Polymerization of Triglycerides?

Question

Fats and oils are commonly made up of triglycerides. When subjected to frying (i.e. at approx 200 degrees celsius), these triglycerides tend to polymerize. Suggest the mechanisms in which they could polymerize.

I would appreciate it if you can cite some journal articles to back your view. :)

Thanks.

Answer 1

A lot of information in the first two answers, but neither actually answered your question on polymerization.

In order for a polymerization to take place, a polymerizable functional group must be present in the molecules in question. For fats, these would be unsaturations (carbon-carbon double bonds) on the fatty acid portions of the triglycerides. So that means unsaturated fats (like animal fat) would not polymerize. Triglycerides isolated from olive oil are esters of oleic acid and have a single unsaturation on each fatty chain. Linoleic acid derived triglycerides are found in sunflower oil, and have two unsaturations on each fatty acid chain. These would polymerize better. A conjugated (adjacent C=C double bonds) unsaturated fat actually would be difficult to stop from polymerizing. No conjugated unsaturated fat exists in nature to my knowledge, but the synthetic molecule “Rumenic acid” is a conjugated fatty acid; and so such a synthetic fat could be prepared easily.

So, given an unsaturated tryglyeride, how can we polymerize it? The application of great heat, as in frying, will cause the homolytic cleavage of C-C and C-H bonds in the oil; the resultant carbon and hydrogen atom free radicals can add to the double bonds of the unsaturated triglycerides. This addition product is itself a free radical; it can add to another C=C double bond, and so forth. The polymerization then proceeds.

And heat is actually not needed to effect polymerization. Oxygen from the air will do this as well, but not as fast of course. This is a free radical reaction as well. Alkyds are paints and coatings consisting of unsaturated polyesters, which have been mixed with unsaturated fatty acids. Once the alkyd paint dries, oxygen starts reacting with the fatty acids, and a free radical polymerization starts slowly. (Google “alkyds” for the mechanism.) There is no reason to think that triglycerides would not do the exact thing.

Answer 2

-Besides the radical mechanism for the lipid peroxidation and polymerisation of triglycerides another non radical mechanism for the formation of non-oxidised ...
article :A new method to determine oxidative stability of vegetable fats and oils at simulated frying temperature

Oléagineux, Corps Gras, Lipides. Volume 8, Numéro 1, 82-8, Janvier - Février 2001, Dossier : Deutsche Gesellschaft für Fettwissenschaft - Association française pour l'étude des corps gras

- One molecule of glycerol joins togther with three fatty acid molecules to form a triglyceride molecule, in another condensation polymerisation reaction: ...
-There is evidence which supports a co-relationship between the unsaponifiable matter content and oxidative stability.
It is believed that a radical peroxidation mechanism predominates at lower temperatures. When a large volume of oil is heated in a fryer and the oxygen supply is poor, non-radical reactions such as elimination (acid catalysed dehydration) or nucleophilic substitution take place.

Testing and comparing oxidative stability of vegetable oils and fats at frying temperature
Christian Gertz 1 *, Sabine Klostermann 1, S. Parkash Kochhar 2
1Chem. Untersuchungsamt Hagen, Hagen, Germany
2Good-Fry International NV, Reading, UK

email: Christian Gertz ([e-mail])

*Correspondence to Christian Gertz, Chemisches Untersuchungsamt Hagen, Pappelstr. 1, 58099 Hagen, Germany. Phone: [phone], Fax: [phone]

Answer 3

It will depend on the fruit or veggie linked to a comparison. In the event that you compare a farreneheit to a carrot, the carrot is the better of the two nutritional. When you compare an avocado to the carrot, then this avocado is better. Equally the apple and avocado, are fruits.

Answer 4

Cooking at high temperatures can damage oils. The more omega 3 fatty acids in the oil, the less suitable it is for cooking. The heat not only damages the fatty acids, it can also change them into harmful substances. Hydrogenated oils are often used for cooking. Because these oil have already been "damaged" by chemical processing, they are less likely to be further damaged by heat. The oils that are higher in saturated fats or monounsaturates are the most stable when heated. These include peanut oil and olive oil. The more fragile oils are best used at room temperature, like salad dressings. To preserve the nutritious properties and the flavor of unrefined oils, try the "wet-sauté," a technique that is practiced by gourmet chefs. Pour around one-fourth of a cup of water in the stirfry pan and heat just below boiling. Then add the food and cook it a bit before adding the oil. Wet-sauté shortens the time an oil is in contact with a hot pan. Stir frequently to further reduce the time the oil is in contact with the hot metal. Never heat oils to the smoking point, as this not only damages their fatty acid content, but also their taste. Best cooking oils and fats are: butter, peanut oil, high oleic sunflower oil, high oleic safflower oil, sesame oil, and olive oil.
Studies done by researcher A. Saari Csallany, a professor of food chemistry and nutritional biochemistry at the University of Minnesota, show that the fatty acid-derived toxin 4-hydroxy-trans-2-nonenal (HNE) accumulates in high amounts in polyunsaturated vegetable oils that have been reheated or used for long periods of time. While the risks for home cooking are small, the concern is for restaurant frying, where oils might be reused or kept hot for most of the day. HNE has been linked to increased risk for a multitude of diseases, including strokes, Parkinson’s, Alzheimer’s, liver diseases, and cancer.
aaaaaaaaIt is not recommended reusing cooking oils or eating foods cooked in oils that have been reheated, whether you're dining at home or in restaurants. A recent study found that a toxin called 4-hydroxy-trans-2-nonenal (HNE) forms when such oils as canola, corn, soybean and sunflower oils are reheated. Consumption of foods containing HNE from cooking oils has been associated with increased risks of cardiovascular disease, stroke, Parkinson'?s disease, Alzheimer's disease, Huntington's disease, various liver disorders, and cancer. Once absorbed in the body, HNE reacts with DNA, RNA and proteins affecting basic cellular processes.

Answer 5

component sugars, also known as simple sugars.

They are generally found either O- or N-linked to compatible amino acid side chains in proteins or to lipid moieties (see glycans).

Contents [hide]
1 Examples
2 Therapeutic effects
3 Sources
4 References



[edit] Examples
Fructo-oligosaccharides (FOS) and inulin, which are found in many vegetables, consist of short chains of fructose molecules. Inulin has a much higher degree of polymerization than FOS. Galacto-oligosaccharides (GOS), which also occur naturally, consist of short chains of galactose molecules. These compounds can be only partially digested by humans.

Oligosaccharides are often found as a component of glycoproteins or glycolipids and as such are often used as chemical markers, often for cell recognition. An example is ABO blood type specificity. A and B blood types have two different oligosaccharide glycolipids embedded in the cell membranes of the red blood cells, AB-type blood has both, while O blood type has neither.

Mannan-oligosaccharides (MOS) are widely used in animal feed to encourage gastrointestinal health and performance. They are normally obtained from the yeast cell walls of Saccharomyces cerevisiae. Some brand names are: Bio-Mos, SAF-Mannan, Y-MOS and Celmanax.


[edit] Therapeutic effects
When oligosaccharides are consumed, the undigested portion serves as food for the intestinal microflora. Depending on the type of oligosaccharide, different bacterial groups are stimulated or suppressed.

Clinical studies have shown that administering FOS, GOS, or inulin can increase the number of these friendly bacteria in the colon while simultaneously reducing the population of harmful bacteria.[citation needed]

Other benefits noted with FOS, GOS, or inulin supplementation include increased production of beneficial short-chain fatty acids such as butyrate, increased absorption of calcium and magnesium, and improved elimination of toxic compounds.[citation needed]

Because FOS, GOS, and inulin improve colon function and may influence the bacterial composition, one might expect these compounds would help relieve the symptoms of irritable bowel syndrome. However, a double-blind trial found no clear benefit with FOS supplementation (2 grams three times daily) in patients with this condition.[citation needed]

Experimental studies with FOS in animals suggest a possible benefit in lowering blood sugar levels in people with diabetes and in reducing elevated blood cholesterol and triglyceride levels[2].

In a double-blind trial of middle-aged men and women with elevated cholesterol and triglyceride levels, supplementation with inulin (10 grams per day for eight weeks) significantly reduced insulin concentrations, suggesting an improvement in blood-glucose control, and significantly lowered triglyceride levels.[citation needed]

In a preliminary trial, administration of FOS (8 grams per day for two weeks) significantly lowered fasting blood-sugar levels and serum total-cholesterol levels in patients with type 2 (non-insulin-dependent) diabetes.[citation needed]

However, in another trial, people with type 2 diabetes supplementing with FOS (15 grams per day) for 20 days found no effect on blood-glucose or lipid levels[citation needed]. Because of these conflicting results, more research is needed to determine the effect of FOS and inulin on diabetes and lipid levels.

Several double-blind trials[citation needed] have looked at the ability of FOS or inulin to lower blood cholesterol and triglyceride levels. These trials have shown that in people with elevated total cholesterol or triglyceride levels, including people with type 2 (adult onset) diabetes, FOS or inulin (in amounts ranging from 8 to 20 grams daily) produced significant reductions in triglyceride levels. However, the effect on cholesterol levels was inconsistent. In people with normal or low cholesterol or triglyceride levels, FOS or inulin produced little effect.


[edit] Sources
FOS and inulin are found naturally in Jerusalem artichoke, burdock, chicory, leeks, onions, and asparagus. FOS products derived from chicory root contain significant quantities of inulin, a fiber widely distributed in fruits, vegetables and plants. Inulin is a significant part of the daily diet of most of the world’s population. FOS can also be synthesized by enzymes of the fungus Aspergillus niger acting on sucrose. GOS is naturally found in soybeans and can be synthesized from lactose (milk sugar). FOS, GOS, and inulin are available as nutritional supplements in capsules, tablets, and as a powder.

Not all natural oligosaccharides occur as components of glycoproteins or glycolipids. Some, such as the raffinose series, occur as storage or transport carbohydrates in plants. Others, such as maltodextrins or cellodextrins, result from the microbial breakdown of larger polysaccharides such as starch or cellulose.