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