Changes of the Microbiota Composition on the Surface of Pig Carcasses during Chilling and Its Associations with Alterations in Chiller's Temperature and Air Humidity.

Xiaonan Jia,Chunbao Li,Juqing Wu,Di Zhao,Yingqun Nian

doi:10.3390/foods10092195

Abstract

In this study, we investigated changes of microbiota composition on the surface of pig carcasses during chilling and their associations with temporal and spatial changes of wind speed, air temperature, and air humidity. The composition of microbiota on a carcass surface varied greatly with sampling sites; in particular, the surfaces of forelegs and neck had higher load of microorganisms and different microbiota composition compared to in the air and other carcass parts. However, such a difference in the microbiota composition decreased as chilling time extended. The positive detection ratios of microbial genes resistant to sulfonamides, quinolones, tetracyclines, and β-lactams were found different greatly with chilling time and sampling sites. The β-lactam and tetracycline resistant genes were observed in higher ratios in airborne microorganisms in the chiller, while the sulfa and tetracycline resistant genes had higher ratios in the microbiota on pig carcasses. Actual measurements and dynamic simulation showed that air temperature and humidity varied greatly among different places in a chiller within the first 8 h of chilling, with higher values close to the door, but the differences became smaller afterwards. The micro-environmental differences and changes in the chiller may cause the different composition of microbiota on pig carcasses.

Highlights

IntroductionLow temperature can reduce the growth of spoilage microorganisms on pig carcasses [1]
Carcass chilling is a critical step for processing of chilled pork
Air temperature is one of the most important factors to inhibit the growth of microorganisms, and uneven temperature may help to increase the growth of microorganisms in a chiller

Summary

Introduction

Low temperature can reduce the growth of spoilage microorganisms on pig carcasses [1]. A chiller is the main place for carcass chilling. The difference in wind speed in a chiller affects the contact area between the cold wind and pig carcasses and the growth of microorganisms. The size, temperature, humidity, and wind speed of a chiller affect the carcass chilling efficiency and meat contamination [5,6]. At a high wind speed, the surrounding environment of a carcass has high humidity and low temperature. When a chiller is full of pig carcasses, the wind speed and air temperature decline rapidly, but the air humidity increases, and the wind speed, air temperature, and humidity tend to be stable [7]

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