Freezing of meat 143 Freezing is either faster for the same refrigerant evaporating tempera- ture, or can take place at a higher evaporating temperature for a given freezing time. Product temperatures are easier to control, especially for smaller cuts Power consumption is significantly reduced -savings of at least 30% nd possibly 50% or more, may be expected because air-circulating fans are not required and because higher evaporating temperatures can be used for the same effective cooling medium temperature. In many cases, less building space is required The product remains uniform and flat after freezing, unlike air-blast frozen cartons which often bulge. The flat cartons result in stable loads, giving up to 30% higher space utilisation in cold stores. For transport, the stable pallets facilitate unitised loading, and some 8-10% more product can be loaded into a container Disadvantages of plate freezers relate mainly to cost aspects Capital costs are significantly higher than for equivalent air-blast freezers. Manually loaded plate freezers are comparable in cost to auto- matic air-blast tunnel freezers. Fully automatic plate freezers are more High circulation rates of liquid refrigerant are required; this results in additional costs for larger accumulators and higher capacity pumps For manual plate freezers, simultaneous loading and unloading may require higher labour input than for a batch air freezer Each plate must be loaded with product of the same thickness Damp cartons can stick to plates or cause jams when ice forms. Air infiltration must be minimised to prevent frost build up on plates. Freezing unpacked meat has significant advantages because of the sub- stantially shorter freezing times( Fleming et al., 1996). Twice as many freez ng cycles per day can be achieved with the bare product Table 7. 4) Overall costs for plate freezing can be comparable to those for air-blast freezing. De Jong(1994)carried out a cost analysis(Table 7.5)for a beef plant using either plate or air blast freezers in New Zealand which assumed Table 7. 4 Predicted freezing time of meat blocks in a plate freezer operating at -30C Thickness(mm) Freezing time(h) Cycles per day Cartoned Bare Cartoned Bare ource: Fleming et al., 1996• Freezing is either faster for the same refrigerant evaporating tempera￾ture, or can take place at a higher evaporating temperature for a given freezing time. • Product temperatures are easier to control, especially for smaller cuts. • Power consumption is significantly reduced – savings of at least 30%, and possibly 50% or more, may be expected because air-circulating fans are not required and because higher evaporating temperatures can be used for the same effective cooling medium temperature. • In many cases, less building space is required. • The product remains uniform and flat after freezing, unlike air-blast frozen cartons which often bulge. The flat cartons result in stable loads, giving up to 30% higher space utilisation in cold stores. For transport, the stable pallets facilitate unitised loading, and some 8–10% more product can be loaded into a container. Disadvantages of plate freezers relate mainly to cost aspects: • Capital costs are significantly higher than for equivalent air-blast freezers. Manually loaded plate freezers are comparable in cost to auto￾matic air-blast tunnel freezers. Fully automatic plate freezers are more expensive. • High circulation rates of liquid refrigerant are required; this results in additional costs for larger accumulators and higher capacity pumps. • For manual plate freezers, simultaneous loading and unloading may require higher labour input than for a batch air freezer. • Each plate must be loaded with product of the same thickness. • Damp cartons can stick to plates or cause jams when ice forms. • Air infiltration must be minimised to prevent frost build up on plates. Freezing unpacked meat has significant advantages because of the sub￾stantially shorter freezing times (Fleming et al., 1996). Twice as many freez￾ing cycles per day can be achieved with the bare product (Table 7.4). Overall costs for plate freezing can be comparable to those for air-blast freezing. De Jong (1994) carried out a cost analysis (Table 7.5) for a beef plant using either plate or air blast freezers in New Zealand which assumed Freezing of meat 143 Table 7.4 Predicted freezing time of meat blocks in a plate freezer operating at -30 °C Thickness (mm) Freezing time (h) Cycles per day Cartoned Bare Cartoned Bare 80 6.3 2.5 3 6 160 16.5 8.5 1 2 Source: Fleming et al., 1996