Chapter 4 Flashcards
How fats and oils are usually characterized
Hydrolyzing all the ester bonds with a strong base and then analyzing the composition of the resulting mixture with Gas chromotography
How much free FAs are there in fat or oil
Less than 1 % with the exception of olive oil
Physical properties of fats and oils are determined by
Fatty acid composition
Relationship of FAs structure and melting points
increases with increasing chain length
decreases with increasing number of cis double bonds
increases with isomerization of cis double bonds to trans double bonds
Why coconut oil is the exception from the rule
Lipids from animal sources tend to be more saturated and are fats .
Lipids from plant sources tend to be more unsaturated and are oils .
Tropical oils such as coconut and palm are exceptions : They are
highly saturated but have relatively low melting points because the
fatty acids have short chain lengths
Lipids from fish sources are highly___
PUFAs
What is catalytic hydrogenation
A process of conversion of vegetable oils to fats by decreasing their degree of unsaturation (addition of H 2 across the double
bonds)
Risk of catalytic hydrogenation
Cis to trans isomerization
Hydrogenated fats have been widely used for
Hydrogenated fats have been widely used in the manufacture of
margarines and vegetable oil based shortenings
Now research show that trans fats are bad for cardiovascular disease, what industry have done with it
The fats & oils industry is now extensively using an alternative process
interesterification ) to convert liquid oils to solid
Advantages of hydrogenation
longer shelf life than oil or lard
greater stability and lower production costs than lard
faster dissolving and setting properties in chocolate production
Nutrition importance of fats and oils
Concentrated source of energy Source of essential fatty acids : linoleic acid, linolenic acid Precursors for membrane lipids and prostaglandins Carriers of fat soluble vitamins (A, D, E, Help regulate body temperature Protect vital organs from injury Participate in cell production Produce hormones and other secretions
Role of fats and oils in frying
Heat transfer agents : Frying oils can reach very high temperatures
200 o C).
Transfer of heat to the surface of a food immersed in the oil drives
off water as steam.
Both the high temperature and the loss of water are conditions that
promote the Maillard reaction
During frying, oil is absorbed by the food and contributes to the
sensory characteristics of the product (as well as its caloric content
What do fats do in backed goods
Lipids tenderize baked products
Fats shorten flour s protein strands , which cause chewiness and toughness
Aeration : Because lipids and air are both hydrophobic ; one of the
functions of fats in baking is to incorporate air bubbles , which expand
at baking temperatures and contribute to the volume and height of the
baked product.
Fat to flour ratio determines ___ of the baked good
Flakiness
Lipids with high melting point work best for ___
work best for biscuits, pies, and puff pastry
Oils can be used in ___ (baking)
mix batters for products like pancakes, muffins,
and waffles
Function of fats and oils in bread and salads
Lubricating agents : for foods such as bread and salads , usually in the
form of emulsions : oil in water (o/w) or water in oil (w/o).
Salad dressing is an o/w emulsion.
Butter is a w/o emulsion.
Much of the flavor of the food is due to
Much of the flavor in food is due to the addition of salt, sugar, and fats
Common lipids that season foods
Common lipids that season foods are butter, margarine, and mayonnaise
Fats ___ and ___ flavor compounds
Dissolve and disperse
Rating of the most flavorless oils
Cottonseed oil is one of the most flavorless oils, followed by vegetable shortening and soybean and canola
Other properties of fats and oils in products
Contributors to texture/mouthfeel
Contributors to feeling of satiety (feeling
What is plasticity and solid fat content
However, fats and oils are always composed of mixtures of
triglycerides , and hence they melt ” over a wide temperature range
Within this temperature range, the substance is a mixture of solid fat
and liquid oil , defined by its solid fat content (SFC).
The plasticity of the fat ( ability to be molded or spread ) depends on
the SFC.
Substituents of fat in calorie-reduced products
olestra, a sugar polyester . It is not absorbed or
metabolized by the body; hence, it does not contribute calories, but have laxative effect
What is fat/oil autoxidation
refers to reactions that occur in fats and oils over time in
the presence of O 2
Autoxidation causes fats and oils to become unpalatable because the
oxidation products are responsible for off flavors (oxidative
rancidity).
Type of fat and autoxidation properties
The rate of autoxidation is very slow for totally saturated fat but
increases exponentially with increasing number of double bonds in
the fatty acyl (aliphatic) chains of triglyceride molecules.
Accordingly, highly polyunsaturated oils are particularly susceptible
to oxidative rancidity-> cancer risk, oxidative stress
What are added to oils to delay autoxidation
Antioxidants
What is lipolysis
Hydrolysis of triglycerides, producing free fatty acids.
Lipolysis occurs at high temperatures in the presence of water : these
conditions are encountered during frying (with the water coming from
the food immersed in the oil).
Result of different smoke points between TGs and FFAs
Because free fatty acids have a much lower boiling point than triglycerides, lipolysis results in a reduction in the smoke point of a frying oil (making it necessary to discard the oil).
What is smoke and flame points
Smoke point is the temperature at which fatty acids break apart and
produce smoke
Flash point is the temperature at which lipids will flame
Phospholipids are natural ___, because they have hydrophylic and hydrophobic chains
Emulsifiers
Composition of phospholipids
2 FAs, glycerol and phosphocholine
Phospholipids are important for food scientists as ___ and ___
Structural ad nutritional
Phospholipids are abundant in ___
Egg yolk
Third group within the lipids is ___
Sterols
Sterols include
Vitamin D
Steroid hormones, including sex hormones
Cholesterol
Recommendation for healthy living in terms of cholesterol
- exercise
- healthy weight
- limit saturated fat and cholesterol
- and read labels
how many calories can come from fat
20-35%
