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ISOMALT

Prepared at the 39th JECFA (1992), published in FNP 52 Add 1 (1992) superseding specifications published in the Compendium of Food Additive Specifications (1992)


SYNONYMS

Isomaltitol, hydrogenated isomaltulose; INS No. 953

DEFINITION

Chemical names

6-O-alpha-D-Glucopyranosyl-D-sorbitol (1,6-GPS) and

1-O-alpha-D-Glucopyranosyl-D-mannitol dihydrate (1,1-GPM)

C.A.S. number

64519-82-0

Chemical formula

6-O-alpha-D-Glucopyranosyl-D-sorbitol: C12H24O11

1-O-alpha-D-Glucopyranosyl-D-mannitol dihydrate: C12H24O11 · 2H2O

Structural formula

6-O-alpha-D-Glucopyranosyl-D-sorbitol

1-O-alpha-D-Glucopyranosyl-D-mannitol (without molecules of crystal water)

Formula weight

6-O-alpha-D-Glucopyranosyl-D-sorbitol: 344.32

1-O-alpha-D-Glucopyranosyl-D-mannitol dihydrate: 380.32

Assay

Not less than 98% of hydrogenated mono- and disaccharides and not less than 86% of the mixture of 6-O-alpha-D-glucopyranosyl-D-sorbitol and 1-O-alpha-D-glucopyranosyl-D-mannitol on the anhydrous basis

DESCRIPTION

Odourless, white, crystalline slightly hygroscopic substance

FUNCTIONAL USES

Sweetener

CHARACTERISTICS

IDENTIFICATION

Solubility

Soluble in water. Insoluble in ethanol

Specific rotation

[á]20D : between 90.0 ± 0.2 to 92.0 ± 0.2

Melting range

145 o - 150o

PURITY

Water

Not more than 7.0% (Karl Fischer Method)

Sulfated ash

Not more than 0.05%

Test 5 g of the sample (Method I)

D-Mannitol

Not more than 3%

See Method of Assay

D-Sorbitol

Not more than 6%

See Method of Assay

Reducing sugars

Not more than 0.3%

Proceed as directed under Reducing Substances (as glucose), Method II. The weight of cuprous oxide shall not exceed 50 mg.

Isomaltulose (as glucose)

Not more than 0.8%

See Method of Assy

Nickel

Not more than 2 mg/kg

See description under TESTS

Arsenic

Not more than 3 mg/kg (Method II)

Lead

Not more than 1 mg/kg

Prepare a sample solution as directed in the Limit Test for organic compounds and determine the lead content by atomic absorption spectrometry

Heavy metals

Not more than 10 mg/kg

Test 2 g of the sample as directed in the Limit Test (Method II)

TESTS

PURITY TESTS

Nickel

Test solution

Dissolve 20.0 g of the substance to be examined in a mixture of equal volumes of dilute acetic acid TS* and water and dilute to 100 ml with the same mixture of solvents. Add 2.0 ml of a 1% w/v solution of ammonium pyrrolidinedithiocarbamate and 10 ml of methyl isobutyl ketone. Mix and allow the layers to separate and use the methyl isobutyl ketone layer.

Reference solution

Prepare three reference solutions in the same manner as the test solution but adding 0.5 ml, 1.0 ml, and 1.5 ml, respectively, of a standard nickel solution containing 10 mg/kg Ni, in addition to the 20.0 g of the substance to be tested.

Procedure

Set the instrument to zero using methyl isobutyl ketone as described for the preparation of the test solution but omitting the substance to be examined. Measure the absorbance at 232.0 nm using a nickel hollow-cathode lamp as source of radiation and an air-acetylene flame.

METHOD OF ASSAY

Internal standard solution:
Dissolve suitable quantities of phenyl-ß-D-glucopyranoside and maltitol in water to obtain a solution of about 1 mg phenyl-ß-D-glucopyranoside and 50 mg maltitol per g water.

Standard solutions:
Dissolve accurately weighed quantities of 1-O-alpha-D-glucopyranosyl-D-mannitol (1,1-GPM) and 6-O-alpha-D-glucopyranosyl-D-sorbitol (1,6-GPS), calculated as dry substance, in water to obtain two separate solutions having a concentration of about 50 mg per g each. Also prepare an aqueous standard solution containing approx. 1 mg mannitol and 1 mg sorbitol per g.

Sample solution:
Dissolve an accurately weighed quantity of the sample (approx. 1 g) in water to obtain a concentration of about 10 g per 100 g.

Procedure

Pipet 100.0 mg of standard solution or sample solution into a glass tube fitted with a screw cap and add 100.0 mg of internal standard solution. Remove the water by lyophilization and dissolve the residue in 1.0 ml of pyridine. Add 4 mg O-benzyl-hydroxylamine hydrochloride, and cap the tube and set it aside for 12 h at room temperature. Then, add 1 ml of N-methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA) and heat to 80º for 12 h shaking occasionally and allow to cool. Inject 1 µl portions of these solutions directly into a gas chromatograph under the following operating conditions with helium as carrier gas (initial flow rate: approx. 1 ml/min at 80º and 1 atm; split flow: 25 ml/min):

Column: Fused silica HT-8 (25 m x 0.22 mm x 0.25 µm), or equivalent

Injector: Programmed temperature vaporizer: 30º; 270º/min to 300º (49 min)

Detector: Flame ionization detector; 360º

Temperature program: 80º (3 min); 10º/min 80º (3 min); 10º/min to 210º; 5º/min to 350º (6 min)

Approximate retention times

Hydrogenated monosaccharides:

Mannitol 19.5 min

Sorbitol 19.6 min

Internal standards:

Phenyl-J-D-glucopyranoside 26.8 min

Maltitol 33.5 min

Hydrogenated disaccharides (32 - 36 min)

1,1-GPS 33.9 min

1,1-GPM 34.5 min

1,6-GPS 34.6 min

Calculate the percentages of the individual components, wI, in the sample according to the following formula:

where

aI = peak area of component I (µV·s)

aS = peak area of internal standard (µV·s)

mS = mass of internal standard used for derivatization (mg d.s.)

mISOMALT = mass of sample used for derivatization (mg d.s.)

FI = relative response factor fI/fS

fI = response factor of component I: fI =(aI/mI)x(100/% purity)

fS = response factor of internal standard: fS =(aS/mS)x(100/% purity)

mI, mS = mass of component I or internal standard used

for derivatization of standard sample (mg d.s.)

Note: Use maltitol as internal standard for the calculation of hydrogenated disaccharides (e.g. 1,1-GPM, 1,6-GPS) and phenyl-J-D-glucoside for the calculation of hydrogenated monosaccharides (mannitol, sorbitol). For the total of other saccharides (hydrogenated or not) substract the sum of 1,1-GPM, 1,6-GPS, sorbitol and mannitol from 100%.


Source: Joint FAO/WHO Expert Committee on Food Additives (JECFA)


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