Sensory and chemical analysis of cooked porcine meat patties in relation to warmed-over flavour and pre-slaughter stress.

Two independent sensory profiles were carried out to evaluate warmed-over flavour (WOF) development in cooked, chill-stored and reheated pork patties. The patties were derived from the Musculus semimembranosus of animals subjected to different pre-slaughter stress treatments. All patties were stored in oxygen permeable bags at 4°C for 0, 1, 2, 3 and 5 days to facilitate WOF development. In addition, thiobarbituric acid reactive substances (TBARS), conjugated dienes, pH, water content, total lipids and the fatty acid compositions of phosphatidyl choline (PC), phosphatidyl ethanolamine (PE) and total lipids, were measured in the cooked meat patties. A data analytical strategy involving Analysis of Variance-Partial Least Squares Regression (ANOVA-PLSR), to determine relationships between the design variables (WOF and pre-slaughter stress) and the sensory-chemical data, and PLSR to elucidate predictive links between the sensory and chemical data was utilised. WOF was found to involve the development of lipid oxidation derived nuance off-flavour and odour notes, e.g. rancid-like flavour and linseed oil-like odour, in association with a concurrent decrease in cooked pork meat-like flavour. The reduction in "meatiness", over the initial days, 0-2 of WOF development was attributed to the degradation of both, unstable sulfur-containing amino acids in meat proteins and sulfur-containing "meaty" aroma compounds. Whereas, at the later days, 3-5 of WOF development the "meaty" loss was ascribed to perceptual masking by lipid oxidation products. TBARS and conjugated dienes were found to be significant (P<0.05) predictors of the sensory terms related to the lipid oxidation aspect of WOF. Whilst the polyunsaturated fatty acid (PUFAs) contents of PE, PC and the total lipids were found to decrease with WOF development, reflecting their loss in lipid oxidation reactions. The sensory variation related to pre-slaughter stress appeared to be distinct from WOF variation and was described by a sour to sweet taste continuum. However, interactions were noted that indicated increasing pre-slaughter stress resulted in a decreased sensory perception of WOF. Moreover, pH and water content were found to significantly (P<0.05) predict the sensory effects resulting from pre-slaughter stress.

Warmed-over flavour in porcine meat - a combined spectroscopic, sensory and chemometric study.

The effectiveness of applying rapid spectral techniques in the prediction of meat quality in relation to pre-slaughter stress and warmed-over flavour (WOF) was investigated. The effect of pre-slaughter stress on the development of WOF is a relatively new area of interest in WOF research. The present study investigated the relationship between pre-slaughter stress and WOF characteristics (after 0 to 5 days' storage) in porcine meat as evaluated by chemical, sensory and spectroscopic methods. Sensory evaluation, visual reflectance spectroscopy (VIS) and low-field (1)H NMR (LF-NMR) proved efficient in describing the different stress groups and the storage period, whereas fluorescence spectroscopy and the TBARS test were only able to follow WOF during storage. Near Infrared Reflectance (NIR) and Raman scatter showed a very weak relationship to pre-slaughter stress and levels of WOF during storage. Good correlations (up to r=0.93) of sensory terms were achieved with VIS and fluorescence spectroscopy and LF-NMR.