An MCB protects cables, not people. When the current through a circuit stays above its rating for too long, a thermal element trips it; when a short circuit causes a very high current, a magnetic element trips it almost instantly. Once the fault is cleared, the breaker can be switched back on.
MCBs come in different trip curves. Type B trips at relatively low surge currents, suited to lighting and resistive loads. Type C allows higher brief surges and is commonly used for motor loads such as compressors, so their starting current does not cause nuisance tripping. An electrician chooses the rating and curve to match the cable and the load.
Ideally each large refrigeration unit has its own dedicated circuit and MCB. Sharing a circuit with ovens, fryers or a dishwasher risks tripping during peak hours, which can switch off a freezer without anyone noticing. Label the breaker clearly so staff know which unit it supplies.