I'm really struggling to find a way of keeping frozen product below -12°C, as per our delivery policy, on our chilled vehicles. In our freezer we have various frozen fruits and vegetables (no meat, just things like peas, sweetcorn and blackberries for example) and whatever trials I run on keeping the product cold don't seem to work.
I've used polystyrene boxes, put ice packs in them and also trialed Thermos cool boxes with ice packs but within 2 hours with the boxes closed and sat at 4-5°C the temperature drops significantly. And our drivers can spend over 6 hours on the road sometimes. Most of the time the temperature drops from between -12° and -17°C to anywhere between -4° and 0°C within those first 2 hours.
Can anyone recommend a better method to try and keep the temperature right down? This just happens to be our final action point from an audit we've never had before and are desperate to pass.
Failing that, is there any reason I couldn't be naughty and change the procedure to a slightly higher frozen temperature to aid compliance?