Class #10: Fats & Oils Flashcards
True or False: Triglycerides make up 95% of all dietary lipids
True
How long are typical FA chains?
2-24 carbons
True or false: Trans fatty acids have their hydrogens on the same side.
False
What foods contain omega 6 fatty acids?
a. Grains
b. Soybean
c. Meat
d. Leafy greens
C
What foods contain omega 3 fatty acids?
a. Walnuts
b. Chia
c. Flax
d. All of the above
D
True or False: Eicosanoids are fatty acids
False
C10:3-2 contains how many double bonds?
3
Which oils are high in omega 9 (oleic acid)?
Olive, sunflower, safflower
What are the two types of emulsions involving phopholipids?
Oil in water, Water in oil
How do phopholipids act as emulsifying agents?
They go to the boundary between the two liquids, and lower the surface tension (act as surfactant)
In water in oil emulsions, do phopholipid tails face in or out of the micelle?
Out
True or False: Cholesterol is an essential nutrient.
False
True or False: Phytosterols lower cholesterol
Probably, still being researched but yes for the sake of the test
What is the structure of a wax?
Fatty acid+ alcohol hydrocarbon chain
True or False: The smoke point of oils is when the oil boils.
True
What happens at the smoke point of oils?
The fat breaks down to glycerol and fatty acids. Glycerol gets broken down to acrolein, a blue foul smoke.
What kind of oils are recommended for deep frying?
High smoke point, neutral flavour (ie peanut, canola, sunflower, cottonseed, safflower)
True or False: Shorter fatty acids have a lower melting point.
True
How long can you store unrefined oils?
6 months
What accelerates rancidity?
Light, heat, O2, food particles
What are the two types of rancidity?
Hydrolytic and oxidative
What causes hydrolytic rancidity?
H2O breaks larger molecules into smaller ones.
-H2O hydrolyzes bonds in TG’s to break them down
-Reaction is catalyzed by lipase and heat
occurs when cold wet food is put in oil, or when oil has not been heated to the point when lipase has been destroyed by heat
What causes oxidative rancidity?
Double bond of FA reacts with O2, more unsaturated fats are more susceptible (particularly omega 3)
- Initiation: free radical is formed, triggered by light, high temp, metals etc.
- Propagation: O2 combines with free radical to form peroxide, then domino effect occurs until all double bonds are gone
- Termination: No more H’s at double bonds to react with O2
How do antioxidants prevent oxidation?
They get oxidized themselves, donate an H to FA’s, or act as a chelating agent (form bonds with metal to prevent oxidation)
What are the disadvantages of chemical extraction of oils?
Loss of nutrients due to heating oil, some solvent can remain in the oil.
What is the difference between expeller pressed and cold pressed oils?
Expeller pressed generated very high temperatures, therefore oil integrity lost.
What are the 5 ways oil can be refined?
- Degumming: Removal of phosphatides
- Neutralization: Removal of free fatty acids
- Bleaching: Removal of colour
- Deodorization: Removal of odors, flavours
- Winterization: removal of waxes
What is intersterification?
Rearrangement of FA portion in triglyceride on glycerol backbone. Can modify physical properties without creating trans fatty acids.
What is winterization?
Separation of oils into 2 or more fractions based on melting point. Oils are cooled and kept at low temp and liquid and solid are separated.
What is fractionization?
Similar to winterization, but more sophisticated process, cooling and separating with more control
Name 3 ways you can reduce fat in cooking.
- Use non stick pans
- Use parchment
- Steam/grill/bake/poach foods
- Use lower fat versions of foods (ie skim milk)
- Use leaner cuts of meat
- Use fat substitutes in baking
