Lipids II Flashcards
What is a simple triglyceride? Give examples.
- Triglyceride that only has one type of fatty acid attached to the three positions on the glycerol molecule
- ex: tristearin, triolein
What are mixed triglycerides? How are the names of the fatty acid?
- More than one type of fatty acids
- Names of fatty acid are run together
- ex: stearodilinolein, dipalmitolinolenin, palmitostearolinolein
There are no simple, analytical methods for separating, isolating and identifying individual _________.
triglycerides
If you can’t determine the triglyceride composition, what can you quantify?
Determine the overall fatty acid composition of a fat and quantify the relative amounts of the individual fatty acids fairly easily
How can you determine the overall fatty acid composition?
Through saponification
What are FAMEs?
Fatty acid methyl esters
What is GC analysis? What has it demonstrated?
- Gas chromatography
- Demonstrated that each natural fat source tends to have a relatively consistent fatty acid composition
Fats from plant and fish sources tend to be ______
Oils
What parts of plants are exceptionally good sources of lipids?
Seeds and fruits
In plant seeds, what kind of lipids are used as a source of energy for germination?
Triglycerides
What are common primary plant sources of edible oils in North America? What are common regional sources?
- Soybean, rapeseed (canola) and peanut
- Olive, coconut, cacao, and palm
Lipids are also obtained as by-products from crops, such as what?
Corn and cotton seeds
What are non-edible oils obtained from plant sources? What are they used for?
- Castor oil, linseed (flax) oil
- Industrial paint/chemical (plasticizer) purposes
How has biotechnology changed linseed oil?
Linseed (flax) oil has been transformed to edible Linola
Can oilseeds be consumed?
Yes, can be consumed directly
What kind of fats and oils are much more valuable and useful commercially for margarine manufacture, and for the preparation of salad dressings?
Extracted and processed fats and oils
How are animal sources of fat obtained?
Fat rendered as a by-product of meat production, produced from the trimmings and the carcasses of cattle, hogs, and sheep
How is cream obtained?
- Fat separated from the milk of ruminants, especially cows
- In other parts of the world, other ruminants are important sources of milk fat (water buffalo)
What are good sources of fish fat? Where are fish oils used in the world?
- Fatty fish (sardines, herring, menhaden)
- Used extensively in Europe, less so in North America
What technique determines the fatty acid composition/distribution? How can its characterization be used?
- Gas chromatography
- Characterizing fats and oils to classify them into various characteristic groups (classifying major sources, has limitations)
What are the seven classifications of fats by group characteristics determined by GC?
1) Milkfat
2) Lauric Acid
3) Oleic-linoleic
4) Linolenic
5) Animal fat depot
6) Marine oil
7) Erucic acid
What type of fat does the milkfat group contain?
Includes fats from the milk of lactating ruminants (cow, goat, yak, sheep, water buffalo)
What are the distinguishing features of the milkfat group?
- High levels of long-chain saturated fatty acids
- Unique and substantial portion of short chain (< C12) fatty acids, butyric acid (C4:0)
What kind of lipids are responsible for a bad “rancid-like” odor when released from the triglyceride by lipolysis?
Short-chain fatty acids
What is the general fatty acid composition for cows’ milk fat?
- 25-32% palmitic acid, C16
- 10-12% stearic acid, C18
- 30-40% oleic acid, C18:1
- 4-15% butyric acid and other short-chain fatty acids (up to C10)
Do cows’ milk fat contain trans forms of their unsaturated fatty acids? If so, why?
- Yes
- Due to (bio)hydrogenation in the rumen by microorganisms
What lipid is responsible in part for the desirable flavour of aged cheese?
Short-chain fatty acids
What does biotechnology use to speed up the maturation of cheese and enhance cheese flavour?
Microbial lipases
What are the major uses of the milkfat group?
Production of butter (water-in-oil without emulsion) as a spread and as a cooking fat (ghee)
How many carbons does the lauric acid group contain?
12
What are the sources of the lauric acid group?
- Oil palm (tropical oils)
- Palm kernal oil, coconut and babasu
How does palm kernal oil differ from palm oil?
- Palm kernal oil (extracted from palm oilseeds)
- Palm oil (from palm fruit), which is much more highly unsaturated and is not part of the lauric acid group
Is palm oil a part of the lauric acid group?
No
What are the distinguishing characteristics of the lauric acid group?
- High content of lauric acid (C12)
- Which can account for 40-50% of the total fatty acid content
Are most of the fatty acids in lauric acids unsaturated or saturated?
- Most are saturated
- Only small amounts of unsaturated fatty acids are present
Are lauric acids solid or liquid at room temperature?
- Although largely saturated
- They are oils owing to the high proportion of C12 fatty acids in their triglycerides
What kind of fatty acids are resistant to oxidative rancidity? Which group is an example of this?
- Low degree of unsaturation
- Lauric acid
How can lauric acids produce distinct fat and oil fractions?
Can be fractionally crystallized (fractionated)
Palm and palm kernal oils are highly valued oils. How are they mostly used?
Oil or fat in baked gods which need a long oxidative shelf life
The bulk of our common oils fall into which group? Give examples.
- Oleic-linoleic acid
- Cottonseed, sunflower, safflower, olive, peanut, corn oil
Saturated fatty acids make up ______% of the total fatty acid composition in the oleic-linoleic group.
<20%
What are the predominant fatty acids in the oleic-inoleic group?
- Long chains
- Oleic (C18:1)
- Linoleic (C18:2)
Oleic-Linoleic acids have negligible amounts of C18:3. What is the consequence?
The oils in this category do not suffer from reversion and are relatively stable
How can oleic-linoleic acids be turned into plastic edible fats? Give an example.
Partial hydrogenation (shortenings)
What fatty acids do the Linolenic acid group contain?
- Significant linolenic acid
- C18:3
- In conjunction with oleic and linoleic acids
The linolenic acid group is high in: A) Saturated fatty acids B) Trans fatty acids C) Monounsaturated fatty acids D) Polyunsaturated fatty acids
Polyunsaturated fatty acids
Which group is particularly reactive and readily oxidized?
Linolenic acid
Most oils in this group tend to be categorized as industrial “drying oils”. Which group does this passage refer to?
Linolenic acid
Why are linolenic acids sometimes referred as “drying oils”?
Because of their ability to polymerize into a hard film if applied as a thin layer on surfaces (paint)
The polymerization capability is present in all _____________ oils, but those containing high levels of _____________ are more reactive
unsaturated oils, linolenic acid
What are common examples of the linolenic acid group?
Soybean, linseed, castor, hempseed and perilla oils
What was soybean oil used for originally? What is it used for nowadays? What led to this conversion?
- Originally: industrial drying oil
- Nowadays: predominantly as an edible oil
- Application of food technology and plant breeding
Processed soybean oil, if stored after extraction without modification, suffers from a problem commonly termed _______.
Reversion
What is reversion?
Relatively rapid transition from a bland, tasteless oil shortly after processing to a grassy, hay-like and then fishy flavour
How is reversion overcome? What fats are converted to what?
By hydrogenation to convert a substantial portion of linolenic to oleic and linoleic acids
What fat is an essential omega-3 fatty acid?
Linolenic acid
What are the sources of the animal fat depot group?
Lard from pigs, tallow from sheep and cattle
What are the characteristics of the animal fat depot group? How is their melting point? How do they compare to oleic-linoleic acids?
- Relatively high melting point
- Yet, contain similar levels of unsaturated fatty acids as the oils in the oleic-linoleic acid group
What is the animal fat depot group composed of?
- 50-60% oleic and linoleic acid
- 30-40% palmitic and stearic acid
Why are animal fat depot lipids fats rather than oils?
Due to a selective fatty acid distribution on the glycerol backbone which influences the overall physical properties on the lipid
Animal fat depot group has a higher ratio of what compared to the oleic-linoleic acid group?
Di-saturated (gs2u) and tri-saturated (gs3) glycerides
Compare GS2U and GS3 of beef tallow and peanut oil.
Beef tallow: 12% GS3, 44% GS2U
Peanut oil: 0.1% GS3, 10% GS2U
The presence of relatively high amounts of ____ can change the physical characteristics of the lipid system from an oil to a fat.
GS3
The fatty acid distribution can have a strong influence on the plasticity and predominance of specific ______ forms in a fat; affecting its funcitonality.
crystal forms
What are the sources of the marine oil group? What are they a rich source of?
- Fish oils
- Rich source of omega-3 fatty acids
What are the characteristics of the marine oil group?
- Contain low levels of saturated fatty acids
- High in long-chain unsaturated fatty acids (C16-C22)
Some fish oil fatty acids can be highly unsaturated. Up to how many double bonds do they contain?
Up to 6 double bonds
Why do marine oils possess their own particular processing problems? What do they suffer from? What are they susceptible to?
Due to their very high degree of unsaturation
- Suffer from reversion, and are susceptible to autoxidation
How are processed fish oils used in Europe?
Extensively for margarine and shortening production
What are two examples of the erucic acid group?
Rapeseed oil and mustard oil
How was rapeseed oil used originally?
Used extensively as a marine motor oil
Why does the erucic acid group have excellent lubricating properties?
Due to its high erucic (C22:1) acid content
Natural rapeseed oil contains __%-__% erucic acid, which is considered a health hazard. Why?
- 40-50%
- Infuses into the heart muscle in rats
What is canola oil? How is it produced?
Indigenous rapeseed has been converted by plant breeding to a variety which produces a low erucic acid edible oil
Canola oil, which is a low erucic acid edible oil, contains similar properties to which oil?
To oleic-linoleic acid oils
What are high-erucic oils being used as now?
Biodegradable lubricants
What kind of canola oils can now be produced thanks to genetic engineering?
Lauric acid canola oils
How will we custom engineer oils in the future?
- Control fatty acid composition and distribution genetically in plants
- To custom engineer oils with properties which are desirable
