ISOMERIZATION AND DEXTRINIZATION

ISOMERIZATION

Isomers : same molecular formula but different configuration/structure

In carbohydrate chemistry

Glucose isomerase (D-glucose ketoisomerase)

HIGH FRUCTOSE CORN SYRUPS

Source : Applexion® Process for the Production of HFS 55 from Starch, Novasep

GLUCOSE ISOMERASE (GI)

D-Glucose/xylose isomerase : most important industrial enzyme

The production of HFCS by using glucose isomerase was developed first in Japan and later in the United States.

This isomerase also has capability to convert xylose into xylulose , in vivo . This property is utilized in bioethanol formation(as xylose accumulation forms a metabolic block in ethanol formation)

HFCS, an equilibrium mixture of glucose and fructose (1:1) is 1.3 times sweeter than sucrose and 1.7 times sweeter than glucose

High fructose corn syrup is composed of either 42 percent or 55 percent fructose, with the remaining sugars being primarily glucose and higher sugars.

Major Use of HFCS :

In food and beverage industry : AS SWEETNER (Replacing sucrose)

GIS IN MARKET

Brand Name Producer MO System

Sweetzyme Novo-Nordisk Bacillus coagulans suspension

Swetase Nagase Streptomyces phaeochromogenes

suspension

Sweetzyme T Novo-Nordisk S. murinus Bacillus coagulans

Whole cell immobilization

Spezyme Genencor International

S. Rubiginosus Cell freeimmobilization

IMMOBILIZED ENZYME SYSTEMS– MORE EFFICIENT

DEXTRINIZATION

Browning Reaction in Food material :

Reasons :

1. Caramelization [ at High Temp, sugar/starch breakdown]

2. Dextrinization [Starch in Dry conditions]

3. Enzymatic Browning [at low/moderate temp]

4. Sugar-Amine Browning [usually at cooking temp]

DEXTRINS

Dextrins : carbohydrate intermediates between sugar and starch , produced by enzymatic or thermal degradation of starch

Oligomers (-glucose-)n

Amorphous Yellow or white powder

Partially water soluble

Low viscosity (compared to starch)

DE*(degree of hydrolysis on dextrose equivalency) =< 20

*DE (starch)= 0 , DE(dextrose)=100, DE(Corn syrup)=20-99.4

DEXTRINIZATION-PROCESS

Not fully understood

Apparently 3 steps*

1. Hydrolysis (acidic) – α (1-4) and α(1-6) glycosidic bonds (controlled hydrolysis using endo amylases)

2. Transglucosidation

3. Repolymerization

Endo-amylases and Debranching enzymes (isoamylase ,pullulanase and amyolpullulanase) are used.

*Source : Modified Starches: Properties and Uses", O. B. Wurzburg, CRC Press Inc., 1987.

DEXTRINS

Malto-dextrins (Enzymatic)

Pyro-dextrins (Thermal) – Non food applications

Cyclo-dextrins : closed ring oligosaccharide(6,7 or 8 residue)(Intramolecular transglycosylation)

3 types of Dextrins in Market

1. British gum

2. White Dextrin

3. Yellow Dextrin

COMPARATIVE ACCOUNT

Property White Dextrin Yellow Dextrin British Gum

Hydrolysis - - Low (higher pH)

Transglucosidation - higher -

Repolymerization - Very high -

Temperature 80-110 C 150-170 C High temp

Water solubility poor high Poor

COMMERCIAL PRODUCTS

SEBAmyl XCP ( alpha amylase) – Advanced Enzymes (Grain Processing and bakery)

SEBAmyl MTL (alpha amylase) - Advanced Enzymes (Malting and Brewing)

SEBStar MTL (alpha amylase) (malting)

APPLICATIONS OF DEXTRINS

Thickener in Sauces and Soups

Gel Former in Puddings

Suspension Stabilizer

Bodying agent in Baking

adhesive industry AND the paper industry,

the pharmaceutical industry(cyclo-dextrins in controlled drug release )

the food industry, and the textile industry.

Rocket Propelent Binder (Nitropulse Ltd.)

THANK YOU!