Medycyna Wet. 65 (1), 46-50, 2009
| Bełkot Z., Pełczyńska E. |
| The influence of various chilling methods on the bacterial contamination and quality characteristics of chicken carcasses during storage in a chilling room |
| The research objective was to assess the impact of different chilling systems on the bacterial contamination and quality characteristics of chicken carcasses during storage in a chilling room. The research was carried out on 90 carcasses of chicken broilers of 1.2-2.5 kg body weight aged 6-8 weeks, 30 from each of three plants using different chilling methods: air chilling, immersion chilling and evaporative chilling. After slaughter the carcasses were stored in a chilling room at the temperature of 0ºC - 4ºC and relative humidity of 80 % ± 2 %. The total cold storage time was 6 days. The starting time (time 0) was assumed to be the 24 h after slaughter. Chosen parameters were determined on the first day of storage (time 0) as well as on its 3rd and 6th day. The parameters comprised microbiological contamination (total count of aerobic bacteria, the number of psychrotrophic and proteolytic bacteria), the pH value of the meat and the ammonia content. Additionally, a sensory assessment of the muscle tissue appearance and odour was performed (5-point scale) The bacterial contamination of carcasses after the immersion chilling was found to be significantly higher than in the other two chilling systems. Significant differences in the total count of bacteria between carcasses chilled in the immersion system and those chilled in the other two systems were observed on all days of storage. The highest contamination during the entire storage period was observed in the carcasses chilled by immersion. The contamination of air-chilled carcasses was similar to that of carcasses chilled in the evaporative system at the beginning (day 0) and towards the end of storage (day 6). The number of psychrotrophic bacteria on the 1st (day 0) and 3rd days of storage significantly depended on the chilling system. On those two days significant differences were observed between the carcasses chilled in each of the systems. On the 6th day, however, those differences were noted between the carcasses chilled in the immersion system and the ones chilled in the air and evaporative systems. In all storage periods the highest psychrotrophic contamination occurred in the immersion-chilled carcasses and the lowest in those chilled with air. The chilling method affected also the contamination of carcasses with proteolytic bacteria. Significant differences in the contamination with these bacteria occurred only between the immersion-chilled carcasses and the other two groups in all three periods of storage. Proteolytic bacteria count was the highest in the water-chilled carcasses and the lowest in those chilled with air. The pH value of meat was significantly higher in the carcasses chilled by means of the air and immersion systems than in those chilled in the evaporative system. The impact of the chilling system became apparent only on the 3rd and 6th days of storage. The ammonia content was the lowest in the air-chilled carcasses and the highest in those chilled in the evaporative system. The impact of the chilling system on the value of that parameter was observed only on the 6th day of storage. Significant differences occurred between carcasses chilled in all systems examined. Adverse changes in the appearance and odour of carcasses chilled by all three methods began after 3 days of storage, but on the 6th day they were the most noticeable in the carcasses chilled by the air and evaporative methods. In terms of both these characteristics carcasses chilled in the immersion system were evaluated higher than those chilled by the other two methods, though the evaluation was negative in all three cases. The research results suggest that the chilling system has no significant impact on the durability of chicken meat during cold storage. However, in the case of poultry meant for sale as fresh the 6-day cold storage period set by Polska Norma (Polish Standard) should be considered as too long, since the adverse sensory changes in carcasses begin already after 3 days of storage. |
| Key words: chicken broiler, chilling systems, bacterial contamination, quality characteristics of meat, cold storage |