derivatives

Question 17

Fehling’s

Answer 17

Copper sulfate, potassium tartrate

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

Question 18

Enzymatic pros

Answer 18

Cheap
Simple to use
Any sugar
Convenient
Specific to substrate

Question 19

Enzymatic reaction types

Answer 19

Measuring reaction

Indicating reaction

Question 20

Measuring reaction

Answer 20

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

Useless on its own

Question 21

Indicating reaction

Answer 21

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

Question 22

Only reliable starch method

Answer 22

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

Question 23

Dietary fiber

Answer 23

Sum of non digestable components of food

Question 24

Soluble fiber

Answer 24

Pectin
Hydrocolloids
Gums

Question 25

Insoluble fiber

Answer 25

Cellulose Lignin Hemicellulose

Question 26

Crude fiber method

Answer 26

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

Question 27

Crude fiber cons

Answer 27

Hemicellulose and pectin are solubilized

Question 28

Crude fiber foods

Answer 28

Grains, soybeans, pet food

Question 29

Detergent methods measure

Answer 29

Lignin Cellulose (Acid detergent fiber) Hemicellulose (Natural detergent fiber)

Question 30

Detergent methods cons

Answer 30

Doesn't include pectin and gums

Question 31

Fiber methods

Answer 31

Often measured gravimetrically Gelatinization and hydrolysis of starch Inulin and oligosaccharides can be lost in extract Best when samples are low fat, dry, ground

Question 32

Microscopy

Answer 32

Examine starchy fooods Granule size, shape, form Polarized light microscope Can see biofringence

Question 33

Microscopy uses

Answer 33

Eval gelatinzation Look at mechanical damage Extent of starch hydolysis

Question 34

Specific gravity

Answer 34

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

Question 35

Refractive index varies with

Answer 35

Concentration Temp Wavelength

Question 36

Polarimetry

Answer 36

A way to measure the optical activity of compounds Optically active = rotates polarized light Different sign/values based on the direction of light rotation

Question 37

Rotating capacity/angle is proportional to

Answer 37

concentration and length of column

Question 38

Polarimetry pros

Answer 38

Nondestructive and fast

Question 39

Polarimetry cons

Answer 39

Need a clean and colorless solution Make standards to calculate unknown concentration

Question 40

Polarimetry uses

Answer 40

analysis of invert sugar, purity of sucrose

Question 41

Optical rotation

Answer 41

Sample rotates the plane of a polarized light beam

Question 42

How does polarimetry work

Answer 42

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