Posts Tagged ‘fractionation’

Wonders of extraction: Oil

Friday, October 24th, 2008

Brazilian chiles in oil (very nice with Moqueca!)

Oils and fats are long molecules which are mainly non-polar and hence the opposite of water which is a polar molecule. Ethanol which has both a polar and a non-polar end falls in between oil and water. I’ve covered extractions using water and ethanol previously. That water and oil are opposites is easily observed by the fact that they don’t mix, and because of it’s lower density oil floats on top of water. This property allows us to easily separate water and oil.

Volatile molecules – the molecules that we detect by their smell – are mainly non-polar and therefore soluble in oil. This is one reason why foods with fat often have a different and often better flavor compared with their fat-free counterparts (fat of course also influences mouth feel etc.). Everytime you cook with oil it will actually help extract aroma (or smell flavorants) from the food ingredients and deliver these to your nose.

There are several oil extracts used in the kitchen, and the nice thing about them is that the oil extracts aromas and then protects them from the air. This is good as it prevents oxidation of the aroma molecules, but in some extreme cases bad because the anaerobic conditions may promote growth of botulinum spores – more on that in the last paragraph. When the flavored oil is added to a dish you get can immediately perceive the aroma. If the oil is tasted pure it serves as a carrier for the aroma giving a small explosion in the mouth (or nose to be more precise…). Some examples I can think of where the oil plays an important role in extracting and delivering aromas are: pesto, tapenade, mayonaise, aioli, curry paste (and all other spice pastes), chili oil and truffle oil to mention a few. Notice that in most of these the source of the aromas is still present in the oil.