Warmed-over flavor (WOF) is a major hurdle facing the meat and food industries that deal with pre-cooked meat products. It has been suggest that WOF develops due to the loss of fresh meat ...characteristics and the increase in undesirable lipid oxidation notes (Kerler and Grosch, 1996). This research was conducted in three experiments to determine the onset of WOF. In experiment 1 WOF was investigated in raw vs. cooked beef patties products. Results of experiment 1 indicated that sensory panel was able to differentiate between cooked beef patties that stored for 3 hours, and reheated from cooked patties stored for 48 hours at 4°C and reheated. Gas chromatography profile showed that hexanal did not increase significantly, and pentanal and heptanal increased significantly for some these same products. In experiment 2 WOF was investigated in beef patties stored at 4°C or −18°C for 0, 3, 6, 12, 24, or 48 hours, and reheated using convection or microwave ovens. Sensory analysis revealed no significant difference (p > 0.05) due to all treatments. TBARS values showed that some significant differences existed due to storage temperature and storage time's interactions. Further, GC-MS profile showed that hexanal production increased but insignificantly, and other compound such as octanal and heptanal increased significantly at certain storage times. In experiment 3 WOF was investigated in beef patties cooked at oven temperature of 121°C vs. 232°C and stored at 4°C for 0, 6, 12, 24, or 48 hrs. and reheated using a microwave oven. Sensory panel were unable to detect difference in WOF in all treatments. TBARS values of beef patties cooked at 121°C were greater than patties cooked at 232°C. GC-MS analysis revealed that hexanal is the only compound detected in all treatments. Three additional experiments (4, 5, and 6) were conducted to investigate the use of Mass spectrometry (M-S) based Electronic nose (EN) in meat research. Experiment 4, focused on the use of EN in Electron impact (EI) and Negative chemical ionization (NCI) modes to differentiate between beef patties, raw and cooked to an internal temperature of 54.4°C and 82.2°C. This data were analyzed using Hierarchic Cluster Analysis (HCA) and Principal Component Analysis (PCA) and showed that the EN in both modes could differentiate between the beef products in experiment 4. However, EN in EI mode was unable to differentiate between beef patties containing 10 and 30 percent fat either raw or cooked (experiment 5). Further, EN in NCI mode was unable to differentiate between cooked beef patties made from meat tissues produced in different locations (experiment 6).
