Topic 3A Flashcards
lipid
Soluble in organic solvents (ex: alcohol) but not water
oils
lipids liquid at room temp
fats
lipids solid at room temp
what are the 3 major groups of fats & oils?
o Triglycerides
o Phospholipids
o Sterols
o In addition: waxes
triglycerides
• Composed of 3 FAs combined with one molecule of an alcohol called glycerol
FA
hydrocarbon chain with carboxyl grp (acidic) at the end
glycerol structure
3 C atoms + 3 OH grps
what type of FA is found in fat in food?
mixed triglyceride
what type of bond joins 3 FAs to the glycerol in triglycerides? & what type of rxn occurs for this to happen?
ester linkage
condensation
how are triglycerides classified?
number of C atoms & saturation
FAs have C chains as short as ____ Cs & as long as _____
4
24+
short chain FAs
up to 12 C atoms
medium chain FAs
12 or 13 C atoms
long chain FAs
16 C atoms
saturated fats
all H-C can bond to & no double bonds b/w C atoms
consumption of what type of fat is linked to heart disease?
saturated fat
are saturated fats solid or liquid at room temp? & why?
solid
Straight chain enables close packing
what type of food fats are saturated?
animal fat, butter, coconut oil, palm oil, milk fat
unsaturated fats
contain double bonds b/w C atoms & don’t have all H atoms
are unsaturated fats solid or liquid at room temp? & why?
liquid
Double bonds cause bends in the chain, aren’t as compact causing it to be liquid
what is a benefit of unsaturated fats?
prevent clotting of blood
good for the heart
what type of food fats are unsaturated?
canola oil, soybean oil, fish oil, duck oil
linoleic acid (omega-6)
has 18 C atoms, 2 double bonds, found in most foods especially oilseeds such as canola & soybeans
what is the stability of linoleic acid (omega-6)? & what is the effect of its oxidation?
Stable at high temperature, but can be oxidized
Once oxidized, not as beneficial
linolenic acid (omega-3)
18 C atoms, 3 double bonds, found mostly in soybeans, flaxseeds & hempseeds
what is the stability of linolenic acid (omega-3)?
More sensitive to oxidation
what does the number in omega-6 & omega-3 FAs indicate?
where first double bond appears
what is the recommendation of omega-3 & omega-6 acquirements in an American diet?
increase omega 3 & decrease omega -6
what determines the shape of FAs?
presence of double bond, configuration of the bond
cis configuration
H atoms all on the same side of the double bond
Repel one another & cause a bend in the chain
what configuration of FAs is natural in nature?
cis
trans configuration
H atoms are on the opp sides of the double bond
Balanced, less repulsion causing it to be straight & solid
how are trans FAs formed?
when heating cis
what physical property does the shape of a FA effect?
melting point
trans FAs have ____ melting point than cis FAs
higher (cis molecules cannot compact as closely therefore, less E is required)
trans FAs behave similarly to what molecule? & how?
saturated FAs
raising cholesterol
hydrogenation
Forced addition of H atoms to the unsaturated bonds in an unsaturated fat
unsaturated to saturated FA
how does hydrogenation effect the melting point of a fat?
raises
what is the side effect of hydrogenation?
trans bond
when is hydrogenation used in the food industry?
used to harden liquid oils into semi-solid fats
hydrogenation makes the oil more resistant to what?
oxidative rancidity
what is the effect of hydrogenation of linoleic acid?
becomes biologically inactive when converted to the trans form
why is hydrogenation carried out?
make the oil more solid at room temp (ex: margarine & shortening)
increase the stability of these oils to thermal temps
shortening
medium level hydrogenation, contains 10-20% trans FAs
soft tub margarine
medium level hydrogenation contains 13-20% trans FAs
hard margarine
High-level hydrogenation, contains 25-28% trans FAs
trans FAs
hydrogenation converts cis –> trans
which FA is less stable & why?
unsaturated FAs –> double bonds are more reactive
when exposed to oxygen it will undergo an oxidative rxn at the point of unsaturation
are trans FAs or saturated FAs more harmful?
trans FAs
why is hydrogenated margarine more harmful than butter?
Butter doesn’t have trans-fats, margarine does have trans-fat
Short-chained FAs in butter are good for the bacteria in the large intestine, margarine has long chained FAs
how is non-hydrogenated margarin produced?
emulsification of water & oil creating a soft solid
phospholipid
Glycerol molecule with 2 FAs attached & a phosphate molecule
how do phospholipids & triglycerides differ?
phospholipids have a phosphate & triglycerides don’t
longer the FA chain =
the more hydrophobic
how does a phospholipid act as an emulsifier?
Hydrophilic head & 2 hydrophobic tails
Hold water & fat together with the hydrophilic & hydrophobic properties
lecithin & ex of where its used
phospholipid used in various foods including margarine
emulsifier
mayonnaise
what food source is a good source of phospholipids?
egg yolk & soybean oil
sterol
Hydrophobic, complex
Composed of multiple benzene rings held together
what type of sterol is found in animal foods?
cholesterol
what happens if cholesterol levels are too high in the blood?
can lead to heart disease & prevent normal flow of blood
what is cholesterol a pre-cursor for?
vit D
what is bile made from?
cholesterol
pre-cursor
something that can be transformed into an active compound
what type of nutrient is cholesterol?
non essential
cholesterol is involved in the production of what 3 substsnces?
bile
vit D
some hormones
what lipid is used as a protective coating in foods?
waxes
plasticity & when is it desirable
a plastic fat will become deformed when force is applied but keeps its new shape on a flat surface
spreadable products (ex:butter)
aeration & when is it used in food?
trapping air in the product, solid fats can retain the air
cookies, cakes & other baked goods
what role does lipid have in bread?
Slows down staling of bread starch, prevents starch from forming crystals
how do lipids effect flavouring of food?
Fat has the unique ability to absorb & preserve flavors
Often infused with herbs & spices for preservation
Also contain compounds that lend specific flavor of their own
how do lipids effect heat transfer?
As food contacts hot oil, moisture from the food escapes & oil enters the food
Enables the food to be cooked faster b/c oil can reach a higher temperature than water
Heat also seals the food surface minimizing the entry of oil & escape of moisture
If the temp isn’t high enough, the surface takes longer to seal allowing more oil to penetrate the food
High oil food will absorb more moisture
what advantage do lipids serve in smoking point?
fats have a higher smoking point than oil
what are the functional properties of lipids?
plasticity
aeration
texture & flavour
heat transfer
melting point
smoking point
how does oxidation effect lipid quality?
Unsaturated bonds react with oxygen
Causes oxidative rancidity
Staleness of the oils
Can damage esophagus leading to a burning sensation heart burn
Damages cells
how can an oxidation rxn with lipids be prevented?
storing used oil in lower temps
store in air tight containers
store in dark containers
fractionation & how is it done?
separation of HM point & LM point components by controlled cooking (HM –> fats & LM –> oils)
Winterization: placing oil in cold place Saturated FAs solidify & unsaturated liquid FAs will separate
why is fractionation done?
Consumer oil products (Ex: salad dressings) will become hazy & consumers won’t find it appealing, industries separate the FAs to prevent this
what 2 products are obtained by fractionation?
Good frying oil
Good plastic fat for making shortening
hydrolysis in a triglyceride
addition of a water molecule to a triglyceride releasing 3 FAs & a glycerol
hydrolytic rancidity & what is it a result of?
Glycerol & SFA contributing to the rancid flavors
hydrolysis
what is more likely to get rancid –> butter or shortening?
BUTTER –> lots of SFA
Happens when: water is available, when the enzyme can access the position to break down the bond & it is easier when FAs are shorter
BUTTER lots of SFA & water in butter (not 100% fat) will become rancid when stored at room temp
Shortening has long chained FAs, no water & is saturated
intersterification
rearranging the FAs in triglycerides can produce desirable consistency of the product
how does the interesterification rxn occur?
Hydrolyzes bonds b/w FAs & glycerol molecule –> FAs can reattach to the free glycerol molecule
Diff combinations of FA attachment can occur
what is the result of an interesterification rxn?
Produce more hydrogenous triglycerides composition (all 3 of the same FAs will attach to one glycerol molecule)
polymerization
polymer of FAs formed when oil is heated to smoking point
triglycerides start to form polymers, in nature they are separate
how does polymerization effect fats & oils?
increases the viscosity
how is the rate of polymerization determined?
how long it was heated
what effect does polymerized oil have on human health?
toxic towards humans
