Many of the foods that last for a long time are high in sugar and salt.
很多保質(zhì)期很長的食物都含有很多糖和鹽。

In simple terms, they draw water out, so if bacteria try to grow on it, they will simply shrivel up.
簡單講，這是因為它們能把水分吸出來，所以如果細(xì)菌嘗試在上面生長就會失水變干。

This is why we use salt to make ham, sugar to make jam, and both to make gravlax.
也正是因為這個，我們才會用鹽來制作火腿，才會用糖來制作果醬，才會同時用這兩種東西來制作漬鮭魚片。

As foods in their own right, if salt and sugar are stored away from moisture in airtight containers, they will last indefinitely.
而鹽和糖作為食物本身來講，如果能存放在隔絕水分的密閉容器里，它們就能夠保質(zhì)到天荒地老。

But additives, such as iodine added to salt, can reduce its shelf life to about five years.
但是，鹽里面的食品添加劑，比如碘，則可能把它的保質(zhì)期縮短至五年。

（翻譯：能貓）