Where does the food in your fridge come from and how did it get there? More than likely it made its way along the cold chain - the refrigerated transport of food and drink around the world. As part of the BBC World Service's special series called Fridgenomics, The Food Chain looks into the wider networks at play when it comes to getting fresh food to your plate. Manuela Saragosa experiences minus 24 degrees Celsius at the London Gateway port to see how chilled food coming in from abroad is stored and inspected. We also hear about one man's efforts to implement his own cold chain in Tanzania. Plus, refrigeration has come a long way, from Icelandic traders using salt, to compressing liquids into gas. But what effect does our demand for chilled or frozen out-of-season food have on our environment and our diets?