Fridge Freezer in Autodefrost mode

Question

HELP!

Our Fridge Freezer has decided to go into autodefrost mode and we dont know why. Our power supply tripped out in our home briefly for a few seconds until we reset the power (which has happened before) but on this occassion our Beko Fridge/Freezer has decided to start defrosting. There is power to the applicance and every 5 mins or so we hear a short "hum" coming from what I think is the thermostat. Our Fridge part seems also to be starting to warm. We've just done our weekly shopping and look set to loose our food!. Can anyone help explain whats going on and can we do anything about it?????