Cold pressing is used to extract the essential oils from citrus rinds such as orange, lemon, grapefruit and bergamot. The rinds are separated from the fruit, are ground or chopped and are then pressed. The result is a watery mixture of essential oil and liquid which will separate given time.
Cold pressed oil is oil which has been produced with the use of a low heat technique. The introduction of heat to the process of making oil will degrade the flavor, nutritional value, and color of the oil. Heat, however, increases the yield. For this reason, cold pressed oil tends to be more expensive, although it is also of higher quality.
The term “cold pressed oil” is subject to different regulations, depending on the part of the world in which it is made. In the European Union, for example, oil which is labeled as cold pressed must be produced in an environment which never exceeds a certain temperature. The temperature varies, depending on the oil, but is generally around 80 degrees Fahrenheit (27 degrees Celsius). In the United States, oil labeling is not regulated, so “cold pressed oil” may not actually be cold pressed oil at all. Consumers will need to smell, taste, and see the oil to determine whether or not it is truly cold pressed.
When oil is made, the nuts, seeds, or fruits being used to make the oil are first ground into an even paste. The paste goes through a malaxation process, a slow stirring which encourages the oil in the paste to clump. To extract the oil, pressure is applied, forcing the oil out of the paste. Heating the paste will increase the yield of oil. Some producers mix the paste with warm water, or heat it before pressing. Others make cold pressed oil by using an oil stone alone to remove the oil. After the oil has been produced, it is graded and bottled.
Some companies manufacture “expeller pressed oil” which is made in a high pressure environment. The high pressure is sometimes necessary with thick nuts and seeds, but it creates heat through friction. Some expeller pressed oil can be termed cold pressed, because the temperature does not rise a great deal. Other expeller pressed oil, however, is made at very high temperatures, and cannot be considered cold pressed oil. Companies may clarify by specifically labeling a product “expeller cold pressed oil.”
We are all familiar with the spray of orange essential oil that can be released by scoring or zesting the skin of the fruit. The cold pressed citrus oils are commercial produced just this way, by machines which score the rind and capture the resulting oil. Although many citrus oils are also produced by steam distillation, they seem to lack the vibrancy of the cold pressed oils.
It is important to note that oils extracted using this method have a relatively short shelf life, so make or purchase only what you will be using within the next six months.