Even when frozen, food slowly loses moisture. Ice on the surface sublimes, turning directly into vapour, and the dry spots left behind look grey, white or brown and taste flat. Fats in exposed areas also oxidise and develop off-flavours. Freezer burn is not usually a safety hazard, but it ruins texture, colour and taste, and the affected portions are often thrown away.
Three things make it worse: air contact, time and temperature fluctuation. Food that is loosely wrapped or stored in half-empty containers exposes more surface to air. Stock left for months in a forgotten corner of a chest freezer suffers more. And a freezer that warms up and recools, from frequent opening, defrost cycles, power cuts or an overloaded system, drives moisture out of the food and onto the walls as frost.
A cloud kitchen in Delhi storing frozen chicken in torn bags might find grey, dry edges after a few weeks. Vacuum packing or tight wrapping, dated labels, FIFO rotation and a freezer that holds steadily at −18 °C or colder prevent most of this.