Final answer:
Polyunsaturated fatty acids are the most prone to rancidity due to their multiple carbon-carbon double bonds which make them susceptible to oxidation and hydrolysis, leading to off-flavors and odors. Antioxidants can help prevent this process.
Step-by-step explanation:
Polyunsaturated fatty acids are most susceptible to rancidity because they contain many carbon-carbon double bonds. Fats and oils undergo a process known as rancidity when they get contaminated with enzymes like lipase or are exposed to atmospheric conditions that lead to oxidation and hydrolysis of unsaturated fatty acids at the double bonds, resulting in substances like hydrogen peroxide that give a bad odour and taste to the fat.
Fatty-acid chains can be grouped based on the presence of carbon-carbon double bonds; saturated fatty acids have none, monounsaturated fatty acids have one, and polyunsaturated fatty acids have two or more. These double bonds introduce kinks in the fatty acid chains, making them less tightly packed and more prone to oxidation. Saturated fats, which are solid at room temperature, are more stable as the straight chains pack closely together, limiting rancidity. In contrast, polyunsaturated and monounsaturated fats, which tend to be liquid at room temperature, are less stable and more prone to rancidity.
Antioxidants, like vitamin E and vitamin C, can prevent rancidity by protecting the double bonds in unsaturated fats from oxidation.