Analysis of Carbs Flashcards
Carbs importance
Source of NRG
Textural properties
Physiological properties
A large % of the diet
Carbohydrates by difference
Easiest way to measure carbs
(100 - protein - fat - water - ash) / 100 g of food
Qualitative methods
Color reaction in strong acids
Yields furan derivatives (furfurals)
Alpha naphthol
For all carbs (mono, di, and polysaccharides)
Purple color
Resorcinol
Test for ketoses
Fructose, allulose
Red color
Orcinol
Test for pentoses
Aribonse, xylose, ribose
Yellow –> blue
Tollens
Test for aldoses
React with silver
Create a precipitate
Reducing sugar tests
Somogyi Nelson
DNS
Tollens
Fehling’s
Somogyi Nelson
Reduction of Cu ions
Cu ions reduce an arsenomolybdate complex
Create a blue color
Quantative analysis
Cuprous oxide measured gravimetrically
Titration
Calibration curves
DNS test
3,5-dinitrosalycilate is reduced to 3 amino 5 nitrosalicylic acid
Absorbs in UV range
Reducing sugar test
Analysis of mono and oligosaccharides
Chromatography (paper, thin layer, GC, HPLC)
Paper + thin layer chromatogrphy
Polar solvents
Develop with heat, acid, chromogen
TLC densitometry
Specific analysis of mono and oligosaccharides
Electrophoresis
Capillary electrophoresis
HPLC
Quantative and qualitative
Analyze complex mixtures
Anion/cation exchange colums
Sugars might hydrolyze, be careful with temp and pH
GC
Sugars converted into volatile derivatives
Fehling’s
Copper sulfate, potassium tartrate
Distinguish between functional groups of ketones and carbohydrates that are water-soluble
Enzymatic pros
Cheap
Simple to use
Any sugar
Convenient
Specific to substrate
Enzymatic reaction types
Measuring reaction
Indicating reaction
Measuring reaction
Molecule we want to quantify is used by the specific enzyme to create products
Useless on its own
Indicating reaction
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
Only reliable starch method
Complete conversion of starch into D glucose w/ a specfic enzyme
Dietary fiber
Sum of non digestable components of food
Soluble fiber
Pectin
Hydrocolloids
Gums
Insoluble fiber
Cellulose
Lignin
Hemicellulose
Crude fiber method
Fat extracted with a solvent
Digestion w/ H2SO4 and NaOH
Insoluble residue collected, dried, weighed, ashed
Crude fiber cons
Hemicellulose and pectin are solubilized
Crude fiber foods
Grains, soybeans, pet food
Detergent methods measure
Lignin
Cellulose
(Acid detergent fiber)
Hemicellulose
(Natural detergent fiber)
Detergent methods cons
Doesn’t include pectin and gums
Fiber methods
Often measured gravimetrically
Gelatinization and hydrolysis of starch
Inulin and oligosaccharides can be lost in extract
Best when samples are low fat, dry, ground
Microscopy
Examine starchy fooods
Granule size, shape, form
Polarized light microscope
Can see biofringence
Microscopy uses
Eval gelatinzation
Look at mechanical damage
Extent of starch hydolysis
Specific gravity
Ratio of density of a substance compared to refernece substance (water)
Refractive index varies with
Concentration
Temp
Wavelength
Polarimetry
A way to measure the optical activity of compounds
Optically active = rotates polarized light
Different sign/values based
on the direction of light rotation
Rotating capacity/angle is proportional to
concentration and length of column
Polarimetry pros
Nondestructive and fast
Polarimetry cons
Need a clean and colorless solution
Make standards to calculate unknown concentration
Polarimetry uses
analysis of invert sugar, purity of sucrose
Optical rotation
Sample rotates the plane of a polarized light beam
How does polarimetry work
Polarized light oscillating in 1 plane –> tube with solution –> plane of light rotates
