Term
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Definition
Non-polar, water insoluble
Contain carbon, hydrogen, and a little
oxygen
Commonly called fats and oils
depending on whether they are solid
or liquid at room temperature |
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Term
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Definition
Mono, di, and triglycerides
Consist of a glycerol backbone (3
carbon polyhydric alcohol) and one or
more fatty acid attached to the
glycerol with ester linkages |
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Term
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Definition
Contain an acid group at one end
Contain an even number of carbons
Range form 2-20 carbons
Carbon 1 is the COOH |
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Term
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Definition
have no double
bonds (contain all the hydrogen they can
hold) |
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Term
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Definition
contain one or
more double bonds – the more double
bonds the lower the melting point |
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Term
| Types of Double Bonds-Trans |
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Definition
hydrogen atoms attached on
opposite sides of the double bond |
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Term
| Types of Double Bonds- Cis |
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Definition
hydrogen atoms attached on the
same side of the double bond |
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Term
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Definition
can combine with a mixture
of different fatty acids – lipid materials
commonly contain a mixture of fatty
acylglycerols as a result
Also see different fatty acids within
each acylglycerol |
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Term
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Definition
Each acylglycerol has an individual
melting point affected by:
1. Chain length (number of carbons)
2. Number of double bonds (also known
as the degree of saturation)
3. Types of double bonds (cis vs trans)
Melting point -
Chain length
• As chain length (number of carbons) increases,
melting point increases
• ie as chain length increases, the fat can become
more solid
Number of double bonds/degree of
saturation
• As number of double bonds increases, melting
point decreases
• ie the more double bonds present, the lower the
melting point
• Polyunsaturated fatty acids on triacylglerols will
tend to make them liquid at room temperature
Melting point, con’t
Types of Double bonds
• Cis – have lower melting points than
trans because cis-configurations puts a
“kink” in the chain, therefore there are
less Van der Waals interactions
• ie cis tend to be oils, trans tend to be solid at
room temperature |
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Term
Melting Point and Plasticity
Range |
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Definition
Due to the mixed nature of lipids, a fat does
not have a discrete melting point
temperature
Rather fats will have a melting point range
where it will change from solid to liquid
Cocoa butter has the smallest melting point
range – liquefies very quickly
For the same reason, fats have a plasticity
range – a range of temperature over which
they are moldable |
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Term
Lipids –
Physical Properties |
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Definition
Number of fatty acids attached to
the glycerol backbone
Mono, di, tri
Configuration of the triglycerides
Tuning fork vs chair
Crystallinity
Exhibits polymorphism (more than one
crystal form) – alpha, beta, beta prime, and intermediate |
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Term
| Crystal Form in Solid Lipids |
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Definition
Alpha – first formed
- Fine, unstable, quickly melt and recrystallize as beta
prime if fat is agitated during recrystallizing
Beta prime –
-fairly stable, very fine (small), best form for baked
products for fine texture, if stored at warm
temperatures can recrystallize into intermediate form
Intermediate
– form under improper storage
conditions (too warm)
Larger, coarse, very stable, undesirable
Beta – form when fat Is melted and allowed to
recrystallize undisturbed
-very large, very coarse, very stable |
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Term
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Definition
Not all the material in solid fat is in crystal form
there is oily material which does not solidify due to the
mixed nature of triacylglycerols in the native lipid
This material makes the fat moldable (can be formed)
and contributes to is plastic nature (deformable)
The relative portion (ratio) of solid (crystalline)
material to oily (liquid) material in a fat is called the
solid fat index (SFI)
• The higher the SFI the harder the fat
• Example – cocoa butter is a very hard fat but melts
very quickly |
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Term
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Definition
Hydrogenation
Interesterification
Hydrolytic Rancidity
Oxidative Rancidity
Flavor Reversion
Smoke Point
Polymerization |
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Term
Lipid Chemical Reactions –
Hydrogenation |
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Definition
Hydrogenation
Oil under heat in the presence of hydrogen
gas using a nickel catalyst
• Eliminates double bond
• Makes the material more solid (increases melting
point)
• Can form some trans (health issue)
• Used to make margarines, vegetable shortenings,
and peanut butter homogenous
See handout for chemical equation |
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Term
Lipid Chemical Reactions –
Interesterification |
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Definition
Done to change the types of fatty acids on
the triglycerides (relocation and new
combinations)
• Randomized – done using melted fat so there is a
complete fat change
• Makes the plastic range of lard larger
• Decreases crystal sizes to make fat function better
• Directed – done on fats below the melting
temperature of the fat so only the amount of the
fat that is not crystalline will interesterify
• Raises the melting temperature of the fat
• Makes the fat more plastic (but not as much as
randomized interesterification does) |
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Term
Lipid Chemical Reactions –
Rancidity |
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Definition
Rancidity
Hydrolytic
• Involves hydrolysis of lipid, usually via
enzyme, but can also occur at high heats
(lipids used for frying)
Oxidative
• Chemical free radical reaction, involving
uptake of oxygen and production |
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Term
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Definition
At high temperatures (in fryers):
Lipid will be hydrolyzed yielding glycerol and
free fatty acids due to heat
• Free fatty acids contribute to oxidative rancidity
• Glycerol can undergo dehydration to acrolein
which is volatile and can cause the fat to smoke.
• Acrolein irritates the throat and eyes
• Increased glycerol levels result in lower smoke
points for this reason
During lipolysis, the triacylglycerol
molecule is split so that free fatty acids
are released
Free fatty acids can cause:
1. Off-flavors to develop if they are short-chain
(butyric, caproic, caprylic) via enzymes
2. Contribute to acclerated oxidative rancidity if the
free fatty acids are long-chain
Enzymatic rancidity can occur in butter
when lipases attack the butter fat
• Salt in butter inhibits the lipases |
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Term
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Definition
Oxidative Rancidity
Occurs in three stages:
1. Initiation – formation of free radicals (occurs on the Carbon
adjacent to the carbon involved in the double bond)
• Catalyzed by metals (Fe, Cu) light and heat
2. Propagation (autooxidation) – formation of peroxide free
radicals and hydroperoxide.
• Process will continue along with the formation of additional free
radicals and other compounds (ketones, aldehydes,
malonaldehyde) until termination occurs
• Requires oxygen to occur
3. Termination – where the oxidative reaction is terminated by
the reaction of free radicals or peroxides with compounds
which do not involve the formation of new free radicals from
lipids
1. Antioxidants – BHA, BHT
2. Sequestrants (chelating agents) – EDTA, ascorbic acid, citric |
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Term
Oxidative Rancidity -
Prevention |
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Definition
Ways to prevent oxidative rancidity
Use of antioxidants
• Provide an H+ molecule which returns the free radical to the
original fatty acid or combines with the peroxide molecule,
stabilizing it
• Examples – TBHQ, BHT, BHA, PG
• Natural antioxidants – tocopherols, tocotrioenols, polyphenols,
caratenoids
Use of sequestrants
• Chelating agents which bind to the metals that facilitate the
free radical formation
• Examples – EDTA, ascorbyl palmitate, ascorbic acid, citric acid
Keep in low temp/low light
• Proper storage temp and foil packages
Removal of O2 from the package |
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Term
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Definition
Oxidation of linoleic (18:2) and linolenic
(18:3) fatty acids, specifically
Can occur in only a small amount of O2
Common in soy oils but can also happen in
rapeseed or fish oils
Results in fishy or beany flavors
Heat reversion – can also happen due to
high heat
Research has shown this to be a problem in
industry but no solutions |
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Term
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Definition
Smoke point – the temperature at which fats or oils
begin to emit smoke (~374°F) or higher
This is the temperature at which the fat degrades –
lipolysis to glycerol and free fatty acids occurs
Continued heating can lead to dehydration of the
glycerol molecule and the formation of acrolein
Smoke point not a discrete temperature – over
continued cooking time, smoking point drops gradually
Cooking oil must be changed frequently
Shortenings and other monoglycerides – have only
one fatty acid to be removed before free glycerol is
left – therefore these fats are not suitable for frying
(acrolein forms quickly) |
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Term
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Definition
Continued heating causes release of
2 water molecules from glycerol
Formation of an unusual aldehyde:
acrolein |
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Term
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Definition
“The grunge on the wall behind the
stove”
Formation of dimers and trimers of
fatty acids containing at least one
double bond – form due to intense
heat
Formation of larger lipid molecules
results in increasing viscosity,
foaming, and darkening of frying oils |
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Term
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Definition
Acrylamide
Carcinogen formed in starchy fried
foods and baked products |
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Term
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Definition
Color – can contribute yellow to brown
Flavor
Richness (mouth feel), short chain fatty acids
(butyric), aldehydes, ketones, other unique
flavors and odors
Texture – flakiness, aeration
Tenderness (including in baked products as
well as meats)
Emulsification (mayo, sauces)
Cooking medium (frying) |
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Term
Functional Role -
Tenderness |
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Definition
---Due to interference with the development of
proteins (such as gluten formation in baked
products)
---Related to shortening power: the ability of
the fat to cover protein in batters or doughs
to prevent contact with water
-Shortening power is increased by the
presence of double bonds in fatty acids,
fluidity of the lipid, and plasticity
• Note – lard and shortening have higher shortening
power than margarine or butter (margarine and |
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Term
Functional Role -
Emulsification |
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Definition
Cake batters – emulsification of fat and milk
within the batter – stable emulsifications
result in fine-textured products
Lipids – usually the dispersed phase (as in
salad dressings) but can be the continuous
phase (as in butter or margarine)
Mono and diglycerides act as emulsifiers
Phospholipids (lecithin) act as emulsifiers
Hydrophyllic and hydrophobic ends form
micelles |
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Term
Functional Role –
Cooking Medium |
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Definition
Very effective cooking medium – can heat well above
100°C
Dehydrates foods as well – loss of moisture from
foods during deep fat frying
Best lipids for frying do not have water/protein (butter
or margarine) or mono or diglycerides (which have
lower smoke points)
Best lipids for frying:
Peanut, cottonseed, soy, canola, or safflower
Olive oil is not a good medium for frying |
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Term
Lipids –
Food Applications |
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Definition
Frying – dehydration process results
in loss of water at food surface and
prevents quick burning
Heat must be at the right temperature
to get proper texture
Salad dressings
Cold – oil in dressings
Hot – fat in sauces (hollandaise type)
Cakes – creaming creates air pockets for leavening of
cakes
Fats are suitable; oils are not
• Shortening best suited, margarine next, then butter
• Example – high-ratio shortenings specially formulated
for cake baking
Pastry – flakiness desired – layers of dough separated
by layers of solid
Oils are too liquid to produce flakiness
Breads – flakiness in biscuits, tenderness in muffins,
yeast breads (properties depends on physical state at
mixing) |
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Term
| Lipids –Production -- Extraction |
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Definition
-Rendering – heating with or without steam
to separate out lipid portion from animal
tissues
• Examples – lard, tallow, suet
-Cold pressing – mechanical means of
expressing oil from vegetable materials
• The best oils are cold pressed but it’s not very
efficient. 2nd pressing is lower quality
-Hot pressing – (used for seeds). Done at
70°C with steam
• Problem – also extracts some gums, off-flavors,
and free fatty acids |
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Term
| Lipids –Production --Refining |
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Definition
Removal of gums (degumming), lipoproteins,
lecithins, ketones & aldehydes (deodorizing
and bleaching), free fatty acids
(neutralization) |
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Term
| Lipids –Production --Winterizing |
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Definition
Chilling of oils to remove high MP
triacylglycerols that make oils solid at
refrigerated temperatures
• Used often by salad dressing companies |
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Term
| Lipids –Production-- Fractionation |
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Definition
(done on tropical oils)
Oils are separated under controlled
temperature to remove the fatty acids that
crystallize at higher melting points
• These have high levels of saturated fats but no
trans fat
• These high melting point saturated fats are then
added to other oils to achieve the desired physical
properties for food manufacturing without using
shortenings or other hydrogenated fats that
contain trans-fats |
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Term
Lipids –
Production--Crystallization |
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Definition
Tempering to produce Beta prime crystals –
done at controlled temperatures with
agitation
In chocolate – beta prime crystals are
desirable. Beta crystals, on the other hand,
occur when chocolate is stored improperly
(at elevated temp for long periods of time)
and results in white “bloom” on the surface
along with large, coarse crystals |
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Term
Lipids –
Sources- Spreads – |
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Definition
butter or margarine (stick, tub,
whipped, diet)
Whipped and diet have more air and water
added to lower calories
Tub version have more polyun |
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Term
Lipids –
Sources- Shortenings/lard |
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Definition
processed by
hydrogenation or interesterification to
produce desired plasticity, deodorized, color
& flavoring may be added to some
shortenings |
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Term
Lipids –
Substitutions.. considerations |
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Definition
Consider:
Amount of fat in the product – ie
butter and margarine are only 80% fat
Melting point – so fat has similar
function for texture
Consider color, other flavors
Shortening power – could get too
tender a product or one which will not
flake
*solid fat produces more flakiness |
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Term
Lipids –
Substitution.. types of subsitutes |
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Definition
---Protein-based
• Simplesse – made of milk proteins and egg white
proteins and water
-• Tiny particles that move like fat in mouth
-• Cannot be heated
-• 1.3 cal.g
-• GRAS
--- Starch-based
• Corn starch, pectin, gums & non-fat dry milk, oats (Beta
glucan), rice, microcrystalline cellulose, other gums
-• Stellar – made from cornstarch – used in cheese
spreads and frostings
-• Oatrim – used in salad dressings, milk-containing
beverages, meats, cheese spreads, and high fiber
breads
Types of substitutes:
---Sucrose polyesters (sucrose with attached
fatty acids) –– the resulting molecule is not
digestible
• Olestra (approved in 1996)
• At high levels may cause diarrhea/flatulence –
2003 FDA allowed warning labels to be dropped
---Structured lipids
• Interesterification of medium chain triglycerides to
get molecules not stored in adipose (smaller
carbon unit fatty acid replacements that are not
utilized effectively by the body – yielding only 5
cal/g)
• Metabolized to a limited extent in some lipids |
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