One of the major causes of quality deterioration in foods is related to lipid oxidation or rancidity. During this process, lipids oxidize through a complex series of reactions generating undesirable aromas, off-flavors, color fading, browning, and/or color degradation. The products of oxidation also reduce the nutritional value of the food and can pose health risks due to the formation of oxidation products that are suspected to be toxic. Various technologies are used to determine the oxidative state of food products. Alpha MOS e-nose system proposes a fast, flexible and complementary solution for assessing the quality and the oxidative state from raw material to finished pet food products. Data analysis illustrating the use of the e-nose system to rapidly discriminate, identify and quantify off-flavors affecting pet food products will be presented. Predictive models using the e-nose profiles, hexanal concentration, peroxide values and aroma descriptions of pet food products were established.