U2 Flashcards
definition of fatty acids
carboxylic acids with a short to long aliphatic chain
aliphatic
organic compounds where carbon atoms form open chains rather than rings
relationship between saturation and melting point
melting point decreases as number of double bonds increases
fatty acid typical characteristics
unbranched varying length and degree of saturation 4-28C even numbered usually usually cis
characteristics of short fatty acids
- more volatile
- lower melting point
- liquid at RT
- more soluble in water
characteristics of longer fatty acids
- not volatile - dont contribute to flavor
- higher melting point
- solid at RT
- less water soluble - more hydrophobic
fatty acids present in milk and plant oils
pentadecanoic acid and heptadecanoic acid
what is soap
the salt form of a fatty acid
water soluble and has strong surface tension reducing properties
nomenclature systems in saturated fatty acids
trivial and IUPAC
nomenclature systems in unsaturated fatty acids
IUPAC and trivial and omega
- -enoic acid
- positional reference
- configuration
IUPAC v omega naming in unsaturated fatty acids
IUPAC - count from COOH
omega - count from CH3
cis characteristics
- kinked, not linear
- 1 bond = 40 degree turn
- harder to form a lattice structure so…
- lower melting point
- lower density
trans characteristics
- linear
- metabolized like saturated fatty acids
- higher melting point
- higher density
trans-oleic acid is called
elaidic acid - a lot like stearic acid
unconjugated
double bonds are separated by a methylene group (CH2) - normal
conjugated
double bonds are adjecent. formed during processing.
more thermodynamically stable but more susceptible to autoxidation
mixed bonding system
mixture of conjugated and unconjugated. occurs since linolenic and polyunsaturated fatty acids are unstable and reactive, thus easily converted to having both conjugated and unconjugated elements
lattice crystalline
stabilized by hydrophobic interaction along acyl residues. temperature required to melt the crystal increases with number of carbons in the chain (length)
what can form a lattice crystalline structure? what can’t?
can - saturated, even, trans
can’t - unsaturated, odd
phenomenon that occurs when there is a cis bond at the end of the carbon chain
the angle the fatty acid is bent at is lower, thus the molecule is more linear and the melting point is higher
assumptions in omega fatty acid nomenclature
- cis
2. unconjugated
grouping of omega fatty acids
due to the relationship between unsaturated, unconjugated fatty acids there are 3 groups:
- w3
- w6
- w9
malvalic acid
branced fatty acid found in cottonseed oil
contains a cyclopropanic ring (triangle)
ricinoleic acid
hydroxy side chain. in castor oil
true or false: fats consist of one type of triglyceride
false: they consist of a mix of triglycerides that contribute to their physiochemical characteristics
how do we determine the overall fatty acid content of a fat and the relative amounts of each fatty acid?
gas chromatography:
- extract
- saponify - fat + NaOH –> free fatty acid
- methylate - convert fatty acids to volatile fatty acid methyl ethers (FAME)
- separate FAMEs with GC
- compare to FAME standards
3 oil sources
plant
animal
fish
where are plant sources extracted from
seeds and fruits of plants
most common plant sources
soybean, rapeseed, peanut
non-edible plant sources
castor and linseed(flax)
2 ways animal fats are extracted
- by-product of meat production
2. separated from milk of ruminants
common fish sources
sardines, herring, menhaden
classifications of fats and oils based on gas chromatography
- milk fats
- lauric acid
- oleic-linoleic
- linolenic
- animal fat
- marine
- erucic acid
defining feature of milk fat group
high levels of long-chain saturated fatty acids. have a substantial amount of short chain fatty acids
source of milkfat
milk of lactating ruminants - cows, goats, yaks, sheep, water buffalo
source of rancid odor in milkfats
short chain fatty acids released by lipolysis (also responsible for aged cheese flavor)
do milkfats contain unsaturated fatty acids? what kind?
yes; trans due to biohydrogenation in the rumen by microbes
defining feature of lauric acid group
high content of lauric acid (C12). mostly saturated, but since the fatty acid chains are short they exist as oils
source of lauric acid group
tropical oils (palms) - palm, coconut, babassu oil
difference between palm kernel oil and palm oil
source!
palm kernel oil - palm oil seeds
palm oil - palm fruit. not in lauric acid group; more unsaturated
true or false: lauric acid group fats are highly resistant to oxidative rancidity
true! low degree of unsaturation
defining feature of oleic-linoleic group
predominantly long-chain oleic and linoleic fatty acids. rarely C18:3. 20% saturated fats
sources of oleic-linoleic group
cottonseed, sunflower, safflower, olive, peanut, corn
true or false? oleic-linoleic group undergoes reversion
false - rarely has C18:3 and this group is relatively stable
formation of shortening
partial hydrogenation converting oleic-linoleic group to plastic edible fats
defining feature of linolenic group
very high polyunsaturated fatty acid content - linolenic, oleic, and linoleic acids - contributing to its high reactivity and ease of oxidation
function of linolenic group
paint - polymerizes into a hard film if applied as a thing layer on a surface
sources of linolenic acid group
soybean, linseed, castor, hempseed, perilla
what is reversion and what oil does this happen to
rapid transition from bland, tasteless oil to grassy, hay-like and eventually fishy flavor. occurs in processed (but not modified) soybean oil
how to fix reversion
hydrogenation - converts linolenic to oleic or linoleic acids
soybean oil functions
industrial drying oil traditionally. now it us edible due to plant breeding and food technology
defining feature of animal fat depot group
high melting point though the unsaturated fatty acid content is similar to that of the oleic-linoleic group
why is animal fat solid at room temperature despite it’s composition
fatty acid distribution on the glycerol backbone. higher ratio of di-saturated and tri-saturated glycerides, affecting the crystal forms
defining feature of the marine oil group
low levels of saturated fatty acids and high levels of long-chain unsaturated fatty acids
marine oil fatty acids are sources of
omega 3
EPA
DHA
true or false: marine oils are reactive
true due to its unsaturated fatty acid content, they readily undergo reversion and are highly susceptible to autoxidation
sources of erucic acid group
rapeseed and mustard oil
function of rapeseed oil
marine motor oil due to its lubricating properties
defining feature of erucic acid group
high levels of erucic acid (health hazard)
how is canola oil produced
rapeseed oil is plant bred into a low erucic acid composed oil. makes it edible
Animal fat is solid because
a. It has a higher ratio of desaturated and trisaturated glycerides
b. It has a higher amount of saturated fatty acids than unsaturated
a
oleic acid 18:1 cis-9 is considered
a. N3 fatty acid
b. N6 fatty acid
c. N9 fatty acid
d. Not an omega acid
c
Long chained polyunsaturated cis fatty acids…
a. Give better packed, more stable crystalline lattice that requires high temperature to melt
b. Give less stable crystalline lattice than their isomers thus the melting point is less
c. Have no effect on the stability of the crystalline lattice
b
The melting point of fatty acids is affected by: A. Chain length B. Number of double bonds C. Double bond configuration D. All E. None
d
all-cis-docosa-4,7,10,13,16,19-hexa-enoic acid is a fatty acid that contains
a. 26 carbon atoms with 6 cis double bonds
b. 22 carbon atoms with 6 cis double bonds
c. 26 carbon atoms with 6 trans double bonds
a
True or false?
Branched FA with odd number of carbon atoms aren’t very common in food.
true
A carboxylic acid with a short to long aliphatic chain is a…
fatty acid
By increasing the number of double bonds in a fatty acid, its melting point will
a. Increase
b. Decrease
c. none
b
Octadeca-9,12,15-trienoic acid is a fatty acid with…
a. 18C atoms and 3 double bonds
b. 9C atoms with 3 double bonds
c. 18C atoms with no double bonds
a
Double bonds that are next to each other and not interrupted by a methylene group are called…
conjugated
When the 1st double bond is located on the 3rd carbon atom starting the count from CH3 end, this fatty acid is labelled as…
omega 3 (w3)
