The Poultry Industry Centre has assisted with the funding of a project by Dr. H.J. Swatland to investigate a probe for the prediction of turkey meat quality. A successful prototype has been developed whose potential and scope are described in the summary of the work reported.

The Problem

Progress in the genetic improvement of meat animals is dependent on feed-back of phenotypic information to breeders. Great progress has been made in growth rate and meat yield, since these attributes can readily be assessed on the live animal. Improvement in meat quality has not kept pace with the improvements in production efficiency as it is much more difficult and time consuming to obtain such information and relate it back to the live animal.

The Challenge

A major advance in improving meat quality genetically would occur if it was possible to measure such traits on live animals. The research undertaken by Dr. Swatland has attempted this through the use of ultraviolet (UV) light.

Connective Tissues

The amount and heat stability of connective tissue has a significant effect on the toughness of meat. In earlier reported work Swatland demonstrated that connective tissue could be measured in beef by UV fluorescence and developed a probe that correlated well with degrees of connective tissues as well as taste-panel evaluation (Swatland et al 1993-1995).

Excessive connective tissue is not a problem with all types of meat. As compared to beef, the problem with turkey breast meat is too little connective tissue which can result in cooked products fragmenting thus causing marketing problems (Swatland 1990). Thus in breeding for beef animals, selection might be for minimal connective tissue while the reverse may be true for turkeys.

Present Research – (Swatland and Barbut 1995)

The first step in developing an assay for turkeys was to miniaturize the probe used for beef carcasses, to the point that it could be mounted in a hypodermic needle. The probe was developed and tested on 12 turkey breasts, selected by industry personnel to represent a range of raw muscle quality normally used for making cooked turkey rolls.

Connective tissue was measured optically at the thickest point of the M. pectoralis muscle. Fluorescence collected by the sample is transmitted back to a photomultiplier for signal processing and interpretation. Measurements were made at 68Hz for several seconds resulting in several hundred measurements made on each muscle sample. Thus the signal provides a stereological sample of the anatomical distribution of the connective tissues in the meat (as if the meat had been cut, a line drawn across it, and connective tissues crossing the line examined microscopically).

Fluorescence signals from raw turkey breast meat were compared with measurements made with a repetitive mechanical compression procedure. Fluorescence signal, indicative of a high connective tissue content, were negatively correlated with muscle weakness as measured by the compression procedure. The frequency of fluorescent connective tissue in raw samples was correlated with the maximum force required for penetration of the cooked product. The UV probe was a better predictor of final product structure than were probe pH and paleness as measured with colorimeter.

Discussion

There are many problems to be overcome before optical measurements, through a hypodermic needle, can be made on live animals. However, the results of the present study demonstrate that it may be possible to predict one of the physical properties of meat (response to repetitive compression) with such an approach. Technical problems that will have to be addressed before the probe is functional is the development of a stable U.V. source for field use. Also within a live animal it is not known whether hemoglobin will prevent the measure of connective tissue fluorescence by blocking U.V. excitation and fluorescence emissions.

The Future

Expansion of turkey production in recent years has been facilitated by the increased amount of further processed product. Thus it is becoming of increased importance to optimize turkey muscle for further processing and this will require an understanding of how biological factors, developed during production, affect further processed product. Since there is a range in raw turkey meat quality, offered for further processing it is important that it be evaluated so as to enhance the quality of further processed products.

At the present time muscle pH is the single most useful measurement for predicting processing characteristics. However, measuring pH industrially has many potential problems. The results of the present study show that neither pH nor colorimeter paleness measurements correlated well with mechanical strength of cooked turkey meat. Thus while the future optical sensor must have the ability to detect U.V. fluorescence of connective tissue, it should also be able to predict pH dependent aspects of quality such as water holding capacity and cooking losses.

The potential for improvements in meat quality through genetic selection for various muscle traits is such to justify a marked increase in funding for the above type of work.

References

Swatland, H.J., C. Warkup, and A. Cuthbirtson 1993. Testing a U.V. fluorescence probe for beef carcass connective tissues. Electron. Agric., Amsterdam 9: 255-267.

Swatland, H.J., E. Gullet, T. Hore and S. Buttenham 1995. U.V. fibre-optic probe measurements in beef correlated with taste panel scores for chewiness. Food Res. International, Oxford 28: 23.

Swatland, H.J., 1990. A note on the growth of connective tissues binding turkey muscle fibres together. Can. Inst. Food Sci. Technol. J. 23: 239-241.

Swatland, H.J., and S. Barbut 1995. Optical prediction of processing characteristics of turkey meat using U.V. fluorescence and NIR birefringence. Food Research International 28: 227-232.

January 2009