Frost formation inside food hermetic packages preserved in domestic freezer was studied. The influence on the product weight loss and on air and product temperature fluctuations of the following parameters was studied experimentally: refrigerator characteristics, product characteristics and package insulation. The frost deposits particularly on the product located in the central zone of the box and on the bottom horizontal surface of the box. An interpretation of the results was carried out by a simplified heat and water transfer model. This model shows that frost develops in the zone where the temperature is low in the box and/or where the temperature variation is low. This is the case at the bottom of the box (thermal stratification) and at the centre (thermal inertia). (c) 2006 Elsevier Ltd. All rights reserved.