Lipids

Fats= lipids

M. Kennedy

Fats

●Fats: also called lipids
●Carbohydrates have a ratio of CH2O, fats do not have a

ratio.

●Fats are mostly long chains of carbon and hydrogen with

a carboxyl (COOH) group at one end.

●Fats are not polymers (made of subunits) while complex

carbohydrates are polymers of sugars.

Functions of fats in food preparation

❖ Transfer heat- fats get hotter than water. Additionally, fats continue to heat,

while water will not get any hotter once it boils.

❖ Tenderize- used in baked goods to shorten the length of gluten molecules.

Gluten can form long chains that toughen baked goods. The flour- fat ratio can
also determine flakiness in baked goods such as biscuits and pie crust. Also
the fat content in meats help tenderize cuts of meat (marbling)

❖ Aerate- fats help trap air bubbles which will make lighter baked goods.
❖ Enhance flavor- different fats have different flavors, also in meats fats provide

flavor

❖ Lubrication- prevents food from sticking to pots and pans
❖ Serve as liquids in an emulsion

https://www.youtube.com/watch?v=Vez4zVrnEXw

Properties of fats

● The properties of fats depend on the length of carbon chain and the

presence or absence of double bonds.

● Also contributing to properties of fats is how many double bonds are

present within the carbon chain. Fats in our body are in three
categories, phospholipids (cell membranes), sterols (cholesterol is one
of these) and triglycerides.

● The most common fat in our food are the triglycerides.
● In our bodies, fats provide essential components for body functions

including hormones and nervous functions.

https://www.youtube.com/watch?v=5BBYBRWzsLA

●Phospholipids- these make up the structure of cell membranes

○ The phosphate group is attached to two fatty acids, the phosphate

group is polar, and the fatty acids are nonpolar.

○ Phospholipids can be used as emulsifiers

●Sterols: these are complex ring structures, with various functions

including the building blocks for hormones
○ Cholesterol is the best known, and is only found in animal tissues

The glycerides

● Triglycerides are a glycerol molecule attached to three fatty acids. The three

fatty acids can be different.
○ The properties of the triglycerides depends on the different fatty acids that form

them

● Fatty acids have a carboxyl group, and chains of carbon and hydrogen,

anywhere between 4 and 24 carbons long.

● Triglycerides are insoluble in water
● There are also monoglycerides and diglycerides, with one or two fatty acids.

Because of the hydroxides on the glycerol, these are partially soluble in water

Fatty acids: The building blocks of triglycerides

●Fatty acids placed in two groups based on the presence or

absence of double bonds between the carbons.

●Saturated fatty acids have all single bonds between the

carbons and are described as saturated with hydrogen.

● Saturated fatty acids tend to be solid at room temperature

because they are straight chains and can pack together
tightly.

●Saturated fatty acids are more common in animal tissues

Fatty acids: the building blocks of triglycerides

●Unsaturated fatty acids have at least one double bond between

carbons. A polyunsaturated fatty acid has many double bonds
between the carbons.

● The double bonds cause the chain to bend, and therefore they

cannot pack tightly together. Unsaturated fatty acids tend to be
liquid at room temperature.

●Unsaturated fatty acids are more common in plants, and are

called oils

Essential fatty acids (must be in our diet)

● The Omega-3 and Omega-6 fatty acids are essential (must be in our diet),

these are present in marine life as well as in plants such as avocados.
These are essential for heart and nerve functions.

● Recall that when we describe nutrients as essential, it means it must be in

our diet because the human body does not have the ability to make the
nutrient.

● An Omega -3 fatty acid has the double bond three carbons from the end of

the fatty acid that does not have the carboxyl group attached. Likewise, the
Omega-6 fatty acids has a double bond six carbons from the end without
the carboxyl group

● The physical and chemical properties of the fats depend on how many

carbons are in the chain (chain length) and how many double bonds exist.

● Hydrogenation: chemically changes unsaturated fatty acids to saturated

fatty acids, this is often done to make oils solid, examples are margarine
and vegetable shortening (Crisco). This also increases shelf life, greater
stability than lard, lower production cost than lard, and has a faster
dissolving and setting properties in chocolate production

● Rancidity: Fats can become rancid (go bad) by oxidation. The double

bonds react with oxygen; rancid fat smells bad. This is more likely in
unsaturated fats. To prevent rancidity, limit oxygen.

●Physical properties include melting range and smoke

point.

●Fats have a melting range because the fats in our

foods are mixtures of fats, and each fatty acid chain
would have a different point depending on the length
of the carbon chain. Fatty acids with a longer carbon
chain will have a higher melting point than a shorter
carbon chain.

Physical characteristics of fats

● Melting point and solidification points:

○ Melting point is the temperature that all fatty acids are liquid
○ Solidification point is the temperature that all fatty acids are solid

● Because the fats we use are mixtures, these tend to have a range of

temperatures.

● The solidification point is lower than the melting points.
● Vegetable oils can become cloudy when refrigerated, some of the fatty acids have

solidified. For commercial use, these oils are chilled and then filtered to remove
the solid fats. This is why commercial salad dressing pours more easily than
homemade

●Smoke point is the temperature at which a fat begins

to smoke, this is considered when choosing which fat
to use. Besides producing smoke, the fat is breaking
down and produces a burned taste.

Re-using fats

Fats can be reused if you are frying things in the fat. They can be
heated, cooled, and reheated if necessary.

They will break down over time and need to be replace.

They also take on flavors from foods you fry in them. (don’t fry onion
rings or fish in oil you will use for French fries, unless you like fishy or
oniony fries)

The temperature at which a fat is used is important, high temperatures
cause the fats to break down sooner.

Choosing a fat

● Choosing a fat has many considerations such as
● What is the desired characteristic of the final

product?

○ Tender vs crispy vs flaky

● What temperature will be used, different fats have

different smoke points, and will yield different
results at different temperatures

● Different fats also have different flavors or some are

easier to work with, both of these are considered when
choosing the fat to use

Health

★ Which fat to use also relies on health issues.
★ Unsaturated fats are described as healthier than

saturated fats.

★ Lard has more monounsaturated fats than butter, is this

healthier?

★ Diets high in fat are reported to contribute to heart

disease,
○Diets containing less saturated fats is recommended
■Eating fish more than beef

■Using oil instead of butter

Health: Trans-fats

★

Trans-fats are unsaturated fats, with a particular arrangement of
hydrogen atoms across a double bond.

★

This configuration that has shown to impact cholesterol levels and is
described as the unhealthiest type of fat.

★

Most trans-fats occur during hydrogenation, and are more common in
partially hydrogenated foods.

★

Trans-fats are used because of the properties and cost the fats provide.

How to make a pie crust: Allrecipes

● https://www.youtube.com/watch?v=2QeKExMgyHQ