food science and tech exam 1 part 2

carbohydrates

hydrates of carbon that contain a carbonyl (C=O) group, Made of carbon, hydrogen and

oxygen as follows: Cn H2n On, Product of photosynthesis, Energy source: sugar, starch, Structural component: cellulose

general formula for a saccharide unit is

(C x H2O)n 6 ≥ n ≥ 3

simple carbohydrates:

sugars, -ose

monosaccharides

1 unit: building blocks for carbs, can be: trioses, simplest sugar: glyceraldehyde, tetroses, pentoses, hexoses

disaccharides

2 units

oligosaccharides

2-10 units

complex carbohydrates (polysaccharides)

starch, pectin, alginate, cellulose, etc, long chains of sugar units (greater than 10 units0, units linked by “glycosidic” bonds

glucose (dextrose): main monosaccharides

main sugar, the body’s predominant fuel

fructose (monosaccharides)

fruit sugar

galactose (monosaccharides)

one of the two sugars in milk

sugar

general properties of monosaccharides

They are generally sweet tasting, Soluble in water, Can participate in chemical reactions to

form color (browning reactions): Reducing

sugars

reducing sugars

sugars capable of reducing

oxidizing agents: have hydroxyl (OH) in

“anomeric carbon” available for reacting.

how to locate anomeric carbon

Locate the oxygen inside the ring, Look at the carbons on either side of the oxygen. One will be attached to a CH2OH group, the carbon on the other side is the anomeric carbon

reducing sugars:

C‐O‐C‐OH

non-reducing sugars

C‐O‐C‐O‐C

glucose: transformations

Monosaccharide, monomer for starch and

cellulose

• Blood sugar: preferred energy source

• Not as sweet as sucrose

sucrose: disaccharides

Glycosidic linkage of glucose and fructose, Linked at the anomeric carbons, NON‐REDUCING!!! fructose-glucose, sweet, and does not change with temperature.

lactose

Glycosidic linkage of glucose and galactose, very little sweetness like galactose

maltose

Glycosidic linkage of two glucoses

what does sugar do: sweetness:

Related to the chemical structure/

conformation

fructose:

sweetness: temperature

dependent, more sweet in low temperature, More or less sweet than sucrose depending on the temperature, can form 4 different rings, more difficult to form crystals

what does sugar do: crystallinity

An ordered arrangement of the

molecules. Is favored by homogeneity (same

structures)

polysaccharides

long chains, with more than 10 units linked together, usually contain more than 100 units

starch

glucose chains (200 or more)

dietary fibers

plant materials- long chains of monosaccharide molecules whose structure is resistant to human digestive enzymes, but can be fermented in colon

starch

Insoluble or limited solubility in cold

water

gelatinization

When heated starch granules absorb and trap

water, When cooled down form gels, increase viscosity

cellulose

Structural component of the cell wall of trees/foods

• Insoluble in water

• Not branched

• Derivatives are soluble in water: carboxylmethyl

cellulose is used in milk, dressings, instant mix, jelly

What does carbohydrate do? hygroscopy

Attract and hold water from

environment through H‐bonding.

 Amorphous sugars more hygroscopic

than crystalline sugar.

what does carbohydrates do: humectant

is a hygroscopic substance used to

keep moisture, make water less available for

microbial growth or other activity.

Non‐Enzymatic Browning: Maillard

reaction

Reaction between sugars and amino

acids

 Must be reducing sugar to participate

 Intact sucrose can not react

 Heat, increased pH, and lowering water

activity favor the reaction

 Affects color, flavor and nutritional value

caramelization

occurs when sugars are heated so

much (>200°C) that their molecules break down.

These molecules will in turn react to brown the

sugar and create hundreds of new and varied

“caramel” flavors, can have a number of

different tastes ranging from fruity to buttery,

sweet, roaster or even flowery.

viscosity

Resistance to flow: body or

mouthfeel

• Concentrated sugar solutions

tend to be very viscous, polysaccharides can provide more viscosity, heat decreases the viscosity

artificial sweeteners

hundreds to

thousands of time sweeter than sugars

• Need to compensate for

 Sweetness: Use hundreds or thousands of

times less volume to achieve same sweetness

 Bulk – e.g. volume of cake

 Color development

 Viscosity and mouth feel

sugar alcohols

carbohydrates with a chemical

structure that partially resembles sugar and

partially resembles alcohol, but they don’t contain

ethanol as alcoholic beverages do, their calorie content ranges from 1.5 to 3 calories

per gram compared to 4 calories per gram for

sucrose or other sugar

lipids

Molecules synthesized by biological

agents with long aliphatic hydrocarbon

chains

 Usually unbranched

 Mostly soluble in organic solvents /

insoluble in water

fats

solid at room temperature

• Lard, butter

oils

liquid at room temperature

• Olive oil, canola oil

saturated fatty acids

Carry the maximum number of possible

hydrogens

 Examples: Animal fat

 Usually solids (fats) in room temperature

unsaturated fatty acids

Presence of double bonds

 Have less hydrogens than the maximum

 Usually fluid (oils)

 Present mostly in vegetables and in sea

foods

saturated fatty acids

4C butyric acid (4:0)

 Abundant in milk

 16C palmitic acid (16:0)

 Meat, cheese, soybean oil

 18C Stearic acid (18:0)

 Cocoa butter

in nature: double bonds are always

“cis”

in food:

“cis” and “trans” double bonds possible

di-or poly-unsaturated

Unconjugated unsaturation:

 Unsaturation is never right next to each

other, but there is one saturate carbon

in between

 Susceptible to oxidation: rancidity

essential fatty acids (polyunsaturated fatty acids): linolenic and linoleic

Can not be synthesized by the body

 Are fluid at room temperature

 Omega 3 or omega 6 fatty acids

 All have “cis” double bonds

hydrocarbon end=

omega end=nonpolar end

carboxylic end=

acid end= polar end

general characteristics of lipids

primarily consumed for energy

• Contribute 30‐50% of calories for

Americans

• Major component of cell membranes

• Cushion the vital organs to protect them

from temperature extremes: insulator

what does lipid do

Flavor (sometimes off‐flavor)

• Aroma, taste, and mouthfeel, e.g.

• Richness of whole milk

• Creamy nature of ice cream

• Phase partition and mass

transport, Texture: shortening effect on gluten and

starch by preventing their interaction

with water, to generate crumbly & flaky

texture

• Color: margarine (yellow) vs. lard (pale)