Known as edible oils – as opposed to the oil you put into your car – cooking oils have been used for many thousands of years. Today, the supermarket oil aisle is full of different oils to cook with, including sunflower oil, olive oil, peanut oil, coconut oil, avocado oil… the list goes on and on.
In fact you can make cooking oil from almost all types of fruits, vegetables, plants, seeds and nuts. Every year, a staggering 560 billion litres of vegetable oil is produced. That’s enough to fill almost a quarter of a million Olympic-sized swimming pools, but how are cooking oils made?
A Short History of Cooking Oil
Humans have been using oils and fats to cook with ever since they started cooking meat over fires tens of thousands of years ago. Archaeological evidence suggests that olive oil was being used from around 6,000 BC, while rapeseed, poppyseed, almond and sesame oils have been used since at least the Bronze Age.
In the Americas, sunflower seeds and peanuts were roasted, ground and boiled and the resulting oils which rose to the surface of their cooking pots were skimmed off. In Africa, the same thing happened to palm kernels and coconut flesh. This process is known as rendering.
Today, there are dozens of different types of edible cooking oils which all have different manufacturing techniques. In this article we’re going to focus on sunflower oil, so how do they make this cooking oil?
Sunflower Oil - The Manufacturing Process
There are in fact a number of methods of extracting oil including: rendering, mechanical pressing, and extraction using volatile solvents such as petroleum ether. The process we’re about to describe is the ‘cold pressing’ method, which traditionally yields less oil than other extraction methods but with a very high quality finished product in terms of purity, fragrance, flavour and nutritional value. So without further ado, here’s how cooking oil is made.
The sunflower seeds arrive at the processing plant and are fed onto a conveyor belt with overhead magnets to remove any trace metal. They’re usually de-hulled using mechanical crushers or centrifugal force, where they’re spun at very high speeds in a rotating drum. However, some producers use the entire seed, shells and all. Some manufacturers will also crush or flatten the seeds to provide a larger surface area to be pressed.
When we answer the question of how cooking oil is made, the press is the most important step. The de-hulled or complete seeds are put into a low-pressure screw press where the internal temperature is kept below 40°C, hence the term ‘cold press.’ With the press continually monitored to ensure it remains at the correct pressure and temperature, the seeds are fed through this press to extract the oil. On average, 100kg of sunflower seeds produces around 40 litres of oil, but this varies depending on what is being pressed.
The Seed Cakes
Unfortunately, seed cakes aren’t sweet treats. Rather they are the solids that are left over after the oil has been extracted. It’s collected and sold for either animal feed or as an ingredient in fertiliser.
When the oil has been extracted, it’s then pumped through a filtration system. Cloth filters allow the liquid oil to pass through, while any remaining seed cake residue is caught. This process is repeated until the oil is perfectly clear.
When we’re answering ‘how is cooking oil produced’, one of the most important elements of the entire process is the packaging. Natural oils that don’t contain any preservatives have to be very carefully handled because exposure to air and light for any length of time will prematurely spoil them. The oil must therefore be bottled in airtight dark plastic or glass bottles with flow control caps (or metal cans for the export market). Once it’s been quality controlled, it’s boxed up and shipped out. This is the final step in the process of how cooking oil is made.