Carbohydrate Analysis Slides Flashcards
What are carbohydrates
Empirical Formula:
Compounds of Carbon, Hydrogen and Oxygen
CnH2nOn
Carbohydrates functional role in food
Bulk
Viscosity
Water Holding Capacity
Classification of CHOs
1) Monosaccharide
2) Disaccharides
3) Oligosacharides
4) Polysaccharides
Examples of monosaccharides
Glucose and Fructose
(easily absorbed)
Examples of Disaccharides
Lactose, Sucrose, and Maltose
Only polysaccharides digested by humans
Starch
Sugars =
sum of all free mono- and disaccharides
Sugar Alcohols =
alditols, polyhydroxyalcohols, polyols, sorbitol, and xylitol
Other carbohydrate =
total carbohydrate - (dietary fiber + sugar)
Total carbohydrate =
100% - (% Moisture + %Ash + %Lipid + %Protein)
Test for Hexose or Pentose
Bial Test
Test for aldose or ketose
Seliwanoff test
Reducing sugars test
+ Benedict’s test
+ Barfoed’s Test
Test for starch or glycogen
Iodine test
Quantitative chemical methods
Phenol-sulphuric
Somoygi-Nelson
Dinitrosalicyclic method
Quantitative chromatography method
HPLC
Gas chromatography
Thin-Layer
Paper
Preparation of sample
1) Drying
2) Grinding
3) Extract lipids
Bial’s Test Reagents
FeCl3 or HCl
to give blue color: positive of pentoses
Dehydrated ketose reacts with resorcinol to produce
cherry red color (Seliwanoff’s Test)
Principle of Phenol-Sulfuric Acid Method
Carbohydrate treated with strong acid/heat form furan derivatives
Benedict’s Test (reducing sugars)
Alkaline solutions of copper are reduced by sugars having free aldehyde or ketone group
Seliwanoff’s Test distinguishes between
Aldose and ketose sugars
When heated ketoses dehydrate
more rapidly than aldoses
Examples of ketose monosaccharides
Dihydroxyacetone
Erythrulose
Ribulose
Fructose
Examples of aldose monosaccharides
Glyceraldehyde
Erythrose
Ribose
Xylose
Glucose
Mannose
Galactose
Barfoed’s test is used for
detecting the presence of reducing monosaccharides
Barfoed’s Test is based on the
reduction of copper (II) acetate to copper (I) oxide (Cu2O) (brick red)
In got acidic medium starch is _______ and dehydrated to _____
hydrolyzed to glucose; hydroxymethyl furfural
Methods for total reducing sugar
Somogyi-Nelson
Munson-Walker
Lane-Eynon
Principle for total reducing sugar
Sugars with aldehyde group act as reducing agents - they reduce Cu2+ to Cu+
Starch contain what two polysaccharides
Amylose (linear) and Amylopectin (branched)
Most starches contain
15 - 35 % amylose
Amylose are linked together by
alpha 1,4 linkage
Amylopectin are linked together by
alpha 1,4 and alpha 1,6 linkage
Amylose is _____ in water, while amylopectin is ______
soluble; insoluble
Amylose gives what reaction in iodine solution vs amylopectin
Blue color vs no reaction
Give rise to; Amylose vs Amylopectin
Gel formation vs Thickened preparation
Starch usually contain more
amylopectin than amylose
Starch Gelatinization: Heat causes
1) Water absorption by amyloplasts
2) Rupturing of the amyloplasts
3) Starch network formed
4) Hydrated network with water pockets
5) Gelatinization
Factors influencing gelatinization
+ Types of starch
+ Water
+ Temperature
+ Stirring
+ Addition of other ingredients
Starch Dextrinization
Starch and dry heat
Starch –> Dextrin; which provides
flavor, color, and aroma
Gel formation: Upon cooling
the realignment of starch molecules with water being squeezed out
