百科知识视频之煎蛋小学堂55 冻灼是什么？

Have you ever noticed that meat or vegetables or ice cream left too long in the freezer,develop a layer of frosty ice on their surface?And when eaten,they're kind of dry and icky?This is freezer burn,and it happens because ice in the frozen food sublimates-that is,the water changes directly from a solid to a gas rather than first melting and then evaporating.

你是否注意到过 当肉 蔬菜或冰淇淋在冰箱中长时间放置后 它的表面上会形成一层冰霜 这些食物吃起来口感有甘有粘?这就是冻灼 它是由冷冻食物中的冰升华造成的 也就是说，水分直接从固态变成气态 而非冰晶先融化成水后再蒸发。

Unlike regular frost(also called"hoar frost"),which forms when water vapor that's already in the air freezs into crystals on top of something cold,the frost in freezer burn comes from frozen water in the food itself.That's why freezer burn happens less to flour and nuts than to vegetables and meat and ice cream,which contain more water,And the ultimate effect is that water is transferred from inside the food to outside the food,leaving it dry and frosty,but still safe to eat.You're basically freeze-drying it,although the food might also oxidize and turn brown.

和平常的霜(又名“白霜”)不同 白霜由空气中的水蒸气 凝固成冰晶 附着在较冷物体表面 而冻灼中的霜 来源于食物中冻住的水 这就是冻灼在面粉或是坚果中发生 频率少于蔬菜 肉类和冰淇淋中 这些食物中所含水分更多 最终 食物中的水分从食物的内部转移到外表面 使得内部 又干又硬 但是还能吃 你仅仅是把它冻干了而已 虽然食物 也可能会氧化变黄。

Of course,ice by itself can also sublimate,which is why ice cubes shrink in their trays over time,And the frost on the walls of a freezer comes partly from water that was once in ice cubes and food in the freezer.

当然 冻本身也能升华 这就是为什么冰块在冰盒中也会渐渐 缩小 冰箱内壁上的冰霜部分来源于曾经在 冰箱内冰块和食物中的水分。

Sublimation happens more easily when the air is dry and when the ice is close to the melting point of water,so you can avoid having your food get freezer burn by keeping your freezer consistently cold and preventing air from contacting the food in it-for example,by sealing food in plastic freezer bags without any air pockets.

当空气干燥 冰块温度临近熔点时 冰更易升华 因此 你可以以此防止食物发生冻灼 可以使冰箱内保持 较低温度 或防止食物和空气接触 比如 可以将食物 密封在没有空气囊的塑料食品袋中。

What's more,freezer burn ISN'T just limited to freezers-it happens in nature,too.Forst-flowers on sea ice,for example,form when water vapor sublimates from warm ice into air too cold to hold it.Homeless,the vapor deposits back onto the surface as icy lilies-sublime sublimation.

同时 冻灼并不只发生在冰箱里 自然界中也会发生 比如 海洋上的 冰花是因温度较高的冰块水蒸气升华 周围空气过冷 无法保持其 原先形态 无处可去的水蒸气聚集在冰表面 形成冰百合---绝美的升华。