Development of a semi - automatic system for the early detection of dark cutting beef

Summary

When animals are killed with low levels of glucose in their muscles (often due to stress), less lactic acid is produced and the pH of their muscles does not fall as far as in unstressed animals. Meat that has low pH is preferable as it has a lighter, brighter colour, is generally more tender, juicy and has a better flavour and will keep better than meat with high pH. High pH meat is referred to in the industry as dark cutting meat and this is justly discriminated against in retail display as it has inferior eating and keeping qualities.

This project tested a system in a commercial environment that comprises a simple and easily sterilisable tool suitable of taking muscle samples and processing them so an ultimate pH level can be automatically read within 25 minutes with the possibility of this being lowered to 15 minutes.

Objectives

The projects objective was to have the developed system installed in one of Woolworths leading contract abattoirs based around a production model machine, rather than a prototype, for demonstration to and evaluation by industry.

It was intended to be set up so that other abattoir operators could inspect the operation of the system for a period of time and that it be accessible for reasonable research use.

The machine was configured so that it is capable of operating at a frequency of a carcass every 15 seconds and to measure pH within 15 minutes of the samples being placed into the machine, up from the pre-proven rate of 25 minutes pre sample. 

Key findings

Abattoir trials indicated that the ultimate pH indicated for samples taken from the m. semitendonosis at the legging stand gave a sensitive and reliable indication of the ultimate pH of the m.semitendonosis and the m. longissimus dorsi.

It was considered that the relationship is sufficiently close and reliable for the machine's pH reading to be used as a basis for identifying at the scales, suspect dark cutting carcases and those yielding low pH meat most suitable for vacuum packaging.

It was found that when errors occur in the system (wrong ultimate pH is determined), they result in a prediction of higher pH than actual, it is considered a particularly safe method for the identification of carcases that will have low pHs. That is, it is unlikely that carcases will have pHs higher than predicted, even when errors occur.

Benefits to industry

The system caters both for conventional beef systems in enabling immediate sorting and marshalling of carcases for next-day dispatch, or for hot boning systems where dark cutting carcasses need to be culled at the scales.

The rapidity of the ‘ultimate pH’ determination provides an opportunity to use the system for the development of in-house procedures to minimise the incidence of dark cutting beef and to identify lines of cattle with a high incidence of dark cutting carcases for feedback to lairage foremen, livestock buyers and growers to reduce the frequency of dark cutting in the wider industry.

MLA action

In 2000, project TR.001 focused on reducing the incidence of dark cutting beef carcases in Southern Australia. The aim of this project was to provide new information on the factors affecting dark-cutting in beef carcasses. The project focused on glycogen depletion and repletion in the M semimembranosus (SM) and M semitendinosus (ST) as an indicator of dark-cutting. Factors which were investigated included nutritional manipulations on-farm and at the abattoir, and handling procedures including mixing, transport, lairage duration and pre-slaughter handling. The overall objective of the project was to demonstrate to industry that the incidence of darkcutting beef carcasses can be reduced by at least 50%.

In 2001, a later project PRTEC.005 looked at the world best industry practice in objective prediction and management of dark cutting in beef cattle in meat processing facilities.

Future research

A number of improvements to the system were identified that should be the target of future work in this area.

• A simpler pH meter that emits continuous digital pH readings would be more appropriate than the relatively sophisticated model used in this system.
• The systems’s software should be modified to enable adjustment of cycle times, pH stabilisation times and the release of liquid nitrogen, without loss of the data on samples already placed into the machine.
• Future versions of the machine should be designed to operate at up to 4 carcasses per minute and be capable of producing its pH reading within 15 minutes of receiving the sample. It is noted that this operation would require two pH mearuement stations operating in parrallel.