Etiket Arşivleri: Pectins

Chapter:1 Pectin

Chapter 1 Pectin

1-1  Structure and Terminology

1-2  Production

1-3  Characterization of pectin gel

1-4  Factors affecting gelation

1-5  Chemical properties

1-6  Pectic enzymes

1-7  Structure and mechanisms of gel formation

1-8  Application

1-1  Structure and Terminology

Pectin is heterogeneous complex polysaccharide

Its composition varies with the source and the conditions applied during isolation

All pectin molecules contain linear segments of (1à4)-linked a-D-galactopyranosyluronic acid with some of the carboxyl groups esterified with methanol.

Some of the hydroxyl groups of the galacturonosyl unit (O-2 and O-3) are esterified with acetic acid.

Pectin molecule with methyl esterified or nonesterified carboxyl groups

Amidated pectin has commercial importance

Terminology

Protopectin

Pectinic acids

Pectic acids

Pectins

Degree of esterification (DE) > 50

High-methoxyl pectins (HM-pectins)

High concentration of soluble solids, low pH

DE < 50

LM-pectins

Divalent cations

1-2  Production

1-2-1 Raw materials

Citrus peel (20-30%), apple pomace(10-15%)

Sugarbeet waste, sunflower heads, mango waste

Sugarbeet pectin is inferior to citrus or apple pectin

Presence of  acetate esterification

A relatively low molecular mass

Presence of large amount of neutral sugar side chain


Pectins

Consists 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. number  9000-69-5 DESCRIPTION White, yellowish, light greyish or light brownish powder

Source