百科知識視頻之煎蛋小學堂55 凍灼是什么？

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.

你是否注意到過 當肉 蔬菜或冰淇淋在冰箱中長時間放置后 它的表面上會形成一層冰霜 這些食物吃起來口感有甘有粘?這就是凍灼 它是由冷凍食物中的冰升華造成的 也就是說，水分直接從固態(tài)變成氣態(tài) 而非冰晶先融化成水后再蒸發(fā)。

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 白霜由空氣中的水蒸氣 凝固成冰晶 附著在較冷物體表面 而凍灼中的霜 來源于食物中凍住的水 這就是凍灼在面粉或是堅果中發(fā)生 頻率少于蔬菜 肉類和冰淇淋中 這些食物中所含水分更多 最終 食物中的水分從食物的內(nèi)部轉移到外表面 使得內(nèi)部 又干又硬 但是還能吃 你僅僅是把它凍干了而已 雖然食物 也可能會氧化變黃。

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.

當然 凍本身也能升華 這就是為什么冰塊在冰盒中也會漸漸 縮小 冰箱內(nèi)壁上的冰霜部分來源于曾經(jīng)在 冰箱內(nèi)冰塊和食物中的水分。

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.

當空氣干燥 冰塊溫度臨近熔點時 冰更易升華 因此 你可以以此防止食物發(fā)生凍灼 可以使冰箱內(nèi)保持 較低溫度 或防止食物和空氣接觸 比如 可以將食物 密封在沒有空氣囊的塑料食品袋中。

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.

同時 凍灼并不只發(fā)生在冰箱里 自然界中也會發(fā)生 比如 海洋上的 冰花是因溫度較高的冰塊水蒸氣升華 周圍空氣過冷 無法保持其 原先形態(tài) 無處可去的水蒸氣聚集在冰表面 形成冰百合---絕美的升華。