Comparison of high oxygen and anaerobic packaging on the oxidative state and tenderness of pork chops during simulated retail display
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Research partner: University of Bristol
Sponsor: BPEX
Duration: July 2009 – September 2009
In the UK modified atmosphere packing (MAP) is currently the most commonly used packaging system for fresh meat products. It is favoured by retailers as the gas combination in the packs, usually around 70-80% O2 and 20-30% CO2, preserves the bright red colour of freshly cut meat whilst inhibiting microbial growth extending the shelf life to over seven days. However, the use of high oxygen MAP has potential negative effects; it can reduce meat quality by increasing lipid and protein oxidation, causing rancidity and negatively affecting functional properties and tenderness.
The aim of this short study was to investigate the effects of high oxygen MAP and vacuum packaging (no oxygen) on lipid and protein oxidation and tenderness of pork loin slices after eight days simulated retail display.
A preliminary test used eight whole loins cut into 20 mm steaks and stored in either MAP (80% O2 20% CO2) or vacuum packs (VAC) which were assigned to either taste panel testing or instrumental texture analysis. The two testing methods gave comparable results (MAP stored steaks were tougher than VAC ones) with a strong correlation between the results of the two methods. Hence, the cheaper and faster instrumental method for the main experiment could be used.
There were no significant differences in toughness between samples stored in MAP (avg. 24.3 kg) displayed for eight days and the 0 day samples (avg. 24.2 kg, p>0.05). There was a highly significant difference in peak force values between the MAP stored chops and vacuum packed chops (avg. 21.8, p<0.001) and between 0 day chops and vacuum packed chops (p<0.01).
Colour reduced linearly in MAP but was virtually unchanged, but less red, when displayed in vacuum.
Average lipid oxidation results, from samples kept in MAP packaging showed much higher values after eight days (1.51) than from vacuum packed chops (0.12), and there was significantly less protein oxidation in 0 day samples) than vacuum packed samples, which in turn was statistically less than in MAP packed samples.
In the first preliminary trial, pre-aged meat was tougher when packed in MAP as opposed to vacuum. In the main experiment, with fresh meat, high oxygen MAP produced more lipid and protein oxidation than vacuum packed meat, yet it was not tougher than pre-packed samples. Conversely vacuum-packed meat tenderised during the extra eight days storage. Hence, for pork it would appear that high oxygen MAP inhibits tenderisation and may actually cause toughening in previously conditioned meat. The differences were small, but it may be advisable for retailers to change to vacuum skin packing, a retail form of vacuum packing, for prime products.
Page last updated 08 June 2010