Pectin – JECFA specification

 Prepared at the 71st JECFA (2009) and published in FAO JECFA Monographs 7 (2009), superseding specifications prepared at the 68th JECFA (2007) and published in FAO JECFA Monographs 4 (2007). A group ADI “not specified” was established for pectins and amidated pectins, singly or in combination at the 25th JECFA in 1981.
DEFINITIONConsists mainly of the partial methyl esters of polygalacturonic acid and their sodium, potassium, calcium and ammonium salts; obtained by extraction in an aqueous medium of appropriate edible plant material, usually citrus fruits or apples; no organic precipitants shall be used other than methanol, ethanol and isopropanol; in some types a portion of the methyl esters may have been converted to primary amides by treatment with ammonia under alkaline
conditions. Sulfur dioxide may be added as a preservative.The commercial product is normally diluted with sugars for standardization purposes. In addition to sugars, pectins may be mixed with suitable food-grade buffer salts required for pH control and desirable setting characteristics. The article of commerce may be further specified as to pH value, gel strength, viscosity, degree of esterification, and setting characteristics.
C.A.S. number9000-69-5
DESCRIPTIONWhite, yellowish, light greyish or light brownish powder
FUNCTIONAL USESGelling agent, thickener, stabilizer, emulsifier
Test for pectinsPasses testSee description under TESTS
Test for amide groupPasses test (amidated pectins only)Add 2 ml of concentrated hydrochloric acid and 50 ml of 60% ethanol to 0.5 g of the sample, and stir well for 20 min. Transfer to a fritted glass filter tube wash with six 10 ml portions of the HCl-60% ethanol mixture. Dissolve in 100 ml distilled water; it may be necessary to add a few drops 0.1 mol/L sodium hydroxide to achieve solution. Transfer 4 ml of this solution into a test tube (recommended dimensions 15.5 mm inner diameter and 146 mm length). Add 1 ml 5 mol/L sodium hydroxide and mix. The mixture will form a gel. Fill a small glass tube (recommended dimensions 7.8 mm inner diameter and 79 mm length) with 2.5 ml boric acid TS and let glide into the test tube. Close with parafilm and incubate overnight at 30°. In case of presence of amide groups the indicator changes its colour from red to green, due to release of ammonia.
Loss on drying (Vol.4)Not more than 12% (105o, 2 h)
Sulfur dioxideNot more than 50mg/kgSee description under TESTS
Residual solvents (Vol.4)Not more than 1% methanol, ethanol and 2-propanol, singly or in combination
Acid-insoluble ash (Vol.4)Not more than 1%
Total insolublesNot more than 3%See description under TESTS
Nitrogen content (Vol.4)Not more than 2.5% after washing with acid and ethanol
Galacturonic acidNot less than 65% calculated on the ash-free and dried basisSee description under TESTS 
Degree of amidationNot more than 25% of total carboxyl groups of pectinSee description under TESTS
Lead (Vol.4)Not more than 5 mg/kgDetermine using an AAS/ICP-AES 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 (under “General Methods, Metallic Impurities.”)
Test for PectinsMoisten 0.05 g of the sample with 2-propanol. Add 50 ml of water on a magnetic stirrer. Adjust pH to 12 using 0.5 mol/L sodium hydroxide and let the solution remain without stirring for 15 min. Reduce pH to 7.0 with 0.5 mol/L hydrochloric acid. Adjust to 100.0 ml with water. Make up samples in 1 cm quartz cuvettes as follows:
 *) Dissolve 6.055 g of tris(hydroxymethyl)aminomethane (e.g. TRIZMA Base, Sigma) and 0.147 g of calcium chloride dihydrate in water to 1 L. Adjust pH to 7.0 with 1 mol/L hydrochloric acid**) Dilute pure pectate lyase 1:100 with buffer pH 7.0. Shake the solutions well, and measure the absorbance at 235 nm at 0 and 10 min.CalculationsA0 = absorbance at 0 min = Sample – (enzyme blank + sample blank)A10 = absorbance at 10 min = Sample – (enzyme blank + sample blank)The amount of unsaturated product produced is proportional to the change in absorbance (A10 – A0). This value should be greater than 0.023. This distinguishes pectins from other gums, which show essentially no change.
Sulfur dioxideSuspend 100 g of the sample in 500 ml of methanol in a 1000-ml round-bottom flask, which is provided with a gas inlet tube reaching almost the bottom and connected to the neck with a reflux condenser. Prepare a glass joint connection from the condenser to an absorption flask or U-tube containing 10 ml of 3% hydrogen peroxide solution neutralized to methyl red TS. Connect the gas inlet tube with an oxygen-free source of carbon dioxide or nitrogen, and maintain a gas stream so as to cause steady bubbling. As soon as the apparatus is flushed free of air, pour 30 ml of hydrochloric acid solution (10 ml conc. HCl + 20 ml H2O) into the reflux condenser, and immediately connect the absorption flask or U-tube. Heat slowly until methanol starts refluxing, and reflux gently for 2 h. Disconnect the apparatus and titrate the hydrogen peroxide solution against methyl red TS with 0.01 mol/l sodium hydroxide. Each ml of 0.01 mol/l sodium hydroxide corresponds to 0.32 mg of SO2.
Total insolublesDry a 70 mm glass fiber filter paper (GF/B (Whatman code 1821 070) in an oven with fan set at 105° for about 1 h. Transfer the filter paper to a desiccator containing silica gel and allow to cool. Weigh the paper (M1). Weigh about 1 g (= S) of the sample into a 250-ml beaker. Add 5 ml of 2-propanol to disperse the sample. While stirring magnetically, add 100 ml of 0.03 mol/l sodium hydroxide containing 0.1% (w/w) ethylene diamine tetra-acetic acid (Na salt), which has been filtered through GF/B paper. Stir for about 30 min at room temperature, then heat to boiling (remove heat if excessive foaming occurs). Filter the hot solution through the glass fiber paper under vacuum using, e.g. a vacuum filtration kit with 3 piece Hartley funnel (70 cm), with heat resistant plate. Rinse the beaker five times and filter the rinsings with 100 ml of warm (about 50°) water that has been filtered through GF/B paper. Dry the filter paper with the residue at 105° for 1 h. Transfer to desiccator containing silica gel and leave to cool. Weigh the paper (M2). Calculate the percentage of total insolubles fromTotal insolubles (%) = [(M2 – M1)/S] x 100
Galacturonic acid and Degree of amidationWeigh 5 g of the sample to the nearest 0.1 mg, and transfer to a suitable beaker. Stir for 10 min with a mixture of 5 ml of hydrochloric acid TS, and 100 ml of 60% ethanol. Transfer to a fritted-glass filter tube (30 to 60 ml capacity) and wash with six 15-ml portions of the HCl-60% ethanol mixture, followed by 60% ethanol until the filtrate is free of chlorides. Finally wash with 20 ml of ethanol, dry for 2.5 h in an oven at 105°, cool and weigh. Transfer exactly one-tenth of the total net weight of the dried sample (representing 0.5 g of the original unwashed sample) to a 250-ml conical flask and moisten the sample with 2 ml of ethanol TS. Add 100 ml of recently boiled and cooled distilled water, stopper and swirl occasionally until a complete solution is formed. Add 5 drops of phenolphthalein TS, titrate with 0.1 mol/l sodium hydroxide and record the results as the initial titre (V1).NOTE 1: If the pectin is known to be of the nonamidated type, only V1 and V2 need to be determined and (B – S) may be regarded as zero.
NOTE 2: For pectins from apple or citrus (A – A0) is usually insignificant in calculating galacturonic acid and degree of amidation.
NOTE 3: If desired, calculate degree of esterification (as % of total carboxyl groups) by the formula:
100 x [(V2 – (A – A0)) / (V1 + V2 + (B -S) – A-A0)]Note 4: If desired, calculate degree of acetate ester (as % of total carboxylic groups from galacturonic acid) by the formula:100 x [(A – A0) / (V1 + V2 + (B – S) – (A – A0))] 
Residual solvents (Vol.4)Apply Method I in Volume 4, General Methods, Organic Components.Standard stock solution: To 500 ml of water in a 1000-ml volumetric flask, add about 5 g each of methanol, ethanol and 2-propanol, accurately weighed. Make up to the mark with water. Internal standard solution: To 500 ml of water in a 1000-ml volumetric flask, add about 5 g of 2-butanol (Wstandard), accurately weighed. Make up to the mark with water.Blank Solution: Omit the blank determinationSamples: Store the sample in a cool, dry place. Mix the sample thoroughly before analysis.Weigh accurately about 1 g of sample (Wsample) in a 100 ml beaker and mix with about 5 g of sucrose. Into a 100-ml Erlenmeyer flask with magnetic stirrer bar, add 95 ml water and 1.0 ml internal standard solution. While stirring fast, slowly add the pectin-sucrose mixture. Stopper the flask and stir for 2 h. The pectin must be completely dissolved. Accurately weigh about 1 g of this solution (Msample) into a headspace vial for GC analysis.Calibration solution: Pipette 2.0 ml of standard stock solution and 2.0 ml of internal standard solution into a 200-ml volumetric flask and make up to the mark with water. Accurately weigh about 1 g of this solution (Mstandard) is filled into a head space vial and used for GC analysis.Procedure
Continue the analysis as described in Vol.4 ‘Residual solvents’, using the given conditions except for the sample heating temperature, which should be 70°, and syringe temperature, which should be 80°.Calculation
Calculate the concentration of each residual solvent using the following equation:% of solvent = (Rsample x Wstandard x Mstandard) / (Rstandard x Wsample x Msample x 1000)] x 100where
Rsample is the relative peak area of the sample;
Rstandard is the relative peak area of the standard;
Wsample is the weight of sample (g);
Wstandard is the weight of solvent used for the standard stock solution;
Msample is the weight of sample solution used for the GC analysis; and
Mstandard is the weight of Calibration solution used for the GC analysis.