food science and tech exam 1 part 3

Fats are good…

IN MODERATION!!!

The Challenges of Fat

Substitutes

Need to compensate for

 Flavor

 Texture

 Stabilization

• Olestra is closest to fat in those aspects

BUT…

 Nutritional loss

 Loss of lipid soluble vitamins and minerals

 Laxative effects

Non‐digestible fat‐like compounds

OLESTRA: sucrose with fatty acids attached

 Can trap and eliminate from the human

body

 Stable at high temperature: cooking

 Approved for use as a fat replacer in

savory snack food items, e.g. potato and

corn chips

biopolymers: fat substitutes

try to use large polymers

that trap water and can give “mouth feel”

similar to fats

 Protein based (whey protein)

 Carbohydrates based (most widely used)

why are fat substitutes important?

Weight loss: obesity

problem

 Medical concerns

 Cholesterol & coronary

heart disease

Antioxidants

vitamin C & E

Hydrogenation

Remove or reduce unsaturations

 Control functionality (shortening)

 Disadvantage: TRANS fatty acid

How to Prevent/Control

Rancidity

Additives

 BHA

 BHT

light

can initiate and accelerate

lipid oxidation and rancidity

Unsaturation degrees

The more unsaturations, the

higher the susceptibility to

rancidity

lipid oxidation

The important lipids involved in oxidation are

the unsaturated fatty acid moieties: oleic,

linoleic, and linolenic.

• The rate of oxidation of these fatty acids

increases with the degree of unsaturation.

Oleic – 1 times rate

Linoleic – 10 times

Linolenic – 100 times

rancidity: oxidative

addition of oxygen to fat. resulting in small chain compounds

rancidity: hydrolytic- enzymatic

Resulting in short chain fatty acids

(Lipase ‐ butter)

 Control: Heat Deactivation, handling

and storage

rancidity

off flavors and odors from

the breakdown of lipids

Disadvantage of Hydrogenation: trans fatty acid formation

Arise when polyunsaturated oils are

hydrogenated

 advantage: control consistency and oxidation

of fats

 disadvantage: increase low density lipoprotein

(LDL)

• found in margarines, shortenings, baked

goods

hydrogenation

used to

add hydrogen to some of the double

bonds and obtain the right “plastic

properties”

Hydrogenated Oils

Fats are solid, oils are liquid

• Spreads can be made semi‐solid

 Having the right combination of

saturations and unsaturations

Post-processing and shelf stability

shear

sensitivity, tackiness, migration, dispersion, and

stability (physical, chemical, microbiological)

Processing behavior:

heat stability, viscosity,

crystallization, aeration

Thermal properties

melting characteristics, heat

transfer coefficient, solid fat index, softening

point, polymorphism

Rheological properties of foods

viscosity, plasticity, yield

stress, thixotropy, spreadability, lubricity,

hardness, stringiness

Chemical

Properties of

Fat or Oil

Length of carbon chain

Degree of unsaturation

Cis-trans configuration

Crystal state of fat

vegetable oils

Mostly present in seeds

 Varied composition of different plants

 Usually rich in unsaturated 16C and 18C fatty

acids

dairy products:

High in C4 – C10 fatty acids

 Most saturated

land animals

Solid or semi‐solid at room temperature

 Mostly saturated 16C and 18C (16:0, 18:0)

 Also some monounsaturated (oleic acid: 18:1)

 Chicken also contains 18:2 (linoleic acid, ω‐6)

Fish / aquatic (marine) foods:

High levels of polyunsaturated fatty acids

(PUFA)

 Mainly 14C‐24C

 Good source of ω‐3 fatty acids

emulsion

a system containing two immiscible

liquids (or fluids), one dispersed in the other as tiny

droplets, Have a polar and a non‐polar end

 Each end soluble in one of those fluids

Lipid Functionality: Texture

Plastic Properties

 Melt over a range of temperature

 Each fat and oil has a characteristic

melting point, Combinations of different fats and

oils can be used to obtain desirable

texture characteristics, Fats also give a “moist” mouth feel, Carrier for

fat‐soluble

vitamins