OIL AND FAT: SOURCES OF FAT
Diagram
Fat from animals, oil from plants
Animal fat
Fat rendered from animal tissue, such as lard from pigs and tallow from cattle. Usually solid at room temperature.
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Vegetable oil
Oil pressed or extracted from seeds, fruits or nuts, such as soybean, sunflower and olive oil. Usually liquid at room temperature.
Figure 1: Animal fats are usually solid and rich in saturated fat, while vegetable oils are usually liquid and rich in unsaturated fat. Drawn in our own style from the fats and oils discussion in O’Brien, Fats and Oils, and in Gunstone, Vegetable Oils in Food Technology.
Introduction
Animal fat and vegetable oil are both cooking fats, but they come from different sources and behave differently. Animal fat is rendered from the tissue of animals, such as lard from pigs and tallow from cattle, and it is usually solid at room temperature because it is rich in saturated fatty acids. Vegetable oil is pressed or extracted from seeds, fruits or nuts, such as soybean, sunflower and olive, and it is usually liquid at room temperature because it is rich in unsaturated fatty acids. That difference in fatty acids decides the melting point, the keeping quality and the cooking use.
Quick comparison
Table 1: Animal Fat compared with Vegetable Oil
| Aspect | Animal Fat | Vegetable Oil |
|---|---|---|
| Source | Animal tissue, rendered by heat | Seeds, fruits or nuts, pressed or solvent extracted |
| Examples | Lard, tallow, butterfat | Soybean, sunflower, olive, rapeseed and palm oil |
| State at room temperature | Usually solid | Usually liquid, except palm and coconut oils |
| Saturated fatty acids | High | Low, except palm and coconut oils |
| Unsaturated fatty acids | Low | High |
| Melting point | Higher, so the fat is solid | Lower, so the oil is liquid |
| Flavour | Meaty, characteristic of the animal | Mild to fruity, by the source |
| Oxidation | More stable, because fewer double bonds are present | Less stable, because more double bonds are present |
| Cholesterol | Present, because it comes from animals | Absent, because plants do not make cholesterol |
| Use | Baking, frying and pastry where a solid fat is wanted | Frying, dressings and cooking where a liquid oil is wanted |
Scientific explanation
Definition
An animal fat is a fat obtained from animal tissue by rendering, and it is usually solid at room temperature and rich in saturated fatty acids. A vegetable oil is an oil obtained from plant seeds, fruits or nuts by pressing or solvent extraction, and it is usually liquid at room temperature and rich in unsaturated fatty acids.
Working principle
Animal fat is made by heating animal tissue so the fat melts out, then separating the liquid fat from the solids. The fatty acids in animal fat are mostly saturated, which means their chains are straight and pack tightly, so the fat is solid at room temperature. Vegetable oil is made by pressing seed or fruit, or by solvent extraction followed by refining. The fatty acids in most vegetable oils are mostly unsaturated, which means their chains are bent at the double bonds and cannot pack tightly, so the oil stays liquid. Palm oil and coconut oil are exceptions: they are vegetable oils rich in saturated fatty acids, so they are solid or semi-solid.
Apparatus
The books used here name no laboratory apparatus for measuring or comparing either term, so no apparatus list is given.
Measurement procedure
The books used here give no standard laboratory procedure with volumes and steps for either term, so no procedure is invented here.
Factors affecting readings
For animal fat, the animal species, the feed and the tissue decide the fatty acid mix and the firmness: lard is softer than tallow. For vegetable oil, the plant species and the extraction and refining steps decide the flavour, colour and keeping quality. Storage matters for both: air, light and heat spoil oils faster than solid fats, because unsaturated fatty acids oxidise more readily.
Formulas and calculations
The books used here give no formula for either term, so no formula is given here.
Industrial applications
- Animal fat: pastry and baking, where lard gives a flaky texture.
- Animal fat: frying, where tallow gives a firm fat that resists oxidation.
- Animal fat: traditional cooking and meat products, where its flavour is wanted.
- Vegetable oil: salad dressings and dipping, where a liquid oil is wanted.
- Vegetable oil: frying and general cooking, where a neutral liquid oil is wanted.
- Vegetable oil: food manufacture, as the base for margarines, shortenings and sauces.
Advantages and limitations
- Animal fat, advantage: it is solid at room temperature, gives a flaky pastry texture, and resists oxidation.
- Animal fat, limitation: it is rich in saturated fatty acids and contains cholesterol, and it is not suited to dressings that must stay liquid.
- Vegetable oil, advantage: it stays liquid, so it pours for dressings, and most vegetable oils are rich in unsaturated fatty acids.
- Vegetable oil, limitation: unsaturated oils oxidise faster than solid animal fats, so they need dark, cool, closed storage.
FAQ
What is the main difference between animal fat and vegetable oil?
Animal fat comes from animals, is usually solid and rich in saturated fat, while vegetable oil comes from plants, is usually liquid and rich in unsaturated fat.
Is every vegetable oil liquid?
No. Palm oil and coconut oil are vegetable oils rich in saturated fat, so they are solid or semi-solid at room temperature.
Which one contains cholesterol?
Animal fat contains cholesterol. Vegetable oil does not, because plants do not make cholesterol.
Why is animal fat solid and vegetable oil liquid?
Animal fat has mostly straight saturated chains that pack tightly, while vegetable oil has mostly bent unsaturated chains that cannot pack tightly.
Which one keeps longer?
Animal fat usually keeps longer, because its fewer double bonds make it slower to oxidise.
References and further reading
- FTN books on disk: Technology of Fats and Oils.
- O’Brien, Richard D. Fats and Oils: Formulating and Processing for Applications. 3rd ed., CRC Press, 2008 (Google Books page read)
- Gunstone, Frank. Vegetable Oils in Food Technology. Wiley, 2011.
- Google Books pages read for this article:
- O’Brien, Richard D. Fats and Oils: Formulating and Processing for Applications. 3rd ed., CRC Press, 2008 (Google Books page read)
