Any kind of oil for cooking, they are all produced either by cold pressing or hot pressing. Cold pressing is the traditional and ancient method whereas hot pressing the modernized Commercial method. Though, one may not be able differentiate while cooking or while tasting food, but the two distinct methods of production – cold pressed and hot pressed end up becoming completely different finished products.
Cold pressing, oil is extracted at room temperature, and hence the acid values are relatively low, so oil products are obtained after precipitation and filtration eventually there is no need for any refinement. These are the traditional oil still sold at Oil mills (Girni).
Hot pressing involves extracting oil at high temperatures, and because the acid value rises significantly, it loses most of its natural quality; therefore hot pressed oils are refined to make them fit for consumption. These are the Oil available conveniently at any departmental store in any package size.
Cold pressed oil retains most of its natural physiological and chemical properties and most importantly its original taste.
Hot pressed oil retains little of its natural composition. The high temperatures not only change the chemical structure of oil, but in the process, a lot of important substances like vitamin E, sterols, and carotenoids. On the bright side, hot pressed oil smells good, especially when extracted from the seeds of oily plants like sesame.
Cold pressed oil on average yield 35% – 50% of the total weight depending upon the variant of oilseeds. Hot pressed oils yield an average of 40% – 60% of the total weight, and hence preferred by oil manufacturers.
Cold pressed oils do not foam or silt and stay natural.
Hot pressed oils have possibility of undergoing these changes while cooking and forming foam.
From a health perspective, cold pressed oil is the clear winner. Hot pressed oils undergo oxidisation, which can cause complications like cancer and inflammation. Moreover, a lot of healthy compounds are lost from the oils while hot pressing, whereas in cold pressing, all beneficial compounds are retained. Another important factor that makes cold pressed oils a better choice is that it involves no refinement, unlike hot pressed oils which are refined to improve taste and acidic content.