LIPIDS

Lipids in PeanutsOpened jar peanut butter: chemical reaction in the oil phase Oxidation of the unsaturated fatty acids in the peanut oil results in production of a rancid odor.Peanut butter represents a special food system called an emulsion

HHHHCCCCHH

oxygenHydrocarbon chain

Solutions and Emulsions

Droplets of dispersed phasewithin the continuous phase

Solutions are homogeneous mixtures in which soluteparticles are small enough to dissolve within solventSolute examples: salt, sugar, vitamin C, other small solid particlesSolute liquid examples: water, ethanol; gas examples: CO2Dispersions (colloidal dispersions) are mixtures in whichsolutes do not dissolve (too large)Examples of colloidsmilk protein (casein)egg white protein (albumen)gelatin proteinpectin polysaccharideCa and Mg (minerals)

MILK

What is an emulsion?Mixture of two immiscible liquids

oilH2OSurface tension acts to keep the liquidsfrom mixing

Result: oil sits ontop of the water phaseStable food emulsions = addition of emulsifierslecithin, sucrose esters, MAG, DAG, etc

O/WemulsionW/Oemulsionmilkice creammayo

Margarinebutter

Common Chemical Bonds in FoodsCovalentSharing 1 or more pairs of electronsVery strong bonds, not easily broken in foodsC-C or C=C bondsIonicFilling of orbitals through the transfer of electronsCations (+) and Anions (-); Na+ + Cl- => NaClHydrogenCompounds containing O or N with bound hydrogenVery weak bonds; C-H or N-H

Functional Groups in Foods

There are 3 other important bonds in foods:

An ester bond (linkage) in lipids

A peptide bond (linkage) in proteins

(3) A glycosidic bond (linkage) in sugars Covalent: Sharing of electrons, strong bonds, C-C or C=C bondsIonic: Transfer of electrons, NaClHydrogen: Weak bonds with O or N with bound hydrogen

An ester bond (linkage) in lipids: O

GlycerolC O fatty acidIn food fats, fatty acids are attached to glycerol molecules, through what is called an ester linkage

Ester linkage

Glycerol is a small molecule, containing only 3 carbons

But, to each carbon atom of glycerol, one fatty acid can attach, via an ester bond.

A mono-, di-, or tri-esterified fatty acid to a glycerol is:A MONOACYLGLYCEROL. A fat molecule that has ONE fatty acid attached (esterified) to glycerol.

A DIACYLGLYCEROL. A fat molecule that has TWO fatty acids esterified to glycerol.

A TRIACYLGLYCEROL. A fat molecule that has THREE fatty acids esterified to glycerol.

Glycerol H

H C O H

H C O H

H C O H

H H O

H C O C - (CH2)n CH3

H C O H

H C O H

H

Ester

Fatty acid chain

a monoglyceride

LIPID chemical reactions

OxidationHydrolysisHydrogenation

Chemical Bonds to Chemical Rxns

Oxidation vs Oxidized

The removal of an electron is oxidation (redox reactions).When a food system is oxidized, oxygen is added to an active binding siteFor example, the result of lipid oxidation is that the lipid may become oxidized.

In the food industry, we common speak of oxidizing agents versus reducing agents. Both are used in foods.Reducing agents are compounds that can donate an electron in the event of an oxidation reaction.L-ascorbic acid is an excellent reducing agent as are most antioxidants Oxidizing agents induce the removal of electronsBenzoyl peroxide is commonly added to bleached wheat flour

Enzyme Applications in the Food IndustryCarbohydrases: making corn syrup from starchProteases: Meat tenderizersLipases: Flavor production in chocolate and cheese

Pectinases Glucose oxidase Flavor enzymesLipoxygenasePolyphenol oxidaseRennin (chymosin)

Legumes and OilseedsSoybeans = used for both oil and proteinPeanuts = whole nut, oil, peanut butter