A refrigeration unit that rapidly lowers the temperature of hot cooked food so it passes through the danger zone quickly.
A blast chiller uses much colder air and strong fans to remove heat quickly, so it chills hot food in a fraction of the time. A normal fridge is designed to hold already-cold food, not to cool hot food.
Yes. It makes it far easier to meet the guide of cooling from 60 degrees C to 21 degrees C within two hours and then to 5 degrees C within a further four hours.
Yes. Always confirm the core temperature has reached 5 degrees C or below with a probe thermometer before moving food to normal cold storage, even if the unit logs its own readings.
Yes, and overloading slows cooling. Use shallow trays and leave space for cold air to circulate so heat is removed evenly from every portion.
Not necessarily. Businesses that cool small amounts can use shallow trays and ice baths, but any operation cooling large volumes in advance will find a blast chiller far more reliable.