• Question: If you froze a food, could it be eaten in hundreds of years time?

    Asked by to Edward, Ian, Mathew, Naomi, sakshisharda on 24 Jun 2014. This question was also asked by .
    • Photo: Ian Stephenson

      Ian Stephenson answered on 24 Jun 2014:


      Sort of… there’s frozen, and theres FROZEN.

      Cooling things down slows the decay process because chemicals react more slowly at low temperatures, and bacteria are also either slowed down or stopped completely.

      A regular kitchen freezer runs at about -18C, which is pretty cold, and slows things down quite a lot so food keeps for months, or even years.

      When scientists want to freeze something the first thing they think of is liquid nitrogen. It gets delivered in big gas cylinders and its used for cooling all sorts of scientific equipment. It has a temperature of -196C or less.

      If you put something in liquid nitrogen its FROZEN. It would last hundreds of years without much of an issue (other than you need to keep your freezer topped up with nitrogen).

      However liquid nitrogen isn’t that big a deal. It’s something that gets used without much of a thought. It’s used in hospitals to store samples, and you can even use it to make GREAT ice-cream (the rapid cooling prevents crystals forming in the ice, so its super smooth).

      Liquid Helium has to be below -269 degrees!!! That IS a big deal. When we’re dealing with stuff that cold, then comparing them to ice (freezing at 0, boiling at 100) is a bits silly, as it turns out there’s a much better way to measure temperatures. Heat is energy, and things are cold when they have less energy… how cold would they be if we took ALL the heat out? Turns out its -273C, which we call absolute zero, of 0 Kelvin. On that scale liquid hydrogen is about 4 degrees (while regular ice is about 270K – pretty hot!!!).

      However for people who are into COLD, then 4K is kinda warm. NASA (why is it always NASA, everything they get to do is SOOO COOOOL!!) cooled some stuff down to 0.000000001K.

      At that temperature you can keep stuff forever.

    • Photo: Sakshi Sharda

      Sakshi Sharda answered on 24 Jun 2014:


      Depending on the type of food, it stays fresh for different times. food or biological items have to be frozen as fast as possible or they start decaying!

      Example- salads can sty fresh for 3-5 days, meat can sometimes stay for a month or so, however not longer. Generally foods that have preservatives for increasing storage times can be stored for longer. bu as Ian mentions liquid nitrogen stored foods or samples stay for many many years.

    • Photo: Naomi Osborne

      Naomi Osborne answered on 24 Jun 2014:


      Like Ian mentioned, when you freeze food the reason it preserves it is because bacteria and moulds become inactivated – this means they stop reproducing because it’s too cold and there’s not enough water available, but it doesn’t kill them.

      However, food that’s frozen for years won’t taste very good at all as it gets ruined by losing moisture (through ice absorbing moisture and evaporating), which is why it’s recommended to eat it within a few months of storing it. Liquid nitrogen will keep the food edible for longer, as it forms ice crystals that help retain moisture and texture.

Comments