Foodchem 1 lecture 3
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When are short chain saturated aliphatic hydrocarbons of interest in food systems?
The presence of double bonds and/or oxygen in the form of functional groups such as aldehydes, ketones. alcohols, and carboxylic acids can give rise to distinct flavor and aroma responses
Non-isoprenoid based short chain oxygenated hydrocarbons are common by-products of what?
- Fermentation or microbial metabolism
- Commonly produced by yogurt starter cultures
The end products of lipid autoxidation have similar characteristics to which other group of oxygenated starter cultures?
Non-isoprenoid based short chain oxygenated hydrocarbon compounds, (but we don't like the end products of lipid autoxidation as much as these)
What are triglycerides?
FFA + alcohol (glycerol)
What are waxes?
FFA + alcohol (other than glycerol)
What are compound lipids?
- Phospholipids (like lecithins, cephalins, and inositols)
What are phospholipids?
Triglyceride base + PO4
What are glycolipids?
Ceramide + sugar/phosphate
What are lipoproteins?
Simple/compound lipids + proteins
What are derived lipids?
- Fatty acids/alcohols
- Oxidation products (C=O, C=OOH, C=OH, COH)
Food scientists are mainly interested in bulk lipid components (for practical purposes) like:
- Fats from the simple lipid class
- Phospholipids from the compound lipid class
Approximately what percent of hydrophobic material extractable from biological systems is fat?
- 90% Triglycerides
- 2-5% Phospholipids
What are minor hydrophobic constituents?
- Essential oils
- Shorter chain oxygenated products
Terpenes are important for which sense?
Shorter chain oxygenated products are important for which sense?
Carotenoids are important for which sense?
Waxes are mainly used as what?
Sealing agents that are nutrional (cholesterol, vitamin A)
Triglycerides and phospholipids are used in the formulation of what kinds of things?
- Plastic fats
- Food products
- Frying foods
In plants that produce oilseeds, what are the main source of energy for plant germination?
Many seeds and some fruits of a wide variety of plants are exceptionally good sources of what?
What are the three primary edible oil sources in North America?
- Rapeseed (canola)
What are some common regional oil sources from around the world?
- Olive (Mediterranean)
- Coconut (Pacific Islands)
- Cocoa (Africa)
- Sesame (China)
- Palm (Malaysia/Indonesia)
Lipids are also obtained as by-products from which non-oilseed crops? How is this possible?
- Corn and Cottonseed
- They may have relatively low lipid contents, but are harvested enormous volumes making this possible.
What are some "industrial" or "non-edible" oils obtained from plant sources?
- Castor oil (Ricin toxin)
- Linseed oil (Flaxseed)
What is the main use for "industrial" oils?
Generally used for the formulation of oil based paints and as plasticizers in the production of plastics
How is biotechnology blurring the line between "industrial" and "edible" oils?
- Genetic transformation makes it possible to turn otherwise inedible oils into edible ones.
- Example: Linseed (flax) oil is being transformed into an edible version called "linola" using similar technology to how they made inedible rapeseed oil into canola
Which oils are the most versatile/valuable/useful?
Extracted and processed ones
What are some uses for extracted and processed oils?
- Cooking/frying oils and fats
- Plastic margarines
- Plastic shortenings
- Salad dressings (emulsions)
What is a "visible" fat vs. an "invisible" one?
- Visible means it is obvious as a source of fat, like a margarine or a shortening.
- Invisible means it is either naturally present in a food source (like in an avocado for example), or it has been incorporated into a product (like in a cookie).
Does the dominant lipid supply come from plant or animal sources?
What are the common animal sources?
- Animals - as in as a by-product of meat production, produced from the carcasses and trimmings of cattle, hogs, and sheep
- Fatty fish - very good sources, come from rendered sardines, herring and menhaden as well as rendered from discarded skeletal tissue
- Milk - fat separated from the milk of ruminants (cows, goats, water buffalo, camel), it is cream from which butter and ghee are made
Where are fish oils mainly used?
In Europe, not so much in North America
What is the main use for fish oils in Canada?
Mainly used as a source of omega-3 fatty acids destined for use as supplements to provide these essential FFAs
Which kinds of oils are particularly unstable?
What is the mechanism behind biodiesel?
Uses triacylglycerols as feedstock to make fatty acid methyl esters
Are all triglycerides alike?
No - mixed glycerides give rise to the possibility that they can have unique physical properties based on what source they are from. There can be millions of unique triglycerides. The unique physico-chemical characteristics explain why lipids from milk are plastic fats, while lipids from olives are oils.
Are there any simple analytical methods to separating, isolating, or indentifying individual triglycerides?
No, this is largely because even though each TG may be structurally different, they are insufficiently different to separate physically.
How can we determine the overall fatty acid composition of a fat or oil?
Through gas chromatography, and we can even accurately quantify the relative amounts of individual fatty acids from any lipid source.
What is the analytical procedure to gas chromatography?
- 1. Saponify the fat (strong NaOH) to release the fatty acids from glycerol: TG-->(NaOH)-->Glycerol + 3FFA
- 2. Methylate the fatty acids to make them more volatile: R-COOH-->R-CO-OCH3
- 3. Inject the methyl ester mixture into gas chromatograph (GC): separate them on a column
Do common natural fat sources tend to have fairly consistent or inconsistent fatty acid compositions and fatty acid distributions?
Fairly consistent, this has been determined through extensive GC analysis
What are the 7 most common groupings we can classify lipids into?
- 1. Milkfat group
- 2. Lauric Acid group
- 3. Oleic-Linoleic Acid group
- 4. Linolenic Acid group
- 5. Animal Fat Depot group
- 6. Marine Oil group
- 7. Euricic Acid group
What are the sources of milkfat?
Lactating ruminants - cow, goat, yak, sheep, water buffalo and camel
What is the dominant milkfat source in North America?
What is the major use for milkfat?
- Production of plastic spread called butter (a water in oil emulsion)
- Or a clarified, anhydrous butterfat (ghee, clarified butter)
What are the fatty acids like in butter?
- High levels of longer chain, saturated FAs
- Substantial amount of short chain FAs, like butyric acid in particular
Are TGs containing shorter or longer chain FAs easier to digest?
Are shorter or longer chain FAs responsible for "rancid" taste and odor released by butter over time?
What is the process by which FAs develop a rancid taste and odor?
Why are some of the unsaturated FAs in milkfat in the trans form?
This is due to hydrogenation in the rumen by bacteria
What is conjugated linoleic acid (CLA)?
- An unusual fatty acid that butterfat contains
- It is cosidered anti-carcinogenic and many health claims are made about it.
- It is interestingly a trans fatty acid, which are generally considered bad
How do we use biotechnology in cheese making?
- Use microbial lipases to speed up the maturation of cheese and enhance cheese flavor
- This allows us to develop desirable flavors at a lower cost
What are the sources of lauric acid?
Obtained from species of palms such as oil palm, coconut, and babasu (all commonly known as "tropical oils")
How many carbons is lauric acid?
Are tropical oils stable to oxidation?
Do tropical oils contain a high or low concentration of trans fats?
What are the fatty acids like in tropical oils?
- Most are saturated with only small amounts of unsaturated
- High content of lauric or palmitic acid (40-50% of total FA content)
- Still oils because have short average chain length
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