• Question: Hi! I have a few questions about freeze dried food. First, what do you think about that? Then, do they add chemicals to that kind of food, to preserve it up to 25 years? And even if for now, eating freeze dried food doesn't seem dangerous, could it have an impact on our health in the future/th digestive system?

    Asked by Mahaut and Angele to Ruth, John, Dilip, Andrew on 18 Nov 2015.
    • Photo: Andrew Quigley

      Andrew Quigley answered on 18 Nov 2015:

      Hi guys! I think freeze drying (or lyophilisation as it’s technically known as) food is great way to store foods for extended periods of time. I think the flavours and nutritional content should stay about the same, but I’m not 100% about that.

      As far as I know, chemicals aren’t added to help preserve food once it’s freeze dried. Food tends to go off due to the action of various microorganisms and enzymes on the food. Water is mostly removed by the freeze drying process and this greatly reduces the action of the enzymes and microorganisms, which stops food from going off.

      Once the food is rehydrated, I don’t think eating food that’s been freeze dried would have any negative effects on out health or digestive system.

      This isn’t an area that I’m familiar with so possibly the other scientists have different ideas?

    • Photo: John Gleeson

      John Gleeson answered on 18 Nov 2015:

      Great question!

      So as Andrew said for freeze drying we put it in a machine that literally sucks all the water and moisture from the food. It depends on the food weather it’s successful for not :/ some foods crumble after freeze drying others are fine. It’s similar to dehydrating them but this usually uses heat (like raisins are dehydrated in the sun).

      Nope you wouldn’t need to add any preservatives but you’d need to store them in pouches that have no moisture and won’t let moisture in… Otherwise they’d slowly reform.

      There’s no way freeze drying could effect your health thankfully. ?