Polysaccharides (Complex Sugars)

What is the largest food starch?

POTATO

Starch definition

plant polysaccharide; stored in roots, seeds, and in endosperm of grain kernels; hydrolyzed to glucose; provides energy; 4 calories per gram; most common carb in diet; not water soluble

What are sources of gums?

plants, seeds, microbes, seaweed, and synthetic

Starch

present in most foods; occurs naturally in foods; used as an additive;

Sugar (needed in pectin gel formation)

preservative; high osmotic pressure in jelly (microorganism can't grow); optimum sugar concentration (65% soluble solids)

Starch gelatinization

process where a starch and water mixture is heated; causing the starch granules to swell; increases volume; increases viscosity (becomes gel); becomes transparent/translucent; is irreversible

Starch properties depend on what factors?

quantity and type of polysaccharide components

Amylose vs. Amylopectin

ration between them in starch content varies between different food starch types

How are modified starches made?

*1. begin with "base" starch* -rice, corn, wheat, potato, tapico *2. blend with another starch to enhance properties* *3. implement action such as acid treatment, toasting, sodium hydroxide treatment, potassium hydroxide treatment, treat w/ emulsifier & w/ starch ethers* *4. more than one process is applied to create a modified starch w/ the desired properties

Pectin substances

*Degree of Esterification (DE)* -proportion of galacturonic acids that are in the methyl ester form - a.k.a. Degree of Methoxylation -quoted as a precentage of DE -%DE affects the behavior of pectin

Pectin production

*Pectin obtained from citrus peel through extraction process* -citrus peel is prepare in specific conditions ( 1.5-3.0 pH, 140-212 degrees F) -pectin becomes soluble and is present in extract -extract in filtered to remove solid substance (peel) -pectin is precipitated by adding isopropanol -precipitate (pectin) is dried and processed

Amylopectin

*branched polysaccharide of glucose units* -20-30 units *large size and branches* -reduces mobility -interferes tendency to form hydrogen bonds *resistant to gelling*

Which amylose content effects the transparency of gelatinization?

*corn starch* -higher amylose content - more translucent *tapioca and potato starch* -lower amylose content -more transparent

What helps during starch gelatinization?

*dependent on:* -amount of water available -temperature -timing -stirring *presence of:* -acid -sugar -fat -protein

Heteroglycans (polysaccharides by monomers)

*di-heteroglycans (2 types of monosaccharides)* -agars -alginate -carrgeenans *tri-heteroglycans (3 types of monosaccharides)* -xanthan -gellan -arabinoxylan

Two classes of pectin substances

*high methoxyl (HM) pectins -high proportion (50-80%) of esterified carboxyl groups *low methoxyl (LM) pectins -mostly free carboxyl groups -only 20-40% are esterified

Uses of gums in the food industry?

*ice cream* -provides smooth, creamy texture; reduces ice crystals *bakery products* -provides texture and moisture retention *beverages* -provides body and mouthfeel in "thick" beverages *meat products* -used as a binder and provides moisture *dressing* -thickener and emulsion stabilizer

Effect of Degree of Esterfication (DE)

*lower DE* -longer setting time -lower temp *higher DE* -shorter setting time -higher temp

Acetylated galacturonic acid (pectin substance)

*occurs in pectin from some plants* -sugar beets, potatoes, pears *acetylation effects on pectin* -prevents gel formation -increases stabilizing effects -increases emulsifying effects

Plant based polysaccharides (by source)

*plant cell wall* -cellulose (insoluble) -pectin (soluble) *plant seeds* -cereal starch -guar gum locust bean gum *plant tuber and root* -potato starch -tapioca starch *plant exudates* -gum arabic -gum tragacanth

Pectin sources

*present in all fruits and veggies* -amount of pectin varies between each type -high pectin content fruits include limes, lemons, oranges, apples; located in albedo (white pitty part under citrus skin) and peel -average pectin content fruits are apricots, blackberry -low pectin content fruits include cherries, peaches, pineapples

What is the process of starch retrogradation?

*retrogradation occurs when gel cools* *water seeps out of aging gel* *which leads to* -syneresis or weeping (expelling water form polymer network) -contraction of gel -amylose molecules tighten bonds

What are gums?

*select group of plant polysaccharides* -highly branched polysaccharides -have the ability to contribute to food viscosity -most do not form gels -they are hydrophilic -excludes: unmodified starch, cellulose, and pectin

Xanthan gum

*source* -bacteria: xanthomas campestri *structure* -cellulose-like backbone *function* -water soluble, viscous, non-gelling

Gum arabic (aka Acacia gum)

*source* -hardened sap from acacia tree (extrudated gum) *structure* -glycoproteins and polysaccharides *functions* -low viscosity -non-gelling *hard to source, expensive

Carageenan gum

*source* -seaweed *structure* -linear D-galactopuranosyl chain -several variations *function* -pH independent thickening

Dietary fibers

*sources* -foods derived from plants -includes polysaccharides, cellulose, hemicellulose, pectin, gum, lignin (non- polysaccharide) *indigestible* -not a source of energy -gut flora (GI tract bacteria) can breakdown some fiber

Insoluble dietary fiber

-cannot dissolve in water -promotes movement of material through the digestive system and increases stool bulk to battle constipation and irregular stools -found in whole wheat flour, wheat bran, nuts, beans, cauliflower, green beans, and potatoes

Soluble dietary fiber

-dissolves in water to form a gel-like material -help lower blood cholesterol and glucose levels -found in oats, peas, beans, apples, citrus fruits, carrots, barley, and psyllium

Pectin (needed in pectin gel formation)

.5% - 1%; peach: pectin contains acetyl group, poor gel; citrus: good pectin, good gel juice/fruit with low pectin or with acetyl groups: concentrate by boiling (evaporate off water); add more commercial pectin

Homoglycans (polysaccharides by monomers)

1 type of monosaccharide; starch, cellulose

Pectin gel need 3 important constituents

1. pectin 2. acid 3. sugar

Polysaccharide

a carb, as a starch, inulin, or cellulose, containing more than three monosaccharide units per molecule, the units being attached to each other in the manner acetals, and therefore capable of hydrolysis by acids or enzymes to monosaccharides

What is a pre-gelatinized starch?

a.k.a. "instant" starch; base starch is gelatinized, dehydrated, or powered; retains most of the functional properties and viscosity of the base starch

What is acid's purpose in pectin gel formation?

adds hydrogen ions; reduces charge on pectin molecule; increases pectin-pectin attraction; water becomes trapped in the "pockets" within the gel network

Polysaccharides from seaweed extracts (by source)

agars, alginate, carrageenans

Anionic charged polysaccharides

alginates, carrageenens, gellan, gum arabic, xanthan

Branch on branch polysaccharides

amylopectin, gum arabic, arabinoxylan

What are the major starch polysaccharides?

amylose (10-30%) and amylopectin (70-90%)

Neutral charged polysaccharides

amylose, amylopectin, cellulose, guar gum

Linear polysaccharides (by structure)

amylose, cellulose, pectin, alginate

Structural polysaccharides (by function)

cell structure; cellulose, chitin

What is sugar's purpose in pectin gel formation?

competes for water and decreases the pectin-water interaction; increase pectin molecule attraction to each other; decrease pectin molecule attraction to water

Acid (needed in pectin gel formation)

contributes to flavor; optimum pH=3.2; if juice/fruit is low pH add lemon juice

Low methoxyl pectin characteristics and uses

for gel without need of sugar; widely used in food industry as a gelling agent, thickening agent, & stabilizer (for acidic protein drink); used as fat substitute in baked goods

What is starch retrogradation responsible for?

for staling or aging of bread and other baked goods

high methoxyl pectin characteristics and uses

form gels in aqueous systems with high content of soluble solids and low pH range

Starch form and shape

form is semi crystalline granules (starch granules); size/shape is based on plant species and part of plant; shapes are generally polygonal, oval, or round; size/shape serve a "fingerprint" to determine origin

Pectin gel formation process

formed by cross-linking the polymer at junction zones (hydrogen bonds); repulsion of methyl groups; creates area where sugar and water is trapped in pectin network

Uses for pre-gelatinized starches

forms of gel without heating like instant puddings

What accelerates the starch retrogradation process?

freezing

What are functional uses of modified starches?

generally the same as unmodified starches but over wider range of conditions; used a s thickeners, stabilizers, binders, emulsifiers

Short branched polysaccharides (by structure)

guar gum, locust bean gum, xanthan gum

What are other advantages of modified starches?

helps "powered" food less lumpy when reconstituted (cheese sauce, gravy); serves as a fat substitute in low-fat foods; acts as an emulsifier in salad dressings; forms hard "shell" on soft candies (jelly beans); increases shelf life

What is the importance of pectin and gums?

important food polysaccharides; source of dietary fiber; used as: -gelling agents (jams, jellies) -thickeners (fillers, medicines) -stabilizers (fruit juices, milk-based drinks)

Why use modified starches?

improve starch performance; meet other consumer needs: -improve solubility in cold water -improve viscosity stability (in wide temp. range and in wide pH range) -improve cold storage stability

Modified starches

in many food products, conditions are not suitable for proper gelling of starch such as foods with low pH, food that can't be heated to high temps.; used to meet the desired starch effects in these foods (modified food starches); have many non-food uses in industrial and consumer products

Amylose

linear polysaccharide of glucose units; starch granules contain 10-30% amylose; separated by selective precipitation; has affinity for iodine, fatty acids, and long chain alcohols; form helical complex around these molecules

Polysaccharides derived from processes (by source)

modified starch, carboxymethyl cellulose, propylene glycol alginate

What are modified food starches?

natural starches that are chemically treated in a variety of ways to achieve desired effects

What is starch retrogradation?

occurs during gelatinization process; amylose and amylopectin chains realign themselves and cause liquids to gel

Low methoxy pectin (LM)

only forms gel *IF* polyvalent cations are present; typically calcium

High methoxy pectin (HM)

only forms gel *IF* soluble solids contents greater tahn 65%; pH is 2.0 to 3.8

What are the two classification of dietary fiber?

soluble and insoluble

Examples of polysaccharides

starch, pectin, gum, cellulose

Starch properties

starches undergo several changes during processes of food prep such as gelatinization, retrogradation, dextrinization; these changes are essential for different food preps

What are pectins?

structural polysaccharides (dispersible in water); hetero-polysaccharides present in cell walls of plants; commercially produced pectins (white to light brow, obtained form citrus fruit)

What are general uses of gums?

thickeners, stabilizers, and common substitute in low-fat foods

Uses for starch

thickening agents, edible films, starch syrups, gums (not the chewing kind), sauces

Syneresis

unmodified exhibits more syneresis; modified exhibits less syneresis *examples* -liquid weeping fro a pie filling -pudding that contracts from the edge

Storage polysaccharides (by function)

used for energy; starch, glycogen

What is starch gelatinization used in?

used in sauces, puddings, creams; more easily digestible

In gelatinization what control the gelling effect?

waxy hybrid starch such as corn and sorghum cross (do not gel)

Polysaccharides from microorganisms (by source)

xanthan gum, gellan gum