A temperature log is the basic evidence of cold storage control. At fixed times, usually at opening, during service and at closing, a staff member reads the temperature of each refrigerator, freezer and display unit, writes it down with the time and their initials, and notes what was done if a reading is out of range. Digital loggers and connected sensors can record readings automatically every few minutes.
Paper logs are cheap and familiar but can be filled in carelessly or after the fact, and they only capture moments. Automatic logging records continuously, including at night and during power cuts, and can raise alarms. Whichever method is used, the reading must come from a reliable thermometer placed in a representative position, and someone must review the records.
A restaurant in Hyderabad preparing for a hygiene audit might keep a clipboard log on each cabinet and a weekly review by the head chef. A diagnostic lab in Mumbai might use a data logger in each reagent refrigerator, with alerts to the lab manager's phone.