Effects of defatting and cooking methods on pig large intestines volatile compounds by flavor omics and fatty acids

Pig large intestines (PLIs) are a food with a selective preference globally because of characteristic odors. To investigate the effect of defatting and different cooking methods on the volatile compounds of PLIs, defatted and nondefatted samples were cooked using steaming, water boiling, and frying. A total of 63 volatiles were identified, including 22 compounds detected in all samples. Using odor activity value (OAV) and sensory evaluation, 3-methyl indole and p-cresol, with animal and fecal odors, respectively, were identified as the key off-odors of PLIs. The three cooking methods increased the concentration of aldehydes and endowed samples with fatty and green odors derived from lipid oxidation, especially C18:1n9c and C18:2n6c. Frying significantly increased the content of (E)-2-heptenal and (E,E)-2,4-decadienal (P < 0.05) due to higher contents of C18:2n6c. Compared with steaming and frying, water boiling could significantly reduce the occurrence of off-odors and had the best result combined with defatting. Using orthogonal partial least squares-discriminant analysis (OPLS-DA) and variable importance for the projection (VIP), p-cresol could act as a marker to discriminate samples with different treatments.