Psychrotrophy is an extremely important growth capability in food science. It has relevance from both the perspective of food safety (for example with Listeria monocytogenes) as well as food quality and spoilage (for example with Pseudomonas fragi). Psychrotrophic microorganisms are those that have a optimal growth temperature similar to mesophilic microorganisms, yet, they are capable of growth at refrigeration temperatures. They are typically present in low concentrations in food products, but refrigerated storage selects for these psychrotrophs as the lower temperature inhibits the growth of mesophiles. The inhibition of mesophilic growth allows the psychrotrophs to grow, essentially without competition, thereby eventually spoiling the product if given enough time. Therefore, it is important to remember that refrigeration delays microbial spoilage of food because it largely selects for psychrotrophic microorganisms. This short video explains more.