Transcript Fats - Marblehead High School

Fats
Foods that are mostly fat
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Trends
Total fat consumption in 2000 was 82.3 lb per
capita. Total fat consumption in 2004 was 87.5
lb per
Between 2000 and 2004, salad, cooking, and
other edible oils has increased from 34.8 to 40.8
lb per capita. Butter and margarine
consumption has decreased from 12 lb to 9.9 lb
per
In 2004, soybean oil accounted for 87% of all oil
production in the US.
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Sources
Animal-beef tallow, butter fat (milk), lard from
pigs
Vegetable-olives, palm berries and palm
kernels, cottonseeds, soybeans, rapeseed
(canola oil), corn, sunflower seeds, safflower
seeds, coconuts, peanuts, cocoa beans,
walnuts, macadamia nuts, rice bran
Fish oils-decosahexanoic acid (DHA) and
eicosapenanoic acid (EPA) are omega-3
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Processing
Crude fat is extracted under pressure,
extracted by solvents, or rendered from fat
tissue by heating
Impurities, color, and odor are removed
Fats may be further treated to promote
specific qualities through hydrogenation,
winterizing, or plasticizing
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Other Processes
Winterization-chilling oils to remove crystals
Hydrogenation-unsaturated fatty acids are
exposed to hydrogen gas in the presence of a
catalyst. Double bonds may migrate and
change from cis to trans configuration.
Interesterification or rearrangement-heating fat
with a catalyst rearranges fatty acids on the
glycerol molecule making fat more
heterogeneous with wider range of melting
points. Used to give lard a wider plastic range
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Other Processes Continued
Acetylation-acetic acid replaces a fatty
acid making a fat with lower melting point
and the ability to stay in alpha form. Used
as coating agent on raisins, meat, etc
Superglycerinated-emulsifier (often
glycerol monstearate) added to give a
wider range of melting points, more plastic
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Deterioration
Hydrolytic rancidity-breaking of chemical bonds
with the addition of water. Lipase may cause
the breaking of bonds. The release of short
chain fatty acids give off flavors and odors
Oxidative rancidity-reaction is initiated with the
loss of a H from a carbon located next to a
double bond. Carbon atom becomes a free
radical which is very reactive and combines with
oxygen to form a peroxide free radical which
pulls H from another carbon and continues the
chain reaction. These peroxide free radicals
break into smaller volatile compounds which
give the odor of rancid fat
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Deterioration Continued
Flavor reversion-oxidative deterioriation
which involves changes in fat due to
ultraviolet or visible light or heat in the
presence of oxygen catalyzed by metals.
Off flavors develop that may be called
fishy, beany, or warmed over. Linolenic
acid is especially susceptible to flavor
reversion
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Antioxidants
Butylated hydroxyanisole (BHA)
Butylated hydroxytoluene (BHT)
Tertiary butyl hydroquinone (TBHQ)
Propyl gallate
Natural antioxidants like vitamin E or
tocopherols, vitamin A or beta-carotene, or
vitamin C
Rancidity may also be controlled by cold
temperature and the exclusion of light, moisture,
and air
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Properties of Fat
Solubility-fats are insoluble in water and soluble
in organic compounds
Appearance-natural pigments, sheen, browning
Satiety-sense of fullness
Flavor-used for flavor they impart, olive oil,
butter, peanut oil, bacon fat
Texture-flaky pastries, smooth ice cream, crispy
fried foods
Shortening power-tenderness in baked products
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Melting point determines whether a fat is liquid,
plastic, or solid at room temperature.
1. Food fats are neutral fats and phospholipids.
The fatty acid attached to the glycerol molecule
gives a fat it’s characteristics. As fats cool,
molecules slow down, align and crystallize.
The melting point of a fat is a measure of the
strength of bonding forces between fatty acid
radical and crystals. A higher attraction means
less slowing is needed giving a higher melting
point.
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Attraction between molecules or
melting point depends on
1. Saturation
versus
Unsaturation
•
CH3CH2CH2COOH
CH3CH=CHCOOH
•
High
Low
2. Length of chain
•
Long Saturated
Short Saturated
•
Low
High
3. Cis or trans configuration
•
Low High
4. Crystalline structure-polymorphism
•
Melting point increases with crystal size
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Polymorphism-Variation in
Crystalline Form
1. Alpha-small, transparent crystals, seen
in frozen desserts and candies
2. Beta prime-delicate needles, seen in
shortening
3. Intermediate-3 to 5 microns long
4. Beta-25 to 100 microns long, seen in
lard
5. Alpha crystals have low melting point
which increases with beta crystals
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Plasticity-fat has two phases
1. Solid-crystals of fat
2. Liquid-oil surrounds crystals
3. Plastic fats allow for the incorporation of
air in the mixing or beating process, such
as creaming shortening with sugar when
making cakes
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Heat Transfer
1. Fat conducts heat well, gives high
temperature without boiling, browns
foods.
2. Smoke point-temperature fat begins to
smoke, decomposition occurs
3. Acrolein-decomposition product which is
a derivative of glycerol is irritating to the
eyes and mucus membranes
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Choosing a Frying Fat
High smoke point
Bland flavor, light color
Resistance to rancidity
Uniformity of quality
Stability for long term use
Gives excellent taste, texture, and
appearance
7. Ease of use-form and packaging
1.
2.
3.
4.
5.
6.
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Care of Fat
1.
2.
3.
4.
Use appropriate temperature
Adequate turnover
Filter fat daily
Remove food particles, as they can
lower the smoke point and cause
darkening with reduces the appearance
and flavor of the product
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Fat Absorption
1.
2.
3.
4.
High even temperature-less absorption
Shorter time-less absorption
Increased surface area-more absorption
Character and composition of food
a.
b.
c.
d.
High fat + sugar-increases absorption
Egg-increases absorption
Stiffer doughs-decrease absorption
Softer doughs-increase absorption
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Low-Fat Cooking
1. Use lean, trimmed meats and less meat
2. Use roasting or broiling cooking techniques
3. Reduce the amount of fat used in the recipe, may
replace with fruit puree in baking
4. Use non-stick pans
5. Use vegetable oil spray, chicken broth or water to
saute foods
6. Use skim milk instead of whole milk or cream
7. Use egg whites
8. Use low-fat cheeses, salad dressings, and table
spreads
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Fat Substitutes

Fat-Based Replacements
1. Salatrim-structured triglyceride with long and
medium chain fatty acids where breakdown is
decreased in the intestine
2. Caprenin-structured triglyceride of capric,
caprylic, and behenic acid which are
inefficiently absorbed from the intestine
3. Olestra-hybrid fat and CHO substitute.
Sucrose polyester-sucrose molecule with 6 to
8 medium chain fatty acids attached. Molecule
cannot be digested or absorbed
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Fat Substitutes Continued

Protein-Based Replacement
1. Simplesse-microparticulated egg white and milk
protein
 Carbohydrate-Based Replacements
1. Oatrim-maltodextrin and beta-glucan
2. N-oil-hydrolyzed tapioca starch
3. N-lite-starch, gums, and non-fat dried milk
4. Stellar-cornstarch
5. Slendid-pectin base
6. Maltrin-maltodextrin from corn starch
7. Rice*Trim 3 Complete-rice
8. STA-SLIM-potato starch
9. Avicel cellulose gel-a microcrystalling CHO derivative
10. Polydextrose-water soluble fiber
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Emulsions
1. Dispersion of one liquid in another where the
two liquids are immiscible
2. Three phases
•
Dispersed phase-suspended droplets
•
Continuous phase-solution in which
droplets are dispersed
•
Emulsifier-a substance with affinity for both
liquids but it is unequal
•
a. Prevents coalescence of droplets
•
b. Decreases surface tension
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Types of Emulsions
1. Temporary-lowers surface tension but does
not prevent coalescence. Example: Italian
dressing or home-made French dressing
2. Semipermanent –stabilizers used to decrease
separation. Example: commercial French
dressing
3. Permanent-lowers surface tension and
prevents coalescence. Example: mayonnaise
4. Emulsifying agent-phospholipids, lecithin,
phosphatidyl ethanolamine from gelatin, egg
whites, egg yolks, casein, whey, cellulose
derivatives, spices, vegetable gums, and
starch pastes
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Power Point Author
• Dr. Jane Ross
• The University of Vermont
• Foods and Nutrition
• Basic Concepts of Food
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