Carbohydrates

Question 1

Importance of carbohydrates

Answer 1

Major energy source
Sweet taste
Provide structure and texture in food
Lower aw and affect crystallization (ice cream)
Fat substitute (modified starch)
Impart flavors and colors (Maillard browning)
Energy source in fermentation (yogurt)
Health benefits (dietary fiber)

Question 2

Monosaccharides

Answer 2

Glucose
Fructose
Galactose

Question 3

Disaccharides

Answer 3

Lactose
Maltose
Sucrose

Question 4

Oligosaccharides

Answer 4

a few monosaccharides linked together

Question 5

Polysaccharides

Answer 5

Many monosaccharides linked together

Question 6

Inulin

Answer 6

polysaccharide

extracted from chicory root, used to replace sugar, fat, and flour

Question 7

Pectin

Answer 7

polysaccharide

in cell walls of plants, used as gelling agent, thickening agent, stabilizer

Question 8

Sugar alcohols

Answer 8

C=O (carbonyl) replaced with –OH
Small amounts in fruit
Synthesized industrially
Non-metabolized sweeteners

Question 9

Caramelization

Answer 9

Series of non-enzymatic reactions when sugar heated above 150°C
No proteins involved
Sucrose inverts to glucose and fructose; isomers, fragments, and polymers form; dehydration and condensation occur
Flavor compounds and brown pigments arise
In ring form
Have free radicals: molecules that do not have enough atoms to fill all of the bonding requirements
Part of reason why caramels are sticky

Question 10

Maillard reaction

Answer 10

Amino acid, sugar, usually heat reaction
Toast
Beer
Steak sear

Question 11

Starch

Answer 11

Produced by plants from CO2 and H2O through photosynthesis
Their major food and nutrient reserve
Hundreds or thousands of glucose molecules chained together
Bonds between glucoses easily broken, used as energy source by plants and those eating them
Classified by three-dimensional structure

Sources:
From arrowroot, corn, tapioca, wheat
Comprises 85% of corn flour, 70% of wheat flour
Different properties depending on amylopectin-amylose ratio

Question 12

Amylose

Answer 12

Starch
Helical, little branching
Tight packing

Question 13

Amylopectin

Answer 13

Starch
Branched, fold into sheets
More soluble
Around ¾ of starches in plants

Question 14

Gelatinization

Answer 14

Starch heated in water, goes from practically insoluble semi-crystalline product to soluble amorphous substance
Produces viscous solutions which set to a semisolid elastic mass (jelly or gel) after cooling
Onset characterized by loss of granular structure, promotes swelling
Gelatinization point partly depends on granule size: smaller granules more resistant to swelling

Question 15

Retrogradation

Answer 15

Thickening of cooked, unmodified starch when cooled for long enough time
Starch molecules gradually aggregate to form gel, rearranging to more crystalline structure
Molecular associations occur between amylose and amylopectin
Tightly packed organization of small granule starches causes retrogradation to occurs much more slowly
Ex: staling of bread

Question 16

Modified starch

Answer 16

Tailored for specific applications
Pre-gelatinized: cooked with water to gelatinize and dehydrated, swells to desirable thickness with addition of water, no heat needed
Thin-boiling: treated with acid, many amylopectin branches cleaved off, starch can be delivered through pipes in plant, forms strong gels
Cross-linked: produced under alkaline conditions, used as thickening agents, limited retrogradation

Question 17

Soluble fiber

Answer 17

gum, dissolves in water, attracts and binds water, limited calories
Alginic acids: from seaweed, thickener and stabilizer, includes agar and carrageenan
Pectin: from fruit skin, gelling agent in jams and jellies
Psyllium: from plantains, digestion aid
Raffinose: in beans and cruciferous vegetables

Question 18

Insoluble fiber

Answer 18

absorbs water without dissolving in it, provides bulk
Cellulose, hemicellulose, lignin, resistant starch
Hemicellulose: heteropolymer, random structure, little strength
Lignin: cross-linked, in cell walls
Resistant starch: not digested in small intestine, high levels in beans and lentils

Question 19

Carboxymethyl Cellulose (CMC)

Answer 19

Very viscous, used as thickener
Also used in laxatives, toothpaste, water-based paint
Stabilizes emulsions in ice cream
Water-soluble, combines with other gums, imparts body and chewiness
Only 0.1-0.2% needed
Eliminates need for high level of churning and very low temperatures
Absorbs 15-20 times its weight in water
Fibers make texture plumper and fatlike without adding calories
Also imparts glossy appearance
Used in Swiss Miss Hot Cocoa Mix, Wish-Bone Chunky Blue Cheese Dressing, Kraft Macaroni and Cheese

Question 20

Artificial sweeteners

Answer 20

6 types approved by FDA:
Acesulfame-K (Sweet One)
Aspartame (Equal, Nutrasweet)
Neotame
Saccharin
Stevia (Truvia)
Sucralose (Splenda)