Pectin is a complex carbohydrate component found in the middle lamella of plant cells. Pectins are polyuronides and consist of mixture of pectic substances like protopectin, pectin, pectinic acid and calcium pectate. Pectins with a high molecular weight and a high proportion of methyl ester groups have the best jelly ability.
The pectin content of fruits is variable and depends not only on the type of fruit but also on its maturity or ripeness. Under certain conditions, in presence of sugar and acid, it forms jelly like mass. If jellies or jams are made at home, it is best to add commercial pectin to ensure that there is sufficient pectin to form a gel.
The levels of pectin vary for the different plant tissues; apple pomace, sugar beet pulp., and sunflower heads are major sources of this fiber, ranging in pectin concentration from 15 to 25 g/100 g.
Purified pectin is made from apple cores and skin (apple pomade) and from the white inner skin (albedo) of citrus fruits. It is available in either liquid or granular form. The granular products have a longer shelf life than the liquids.
Pectin also has been manufactured from citrus peel for more than 50 years. All citrus contains pectin and the richest sources are limes, lemons, oranges and grapefruit in decreasing importance.
The soft, white spongy layer called albedo, just under the colored portion of the peel is the principle source of pectin.
Low-methyl pectin can be obtained by demethylating pectin with enzymes, acid or alkali until it is 20-40 % esterified.
Since these pectins gel with divalent ions and need no sugar, they can be used commercially for the production of low-calorie jams, jellies, or desserts.
Sources of pectin
