It is the foul smell produced by the oxidation of oils and nuts.
Mostly the bitter taste of peanut and food made by frying is due to rancidity .
Normally the oily substances which are not covered properly , react with the oxygen of air and get oxidised thus give a foul smell.
Removal of oxygen avoids the oxidation of fool items. So during packaging nitrogen gas is used to make inert atmosphere .
That is the reason most of the chips are packed with plenty of Nitrogen gas.