? asks :-

Does food go rotten in space?

Fiona Gordon, a nutritionist at the Health Research Council of New Zealand, responded.

Firstly we may ask, why does food go rotten? Air, water, heat and microbes are needed for food to go rotten. Microbes are sometimes referred to as bacteria or `germs' and cannot be seen without a microscope. A scientist named Louis Pasteur found out that tiny microbes caused food to spoil. He also found that if you applied heat to the microbes, they died. Without air, new microbes could not take their place. The term pasteurisation comes from Pasteur's discovery. Milk is pasteurised before it is sold in the shops to make it last longer. The canning process also reduces the factors that make food go rotten.

Every living thing requires moisture (water), and this includes bacteria. Food kept in the fridge usually has a high water content. Moist food that is left over for a long time provides moisture for the growth of germs. Enzymes (chemicals) that are made inside the microbe move out onto food, combine with the food, and return to the cell. This process cannot happen without water. This is why foods such as dried milk, dried soups and cereals do not spoil. The bacteria are present but they can't eat. Once these foods are open and water is allowed to get in, then they can spoil.

If food was thrown into space, it wouldn't go rotten. This is because in space there is a lack of oxygen and the presence of gamma and cosmic rays. However in a space capsule food can go rotten. Therefore, astronauts take mainly dried food (the water is removed) with them into space. This is because it needs to be lightweight for takeoff and not take up much room. In space the water is recycled so the astronauts don't have to carry much water and can just add it to the food when they need it.