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Additive 245 m1

Konjac flour is obtained from the tubers of various Amorphophallus species. It is composed mainly of glucomannan, a high molecular weight polysaccharide made of mannose and glucose sugars. Konjac flour forms highly viscous solutions in hot or cold water and heat-stable gels when alkaline solutions are added. It is used as a gelling agent, thickener, emulsifier, and stabilizer. Specifications require the konjac flour to contain at least 75% carbohydrates and limit ash, protein, moisture, and lead content.

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35 views2 pages

Additive 245 m1

Konjac flour is obtained from the tubers of various Amorphophallus species. It is composed mainly of glucomannan, a high molecular weight polysaccharide made of mannose and glucose sugars. Konjac flour forms highly viscous solutions in hot or cold water and heat-stable gels when alkaline solutions are added. It is used as a gelling agent, thickener, emulsifier, and stabilizer. Specifications require the konjac flour to contain at least 75% carbohydrates and limit ash, protein, moisture, and lead content.

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rnd lab
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KONJAC FLOUR

Prepared at the 46th JECFA (1996), published in FNP 52 Add 4 (1996)


superseding specifications prepared at the 39th JECFA (1993), published
in FNP 52 Add 3 (1993). Metals and arsenic specifications revised at the
57th JECFA (2001). An ADI 'not specified' was established at the 46th
JECFA (1996)

SYNONYMS Konjac mannan, Konjac, konnyaku; INS No. 425

DEFINITION The hydrocolloidal polysaccharide obtained from the tubers of various


species of Amorphophallus; principal component is a high molecular
weight, slightly branched, non-ionic glucomannan consisting of mannose
and glucose, connected by ß-1,4 linkages, at a respective molar ratio of
approximately 1.6-4:1; acetyl groups along the glucomannan back-bone
contribute to solubility properties and are located, on average, every 9 to
19 sugar units

C.A.S. number 37220-17-0

Formula weight The main component, glucomannan, has an average molecular weight of
200,000 to 2,000,000

Assay Not less than 75% carbohydrate

DESCRIPTION White or cream to light tan powder

FUNCTIONAL USES Gelling agent, thickener, emulsifier, stabilizer

CHARACTERISTICS

IDENTIFICATION

Solubility (Vol. 4) Dispersible in hot or cold water forming a highly viscous solution with a pH
between 4.0 and 7.0

Solubility is increased by heat and mechanical agitation. Addition of mild


alkali to the solution results in the formation of a heat-stable gel that resists
melting, even under extended heating conditions

Gel formation Add 5 ml of a 4% sodium borate solution to a 1% solution of the sample in


a test tube, and shake vigorously. A gel forms.

Formation of heat-stable Prepare a 2% solution of the sample by heating it in a boiling water bath for
gel 30 min, with continuous agitation and then cooling the solution to room
temperature. For each g of the sample used to prepare the 2% solution,
add 1 ml of 10% potassium carbonate solution to the fully hydrated sample
at ambient temperature. Heat the mixture in a water bath to 85º, and
maintain for 2 h without agitation. Under these conditions a thermally stable
gel is formed. Related hydrocolloids such as guar gum and locust bean
gum do not form thermally stable gels and are negative by this test.
PURITY

Loss on drying (Vol. 4) Not more than 15% (105º, 5 h)

Total ash (Vol. 4) Not more than 5% (800º, 3-4 h)

Protein Not more than 8%


Proceed as directed under Nitrogen Determination (Kjeldahl method). The
percentage of nitrogen in the sample multiplied by 5.7 gives the percent of
protein in the sample

Lead (Vol. 4) Not more than 2 mfg/kg


Determine using an atomic absorption technique appropriate to the
specified level. The selection of sample size and method of sample
preparation may be based on the principles of the method described in
Volume 4, “Instrumental Methods.”

METHOD OF The remainder, after subtracting from 100% the sum of the percentages of
ASSAY total ash, loss on drying and protein, represents the percentage of
carbohydrate (glucomannans) in the sample.

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