Effects of lipids and processing conditions on the sensory characteristics of extruded dry pet food

The effects of fat type, fat content, and initial moisture content on the sensory attributes of extruded dry pet food were studied. A "Difference-from-Control" descriptive analysis was used to evaluate the extrudate sensory characteristics every 2 to 3 months for 14 months. There was no significant change of the intensity of attributes over time for no fat added samples and the results indicated their sensory characteristics remained stable within the studied time period. Significant correlation was found between sensory lightness and lipid oxidation of the pet food with fat addition. The instrumental L value was also found to have a high correlation with the sensory lightness. Principal Component Analysis (PCA) plots showed that the addition of fat enhanced the perceived fatty, painty, and cardboardy odors and oily surface of the pet foods; and the effects of beef tallow were more significant than poultry fat on these attributes. The highly correlated attributes of fatty, painty, and cardboardy odors indicated that the strong and characteristic aroma of beef tallow and poultry fat might interfere with the perception of painty and cardboardy odors, which represent the aroma of lipid oxidation.