Effect of shipping practice on quality of frozen manufacturing beef

Summary

Project P.PSH.0200 included three components:A supply chain survey;Simulation of cold chain breaks; andImplication of cold chain breaks for product quality.
This report documented the results of a survey of frozen meat temperatures during shipping to the United States and the effect of cold chain breaks on product quality.
Under the temperature survey, temperature loggers were inserted to record the surface temperatures of cartons of manufacturing beef during transport from Australian meat processing plants to a cold store in Philadelphia on the east coast of the United States. Temperatures were logged in a range of positions in a 6 m (20 ft) container and a 12 m (40 ft) container.
Both shipping containers experienced significant periods during which no refrigeration was applied. There were three off-power periods, the longest of which was 13.5 hours, with the 20 ft container and one period of just over 10 hours for the 40 ft container. During these off-power periods, meat surface temperatures of cartons on the outside of the load rose by about 8 degrees Celsius to between -13 and -8.6°C. Meat surface temperatures within the load did not change.
While on power, temperature control with both containers was very good.
The survey, which was a snapshot of the temperature conditions under which Australian frozen meat is shipped, did reveal some practices that may be considered less than ideal:An off-power period of 12.5 hours occurred with the 20 ft container on board the ship during the voyage.Cartons were loaded too close to the doors thereby restricting air flow, resulting in higher meat surface temperatures at the door end of the container.The container doors were not closed immediately after loading, resulting in higher meat temperatures at the beginning of the trip, which took up to 12 days to reach the carriage temperature of -20°C.
The majority of frozen manufacturing meat is exported in shipping containers, but there has been some trade as palletised cargo in the refrigerated hold of ‘conventional’ ships. However this trade is currently suspended.
In both shipping methods, frozen product may be the cold chain may be broken for brief periods. Containers may be off-power during transport to and from the wharf and pallets of frozen cartons are exposed to ambient conditions on the wharf while loading and unloading the ships.
In order to assess the effect of these practices on quality parameters of frozen manufacturing beef, quite extreme cases of un-refrigerated conditions were simulated and the meat analysed. One set of six cartons was held at a constant -20°C, another set was allowed to warm in a similar manner to a container off-power for two days and a third set exposed to an ambient temperature of 25°C for five hours. The meat was stored at -20°C for four weeks prior to the first abuse, returned to -20°C for four weeks (to simulate the voyage to the U.S.), subjected to a second temperature abuse, then stored at -20°C for a further four weeks.
At the end of the 12 weeks storage period, the 18 cartons were ground using a similar procedure to that followed by the commercial grinders. Samples were taken and analysed for fat content, anti-oxidants and products of lipid oxidation.
There were no differences in the amounts of α- tocopherol and β-carotene in either of the abused groups compared with the control, indicating that they had not been destroyed by accepting the free radicals of lipid oxidation.
Measurement of TBARS, peroxides and head space analysis for hexanal showed no differences between abused groups and the product stored at a constant -20°C. A taste panel could not detect any significant difference between treatment groups.
These results indicate that frozen manufacturing beef exported by either refrigerated shipping container or ‘conventional’ shipping is not affected by short periods of exposure to ambient conditions or container off-power periods when stored for three months.