Project outline

The project consisted of 3 stages

• Off line application of steam to carcases assess effect on campylobacter.
• Building a tunnel with steam jets on the processing line.
• Assessment of carcases after steam treatment for customer acceptability.

A steam chamber was constructed around the main process line just after the inside / outside washer and prior to entering the main in-line chill.  With the steam switched on the impact on product quality (particularly skin structure) and microbiological loading was assessed.

The machine was in operation for approximately 5 minutes and achieved an operating temperature of 90^oC. The birds were in contact with the steam for 5.2 seconds. 5 micro samples were collected pre-steam treatment and 5 samples were collected post steam treatment samples were sent to the lab for campylobacter, TVC, coliforms and pseudomonas analysis.

10 samples were visually assessed pre- & post- steam treatment and post-chilling and trussing; this was to visually assess the birds for any physical defects.

Results

Results showed that at best the treatment had no impact on the microbial loading of the neck skins.

Campylobacter levels were slightly higher on the post-treatment samples, but this was not statistically significant.

It was noted that product which underwent steam treatment had very ‘delicate’ skin and when collecting the product it was noted that the skin was very ‘fragile’. During trussing the skin was torn in the thigh area and the vent.

The microbial benefit of this treatment on campylobacter and other common microflora was not realised during this trial.  This point, coupled the amount of skin damage and disruption, would render the treated whole birds as unsuitable for retail sale in the whole bird, or skin-on portion formats.

Conclusion

Steam is an effective microbiological decontaminant. However, applied directly to the carcase during processing, steam did not provide any significant microbiological reduction.

The organolepic effects on the carcase resulted in changes to the colour and consistency of the skin. The skin was significantly damaged/torn during further processing and handling. The birds were assessed as unacceptable for retail sale.

Project outline

• 5 birds were left with standard neck flap length and 5 with neck skin totally removed. Levels of campylobacter were ascertained using a whole carcase rinse method and testing via ISO 10272
• Work was undertaken to assess the acceptability to the consumer of carcases with short neck skin. Neck skin was removed at various lengths and assessments made of the raw product in pack and the cooked product
• Trial 2 was conducted on 9 carcases with a neck skin length 3.5 cm. Levels of campylobacter were ascertained using a whole carcase rinse method and testing via ISO 10272
• To assess results across the shelf life of the product, 3 carcases were tested on each of the following: Pack day +1, Pack day +5, Pack day +9.
• Trial 3 was conducted on 40 carcases to reduce any variation due to bird size and effectiveness of the total carcase wash in removal of bacteria. A more sophisticated and controlled method of carcase rinse was used and the results expressed as cfu/cm² carcase using a carcase weight to carcase surface area conversion using the formula reported by Thomas.(Thomas N L 1978 J Food Technol 13 81-86)

Results

First Trial

Initial work carried out with complete removal of neck skin indicated a potential reduction in total campylobacter using a whole bird rinse method. The results indicated a potential decrease in Campylobacter of 0.9 log by comparing mean log values between the two groups.

• No neck skin:- mean count 632 cfu/ml rinse
• Standard neck skin:- mean count 4740 cfu/ml rinse

Second trial

• 1 (packing +1 day) / 750 (standard neck skin, cfu/ml) / 300 (short neck skin, cfu/ml)
• 1 / 5000 / 750
• 1 / 190 / 1300
• 5 / 280 / 170
• 5 / 130 / 60
• 5 / 160 / 160
• 9 / 60 / 100
• 9 / 840 / 500
• 9 / 1800 / 200

Although the bird appearance was acceptable prior to cooking, it was assessed as less so after cook because the neck cavity was exposed and the skin did not cover all the breast meat resulting a reduction in meat quality due to possible drying effects. 5cm was considered the shortest acceptable neck skin length.

Third trial

Standard neck skin (cfu/cm² carcass): 4, 13, 49, 55, 74, 87, 151, 166, 218, 306, 653, 656, 656, 665, 680, 697, 705, 912, 925, 1118

Short neck skin (cfu/cm² carcass): 22, 52, 75, 107, 130, 141, 143, 152, 484, 638, 643, 651, 661, 715, 744, 817, 1069, 1874, 4712, 21927

The results were statistically analysed by a two-way analysis of variance. This indicated that any improvement, i.e. lower counts, associated with short neck skins was tiny. There was weak evidence that carcases with short neck skins had a slightly greater risk of carrying campylobacter.

Conclusion

The results indicated that reducing the neck skin length on a chicken carcase to no more than 5cm did not impact on the risk associated with the level of campylobacter on whole chicken carcases.