Food Science Chapter 9 Pectin

Pectin

complex carbohydrate found in plant cells and made of chemical derivatives of sugar called sugar acids

Pectic Acid

overripe plant material

Pectinic acids and Ca

pectinic acids form salts with calcium ions, this is important to form gels utilizing low methoxyl pectins with calcium ions. the salts formed with ions combine with organic acids in pectins and pectinic acids=pectinates

Pectinates

play and important structural role in forming gels

types of pectin

protopectin (unripe)--> pectinic acid (ripe)--> pectic acid (over ripe)--> eventually soluble sugars (mush)

Strucutres of pectin

see chapter 9 ppt

Pectic Substances Definition

term for member of the family of polygalacturonic acid compounds (incluse all types of pectin and pectin)

typical level of pectin used as food additive

.5-1% this is because it is the same amount of pectin as in fresh fruit

Basic Jam recipie

1% pectin 65% sugar 35% fruit juice add acid in pH isn't low enough (lemon juice)

Structure of Fruits

1. cellulose 2. hemicellulose 3. pectin (holds cells together)

How hot can pectin remain stable till

212 F or 100 C

Conversion of protopectin

as demethylation and hydrolsysi gradual occur and protopectin is converted to pectin the fruits gradually soften

Pectin without sugar

bonds with other pectin molecules in the presence of calcium ions (usually calcium chloride added). this is how diabetic jeams are made, it is also the basis for adding calcium in canned things like tomatoes or pickels to keep the firm flavor because the pectin in those foods reacts with calcium to keep pickle firm.

How does degradation occur

catalyzed by enzymes and organic acids ex: in pineapple the enzyme is bromalade, and organic acid is in cell sap.

As fruit ripens

demethylation occurs and hydrolysis of protopectin, if a limited amount of this degradation occurs you get pectin, as more demethylation occurs and hydrolysis you get pectinic acids

Protopectinase

enzyme in fruits and veggies capable of catalyzing hydrolytic cleavage of protopectins ie cuts the chians

Pectinesterase

enzymes deesterfy protopectin and pectin to split off methoxyl groups to lose some of the gel-forming properties of the compounds and softening the fresh fruit too

Pectin in fruits

fruits naturally contain pectin but some don't contain enough to make jellies so companies still add pectin

Pectinic Acids

galacturonic acid (sugar acid) polymers that have .25-.5 of the acid molecules esterfied with methanol. this is formed just as fruit begins to soften a little (sturcutre of galacturonic acid)

Main use of pectin

gelling agent and thickening agent and stabilizer in food. classic is jelly can also stabilize acidic protein drinks, and as fat substitute in baked goods.

If pectin molecule is completely esterfied..

if all organic acid residues are altered to methyl esters then pectin will contain >16% methoxy groups. in contrast there are low methoxyl pectins

Protopectin

immature plant material

Where does pectin occur

in fruits, can produce a strong gel

Pectin with Sugar

in precense of sugar pectin molecules will dehydrate. Acid will cause hydrogen bonding to occur between negatively charged molecules, thus creating a thickened structure. this is key for jams and jellies.

protopectin overview

it is a water insoluble form of pectic substance occurring in immature fruits and to a lil extent veggies. this contributes to the firm texture of unripe, it is a methylated very long polymer consisting of galacturonic acid units joined by alpha 1,4 linkage (see chapter nine structure)

Pectin

mature plant material

Pectinic Acid

mature plant material

Acids in jams and jellies

needs to be between 2-3.5 optimum is 3.2 it is used to keep flavor and hydrolyze some sugars to invert sugars (review invert sugars) acid also stabilizes

Pectic acid

occurs as more degradation occurs, degradation of pectinic acids, makes molecules shorter, lose all methoxy groups. these are the smallest of the pectic substances, lacking mmethyl esters, this occurs in overripe fruits/veggies, LOST GEL FORM ABILITY

Pectin Overview

occurs in plant middle lamella, they cement the cells together, in food use pectin is a gel former

Low methoxyl pectins

these are valued for the ability to form a get structure with very little sugar this is good for diabetic jams

Pectic substances

these constitiute a group of polysaccharides that are polymers of galacturonic acid(sugar acid). the middle lamella between cells is made of pectic substances these are also important in cell will (they combine with hemicelluloses to reinforce structural contribution of cellulose)

As protopectin evolves into pectin and pectinic acid

transition from methylated water insoluble polymer to shorter methylated compound easily dispersed in water, because of this change you can heat fruit juice + pectin + sugar and cool it to get pectin jell.