Food Lipids
Lipids
Lipids are non-polar (hydrophobic) compounds, soluble in organic solvents.
Fatty acids consist of a hydrocarbon chain with a carboxylic acid at one end
Non-Polar Polar
Saturated Fatty Acids
Mono-Unsaturated Fatty Acids
Sphingolipids
Sphingomyelin
Cocoa butter
Coconut oil
– Soybean oil similar
Cocoa Butter vs Animal Fat
bovine milk fat
cod oil
Properties
Crystallization
– entropic considerations
Melt (liquid)
crystal (solid)
Melting Point
Melting
Point Trends
Lipids
Ÿ"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"
Lipids are non-polar (hydrophobic) compounds, soluble in organic solvents.
Fatty acids consist of a hydrocarbon chain with a carboxylic acid at one end
Non-Polar Polar
Saturated Fatty Acids
Systematic name | Trivial name | Shorthand designation | Molecular wt. |
---|---|---|---|
butanoic | butyric | 4:00 | 88,1 |
pentanoic | valeric | 5:00 | |
hexanoic | caproic | 6:00 | 116,1 |
octanoic | caprylic | 8:00 | 144,2 |
nonanoic | pelargonic | 9:00 | 158,2 |
decanoic | capric | 10:00 | 172,3 |
dodecanoic | lauric | 12:00 | 200,3 |
tetradecanoic | myristic | 14:00 | 228,4 |
hexadecanoic | palmitic | 16:00 | 256,4 |
heptadecanoic | margaric (daturic) | 17:00 | 270,4 |
octadecanoic | stearic | 18:00 | 284,4 |
eicosanoic | arachidic | 20:00 | 312,5 |
docosanoic | behenic | 22:00 | 340,5 |
Mono-Unsaturated Fatty Acids
Systematic name | Trivial name | Shorthand designation | Molecular wt. |
---|---|---|---|
cis-9-tetradecenoic | myristoleic | 14:1(n-5) | 226.4 |
cis-9-hexadecenoic | palmitoleic | 16:1(n-7) | 254.4 |
cis-9-octadecenoic | oleic | 18:1(n-9) | 282.4 |
tr-9-octadecenoic | elaidic | tr18:1(n-9) | 282.4 |
cis-11-octadecenoic | vaccenic (asclepic) | 18:1(n-7) | 282.4 |
cis-11-eicosenoic | gondoic | 20:1(n-9) | 310.5 |
cis-13-docosenoic | erucic | 22:1(n-9) | 338.6 |
Systematic name | Trivial name | Shorthand designation | Molecular wt. |
---|---|---|---|
9,12-octadecadienoic | linoleic | 18:2(n-6) | 280.4 |
6,9,12-octadecatrienoic | γ-linolenic | 18:3(n-6) | 278.4 |
9,12,15-octadecatrienoic | α-linolenic | 18:3(n-3) | 278.4 |
6,9,12,15-octadecatetraenoic | stearidonic | 18:4(n-3) | 276.4 |
5,8,11,14-eicosatetraenoic | arachidonic | 20:4(n-6) | 304.5 |
5,8,11,14,17-eicosapentaenoic | EPA | 20:5(n-3) | 302.5 |
4,7,10,13,16,19-docosahexaenoic | DHA | 22:6(n-3) | 328.6 |
Phospholipids
ŸPi is in turn esterified
to OH of a polar head group (X):
e.g., serine, choline,ethanolamine, glycerol, orinositol.
ŸThe 2 fatty acids tendto be non-identical. They may differ in length and/or the presence/absence
of doublebonds.
- ŸSphingolipids are derivatives of the lipid sphingosine, which has a long hydrocarbon tail, and a polar domain that includes an amino group.
- ŸThe amino group of sphingosine can form an amide bond with a fatty acid carboxyl, to yield a ceramide.
Sphingomyelin
Ÿ Sphingomyelin, a ceramide with a phosphocholine or phosphethanolamine head group, is a common constituent of plasma membranes
Ÿ
A cerebroside is a sphingolipid (ceramide)with
amonosaccharide such as glucose or galactose
as
polar head group.
Attributes of Food Lipids
ŸThree major functions in foods
–Energy and health
–Influence food flavors
Ÿfree fatty acids contribute flavors
Ÿlipids act as solvents for
carrying hydrophobic
flavors and aromas
(and nutrients)
–Texture
ŸSolid vs liquid
ŸEmulsions
Attributes determined by types and positions of
fatty acids
on glycerol backbone
Plant Triglycerides
Ÿ
–
Coconut,
palm oil richer in 8:0-16:0
–
~ equal 16:0, 18:0, 18:1
–sn-2 primarily unsat’d (U)
–sn-1,3 mostly sat’d (S)
Coconut oil
–80% of triacylglycerols are trisaturated
ŸLauric at sn-2
ŸOctanoic at sn-3
ŸMyristic or palmitic at sn-1
ŸPeanut Oil
–
~40% oleic; 40%linoleic
–sn-2 largely unsat’d
– Soybean oil similar
Olive Oil
–~75% oleic
–sn-2 99% unsat’d
–homogeneous
Animal Triglycerides
Ÿ Beef Fat (tallow)
Cocoa Butter vs Animal Fat
ŸCompare cocoa butter vs tallow (beef fat)Ÿ
–fatty acid composition quite similar
roughly equal C16:0, C18:0, C18:1
cocoa butter tallow
Cocoa butter homogeneous: melts sharply at body temp; Tallow heterogeneous:
solid/liquid over wide temp range
Animal Triglycerides
cod oil
ŸMilk Fat - Large number of short-chain
fatty acids
Marine Oils
– affects cheese flavor – Long-chain unsaturated fatty acids
– causes milk rancidity
Summary of Fatty Acid Profiles
ŸPlant fats/oils:
–sn-2 largely unsaturated fatty acid (C18:1 & C18:2)
–some plant oils
contain high unsaturated fatty acid contents (peanut, soybean, olive, Canola)
–other plant oils
significantly saturated
(cocoa butter)
–coconut and palm oil
primarily saturated— rich in C8:0- C16:0
ŸAnimal fats/oils:
–broader range of fatty acids/triglycerides found
- milk fat (short chains) vs fish oils (long, polyunsat’d)
–sn-2 often saturated, greater
variation in positions
Crystallization
ŸCrystallization/Melting is balance
- favor increased molecular motion
– attractive intermolecular interactions
- favor packing molecules close together
Melt (liquid)
crystal (solid)
Melting Point
ŸLonger chain fatty acids pack better than shorter chains
– M.P.long > M.P.short
ŸSaturated fatty acids pack better than unsaturated
Ÿ
Trans fatty acids pack better than cis
–M.Ptrans > M.P.cis
–hydrogenation
increases M.P.
Fatty A cid | Comm on N ame | M.P |
---|---|---|
8:00 | Caprylic acid | 16ºC |
16:00 | Palmitic acid | 63ºC |
18:00 | Stearic acid | 69ºC |
20:00 | Arachidic acid | 75ºC |
18:1Δ9 (cis) | Oleic acid | 13ºC |
18:2Δ9,12 (ci s) | Linoleic acid | -5ºC |
18:3Δ9,12,15 (ci s) | Linolenic acid | -11ºC |
18:1Δ9 (trans) | Elaidic acid | 46ºC |
18:2Δ9,12 (trans) | Linolelaidic acid | 28ºC |
Surfactants (Emulsifiers)
ŸSurfactants
are molecules that lower the surface tension
–Part of molecule interacts favorably with water
ŸPolar
or charged (hydrophilic)
–Part of molecule interacts unfavorably with water
ŸHydrophobic
Amphiphilic
Lipid Surfactants
ŸFatty Acids
Monoglycerides and Diglycerides
Phospholipids
Synthetic Emulsifiers
Tweens
Surfactants
ŸMediates interactions between
hydrophobic and hydrophilic phases
Hydrophilic HeadHydrophobic Interior
Hydrophilic Head
ŸDensity differences between droplets
and continuous phase cause droplets to
rise or fall
–In oil-in-water emulsions, droplets
typically rise
ŸCreaming rate depends on
–droplet size
Ÿdecrease drop size (e.g. homogenized milk)
–viscosity of continuous phase
Ÿadd macromolecules
(termed stabilizers) to increase viscosity