Food Science - Pectin

If a pectin molecule is completely esterified/methylated, then the pectin polymer contains over _____% methoxy groups

over 16%

If only limited demethylation occurs, ________ is formed. Continued demethylation results in _________

pectin, pectinic acids

Calcium ions and pectin?

-If calcium ions are present, pectin molecules will bind together and form a thick gel without sugar. This is how diabetic jams and jellies are made. Also why CaCl is added to canned tomatoes and beans as a firming agent. -Pectinic acids will form salts with calcium ions, allowing gels to form with low-methoxyl pectins. These salts=PECTINATES - important for gel-forming

When added to food, pectin composes ___-___% of the food (same in natural fruit)

0.5-1

Basic recipe for jams and jellies?

1% pectin 60-65% sugar 34-39% fruit juice

Uses of pectin (3)

1. Gelling agent (jams/jellies) 2. Stabilizer in acidic protein drinks (eg. drinking yogurt) 3. Fat substitute in baked goods

Degree of esterification in pectinic acids?

Between 1/4 to 1/2 of galacturonic acids are esterified/methylated in pectinic acids

Where does pectin come from?

Complex carbohydrate that occurs in the lamella between plant cells - usually fruit. Made of sugar acids (galacturonic acid)

As fruit ripens, what reactions occur along protopectins?

Demethylation and hydrolysis

What causes pectins to lose gel-forming properties?

Losing their methyl groups

Low-methoxy pectins - function?

Low-methoxy pectins are able to form a gel structure with very little sugar (good for diabetic jams and jellies)

____________ is the enzyme that deesterifies/demethylates protopectin and pectin

Pectinesterase

Stages of pectinic substances

Protopectin, pectin, pectinic acids, pectic acids

Protopectin: solublility? methylated? length? linkages? gel-forming?

Protopectin: water insoluble methylated very long polymer of galacturonic acid units joined by alpha 1-4 linkages no gel-forming

____________ is the enzyme that hydrolyzes galacturonic acid polymers into shorter chains

Protopectinase

Adding acid to pectin? pH range for jams/jellies?

The acid will cause hydrogen bonding/hydrophobic interactions between pectin molecules molecules, creating a thickened structure. Why you want a low pH of 2.0-3.5 for jams and jellies - add lemon juice if fruit used is not naturally acidic.

Adding sugar to pectin?

The pectin molecules will bond together (dehydrate by a condensation reaction)

The transition of protopectin to pectin/pectinic acid allows for....

You can heat fruit juice with pectin and sugar, cool it, and get a gel (jam)

Pectic acid: methylation? length? gel-forming ability?

all methoxy groups cleaved, shortest polymer of the pectinic substances, lost gel-forming ability

Pectins are the complex carbohydrates in _________

fruits

Pectic substances are an important molecule in cell walls because...

they combine with hemicellulose to reinforce cellulose structure of cell walls in plants

Pectin/Pectinic Acid: solubility? methylated? length? gel-forming ability?

water soluble (therefore gel-forming)demethylated, shorter