In Germany, most of the turkey meat is marketed as parts, explained Dr Carsten Krischek in the introduction to his paper at the Turkey Science and Production Conference held in Macclesfield, UK, in March 2011. Dr Krischek works at the Institute of Food Quality and Safety at the Foundation University of Veterinary Medicine in Hanover, Germany, and he was presenting the paper on behalf of co-authors, S. Janisch and M. Wicke of the University of Göttingen and R. Guenther of turkey company, Heidemark Maesterkreis.

The higher proportion of turkey meat sales as parts and usually in modified atmosphere packaging means that any differences in appearance between the parts in packs on the supermarket shelf – for example, blood spots or muscle colour variation – are obvious to the consumer, who does not understand the reasons for the differences and may be put off the purchase. Generally, consumers prefer lighter-coloured poultry meat, Dr Krischek said.

So what is a ‘normal’ colour for turkey meat parts, he asked. Measuring lightness on a scale of L* values, he showed that turkey meat colour shows a normal distribution, with higher L* values indicating pale, soft and exudative (PSE) meat and low L* values defining dark, firm and dry (DFD) meat. The PSE meat is more problematical in the turkey, he said, as the reasons for it are not yet fully understood. However, like pork, PSE turkey meat is harder to process, more prone to drip loss and can affect shelf-life. It can also affect gel strength in further processed products.

Different sources have estimated the incidence of PSE turkey meat between eight and 40 per cent but in practice, about 10 per cent would be described as "too light", said Dr Krischek.

Sorting Parts to Minimise Colour Variation

One possible option for minimising the meat colour variation, he suggested, would be to sort the parts after dissection and before packaging or processing.

He went on to stress that the timing of the sorting is important, showing that lightness (L*) values increased with time post-mortem, up to 72 hours for breast muscle and up to 48 hours post-mortem for thigh muscle. This would present a practical problem in commercial plants, he said, where the meat would not be left for so long before further processing stages.

Whilst sorting the meat by colour was effective, Dr Krishek added that it would be time-consuming and hence, expensive, to carry out on a commercial scale.

Seeking the Causes of Turkey Meat Colour Variation

With sorting before processing or packing an unrealistic option, Dr Krischek and co-authors undertook an investigation into the causes of variation in meat colour 24 hours post-mortem and drip loss, considering gender, genetic line, age and slaughter weight as possible factors. They found some significant differences (P<0.05), with toms having higher values than hens, and heavier birds (>15.6kg) having higher values than lighter birds (<15.6kg). Age had no effect on L* value (106 versus 143 days). None of these factors affected drip loss.

However, for the two genetic lines tested, which were not identified, one had a higher mean L* value and greater drip loss that the other line.

This and already published data support previous assumptions that evaluation of these management factors might be useful to reduce colour variation and other meat quality differences, concluded Dr Krischek. He added that each producer would need to evaluate his/her own thresholds – for example, for L* value – before sorting meat, taking into account the type of bird, processing factors and final product specifications.

April 2011