Lecture 12 - CHO Analysis (Phys, Chrom, Enz) Flashcards
what are physical methods of CHO analysis? (4)
- refractometry
- hydrometry
- pycnometry
- plolarimetry
what are instrumental methods of CHO analysis? (4)
- chromatography
- NMR
- Electrophoresis
- IR
describe the use of refractometry
- 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
where can refractometers be used?
- on processing line
- lab bench
what kind of products are commonly assessed with a refractometer?
- carbonated soft drinks
- orange juice (dissolved solids)
- milke (to assess % solids)
how is hydrometry used?
- based on Archimedes principle:
- object displaces weight of liquid = own weight
what kinds of hydrometers exist?
- lactometer (milk density)
- Baume (salt)
- Brix (saccharometer)
- alcoholometer
which hydrometer measures sugar (sucrose) content?
brix hydrometer
one degree brix equates to how many grams of sucrose per grams of solution?
1 g sucrose/100 g solution
or % sucrose
how is pycnometry used?
based on measuring specific gravity
list the 3 steps of pyncometry
1) weigh empty pycnometer
2) fill with water and reweigh
3) fill with sample liquid
how is polarimetry used?
- 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
what’s it called when light is rotate in a clockwise direction when viewed through a polarimeter?
dextrorotatory
what’s it called when plane polarized light is rotated in a counterclockwise direction and viewed through a polarimeter?
levorotatory
what is specific rotation?
angle of rotation of plane polarized light by 1.00 gram per cm^-3 sample in a 1 dm tube
what is rotation related to?
molecules in solution (aka concentration in g solute/ 1 cc solution)
what methods can be used for the specific analysis of mono and oligosaccharides?
- enzymatic methods
- chromatographic methods (HPLC, GC)
what’s the name of the treatment used to prepare samples for enzymatic analysis?
Carrez
what are the steps of the Carrez treatment?
1) add potassium ferrocyanide
2) add zinc sulfate
3) add NaOH
4) filter suspension
5) use clear suspension for enzyme-catalyzed assays
what does the Carrez treatment accomplish?
breaks emulsions, precipitates proteins, & absorbs colors from food products prior to enzymatic determination of CHO
how can glucose be analyzed?
Glucose oxidase/peroxidase/dye (GOPOD) method
how does the GOPOD method work?
- 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
what’s an example of a dye used for the GOPOD method?
4 aminoantipyrine. produces red quinoneimine
how do you analyze for starch?
- 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