Pectin

pH

A measure of the relative amount of free hydrogen and hydroxyl ions in the water _ water that has more free hydrogen ions is acidic, whereas water that has more free hydroxyl ions is basic

Sugar-Acid-Gel

High DM Gel

Minimum Conditions to Gel for High DM Pectin

1) 55% sugars or 55 Brix 2) pH 3.5 3) 0.3% pectin

Conserved

2 or more fruits together _ commonly raisins or nuts

Pectin

A soluble gelatinous polysaccharide that is present in ripe fruits and is extracted for use as a setting agent in jams and jellies _ naturally occurred primary cell walls of plants

COOH

Acid

Hydrophobic Bonds in High DM Jelly

Act on methyl groups between two pectin chains _ sugars pull the two chain together _ sugars also pull out water --> dehydration reaction

Marmalade

Citrus juice filtered (lemon, lime, orange, etc.) _ like jelly with peeled

DM

Degree of methylation _ percentage of carbonyl group esterifed with methanol _ Or the percentage of methylated groups

Jelly

Filtered juice

Effect of DM on Gelation

Higher DM = faster setting time Lower DM = longer setting time and lower setting temperature

Jam

Include chopped up and fruit pieces

Binding of Ca to Low DM Pectin

Involves intermolecular chelate binding of the cation, leading to the formation of macromolecular aggregates

Low DM

Less than 50% of the carboxyl groups are methylated <50 DM

COOCH3

Methyl groups

High DM

More than 50% of the carboxyl groups are methylated _ usually between 55 to 80

Hydrophilic Bonds in High DM Jelly

Negative repulsion from the acids (COOH) between two pectin chains are cancelled out by the hydrogen in water _ needs pH 3.5 or lower <= higher pH not enough hydrogen

Will it spoil?

No, but depends on pH and water activity. _ low DM pectin tends to have lower water activity, low pH and had some heat treatment _ yeast or mold may still grow on surface

Soluble Solids Content Effect on Gelation

The higher the soluble solids content, the lower the numbers of hydrogen bonds. These bonds are stronger and thus the strongest gels are formed

Preserved

Whole fruits or large fruit pieces

Conditions to Gel for Low DM Pectin

_ 0.3 - 1% pectin _ calcium 0.05% _ pH between 2-7 (over 7 the base will hydrolyze pectin) _ sugar 0-85%

Examples of Fruits with Low Amount of Pecting

_ cherries _ grapes _ strawberries

Low DM Advantages

_ no sugar or low sugar gel _ some thermal and shear reversibility

Optimum Conditions to Gel for High DM Pectin

_ pH between 3.2 and 3.5 _ 68% sugar or 68 Brix

Examples of Fruits with High Amount of Pectin

_ pears _ apples _ guavas _ quince _ plums _ oranges and other citrus fruit