The chilling system used significantly affects pork microbiology, safety, eating quality, and yield.
System design must be market-driven:
Quality-focused markets：prioritize preventing cold shortening.
Cost-focused markets：prioritize minimizing weight loss and maximizing throughput.
Therefore, a tailored cooling approach is essential to fulfill customer expectations.
Overview of Common Chilling Systems
(i) Batch Chilling System
Under this approach, carcasses are placed into a chiller progressively during the slaughter process, with all units within a given room being cooled simultaneously throughout the night. The overall chilling cycle typically spans 14 to 16 hours.
The performance of the chilling process is largely determined by several interrelated variables, including the air temperature and airflow velocity inside the chilling room, the weight spectrum of the carcasses, and the timing and sequencing of loading.
By way of illustration, for pig carcasses weighing less than 110 kg, attaining a core temperature below 7°C within a 24-hour production cycle generally requires an ambient air temperature close to 0°C and an air speed of at least 3.0 metres per second. Facilities with lower-capacity refrigeration equipment will obviously fall short of these benchmarks.
One notable benefit of conventional batch chilling is its ability to prevent cold shortening, which in turn contributes to superior eating quality—particularly in terms of tenderness—relative to more rapid cooling methods.
Additionally, this system tends to preserve good water-holding capacity, making it favourable for further meat processing.
Operational drawbacks of batch chilling include:extended cooling time,poor chilling uniformity,batch-mode inflexibility and large floor space required···
(ii) Blast or Ultra-Rapid Chilling System
This method represents the most widely adopted alternative within the pork processing sector. Its primary objective is to extract heat from carcasses within a compressed timeframe of roughly 3 to 4 hours.
The process is typically carried out in two phases: an initial pre-chilling stage conducted in a conveyorised tunnel operating below freezing point, followed by a conventional chilling phase.
The most conspicuous advantage is the marked reduction in cooling time, which translates directly into enhanced operational efficiency and higher throughput.
Rapid chilling also helps minimise evaporative weight losses from the carcass surface.
However, this system is not without drawbacks, which include:
Substantial upfront capital expenditure
Potential negative impacts on palatability attributes due to cold-induced toughening (unless mitigated by electrical stimulation, as discussed below).
Increased drip loss from retail cuts in cases where significant surface freezing of lean tissue occurs.
Alterations in colour characteristics—rapidly chilled loins, for instance, may appear darker and exhibit slightly reduced colour saturation.
Novel Chilling Systems
A variety of alternative systems exist, such as spray, immersion, and ice-bank chillers. Of particular note is a three-stage ultra-rapid method. This approach reportedly enhances tenderness significantly. Carcasses are first blast-chilled to below 15°C, then held at 10–15°C for 6 hours for equilibration. Finally, they undergo a brief 12-minute blast chill and are stored overnight at 4°C. Compared with conventional blast chilling, this system reduces drip loss and improves tenderness.
