The effect of purge on the shelf life of vacuum packaged chilled meat

Summary

The Egyptian market is an important alternative to Australia's main export markets for chilled meat. Whilst the production of purge during chilled storage of vacuum packaged beef product is generally considered an accepted event, the Egyptian market has in the past rejected Australian product on the basis that the presence of purge is suggestive of product that is no longer 'wholesome'.

Objectives

This study conducted microbiological, biochemical and sensory evaluations of stored vacuum packaged brisket, eye round and topside over a period of up to 32 weeks. Purge, lean and adipose tissue samples were analyses separately for TVC, Enterobacteriaceae, LAB and Brochothrix thermosphacta. As expected, microflora counts increased over time with TVC and LAB counts for lean and adipose samples from all muscle types rising from approximately 2.00 log10CFU/cm2 to <6.00 log10cfu cm2 during 20 weeks of storage at -0.5°c. microflora counts of purge samples were generally 1-2 log10cfu greater in magnitude than lean and adipose samples, however this is mostly attributable to the unit of measurement being analysed with lean and adipose tissue being measured per cm2 and purge being measured per ml. the percentage of purge produced by eye round was greater than topside or brisket and maybe an important consideration when selecting export products for the egyptian market.

Key findings

Sensory evaluation of vacuum, meat colour and fat colour pre- and post-bloom determined that although reductions in score values for each of the attributes occurred during storage, all samples, with the exception of topside fat colour at week 32, were considered acceptable. Odour scores for brisket and topside samples were acceptable up to and including 28 weeks of storage with odour scores for eye round samples remaining acceptable up to and including 20 of storage.

Taste panel assessment determined that mean liking overall scores at week 20 were consistent with and often greater than the corresponding scores at zero, four and eight weeks of storage. Significant differences in mean liking overall scores were observed for brisket samples of weeks 24, 28 and 32 and topside samples from week 32 with these samples being adversely affected by elevated other flavour scores.

This study has determined that the extended refrigerated (-0.5°C) storage of vacuum packaged brisket, eye round and topside along with the associated production of purge within these packs does not negatively impact expected spoilage rates or sensory aspects of these products for at least 20 weeks.