Flashcards in Lipids lecture 2 + 3 Deck (89)
what are the 3 forms of nomenclature of triglycerides?
1 simplest: TGC that has only one type of FA attached to the 3 positions on the glycerol (simple glycerides)
2 mixed glycerides: more than one type of FA
3 position of each FA is numbered
what is sapoinification
hydrolyzing the fat
what is FAME?
FA methyl esters
how to determine overall FA composition of a fat?
1. saponify: hydrolyze the fat and react it with NaOH to release FA
2. methylate the FA to convert them to volatile FAMEs (FA methyl esters)
3. separate FAMEs using gas chromatography
what has GC analysis demonstrated?
that each natural fat source has a relatively consistent FA composition
fats from plants and fish tend to be...
oils (ie liquid at room temp)
what are TGC used as in plant seeds?
source of energy for germination
what are common primary plant sources of edible oils?
cocao and palm
are seeds and fruits of plants good or bad sources of lipid?
very good sources
what are the 3 most common sources of fats?
fat in animal sources?
fat rendered as a by product of meat production (from trimmings and carcasses of cattle, hogs, sheep)
fat in fish sources?
fatty fishes such as sardines, herrings, menhaden
what are fats and oils classified by?
their fatty acid composition and distribution determined by gas chromatography
what are the 7 groups of fat classifications?
2 lauric acid
3 oleic linoleic
5 animal fat depot
6 marine oil
describe the milkfat group classification?
includes fat from milk of lactating ruminants (cow, goat, yak ,sheep, water buffalo)
major use: butter production
features: high levels of long chain sat FA
substantial portion of short chain (
why are some of the unsat FA in the milkfat group trans?
because of the biohydrogenation in the rumen by microorganisms
what is the short chain FA responsible for in the milkfat group?
1. rancid like odor
2. undesirable flavor in milk (due to enzymatic lipolysis)
2. desirable flavor of aged cheese (enhanced by microbial lipases)
what is the major use of milkfat group?
production of butter (water in oil emulsion)
sources of lauric acid C12 group? their distinguishing properties?
from species of palms (oil palm, coconut and babasu)
commonly known as tropical oils
distinguished by: high content of lauric acid. accounts for 40-50% of total FA content
saturation in lauric acid?
are they resistant to oxidative rancidity?
most FA are saturated = oils at room temp = resistant to oxidative rancidity
can be fractionally crystallized (fractionated) to produce distinct fat and oil fractions
why are palm and palm kernal oils (lauric acids) highly valued?
resistant to oxidative rancidity = their major use is as an oil or fat in baked goods = long oxidative shelf life
cottonseed, sunflower,safflower, olive, peanut and corn oil are what type of group?
oleic linoleic acid
compoisition of oleic linoleic acid group?
sat FA make up less than 20% of FA composition
predominant FA are long chain: oleic (C18:1) and linoleic (C18:2)
very little C18:3 = thus oils don't undergo reversion = relatively stable = can be turned into plastic edible fats by partial hydrogenation (shortenings)
describe the linolenic acid (C18:3) group
why are they categorized as industrial "drying oils"?
high quantities of linolenic acid (in conjuction with oleic and linoleic acid)
high in polyunsat FA
linolenic is very reactive and readily oxidized
categorized as industrial drying oils because they can polymerize into a hard film if applied as a thin layer on surfaces
ex: soybean, linseed, castor, hempseed, perilla oils
what is C18:1?
what is C18:2
what is C18:3
linolenic (omega 3)
what is reversion?
how is this overcome by processing?
rapid transition from a bland, tasteless oil to a grassy, hay like fish flavour (common in unmodified processed soybean oil)
can reduce reversion by hydrogenation. Converts linolenic to oleic and linoleic acids
source of animal fat depot group?
lard from pigs, tallow from sheep and cattle