Summary
The limited storage life of vacuum packaged beef and lamb is often the major factor affecting the distribution chain and can limit the versatility and market penetration of these products. Storage temperature is usually limited to a minimum of -1.5°C to prevent the meat from freezing. Chilling has been identified by industry groups as a priority area for improvement. Customer requirements and anecdotal evidence from the industry suggests that storage lives of greater than the current expectations can be achieved, but there is no scientific evidence available for processors to use in validating the process. Previous legislation defined chilled meat as being stored between -1.5°C and 4°C, but the current legislation has no such prescription.
Deep chilling, super chilling or partial freezing are terms used to describe the process of cooling a product to one or two degrees below its freezing point. It has been utilised with some muscle foods, particularly seafood, to extend the storage life of products. In some applications crust freezing occurs without any measurable effect on final product quality. In other cases a portion of the freezable water has been converted to ice.
This report covers some preliminary investigations into the effect of storage of beef at temperatures just below 0°C (namely -1.5°C, -2.5°C or -5°C) on physical, microbiological and sensory aspects, as compared with beef stored at 0°C or -20°C. A small trial was also conducted to investigate the potential of various surface treatments (drying, salting, and coating with sodium lactate, glycerol or carrageenan) to inhibit freezing of beef primals.
Beef stored at -2.5°C or -5°C demonstrates characteristics of frozen meat in terms of microbiology and drip loss. In addition, unsightly small white spots form on the surface of the cuts. Neither temperature would appear to be suitable for a deep chilling process aimed at maintaining the attributes of fresh meat. Sodium lactate appeared to limit drip loss associated with storage at -5°C, as did salting. Salting however resulted in the meat becoming dark in appearance, firm to touch and salty-smelling.
When using deepchill temperatures, slow chilling helps to prevent freezing of beef cuts. This improves the visual quality of the product by reducing the incidence of white spots and reducing the drip loss, particularly during retail display. Slow chilling to -2.5°C resulted in only 12% of cuts being frozen solid, and thus displaying these undesirable attributes.
Deepchilling is feasible, but the product must be chilled slowly to its storage temperature, and strict control over the temperature of the product must be maintained. The temperature of -1.5°C has been confirmed to be the absolute minimum temperature that could be commercially viable for vacuum packed beef, unless it has been treated with a freezing inhibitor such as sodium lactate.
