Food preservation

Refrigeration

Freezing

more than just preservation; freezing changes structure of foods, with some useful effects eg frozen and defrosted tofu is more spongelike and absorbs marinades better

Icecream, sorbet,...

Dehydration

Dehydrators dry food via hot air. The dehydrated food becomes much smaller and needs no energy to preserve and will last for years. Vitamine C gets reduced (by how much?) but vitamine A is mostly preserved.

Other uses for dehydrators can be to make "flax crackers", kale chips,...

Whenever I cut open pumpkins I always wash the pumpkin seeds and dehydrate them.

Dehydrated beansprouts can be easily ground into a nutritious powder.

Fermentation

Lactic acid fermentation and others like miso can preserve foods for long times without energy. They take more space than dehydrated foods because of the extra water and glass containers (usually).