2-FA Flashcards
what is the chemical structure of carboxyl group in fatty acid?
CH3-(CH2)n-COOH
aliphatic chain meaning?
FA part of the compound
which is the simplest and least reactive FA, SFA or UFA?
SFA. they are unbranched naturally.
how many numbers of FA are found naturally?
4-28, even numbers.
what are the 2 FA present in milk?
pentadecanoic (15C) and heptadecanoic (17C) FA
Rule of melting point of FA vs. number of double bond?
melting point decreases as number of DB increases ( = the more unsaturated the FA, lower the MP)
Rule of solubility of FA vs. chain length
shorter the length, bigger and solubility (due to less hydrophobicity)
Can FA dissolve in water? any example?
Yes, C4-C8 FA. miscible in water
What is soap?
salt form of a FA, water soluble + has strong surface tension reducing properties.
What is the name of reaction for FA to become trans from cis?
hydrogenation
how does hydrogenation do to oil conversion?
oil becomes plastic fats.
which food product naturally contain trans FA? How does this happen?
butter
by rumen microorganisms
What does conjugated DB and unconjugated DB mean?
Conjugated DB = DB are right next to each other (happens in oil processing); uncon— DB are seperated by methylene group [natural state of most FA]
which is more stable: con and uncon DB?
Conjugated DB is more stable but more susceptible to autoxidation.
give an example of FA that contains all unconjugated DB?
Linolenic acid (omega 3)
what kind of bond system does linolenic acid has?
mixed bonding system
What does mixed bonding system create for the double bond?
It creates active methylene group btw conju and uncon DB.
what are advantages and disadvantage of mixed bonding system?
good: is preferred thermodynamically
bad: very susceptible to autoxidation
explain Reversion phenomenon; which system is responsible for this?
appearance of bad flavor of soybean + fish oils due to less oxidation than required which produces true rancidity;
this is brought by mixed bonding system
The lattice crystalline structure of acyl residues is stabilized by which chemical interaction?
By hydrophobic interactions
which structure of FA can be packed into a crystalline lattice?
even-numbered + saturated FA
how does melting point change with increasing number of cis DB?
T decreases
what is an omega FA? what is the assumption?
omega carbon counted from CH3 end.
assumption: all natural FA are in cis form & DB will be always unconjugated.
example of omega FA?
linoleic acid; arachidonic acid (omega 6)
which omega 6 FA can’t be synthesized by human body?
linoleic acid
which omega 3 FA is synthesized only by plants?
gama-linolenic acid
which group of FA has anticarcinogenic effects?
conjugated linoleic acid (CLA)
ex. most common Rumenic acid
What are food source of CLA?
milk, meat, butter
what are branched chain FA?
have a hydrocarbon branch in the chain
Which FA is found in cottonseed oil? what is special about this FA?
Malvalic acid.
it contains a cyclopropanic ring —-cause egg color problem
Give a food source of Hydroxy acid?
castor bean tree (蓖麻油)
Give an example of hydroxy acid.
ricinoleic acid —-and makes up 80% of castor oil.
what is acetylenic FA, how is it being used?
contain a triple bond, used as antifungal
is there a simple analytical method for separating, isolating and identifying individual TAG?
NO
4 steps to determine FA composition of TAG
- extract
- saponify (+NaOH)
- methylate —-convert it to FAME (FA methyl ester) and seperate FAME using GC
- identify + quantify
Give example of plants that produces oil ?
soybean, canola, peanut, olive, coconut, cocao, palm, corn, cottonseed
give an example of animal that is important source of milk fat?
water buffalo
Which tool is always used to characterize fat and oil?
GC - gas chromatography
what are characteristic of milkfat in terms of its chemical structure?
high levels of LCSFA; unique: a lot SCFA (<12C), ex. butyric acid (C<4)
Which FA of milkfat is responsible for rancid like odor?
SCFA by lipolysis
what good aspect of flavor does SCFA of milkfat has in food?
it is responsible for desirable flavor of aged cheese.
is butter water in oil / oil in water emulsion?
water in oil
what food is lauric acid (C12) derived from?
Palm
what is the difference between palm oil and palm kernel oil?
Palm kernel oil: extracted from palm oilseed;
palm oil: extracted from palm fruit
Is palm kernel oil part of the lauric acid group? is it SFA or USFA?
NO, since it is extracted from palm oilseed’
it is USFA
Is lauric acid oil / fat in room T with large level of saturation?
Oil. due to C12
Is lauric acid susceptible to oxidation?why
No, due to low degree of unsaturation.
which group of FA does sottonseed, olive, peanut and corn oil belong to?
oleic-linoleic acid
what are the major FA contained in oleic-linoleic acid group? which FA is in low proportion (<20%)?
predominate: long chain: oleic (18:1) + linoleic (18:2)
SFA is in low proportion; C18:3 in trace amount
is olive, peanut and corn oil relative stable? To which phenomenon?
Yes, they don’t suffer from Reversion; and May be turned into
plastic edible fats by partial hydrogenation
which FA is used in conjunction with oleic and linoleic acid`?
linolenic (C18:3)
what are disadvantages of linolenic acid?
reactive + readily oxidized
Which group of FA is referred as “drying oils” ?
Linolenic acid. because of their ability to polymerize into a hard film if applied as
a thin layer on surfaces
which group of FA does soybean, linseed, casto, hempseed and perilla oil belong to? which is used originally an industrial drying oil?
linolenic acid
Soybean.
how does Reversion change soybean oil?
rapid transition from a bland, tasteless oil shortly after processing to
grassy, hay‐like and then fishy flavor
how to overcome Reversion of soybean?
by hydrogenation to convert a substantial portion of linolenic —->oleic + linoleic acid
which animal are lard and tallow from?
lard-pig
tallow-sheep + cattle
does animal fat depot group contain high or low melting point?
high.
is lard and tallow fat / oil? why ?
they are fat.
bc animal fat depot group has a higher ratio of di‐saturated (gs2u) and
tri‐saturated (gs3) glycerides than oleic‐linoleic acid group
can GS3 or GS2 change lipid system? how does it change?
GS3
change from an oil to a fat
What are characteristics of fish oils？
- Contain low levels of saturated fatty acids
- High in long‐chain unsaturated fatty acids [very high degree of saturation]
is marine oil susceptible to autoxidation? why?
yes due to VERY HIGH degree of unsaturation.
Give example of erucic acid (C22)?
rapeseed oil 油菜籽; mustard oil 芥末油
What is rapeseed oil originally used for?
marine motor oil—-excellent lubricating property due to erucic acid.
Why rapeseed oil a health hazard? how does it become edible today?
bc 40-50% erucic acid;
it is changed into low erucic acid —-“canola oil”
