Fat Oxidation and Rancidity

The most important chemical damage suffered by meats is the breakdown of their fats by both oxygen and light into small, odorous fragments that define the smell of rancidity. Rancid fat won’t necessarily make us sick, but it’s unpleasant, so its development limits how long we can age and store meat. Unsaturated fats are most susceptible to rancidity, which means that fish, poultry, and game birds go bad most quickly. Beef has the most saturated and stable of all meat fats, and keeps the longest.