Rehearsal For Thesis Presentation

Carcass cooling is a critical step following animal slaughter, playing a pivotal role in meat quality and food safety. After slaughter, the body temperature of poultry is approximately 37–38°C. Without prompt cooling, not only would the meat quality be adversely affected, but rapid microbial growth could also occur, posing risks to meat preservation and food safety. Currently, poultry carcass cooling methods are primarily categorized into two types: water chilling and air chilling. Water chilling effectively and rapidly reduces carcass temperature, offering high efficiency and operational simplicity. However, it may lead to cross-contamination and excessive water absorption by the carcass, which can adversely impact sensory attributes and food safety. In contrast, air chilling minimizes excessive water uptake and preserves the natural appearance of the carcass. Nevertheless, air chilling has relatively lower cooling efficiency and may result in excessive surface dehydration, leading to weight loss and issues such as surface cracking. This study aims to investigate the effects of water spraying during air chilling on carcass weight, appearance, and shelf life. The experiment was conducted three times, with 30 red-feathered native hens slaughtered in each trial and randomly divided into two groups. In one group, sterile water was evenly sprayed onto the carcasses using a spray bottle every 30 minutes during the air chilling process (WC). In the other group, no treatment was applied during air chilling (AC). The weight of each carcass was measured every 30 minutes until the core temperature of the carcass reached 7°C. In the first trial, the L*, a*, and b* values of the carcass breast and back were measured using a colorimeter after air chilling. In the second and third trials, carcasses were vacuum-packed after air chilling and stored in a refrigerator at 4°C. On days 3, 7, 10, and 14, two carcasses from each group were randomly selected to measure the surface microbial counts. The initial weights of the carcasses before air chilling in all three trials ranged from 1.8 to 2.0 kg. The results showed that it took 120 minutes for the core temperature of the WC group carcasses to drop to 7°C, compared to 200 minutes for the AC group carcasses, indicating that water spraying reduced the cooling time. After air chilling, the weight changes for the WC carcasses across the three trials were 1.6%, 2%, and 2%, respectively, while those for the AC carcasses were 2.6%, 2.8%, and 2.9%, respectively. This demonstrates that water spraying effectively reduced weight loss caused by moisture evaporation during air chilling.In terms of appearance, the AC group carcasses exhibited a waxy yellow color, whereas the WC group carcasses appeared lighter in color with higher brightness. However, measurements of L*, a*, and b* values revealed no significant differences between the two groups. In the second trial, microbial count measurements revealed that on day 3 of storage, the surface microbial count of the WC group was 3.1 log CFU/g, while that of the AC group was 2.9 log CFU/g. By day 7, the surface microbial count in the WC group increased to 5.1 log CFU/g, and in the AC group, it reached 5.7 log CFU/g, both exceeding the spoilage threshold of 5 log CFU/g set by the Ministry of Health and Welfare. On day 10, the WC group’s surface microbial count reached 6.8 log CFU/g, while that of the AC group was 6.6 log CFU/g.In the third trial, on day 3 of storage, the surface microbial count of the WC group was 3.0 log CFU/g, whereas that of the AC group was 3.7 log CFU/g. By day 7, no significant changes in surface microbial counts were observed in either group, with the WC group at 3.4 log CFU/g and the AC group at 3.3 log CFU/g. By day 10, the surface microbial count in the WC group reached 5.4 log CFU/g, while that of the AC group reached 5.1 log CFU/g.These results indicate that spraying water on the carcass surface during the air chilling process effectively reduces weight loss but does not significantly affect the growth of surface microorganisms. Future research could focus on extending the storage period or further improving cooling methods.
 
 
Keywords: Red-feathered local chicken、Carcass chilling、Air chilling、Food shelf life

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