Scientifically oil is one flammable, viscous, volatile or non-volatile, organic or inorganic, edible and non-edible, reusable or non-reusable, and biodegradable or non-biodegradable substance that is insoluble in water and remains liquid at room temperature. Oil can be extracted from a wide variety of sources including plant derivative, microalgae, animal fat, and petroleum (crude oil). Some of these are safe, nutritious and hygienic for human consumption and thus are commonly used as food ingredient and for cooking including sautéing, frying and baking. Such oils are termed as edible oils; while others, which are not safe for human consumption and thus are not used as food, are termed as non-edible oils.
Vegetable oils are all those oils that are derived from plant products like seeds, nuts and fruits. Its popular sources include groundnut, soybean, sunflower, rapeseed, linseed, safflower, peanut, coconut, plum, olive, etc. Such oils usually don’t contain any toxic substance like lectin. With the diversification of crop production over last couple of decades, now-a-days many other sources have been emerged that include neem, tobacco, castor, drumstick, almond, avocado, bean, rice, salmon, etc. Oil extracted from such non-conventional plant sources are not commonly used as food; rather they fulfil growing industrial demands for producing various items. Therefore, vegetable oils may not necessarily be edible; however, they are organic, bio-degradable and reusable.
Mineral oils are petroleum based hydrocarbons that are derived by distillation of crude oil. These are usually by-products of crude oil refining process while extracting gasoline and other petroleum products. These are usually colorless and odourless but not suitable as food ingredient for human consumption as they content various toxic compounds. However, they are overwhelmingly used for several industrial applications such as production of baby oil, cosmetics, laxative, paint, varnish, lubricant, coolant, engine oil, brake fluid, cutting oil, etc. Apart from crude oil, mineral oils can also be extracted from oil shale, especially cannel coal; however, extraction is very costly and are not conventionally done. Various differences between vegetable oils and mineral oils are given below in table format.
Table: Differences between vegetable oil and mineral oil
| Vegetable Oil | Mineral Oil |
|---|---|
| Vegetable oils are derived from plant sources like oilseeds, nuts, fruits, etc. | Mineral oils are derived from crude oil or petroleum based sources. |
| Vegetable oils contain fatty acid. So these are actually fat. | Mineral oils don’t contain fatty acid. They are not true fat. |
| These are bio-degradable organic compounds. | These are also organic compounds but rarely bio-degradable. |
| Vegetable oil can spoil naturally with time. Thus they have less impact towards environment pollution. | Mineral oils show very low spoilage rate. They spilling causes environment pollution. |
| Most of the vegetable oils are nutrient rich and are edible. | Mineral oils are not meant for eating or food ingredient. |
| These oil sources are based on annual, biennial or perineal plants. So it can be reproduced easily. | Global mineral oil (crude) reserves are depleting rapidly. It takes millions of years to reproduce. |
Sources: Mineral oil and vegetable oil are obtained from different sources and thus have different properties. Vegetable oils have predominantly plant based sources like oilseeds, nuts and fruits. Typical sources from where vegetable oil is extracted include seeds or fruits of groundnut, soybean, sunflower, rapeseed, safflower, peanut, neem, tobacco, castor, drumstick, almond, avocado, palm, coconut, olive, etc. Such seeds are first dried and then compressed without or without heating (cold pressing and hot pressing). On the other hand, mineral oils are extracted from crude oil (unprocessed petroleum). These are by-products of crude oil refining process obtained during extracting gasoline and other petroleum products. Mineral oil can also be extracted from candle coal (terrestrial type oil shale) but is not commonly done due to high extraction cost and low output.
Mineral oil is not actually oil: Biologically, fat is considered as oil. So oil must contain fatty acid. Vegetable oils do contain fatty acid and thus are fat; however, mineral oil is not a fat. Outside the boundary of biology, every liquid (at normal temperature) derived from petroleum can be considered as oil.
Bio-degradability and spoilage: Biodegradation is defined as the bio-chemical process by which compound organic substances are gradually broken down (reduced) into simpler compounds by living microbial organisms including bacteria and fungi. Biodegradability is the measure of possibility or rate of biodegradation of specific substance under defined conditions. Organic substances are commonly biodegradable but not all substances depict same level of biodegradability. Vegetable oil, being the simplest form of hydrocarbon, shows high biodegradability as microorganisms can easily digest to reduce it to carbon di-oxide. Their spoilage also has little concern towards environment pollution as these are degraded naturally. Mineral oils, being complex hydrocarbon, show very low bioremediation rate in natural conditions and thus its spilling (either accidentally or due to human activities) poses great hazard for terrestrial and marine ecosystems. Most bacteria fail to establish a favourable condition to enhance degradation rate due to toxicity of mineral oils and thus yeast and fungi became primary decomposer.
Edible or non-edible oil: An edible oil is one that is nutritious and digestible for human when consumed directly or indirectly as food ingredient. They must not contain toxic element that can pose health risk. Majority of vegetable oils are edible; however, certain oils (like oil extracted from groundnut, soybean, sunflower, rapeseed, safflower, peanut, etc.) are nutrition rich and thus are consumed commonly. Other vegetable oils are commercially used for various industrial applications. Mineral oils are non-edible; they are produced for industrial or household usage. Their typical applications include production of animal laxative, lubricant, coolant, engine oil, brake fluid, grease, etc. Some of them also have pesticidal, medicinal and cosmetic usages.
Reproduction: Vegetable oils are extracted from plant derivatives and thus these are renewable and inexhaustible. Mineral oils are based on petroleum or crude oil which has limited storage. Global crude oil reserve is depleting day by day. Crude oil forms naturally by geothermal process when large scale dead zooplankton and algae are buried under sedimentary rock and subjected to intense heat and pressure. Naturally occurring petroleum takes millions of years for formation, which is far longer than can be deemed renewable. So mineral oil cannot be replenished, at least within the time scale of human. This global concern has paved the way for extensive research to find out alternative. Many vegetable oils have showed potential capability in several fields most prominently bio-fuel.