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Korea food additives¡ª¡ªGlucomannan

Author£ºadmin  Source£ºSite Finishing  Click£º6027  Published£º2009-06-17

 

Glucomannan
 
 
Definition
Glucomannan is a polysaccharide (that is purified with isopropyl alcohol and crushed) contained in root stems of dendrobium and Konjac (Amorphophallus konja). It is a mixture that consists of glucose and mannose.
[Compositional Specifications of Glucomannan]
Content
Glucomannan (converted to a dried form) should contain not less than 90% of glucomannan. 
Description
Glucomannan is white¡«pale yellow powder
Identification
(1) 6 g of  Glucomannan is added to a 500 ml beaker. It is wetted with 10 ml of isopropyl alcohol. While stirring, 200 ml of water is added. When it is set aside for 1 hour, it swells and becomes viscous solution.

(2) When 200 ml of 5% calcium hydroxide solution is added to viscous solution in (1), which is well mixed and then set aside, a gel is formed.
Purity
(1) Arsenic £º 0.25 g of Glucomannan is placed in a platinum, quartz, or porcelain crucible. 10 ml of magnesium nitrate in ethyl alcohol (1¡ú50) is added to the crucible and then alcohol is ignited. It is then reduced to ash by heating at 450∼550¡ã. If carbonaceous substance persists, it is wetted with minute amount of nitric acid, which is further heat treated at 450∼550¡ã. After cooling, 3 ml of hydrochloric acid is added to the residue, which is then dissolved by heating in a water bath. When test for arsenic is carried out with this test solution, it should not be more than 4ppm.

(2) Heavy Metals £º 1 g of Glucomannan is carbonized by heating mildly in a quartz or porcelain crucible. After cooling, add 2 ml of nitric acid and 5 drops of sulfuric acid, it is heated until white smoke disappears, which is then reduced to ash by further heating at 450∼550¡ã. After cooling, 2 ml of hydrochloric acid is added, which is then evaporated to dryness in a water bath. 3 drops of hydrochloric acid and 10 ml of hot water are added to the resulting residue, which is then heated for 2 minutes. After cooling, 1 drop of phenolphthalein indicator solution is added, then ammonia solution is added until the color of the solution becomes pale red. The resulting solution is transferred into a Nestler cylinder by rinsing with water. 50 ml of test solution is prepared by adding 2 ml of dilute acetic acid (1¡ú20) and water. When this solution tested for heavy metals, the content should not be more than 30ppm. Color standard solution is prepared by the following procedure. 2 ml of nitric acid, 5 drops of sulfuric acid, and 2 ml of hydrochloric acid are added and evaporated to dryness in a crucible that is made of the same material used for test solution preparation. 3 drops of hydrochloric acid are added to the residue, which is then transferred into another Nestler cylinder as described above. Finally, 2 ml of lead standard solution, 2 ml of diluted acetic acid (1¡ú20), and water are added to bring the total volume to 50 ml.

(3) Lead : 0.8 g of Glucomannan is slowly carbonized by heating, which is reduced ash by further heat treatment at a temperature below 500¡ã. Carefully 20 ml of dilute nitric acid is added to the ash, which is then gently boiled for 5 minutes. It is then filtered (if necessary), the residue is washed with water, which is then added to the filtrate. Water is added so that total volume of this solution becomes 50 ml. This test solution is tested for lead (Dithizone Method). The detected amount of lead should not be more than 10ppm.

(4) Isopropyl alcohol : 5 g of Glucomannan is precisely weighed into a 1,000 ml single neck round bottom flask with 24/40 ground joint, where 1 ml of anti foaming agent (Dow Corning G-10 or its equivalent) and 200 ml of water are added. It is then stirred for 1 hour. A 400 ml reflux condenser, distilling head, and a collector are attached. Approximately 95 ml of distillate is collected (care must be taken so that bubbles are not introduced into the collector). 4 ml of internal standard solution is added to the collected distillate, where water is added to bring the total volume to 100 ml. Test Solution and mixed standard solution are analyzed with gas chromatography and the amount of isopropyl alcohol is obtained by the following equation. The content should not be more than 500ppm. The reaction factor (f) is obtained by the ratio (AIPA£¯ATBA) between peak areas of isopropyl alcohol and tert-butyl alcohol in the mixed standard solution.
                                        aIPA x 4,000                                                                           
    Content of isopropyl alcohol (ppm) = ©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥
                                   f x aTBA x Weight of sample(g)
     aIPA : Peak area of isopropyl alcohol in Test Solution
     aTBA : Peak area of tert-butyl alcohol in Test Solution

[Operation Conditions]
- Column : A stainless steel tube 3.2 mm x 1.8 m
- Column Filler : Porapak QS of 80¡«100 mesh (or its equivalent)
- Detector : (Hydrogen) Flame Ionization Detector (FID)
- Temperature at injection hole : 200¡ã
- Column Temperature : 165¡ã
- Detector Temperature : 200¡ã
- Carrier gas and flow rate : Nitrogen, Flow rate is controlled so that isopropyl alcohol and tert-butyl alcohol is detected in 2 minutes and 3 minutes, respectively.
                       
[Solutions]
∘ Mixed Standard Solution : A mixture of 4 ml IPA standard solution and 4 ml TBA standard solution is diluted to 100 ml with water. 1 ml of this solution contains 40¦Ìg each of isopropyl alcohol and tert butyl alcohol.
∘ IPA Standard Solution : Approximately 500 mg of isopropyl alcohol (chromatography grade) is precisely weighed and diluted to 50 ml with water. 10 ml of this solution is further diluted to 100 ml with water.
∘ TBA Standard Solution : Approximately 500 mg of tert-butyl alcohol (chromatography grade) is precisely weighed and diluted to 50 ml with water. 10 ml of this solution is further diluted to 100 ml with water.

(5) Viscosity £º Viscosity of 1% aqueous solution of Glucomannan is measured by [2. Rotational Type Viscosity Measurement] in Viscosity Measurement. It should be £µ00 cps or higher.
Loss on Drying
When Glucomannan is dried for 3 hours at 105¡ã, the loss should not be more than 15%.
Ash
When Glucomannan is tested for ash content, it should not be more than 4%.
Assay
Same amount (0.5∼1.0 g) each of Glucomannan (defatted with ether if necessary) is placed separately in two 400 ml beakers. 50 ml each of phosphate buffer solution (pH 6.0) is added. After checking the pH of the solution, pH is adjusted to 6.0 ¡À 0.2, if necessary. 0.1 ml of Termamyl solution is added to each beaker, which is covered with aluminum foil and heated for 30 minutes in a boiling water bath (shaken every 5 minutes). Using a thermometer, the temperature inside the beaker is maintained at 85∼100¡ã for 15 minutes. After cooling 10 ml of 0.275 N sodium hydroxide solution is added to each beaker and pH is adjusted to 7.5 ¡À 0.2. 5 mg of protease (or 0.1 ml solution of 50 mg of protease in 1 ml water) is added to the resulting solution. It is covered with aluminum foil and isothermalized for 30 minutes at 60¡ã while shaking continuously. After cooling, pH is adjusted to 4.0∼4.6 with 10 ml of 0.325 M hydrochloric acid and 0.3 ml of amylo glucosidase is added, which is then covered with aluminum foil and isothermalized for 30 minutes at 60¡ã while mixing by shaking. 280 ml of 95% alcohol (heated to 60¡ã) is added to the beaker and well mixed by shaking. It is then set aside for 1 hour at normal temperature to settle down glucomannan. A glass filter containing cellite (previously weighed) is wetted with 78% alcohol so that cellite is evenly distributed. It is vacuum filtered to evenly distribute the cellite. Test Solution (treated with enzyme) is then vacuum filtered through the glass filter. The residue is washed 3 times with 20 ml each of 78% alcohol, twice with 20 ml each of 95% alcohol, and twice with 10 ml each of acetone. If a film is formed, it is broken with a reagent spoon to facilitate the filtration. Filtering time can be shortened if filtration is stopped occasionally. The filter is dried over night at 105 ¡À 5¡ã, cooled in a desiccator, and weighed. The weight of the residue is obtained by subtracting the weight of glass filter. From the residue of one glass filter, the amount of proteins is obtained (protein factor : 6.25). The residue from another glass filter is reduced to ash by heating for 5 hours at 525¡ã and ash content is obtained. Separately, a blank test is carried without sample. The content of glucomannan is obtained by the following equation.

    Blank Test Value B(mg)£½Weight of residue for blank test (mg) - PB - AB
     
    PB £º Amount of proteins for blank test (mg)
    AB £º Amount of ash for blank test (mg)
       
[average weight of residue for sample(mg)-P-A-B]
Content (%) =©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥©¥  ¡Á 100
                    Average weight of sample(mg)

      P £º Weight of proteins (mg)
      A £º Weight of ash (mg)
      B £º Blank test value (mg)

[Reagents and Solutions]
∘ Phosphate Buffer Solution (pH 6.0) £º 1.4 g of sodium phosphate, dibasic (anhydrous) and 9.68 g of sodium phosphate, monobasic (1 hydrate) are dissolved in 700 ml of water, which is diluted to 1,000 ml with water.
∘ 0.275 N sodium hydroxide solution £º 11 g of sodium hydroxide is dissolved in 700 ml of water, which is diluted to 1,000 ml with water.
∘ 0.325 M hydrochloric acid £º 325 ml of 0.1 M hydrochloric acid is diluted to 1,000 ml with water.
∘ Termamyl (heat resistant -amylase) solution £º No.120 L, Novo (refrigerated for   storage)
∘ Protease £º No.P£­3910, Sigma  (refrigerated for storage)
∘ Amylo glucosidase £º No. A£­ 9913, Sigma (refrigerated for storage)
∘ Cellite C£­211(Fischer) £º washed with acid solution

 
Konjac Gum as a Food Additive
    In its purified and unmodified form, naturally acetylated konjac glucomannan produces a highly viscous solution. Typically, a 1% aqueous solution may have viscosities from 12,000 cps to more than 20,000 cps when measured at ambient room temperature. Highly concentrated konjac solution will form a gel by itself at alkaline condition. The modern processed food industry now has taken advantage of its unique gelling, stabilizing, thickening and texturising properties either when used alone or in combinations with other hydrocolloids. Konjac is listed in the Food Chemical Codex (FCC) third supplement of the 3rd edition, and it is generally recognized as safe (GRAS) in the Federal Food, Drug and cosmetics Act. In Europe, konjac has been approved as food additive under E425 since October 1998 (Directive 98/72).
    Konjac glucomannan is very difficult to be isolated. In the form of dried and grounded powder, konjac tuber contains large amount of different raw starches besides the hydrocolloid. The high starch containing konjac flour is presently used in many direct food preparations especially in Asia. When most or nearly all the starches are removed, konjac gum is obtained. It is a valuable natural food additive. (See Table I).
     i. In slight alkaline environment, konjac aqueous solution forms a thermo-irreversible gel after cooling from hot solution.
    ii. Pure grade konjac gum interacts synergistically with kappa-carrageenan to form an elastic thermo-reversible gel. Its behavior is very similar to that of locust bean gum (LBG), except that at the same usage level konjac-carrageenan gel may be 2-4 times stronger.
    iii. Pure grade konjac gum also interacts with xanthan to form a gel which is cohesive and extremely elastic in nature. Maximum gel strength is achieved at a ratio of konjac and xanthan between 1:2.5-1:4.
    iv. Konjac gum interacts with most native or modified starches resulting remarkable increase in viscosity allowing for optimization of starch-rich formulations, whether the purpose is a reduction of calories and/or price or improvement of texture.
    v. Konjac is a powerful film former - both alone and in combinations with other gums such as xanthan or carrageenan.
The main quality requirements of konjac gum are (a) high viscosity of 1% aqueous solution, over 18,000 cps, (b) stable aqueous solution, viscosity drop less than 10% after 24 hours. The extra stable konjac gum will be an excellent locust bean gum replacer.
 
Table I

Application
Main Function
Flour Products
- Noodle and pasta
- Frozen dumpling wraps
Moisture Control; increase elasticity
Resist damage from freeze/thaw cycles
Dairy
- Yoghurt
- Pudding
- Ice-cream
Stabilization
Gelling
Resist freeze/thaw deterioration
Bakery
- Bread
Dough extender and conditioner;
increase bread volume
Water Gel Dessert
Gelling
Edible Films
Film Forming
Drinks
- still drinks
- juices
Thickening, mouthfeel
Thickening, mouthfeel
Meat and Fish
- Cannings
- Minced Meat
- Sausage
- Meat Substitute
Gelling
Meat particle adhesion
Meat adhesive and fat substitute
Oil and fat replacer

 
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