Moisture content in fresh biscuits is about 5% after baking resulting in crisp texture and good storage stability. When they are left open in air they absorb moisture and lose therir crispness. The relative humidity in the atmosphere can vary from 40% during summer to 90% on a cool rainy day. Inside a fridge the temperature is kept low by cooling coils and as well the air is moisture free. As a result the biscuits remain cool as well as crisp.
What is the difference between air cooler and air conditioner?
Humidity is the moisture or water content of air. An air cooler is basically a humidifier. An air cooler mixes water vapour with air by means of rolling pad of moist cloths of fiber and makes the air the more humid with more moisture content.
An air conditioner or regenerator is a dehumidifier which works as follows: The evaporator in an air conditioner consists of a series of zig-zag copper tubes twinning with thin copper plates. The liquid refrigerant evaporates in the tubes under low pressure so than the tubes and fins get cooled. A fan fixed behind the evaporator drives the warm air that comes through cold fins circulates the cooled air in the room. When the warm air passes through the cold fins the atmospheric moisture condenses on them as drops of water that can be drained away.