Food Science - Pectin and Gums

how are pectic substances classified?

# OF METHYL ESTER GROUPS attached to the polymer.

in low methoxyl pectins what percent carboxyl groups are esterified?

*20-40%* most AVAILABLE to form CROSS-LINKS with divalent ions such as calcium.

in high methoxyl pectins, what percent of the carboxyl groups are esterified?

*50-58%* of esterified carboxyl groups. NOT AVAILABLE for crosslinks cannot form gel unless SUGAR AND ACID ADDED jellies

What are gums also referred to as?

HYDROCOLLOIDS

2 factors of junction zones

HYDROGEN BONDS STERIC FIT

What is a demethylated derivative of pectinic acid?

Pectic acid

What kinds of fruit contain pectic acid?

over-ripe fruits - demethylated

Acid effects on pectin?

reduces the pH and the charge on the pectin - form gel

What kinds of fruits contain pectinic acid?

ripen fruits only one that FORMS GEL

what gums can form gels?

seaweed polysaccharide and synthetic gum Methyl cellulose can form gel when cold dispersions are heated- thermal gelation.

Kappa # negativity gel formation with what?

smallest # least negative forms gel with potassium

what are JUNCTION ZONES?

specific regions on polymer chains that align due to an attractive force and form a 3D network pockets between junction zones able to TRAP WATER.

What is locust bean gums used for?

stabilize dairy and processed meats

What is the application (What is it used for) of gum arabic?

stabilize emulsion and control crystal size in ices and glazes

What is guar bean gums used for?

stabilize icecream treating mild diabetes

Why is pectin hydrophilic?

the *large number of polar hydroxyl groups* and *charged carboxyl groups*

what is Steric fit?

the ability of molecules to fit together in space

What is the most common gums?

GALACTOSE that is missing glucose

What kind of water is Guar bean gums soluble in?

cold water

Gums

complex HYDROPHILLIC carbs containing thousands of mono units

What are the 2 synthetic gums and what are they used for? what kind of modification?

*Carboxymethyl cellulose* *methyl cellulose* *alkali-modified* cellulose used to thicken foods

What are the characteristics of Xanthan?

*VISCOUS SOL that is STABLE WITH A WIDE RANGE OF PH AND TEMP.* Does not form a gel by itself used as thickener, stabilizer, and suspending agent

What are the 4 components of hydrocolloids/gums?

1. highly branched 2. form stable dispersions/sols 3. cannot form gels with some exceptions (Seaweed polysacch and MC (synthetic gum) when COLD DISPERSIONS ARE HEATED (THERMAL GELATION) they form gel) 4. very viscous

Low-methoxyl pectins

20-40% of the carboxyl groups are esterified can form cross-links that trap liquid and form gel

What is the ratio of Mannose to Galactose in Guar bean gums?

2:1

What is the ratio of Mannose to Galactose in Locust bean gums?

4:1

High-methoxyl pectins

50-58% of the carboxyl groups are esterified cannot form links/ gel unless acid is added form pectin jellies

What does agar contain?

AGAROSE AND AGAROPECTIN derivatives of *B-D/A-L GALACTOSE STRONG, TRANSPARENT, HEAT-REVERSIBLE

What does alginates form a gel in the presence of?

CALCIUM

Sugars effects on pectin?

COMPETES FOR WATER - form gel

Which gums is obtains from red seaweed- irish moss?

Carrageenan. Agar is from red seaweed too though.

What do alginates contain?

D-mannuronic and L-guluronic

Lambda

Largest # Most negatively charged forms gel by itself

Iota

Middle # forms gel with calcium

What keeps pectin molecules apart to trap water?

REDUCING FORCES

What is the most common microbial exudate gum?

Xanthan

What are the 4 microbial exudates gums?

Xanthan, gellan, dextran, and curdlan

What happens when pectin is dispersed in water?

acid groups ionize and water binds to both charged and polar groups

Seaweed Polysaccharides gums

agars, alginates, and CARRAGEENAN - CAN FORM GELS

What is obtained from brown seaweeds?

alginates

Sources of Pectin

apples and citrus

When do calcium alginate gels NOT MELT?

below the boiling point of water

What is the critical control point of jelly formation?

boiling time

what is pectin gel?

decrease pectin molecules interaction with water (sugar) increase pectin molecules interaction with each other (acid) - pectin interacts at junction zones - water is trapped in the network.

What happens when you boil jelly for too long?

depolymerization of pectin - gel may not set

What is the solubility of gum tragacanth?

forms viscous sols

Agar where is it from? what is noted for?

from red seaweed STRONG, TRANSPARENT, HEAT-REVERSIBLE GELS. can be melted and recooled

What is the application of gum tragacanth?

give a creamy texture stabilize salad dressing, icecream, and confections "creamy dressing"

What are the 2 seeds gums that only contain MANNOES AND GALACTOSE?

guar bean Locust bean

What are the two plant exudates gums that are highly branched?

gum arabic gum tragacanth

Pectins weight and dispersment

high molecular weight and dispersible in water

What is the solubility of gum arabic?

highly soluble in cold water

What kind of water is locust bean gum soluble in?

hot water

What kinds of fruit contain protopectin?

immature fruits methylated galacturonic acid polymer

pectic substances

important constituent of PLANT TISSUES. linear polymers of D-galacturonic acid joined by ALPHA-1,4-GLYCOSIDIC LINKAGES CROSS-PLANAR

why are pectins and gums important?

important polysaccharides in foods because their functional properties. gelling agents, thickeners, and stabilizers.

what are CMC and MC used for?

increase viscosity of foods.

Cellulose - 2 synthetic gum forms

insoluble fiber (2 synthetic gum forms CMC and MC) with over 3,000 glucose molecules joined by *B-1,4 bonds*

Jelly formation

juice, pectin, and sucrose is combined and boiled

Are gums an insoluble fiber?

no - provide few calories SOLUBLE FIBER

What happens when you boil jelly for too short?

not enough invert sugar and no crystilization of sucrose

What is responsible for sol formation of pectins?

the negative charge on the pectin molecule and the attraction for water keeps them APART

Steric fit of pectin

the small components linked to the main galacturonic chain via 1,2 bonds cause KINKS in the molecule and makes it more DIFFICULT TO ALIGN

What are the common uses for gums?

thickening agents. fat replacer, and emulsion stabilizer

what is pectin sol?

water binds to ionic and polar bonds on pectin pectin molecules are negatively charged and hydrated do not react with each other

How do methyl cellulose form gels?

when cold dispersions are HEATED (THERMAL GELATION) used to coat fried chicken before frying to limit fat absorption.