Effect of pre-slaughter physiological conditions on the oxidative stability of colour and lipid during chill storage of sliced, retail packed roast ham

摘要

Pre-slaughter physiological conditions (A serving as control, B subjected to treadmill exercise immediately prior to stunning, C epinephrine injection 15 h prior to slaughter, and D epinephrine injection 15 h prior to slaughter and subjected to treadmill exercise immediately before stunning) were found to significantly affect colour and lipid oxidation of sliced, retail packed roast ham, produced from nitrite-cured (78 ppm nitrite) M. Longissimus dorsi. The pre-slaughter treatment resulted in variations in the level of glycogen, lactate, ATP and IMP and pH development as monitored in Longissimus dorsi muscles, with the lowest ultimate pH (pH_u) in muscles from non-epinephrine treated pigs (treatments A and B). The initial tristimulus L~*-value and the L~*-value during chill storage of sliced roast ham packed in laminates with low or with very low oxygen transmission rate (OTR = 40 and <0.5 cm~3/m~2/atm/24 h, respectively) were significantly affected by treatment, although the effect of the treatments was different during storage for 28 days (interaction between treatment and storage time). Roast ham from treatments A and B generally had a paler appearance (higher L~*-values) than from treatments C and D. No differences in the initial tristimulus a~*-values (redness) were found. During chill storage, a pronounced colour fading (decrease in a~*-values) was seen for laminate with low OTR, with a tendency of better colour stability for treatment C than A, but with no differences for the other treatments. For laminates with very low OTR, the cured meat pigment was stable with no decreases in a~*-values during storage. Lipid oxidation (thiobarbituric acid reactive substances, TBARS) in products in laminates with low OTR increased during storage and was significantly higher for roast ham from non-epinephrine treated pigs (A and B) than for ham from epinephrine-treated pigs (C and D). Statistical analysis relating pH and the level of glycogen, lactate, creatine phosphate, ATP and IMP in the individual pigs to the product quality parameters revealed that the ultimate level of lactate was the most important single parameter affecting product quality. After 28 days of chill storage, roast ham from pigs subjected to treatments C and D were more likely to support bacterial growth than from treatments A and B. In conclusion, the results show that pre-slaughter physiological conditions are of importance for chemical as well as for microbiological changes in retail stored roast ham.