4 The word pectin comes from the Latin pectos that means thickener or something that make things
hardsolid. Pectin was founded by Vauquelin in fruit juice about 200 years ago. In 1790, pectin was not yet to be named. Pectin name was first used in 1824, when Braconnot had continued a research that was
begun by Vauquelin. Braconnot called such gelling substances as pectic acid Herbstreith and Fox 2005. Pectin that used in food is polymer of galacturonic acid unit at least 65. That acid group can be
found in the form of free acid, methyl ester, sodium, potassium, calcium or ammonium compound and the amide groups of pectin IPPA 2002. Composition of protopectin, pectin and pectic acid inside the fruit
varies greatly depend on the maturity degree of the fruit. Generally, soluble protopectin is more abundant inside immature fruits Winarno 1997. Pectin generally presents in the primary cell wall of plants,
particularly on the sidelines between cellulose and hemicellulose. Pectin serves as an adhesive between the cell wall with each other.
Pectin content in plants varies widely, both by types of plants or by parts of its tissues. For example, the skin and albedo of citrus fruits contain more pectin than the tissues from its parenchime Winarno
1997. Table 2 shows the yield of pectin produced from several kinds of fruits. Table 2. Yield of pectin from several kind of fruit source Herbstreith and Fox 2005
Source Pectin content
Apple 10-15
Beet sugar 10-20
Sunflower 15-25
Sugar peel 20-35
2. Structure and chemical composition of pectin
In 1924, Smolenski was the first to assume that pectin is galacturonic acid polymer. In 1930, Meyer and Mark found the chains formation of pectin molecules, and in 1937, Schneider and Bock formed the
formula Herbstreith and Fox 2005. Pectin molecules are composed by galacturonic acid with β-1-4- glycoside binding to form polygalacturonic acid. Carboxyl groups partially esterified with methyl groups
and partially acylated with secondary alcohol groups Herbstreith and Fox 2005. Figure 3 below shows chemical structure of α-galacturonic acid.
Figure 3. Chemical structure of α-galacturonic acid Zamora 2012 According to Hoejgaard 2004, pectin is a polygalacturonic acid that contains methyl ester. Pectin is
commercially extracted from the skin of the orange fruit and apples in acidic conditions. Each ring is a molecule of galacturonic acid, and there are 300-1000 such rings in a typical pectin molecule, which are
connected by a linear chain.
Figure 4. Chemical structure of polygalacturonic acid Zamora 2012
5 Depends on their methoxyl content, pectin is commonly categorized as high methoxyl pectin HMP
or low methoxyl pectin LMP, with methoxyl content is 7 and 7, respectively. HMP can form a gel under acidic conditions in the presence of high sugar concentration Evangliou et al. 2000. On the other
hand, LMP forms gel by interaction with divalent cations, particularly Ca
2+
, according to the “egg box” model Durand et al. 1990. Figure 5 and 6 below show molecular structure of high methoxyl and low
methoxyl pectin.
Figure 5 Chemical structure of high methoxyl pectin HMP Taranathan 2003
Figure 6. Chemical structure of low methoxyl pectin LMP Taranathan 2003 Pectin consists of galacturonic acid monomers that form a long-chain molecule. The main chain is
interrupted by a rhamnose group with branched chain assembling neutral sugars arabinose, galactose. Carboxyl groups acid groups of galacturonic acid can be esterified or amidated IPPA 2002. In addition
to D-galacturonic acid as the main component, pectin also has D-galactose, L-arabinose, and L-rhamnose in various amounts. The chemical composition of pectin varies greatly depends on the source and the
conditions that is used in insulation Willats et al. 2006.
3. Pectin characteristic
