Lipidos

Food Lipids

Lipids
“Lipids consist of a board group of compounds that are generally soluble in organic solvents but only sparingly soluble in water….” “…Glycerol esters of fatty acids, which make up 99% of the lipids of plant and animal origin have traditionally been called fats and oils”
Nawar, “Lipids” Food Chemistry, Fennema Ed. 1996

Lipids are non-polar (hydrophobic) compounds,soluble in organic solvents.
Fatty acids consist of a hydrocarbon chain with a carboxylic acid at one end.

CH3(CH2)n-COONon-polar polar

Saturated Fatty Acids
Systematic name Trivial name Shorthand designation Molecular wt.

butanoic pentanoic hexanoic octanoic nonanoic decanoic dodecanoic tetradecanoic hexadecanoic heptadecanoic octadecanoic eicosanoic docosanoic

butyric valeric caproiccaprylic pelargonic capric lauric myristic palmitic margaric (daturic) stearic arachidic behenic

4:0 5:0 6:0 8:0 9:0 10:0 12:0 14:0 16:0 17:0 18:0 20:0 22:0

88.1 116.1 144.2 158.2 172.3 200.3 228.4 256.4 270.4 284.4 312.5 340.5

Mono-Unsaturated Fatty Acids
Systematic name cis-9-tetradecenoic cis-9-hexadecenoic cis-9-octadecenoic tr-9-octadecenoic cis-11-octadecenoic cis-11-eicosenoiccis-13-docosenoic Trivial name myristoleic palmitoleic oleic elaidic vaccenic (asclepic) gondoic erucic Shorthand designation 14:1(n-5) 16:1(n-7) 18:1(n-9) tr18:1(n-9) 18:1(n-7) 20:1(n-9) 22:1(n-9) Molecular wt. 226.4 254.4 282.4 282.4 282.4 310.5 338.6

Poly-Unsaturated Fatty Acids
Systematic name 9,12-octadecadienoic 6,9,12-octadecatrienoic 9,12,15-octadecatrienoic 6,9,12,15-octadecatetraenoic5,8,11,14-eicosatetraenoic 5,8,11,14,17-eicosapentaenoic 4,7,10,13,16,19-docosahexaenoic Trivial name linoleic γ-linolenic α-linolenic stearidonic arachidonic EPA DHA Shorthand designation 18:2(n-6) 18:3(n-6) 18:3(n-3) 18:4(n-3) 20:4(n-6) 20:5(n-3) 22:6(n-3) Molecular wt. 280.4 278.4 278.4 276.4 304.5 302.5 328.6

Lipids
Storage (neutral) PL O TAG
O OC H2 C HC H2 C OC (CH 2) 16CH 3 O OC O(CH 2) 14CH 3

Membrane (polar) GL
CH=CH(CH 2)12CH 3 HO
O

O H2 C HC H2 C

C(CH2) 14CH3 O

CH N H O

O C(CH2) 22CH3

C(CH2) 7CH=CH(CH 2) 7CH3 O HC P O
-

(CH 2) 7CH=CH(CH 2)7 CH3

O

O

X

H2 C X

Phospholipids
Pi is in turn esterified to OH of a polar head group (X): e.g., serine, choline, ethanolamine, glycerol, or inositol. The 2 fatty acids tend to be non-identical.They may differ in length and/or the presence/absence of double bonds.

O O R1 C O H2C CH H2C O O C O P O− O X R2

glycerophospholipid

Sphingolipids
Sphingolipids are derivatives of the lipid sphingosine, which has a long hydrocarbon tail, and a polar domain that includes an amino group. The amino group of sphingosine can form an amide bond with a fatty acid carboxyl, to yield aceramide.
OH H2C H C OH CH CH HC (CH2 )12 CH3

H3NH N+
O C R

sphingosine ceramide

Sphingolipids
Sphingomyelin, a ceramide with a phosphocholine or phosphethanolamine head group, is a common constituent of plasma membranes A cerebroside is a sphingolipid (ceramide) with a monosaccharide such as glucose or galactose as polar head group.
CH2OH 3 CH
H2 OH H3C N+ O C H OH CH3 H H2 C O O P O H2C− O

O

OH H C H
C NH C OH CH CH HC

H H

H phosphocholine H2C OH

CH

sphingosine
O
O

NH

CH

C

HC

cerebroside with Sphingomyelin β-galactose head group

fatty acid

R R

(CH2 ) (CH2 )12 12 CH CH3 3

Attributes of Food Lipids
Three major functions in foods
– –

Energy and health Influence food flavors
free fatty acids contribute flavors lipids act assolvents for carrying hydrophobic flavors and aromas (and nutrients)

–

Texture
Solid vs liquid Emulsions

Attributes determined by types and positions of fatty acids on glycerol backbone

90 mole % of fatty acid groups 80 70 60 50 40 30 20 10 0

sn-1 sn-2 sn-3 all

Plant Triglycerides
Cocoa butter
–~

equal 16:0, 18:0, 18:1 – sn-2 primarily unsat’d (U) – sn-1,3 mostly sat’d (S)...