Pectin
Pectin.
Pectin [9000-69-5].
»Pectin is a purified carbohydrate product obtained from the dilute acid extract of the inner portion of the rind of citrus fruits or from apple pomace.It consists chiefly of partially methoxylated polygalacturonic acids.
Pectin yields not less than 6.7percent of methoxy groups (–OCH3)and not less than 74.0percent of galacturonic acid (C6H10O7),calculated on the dried basis.
NOTE—Commercial pectin for the production of jellied food products is standardized to the convenient “150jelly grade”by addition of dextrose or other sugars,and sometimes contains sodium citrate or other buffer salts.This monograph refers to the pure pectin to which no such additions have been made.
Packaging and storage—
Preserve in tight containers.
Labeling—
Label it to indicate whether it is of apple or of citrus origin.
Identification—
A:
Heat 1g with 9mLof water on a steam bath until a solution is formed,replacing water lost by evaporation:it forms a stiff gel on cooling.
B:
To a solution (1in 100)add an equal volume of alcohol:a translucent,gelatinous precipitate is formed (distinction from most gums).
C:
To 10mLof a solution (1in 100)add 1mLof thorium nitrate TS,stir,and allow to stand for 2minutes:a stable precipitate or gel forms (distinction from gums).
D:
To 5mLof a solution (1in 100)add 1mLof 2Nsodium hydroxide,and allow to stand at room temperature for 15minutes:a gel or semigel forms (distinction from tragacanth).
E:
Acidify the gel from the preceding test with 3Nhydrochloric acid,and shake:a voluminous,colorless,gelatinous precipitate forms,which upon boiling becomes white and flocculent (pectic acid).
Microbial limits á61ñ—
It meets the requirements of the test for absence of Salmonellaspecies.
Loss on drying á731ñ—
Dry it at 105
for 3hours:it loses not more than 10.0%of its weight.
for 3hours:it loses not more than 10.0%of its weight.
Arsenic,Method IIá211ñ:
3ppm.
Lead—
Add 2.0g of Pectin to 20mLof nitric acid in a 250-mLconical flask,mix,and heat the contents carefully until the Pectin is dissolved.Continue the heating until the volume is reduced to about 7mL.Cool rapidly to room temperature,transfer to a 100-mLvolumetric flask,and dilute with water to volume.A50.0-mLportion of this solution contains not more than 5µg of lead (corresponding to not more than 0.0005%of Pb)when tested according to the limit test for Lead á251ñ,15mLof ammonium citrate solution,3mLof potassium cyanide solution,and 500µLof hydroxylamine hydrochloride solution being used.After the first dithizone extractions,wash the combined chloroform layers with 5mLof water,discarding the water layer and continuing in the usual manner by extracting with 20mLof dilute nitric acid (1in 100).
Sugars and organic acids—
Place 1g in a 500-mLflask,moisten it with 3to 5mLof alcohol,pour in rapidly 100mLof water,shake,and allow to stand until solution is complete.To this solution add 100mLof alcohol containing 0.3mLof hydrochloric acid,mix,and filter rapidly.Measure 25mLof the filtrate into a tared dish,evaporate the liquid on a steam bath and dry the residue in a vacuum oven at 50for 2hours:the weight of the residue does not exceed 20mg.
for 2hours:the weight of the residue does not exceed 20mg.
Organic volatile impurities,Method IVá467ñ:
meets the requirements.
Assay for methoxy groups—
Transfer 5.00g of Pectin to a suitable beaker,and stir for 10minutes with a mixture of 5mLof hydrochloric acid and 100mLof 60percent alcohol.Transfer to a sintered-glass filter (30-to 60-mLcrucible or Büchner type,coarse),and wash with six 15-mLportions of the hydrochloric acid—60percent alcohol mixture,followed by 60percent alcohol until the filtrate is free from chlorides.Finally wash with 20mLof alcohol,dry for 1hour at 105,cool,and weigh.Transfer exactly one-tenth of the total net weight of the dried sample (representing 500mg of the original unwashed sample)to a 250-mLconical flask,and moisten with 2mLof alcohol.Add 100mLof carbon dioxide-free water,insert the stopper,and swirl occasionally until the Pectin is completely dissolved.Add 5drops of phenolphthalein TS,titrate with 0.5Nsodium hydroxide VS,and record the results as the initial titer.Add 20.0mLof 0.5Nsodium hydroxide VS,insert the stopper,shake vigorously,and allow to stand for 15minutes.Add 20.0mLof 0.5Nhydrochloric acid VS,and shake until the pink color disappears.Add phenolphthalein TS,and titrate with 0.5Nsodium hydroxide VSto a faint pink color that persists after vigorous shaking:record this value as the saponification titer.Each mLof 0.5Nsodium hydroxide used in the saponification titeris equivalent to 15.52mg of –OCH3.
,cool,and weigh.Transfer exactly one-tenth of the total net weight of the dried sample (representing 500mg of the original unwashed sample)to a 250-mLconical flask,and moisten with 2mLof alcohol.Add 100mLof carbon dioxide-free water,insert the stopper,and swirl occasionally until the Pectin is completely dissolved.Add 5drops of phenolphthalein TS,titrate with 0.5Nsodium hydroxide VS,and record the results as the initial titer.Add 20.0mLof 0.5Nsodium hydroxide VS,insert the stopper,shake vigorously,and allow to stand for 15minutes.Add 20.0mLof 0.5Nhydrochloric acid VS,and shake until the pink color disappears.Add phenolphthalein TS,and titrate with 0.5Nsodium hydroxide VSto a faint pink color that persists after vigorous shaking:record this value as the saponification titer.Each mLof 0.5Nsodium hydroxide used in the saponification titeris equivalent to 15.52mg of –OCH3.
Assay for galacturonic acid—
Each mLof 0.5Nsodium hydroxide used in the total titration (the initial titeradded to the saponification titer)in the Assay for methoxy groupsis equivalent to 97.07mg of C6H10O7.
Auxiliary Information—
Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 1477
Phone Number:1-301-816-8262