Temporal and Spatial Distribution of Surface Microorganisms during Cooling of Pig Carcass

In order to study the changes in wind speed, temperature, humidity, and the number of microorganisms during the cooling process of pig carcasses, a model of the spatiotemporal changes of microorganisms in pig carcasses during cooling was established to provide a basis for the prevention and control of pollution in cold storage. In this paper, a thermal anemometer was used to measure the wind speed, temperature and humidity in the cold storage during the summer. The total number of microbial colonies on the surface of pig carcasses was measured by the wiping method. The spatiotemporal changes of microorganisms during the cooling process of pig carcass were obtained. The results showed that in the early stage of cooling (cooling time was 0 to 8 h), due to the opening of the cold storage door and the heat dissipation of the pig carcass itself, the wind speed in the cold storage was not uniformly distributed, and the temperature and humidity were gradually increased (P<0.05).And the total number of microbial colonies on the surface of pig carcasses at different locations in the cold storage increased to varying degrees. The total number of colonies on the surface of the carcass in the middle of the cold storage increased significantly (P<0.05), and the total number of colonies on the surface of the carcass in the other positions did not increase significantly (P>0.05).In the late stage of cooling (cooling time was 8 to 14 h), the cold storage door was closed, and no pig carcass entered the cold storage. The temperature and humidity decreased rapidly, resulting in a significant decrease in the total number of microbial colonies on the surface of the pig carcass and tending to be stable (P<0.05). The total number of colonies on the windward side of the pig carcass was slightly higher than the total number of colonies on the leeward side, among which the microorganisms in the front leg and the thoracic cavity were more. The results of correlation analysis showed that the total number of colonies on the surface of pig carcasses had extremely significant correlations with temperature, humidity, cooling time, and sampling locations (P<0.01), and significant correlations with wind speed (P<0.05).In conclusion, with the extension of the cooling time, the total number of colonies on the surface of the pig carcass was significantly different (P<0.05). The total number of colonies on the surface of the pig carcass at different locations in the cold room was different, and there were differences between different parts of the same pig carcass. This laid the foundation for the improved layout of the cold storage and pollution control.