Fats and oil

From the research, it shows that the hazard that fats and oil will have is rancidity.

Rancidification is the decomposition of fats and other lipids by hydrolysis and/or oxidation. Hydrolysis will split fatty acid chains away from the glycerol backbone in glycerides. These free fatty acids can then undergo further auto-oxidation. Oxidation primarily occurs with unsaturated fats by a free-radical-mediated process. These chemical processes can generate highly reactive molecules in rancid foods and oils, which are responsible for producing unpleasant and obnoxious odors and flavors. These chemical processes may also destroy nutrients in food.

So if the fats or oil undergoes rancidity, it will produce unpleasant odours and flavour which will directly affect the quality of the food product.