These two systems of catering have a number of similarities in their basic design and the choice on which to use would depend on the balance of benefits to be obtained for the caterers' needs, as illustrated in Table 7.3. The preservation of food in cook-chill operations is of a limited nature, after which it should be destroyed. Since the storage life is relatively short, the linking of production to service is much tighter than what is needed in cook-freeze operations. In general, the production unit would generally produce food for a known predicted demand 2-3 days in advance, working consistently to the predicted daily requirements. Unpredicted variations in demand will tend to produce either much higher wastage or greater shortages in the catering system than might be encountered ir a cook-freeze operation