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Extraction Methods | Types of Fat Structures | Fat Composition
Extraction Methods
There are numerous oils and fats obtained from plant and animal sources that are used for hundreds of culinary, pharmaceutical, and cosmetic products. Some of the oils and fats are produced with refining or rendering processes that usually involve heat and some are simply obtained through pressing. Oils that are obtained through cold extraction, such as olive oil, are usually more expensive than highly refined oils and fats obtained through high heat extraction methods.
| Cold Extraction Methods |
| Cold Pressed |
Cold pressing refers to oils obtained through pressing and grinding fruit or seeds with the use of heavy granite millstones or modern stainless steel presses, which are found in large commercial operations. Although pressing and grinding produces heat through friction, the temperature must not rise above 120ºF for any oil to be considered cold pressed. The maximum temperature for cold pressed olive oil is somewhat lower. Olive, sesame, peanut, and sunflower are among the oils obtained from cold pressing. (Highly refined versions of these oils are also produced.) Cold pressed oils retain all of their flavor, aroma, and nutritional value. |
| Vacuum Extraction |
Vacuum extraction is another method of cold extraction that produces oils with an expeller process. The process occurs in an atmosphere with no oxygen or light. The temperature during the expeller process may be as low as 70ºF. |
| Heat Extraction Methods |
| Expeller Pressed |
Expeller pressing is like cold pressing except that extreme pressure is added during the pressing. As much pressure as 15 tons per square inch is used to squeeze the oil from the fruit or seeds. The high pressure also produces high heat (as high as 300ºF ) through friction, so the oils produced with the expeller process cannot be considered cold pressed. The oils obtained with this method retain much their flavor, aroma, and nutritional value, but not to the extent of cold pressed oils. |
| Solvent Extraction |
Chemical solvents are used to extract oil, which is then boiled to eliminate most of the solvents. Further refining such as bleaching, deodorizing, and heating to high temperatures cleanses the oil, resulting in a product that has very little of the original flavor, aroma, or nutrients contained in the seeds or fruit before processing. Most of the oils produced with this method have a high smoke point and a long shelf life. |
Types of Fat Structures
All oils and fats are 100% fat, but the components that make up the fat structure of a particular oil are important in determining whether or not the oil or fat is considered healthy. While some oils such as olive and canola oil are considered very healthy, all oils are high in calories (about 120 calories per tablespoon) so they should be consumed in moderation.
| Unsaturated Fats |
| Polyunsaturated Fat |
The main sources of polyunsaturated fats are seeds, nuts, grains, and vegetables. Polyunsaturated fat is usually in a liquid state at room temperature and also when chilled. It lowers the overall cholesterol level, but it also reduces HDL or good cholesterol. Recommended daily allowances of polyunsaturated fats should be part of a balanced diet, but some tests have shown that high consumption may actually be damaging to the digestion and nervous systems, so moderation is the key for a balanced and healthy diet.
Omega-3 fatty acid is a type of polyunsaturated fat that is especially healthy. Omega-3 fatty acids help to reduce the risk of heart disease, lower blood pressure, guard against plaque buildup in the arteries, and aid in brain development. It is found in some plant oils and in the tissues of all sea creatures. Among the plant oils rich in omega-3 fatty acids are flax seed, canola, and soybean oil. Fish that are particularly high in omega-3 are sardines, herring, tuna, and salmon. |
| Monounsaturated Fat |
Most animal and vegetable fats contain monounsaturated fat, but in varying quantities. It is usually in liquid form at room temperature, but it may begin to solidify if it is chilled. Monounsaturated fat is the most desirable type of fat in the diet because it helps to decrease the LDL (bad) cholesterol in the blood and helps to increase the HDL (good) cholesterol. Good sources of monounsaturated fat are macadamia nut oil, olive oil, canola oil, peanut oil, and most nuts. Macadamia nut oil has the highest percentage (about 83%) of monounsaturated fat of any edible oil. |
| Saturated Fats |
| Saturated Fat |
Animal fats, butter, cream, and whole milk are the primary sources of saturated fat, which is the least healthy type of fat. Saturated fat raises the level of LDL (bad) cholesterol, which causes numerous health problems if consumed in large quantities. Most saturated fats are solid at room temperature. |
| Hydrogenated Oils |
Trans-fatty acid, also known as trans-fat, is formed when hydrogen is added to vegetable oil in order to change the liquid oil into a solid at room temperature. This process is known as hydrogenation, which also transforms the unsaturated fats of the liquid oils into saturated fat. Like saturated fat, trans-fat may raise blood cholesterol levels and increase the risk of heart related diseases. Many shortenings, margarine, and commercially baked goods are high in trans-fatty acids.
One advantage that hydrogenated or partially hydrogenated fats have is that they are less likely to turn rancid, which is very beneficial to the commercial food industry in creating foods with a longer shelf life. As with any type of food containing saturated fat, foods containing hydrogenated or partially hydrogenated fat should be enjoyed in moderation in order to maintain a balanced and healthy diet. |
Fat Composition
|
Fat Composition of Various Oils and Fats
(Percentages in bold indicate that an oil contains either the highest
or lowest level among edible oils for a particular fat component.) |
| Type of Oil or Fat |
Saturated |
Monounsaturated |
Polyunsaturated |
| Mustard Oil |
1% |
76% |
23% |
| Canola Oil |
6% |
62% |
32% |
| Almond Oil |
8% |
73% |
19% |
| Hazelnut Oil |
10% |
76% |
14% |
| Safflower Oil |
10% |
13% |
77% |
| Sunflower Oil |
11% |
20% |
69% |
| Grape Seed Oil |
12% |
17% |
71% |
| Corn Oil |
13% |
25% |
62% |
| Macadamia Nut Oil |
14% |
83% |
3% |
| Olive Oil |
14% |
77% |
9% |
| Sesame Oil |
14% |
40% |
46% |
| Walnut Oil |
14% |
19% |
67% |
| Soybean Oil |
15% |
24% |
61% |
| Peanut Oil |
18% |
49% |
33% |
| Avocado Oil |
20% |
70% |
10% |
| Margarine (Soft) |
20% |
47% |
33% |
| Wheat Germ Oil |
20% |
30% |
50% |
| Cottonseed Oil |
24% |
26% |
50% |
| Lard |
41% |
47% |
12% |
| Palm Oil |
52% |
38% |
10% |
| Cocoa Butter |
62% |
35% |
3% |
| Butter |
66% |
30% |
4% |
| Margarine (Hard) |
80% |
14% |
16% |
| Palm Kernel Oil |
86% |
12% |
2% |
| Coconut Oil |
92% |
6% |
2% | |
