Meat Science

FACTORS CONTROLLING EFFICIENCY OF CHILLING

• The temperature of storage is probably the most important factor determining the efficiency of chilling.
• Higher temperatures are less effective in preservation and shrinkage is also high.
• The rate of chilling is another factor that affects the efficiency of chilling, with quick chilling being markedly superior with respect to  both keeping quality (retardation of surface bacterial growth) and sensory qualities (superior bloom) and shrinkage is also lesser as well.
• The air velocity is directly proportional to rate of chilling and hence thus higher velocities enhance bloom and impart greater preservative effect, but cause increased shrinkage. Hence, initial chilling of warm carcasses, sides, or quarters is carried at 7°C and the mean air speed of 0.75m/s, while in the terminal stages of chilling temperature must be maintained between -1°C and 2°C, with mean air speed of 0.5m/s.
• Meat packed on trays or in cartons the temperature must be below 3°C and mean air speed of 0.75m/s.
• Higher air circulation rates are not associated with shrinkage, especially when the carcass is fresh and still wet, wherein higher circulation rates result in rapid decrease of the carcass surface water vapour pressure, thus reducing shrinkage.
• Air circulation rates of up to 70-110 volumes of the room per hour are maintained in quick chilling to rapidly lower the temperature.
• Slower air circulation rates are beneficial once the temperature of the carcass is sufficiently lowered.
• Relative humidity of the chilling room also has an important role to play in the efficiency of chilling. High relative humidity’s will reduce shrinkage but will favour mould growth.
• A relative humidity of 95% may be maintained to chill the carcass and store chilled carcass, if storage is to be for less than 72 hours, if extended beyond 72 hrs, it has to be reduced to 90%.
• Uniformity of air flow throughut the chill room is yet another factor that has a role in determining efficiency of chilling, but this itself is determined by the evenness of hanging the carcass in the chiller room.
• The recommended rail spacing in a chiller or freezer room should be 0.9m for beef, 0.7 m for pork and 0.5 m for lambs and the minimum space between carcasses on these rails should be 0.3 to 0.4m. Futher, the rails should be placed 0.6 m (0.9 m, in case of header and traffic rails) clear off refrigerating equipment, walls and other fixed parts of the building to ensure hygiene and protection to walls.
• The top of the chill rail from the floor level should be atleast 3.3 m foor beef sides, 2.7m for headless pigs and calves, 2.2 m for beef quarters, and 2m for sheep and goat.