How to choose the best oil for cooking

Unrefined oils are very popular today, whether we use them or not we hear about them all the time. Most areas in Bangalore will have shops with  wood oil press units selling non refined oils under various tags like cold pressed and wood pressed. In this blog lets dig around a bit into cooking oils how they are processed 

Necessity of cooking oil – ICMR dietary guidelines state that 30 % of our calories intake should come from fat. For an average person who needs 2000 calories a day that would be 600 calories from oils. Each ml of most edible oil contains around 8 calories, so directly or indirectly we should be consuming 75 ml of oil daily as part of a healthy balanced diet.

Another reason we love cooking with oils has more to do with physics and chemistry.  Oil functions as an excellent heat transfer medium due to its high smoking point, we can’t fry food with water as it would simply evaporate making the food stick to the pan. Oil facilitates Maillard reaction, which is how we get the fried crust on the outer surface of fried foods like samosas and pakoras we love so much. The below video will explain this in detail.

History of Edible oil 

The first oils to be used in antiquity were (However gross it may sound) were animal fat. When cooking meat animal fat would separate and this would be collected and be used as oil for lamps, baking and frying. 

As early as 6000 BCE extracting oil from plant material had already begun. The crudest method by which this was done was by roasting oil seeds, beating into a pulp and boiling the resulting with water. The oil which would rise to the surface would be skimmed off and stored. By this method maybe 10 % of oil contained in the seed could be extracted.

In the middle ages attempts at refining this process were made by using edge runners (Sort of todays wet grinders) to crush seeds and nuts and then applying pressure using lever or screw presses 

Ancient Edge runner used to crush oil seeds

Till the eighteenth century the basic principle of oil extraction remained the same i.e crushing and pressing out the oil. Better crushers and presses were invented and innovated making squeezing out more oil from the seeds possible. We had come from extracting 5% to 85% of oil from oil seeds.

A Breakthrough called solvent extraction invented in 1843 meant that the last few drops of oil could be squeezed out. Solvent extraction as it names implies uses pumping of chemical solvents through the mash, this dissolves the oil in the solvent which will be separated later. From 10 % oil extraction through solvent extraction the process reached efficiency of 95-98 % in some cases. Today solvent extraction is the gold standard of vegetable oil industry   

The Problem with Refined oils 

Refined oil are being called everything from non nutritional to cancer causing, to understand why let’s take a look at various stages of refined oil production and the chemicals used 

Solvent extraction 

Hexane is the main solvent used in extraction of most oils, although it is evaporated and reclaimed for reuse anywhere from 0.2 to 0.8 milligrams gets left behind in the oil. This is claimed as safe for consumption by most food safety standards of the world. But Hexane is a well known air pollutant  and when inhaled causes neurotoxicity. The workers of these factories where hexane is used are exposed to it and continuously at risk.


After solvent extraction the oil undergoes a multistep refining process which makes the oil as flavorless and nutrient less as possible, all this is done in the name of increasing shelf life and look of the oil. Let’s take a look at what the various steps are and which chemicals are used

Degumming  : It is the removal of  natural gums, waxes present naturally in vegetable oil. Un filtered oils will have a small distinct  layer of these gums and waxes  at the bottom. This layer is composed of natural gums and waxes present in the oil seeds. The only reason these are removed is to improve appearance of the along and increase shelf life. Most of the time the degumming is done by hot water or steam, but some oils need the use of phosphoric acid for degumming.  This highly corrosive acid destroys nutrients and changes the PH of the oil.  

Neutralization : Natural free fatty acids in the oil are removed to improve appearance and shelf like. Caustic soda (Lye) is mixed with the oil, the free fatty acids convert to soap after reacting with caustic soda. This soap is washed off using hot water from the oil. This process makes the refined oil have neutral PH. 

Ever wondered why some store bought oils never work the way they are supposed to as skin remedies ?. This is because of this change in PH. An oil which must have been prescribed for a skin ailment because of its alkaline nature wont work because its PH has been changed during the refining process. 

Bleaching :   Ever wondered why most oils on a supermarket aisle have the same golden yellow attractive color ?. Sunflower, soya, groundnut all oils look the same because they have been bleached. This means color pigments like carotenoids and chlorophylls have been removed. A inert absorbent material known as bleaching earth is used for this. Although nothing dangerous is added in this process, carotenoids are antioxidants i.e they protect us from oxidative stress, they help fight against cancer. All these properties are lost due to bleaching.

Winterisation : None of the refined oils solidify. Natural unfiltered oils will have fatty acids and waxes which will start forming crystals at lower temperatures. Although these are perfectly natural and do not affect the long term storage or taste, they are removed because on the supermarket aisle they may make the oil look cloudy at lower temperatures. Winterisation normally does not involve chemicals. Oils are cooled gradually and the waxes and free fatty acids which start crystallizing are removed by centrifugation. But in some cases a small amount of ethanol may also be added to make this process fast.

Deodorisation :  Try smelling different types of refined oil, there may only be a faint smell of peanut or coconut coming from the bottle. To remove the natural smell of oil it is normally boiled at a low pressure at 200 C. This high temperature has a devastating effect on natural carotenoids and  tocopherols ( Vitamin E). Sometimes citric acid is also added after this step to chelate out any trace minerals left after all the previous processing steps. This deodorizer distillate which contains several health beneficial components removed from the oil is again used in a lot of health supplements. Ironically these beneficial components of the oil are separated, packaged and sold to us at premium price.

This is the final process of the industrial oil refining process, now oil out of which everything beneficial has been removed is packaged and sold in good looking bottles to us.

If this processing is done guidelines issued by FSSAI this oil although bereft of most nutritional components should not contain many harmful chemicals above a certain permitted levels. But regular use of these oils like we do in Indian cooking means we are being exposed to these chemicals more than any other population. And the question remains are these chemicals being used in the recommended levels. Who is watching the industries from abusing these chemicals to squeeze out a few more drops of oil.

The bigger problem with refined oils is actually something else. Around 10 metric tonnes of palm oil is imported into India, A third of it is distributed through the public distribution system to those below poverty line. Where does the 7 metric tonne go ?Some may be used by the fast food and food processing industries, the dirty open secret only to those who have contacts in these industries is that it’s used to adulterate all types of cooking oils. The groundnut oil you are buying at 160/liter could contain as much as 70% palm oil which costs about 50 – 60 per liter. So although many may think we are getting refined groundnut oil at a decent price we are actually being sold adulterated palm oil at double the price.

The only way to avoid consumption of nutritionally deficient, adulterated and probably carcinogenic flavorless, colorless oil is to buy cold pressed and wood pressed oils directly from farmers. 

What is the difference between cold pressed and wood pressed oils ?

They are more or less the same nutritionally. Both are processed using the age old method of grinding and pressing the oil seeds to expel the oil. No harsh chemicals, solvents are used in both methods. The nutrition of the oil seed is not lost due to low temperature. Wood pressed oils use a mortar and pestle made of wood, the rotary motion which crushes the seed is provided by an electric motor. In cold pressing the same components are made using stainless steel. 

Generally wood pressed oils may cost more than cold pressed oils as the wooden mortar and pestle will wear out eventually and need replacing. Technically speaking all wood pressed oils are also cold pressed oils but not the other way around.  

At farmizen you will be able to buy both cold pressed and wood pressed oils directly from farmers. The bottles and labels used may not be as fancy as those used by the oil industry giants. Some which may be only once or twice filtered will be a little cloudy with some sediment, but this is only natural and adds flavor to the cooking. The more you filter these the more nutritional is lost.     


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