PECTIN

BIOLOGICAL SOURCE: It is a purified polysaccharide obtained from the dilute acid extract of the inner portion of the peel of Citrus limon (lemon) or Citrus aurantium (orange) belonging to the family Rutaceae and also from the pulp of Apple, papaya, guava, mango, carrot, sunflower head etc.

GEOGRAPHICAL SOURCE: Pectin is produced in India, USA, and Switzerland on a commercial basis.

PREPARATION: Pectin in the fruit is present in an insoluble form known as protopectin and is converted to soluble form by the presence of dilute acids.

          The preserved or fresh lemon peels are heated with 20 times its weight of water at 85- 90˚c for 30 minutes. The p^H   required for maximum extraction is 3.5-4 .The p^H can be adjusted by lactic, citric, or tartaric acids.

           The peels after boiling are pressed and solution is cleared by settling or centrifugation. Starch and proteins are removed by suitable enzymatic hydrolysis and the solution is heated to deactivate the enzymes and decolourised with active carbon or any other suitable agent. Pectin is precipitated out by using water soluble organic solvent (alcohol), washed again and dried in vacuum.

                 Pectin is incompatible with calcium, so precaution should be taken to keep it away from its metallic salts throughout the process of extraction, packed in the containers or polyethylene bag.

CHARACTERS: Pale yellow or cream coloured coarse or fine powder, odourless, mucilaginous taste, hygroscopic in nature, insoluble in alcohol, and other organic solvents, soluble in 20 parts of water to form viscous, faintly acidic colloidal solution. Pectin is more stable in acid medium than in alkaline. It is a reversible colloid.

 Ash value- NMT 4%, Methoxy group-NLT 7%, Galacturonic acid- NLT 78%,Acid insoluble ash- NMT 0.4%, Loss on drying- NMT 10%.

CHEMICAL CONSTITUENTS: Chemically, pectin is a neutral Methoxy ester of pectic acid. Total hydrolysis of pectin yields D-galacturonic acid, methyl alcohol, small amount of galactose and arabinose. Pectin should not contain less than 7% of Methoxy groups and 78% galacturonic acid.

IDENTIFICATION TESTS:

 1.10% aqueous solution forms stiff gel on cooling.

2. To 5 ml of 1% aq. solution, add 1 ml 2% solution of potassium hydroxide and set aside at room temperature for 15 minutes. A transparent gel is formed.

3. When the above gel is shaken with dilute hydrochloric acid, gelatinous precipitate forms which on boiling becomes white and flocculent.

USES: It is used as an adsorbent in the treatment of Diarrhoea, as a haemostatic in external and internal haemorrhage used as an emulsifying agent, a gelling agent in acid medium and as a plasma substitute.

              In food industry, it is used as a thickening agent for sauces, jams ketchups etc.

Pectin in combination with gelatin is used as an encapsulating agent in pharmaceutical formulations to promote sustained release.