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社会上的微波炉使用注意事项不转圈也能均匀加热食物吗

现在的微波炉不转圈还能均匀加热食物吗?这问题引发了社会对微波炉使用注意事项的关注。传统印象中,微波炉与“旋转”紧密相连,但现今许多微波炉已经改变了模样,不再有转盘,只剩下平坦的底部。然而,这并不意味着它们就无法好好加热食物。

其实,微波炉的工作原理是利用内部的磁控管将电能转换成微波,当这些微波被食物吸收时,食物内的水、糖分、脂肪等“极性分子”高速震动,这个过程在我们眼中看到的是“食物被加热了”。但需要提醒的是,用高档位长时间加热后,食品中的水分会蒸发,使得包子、馒头等变得硬如石头。此外,由于生物细胞液吸收微波能力优于周围介质,在micro wave电磁场中细胞迅速破裂死亡,可达到清洁杀菌作用。

与传统炉灶相比,micro wave让能量直接到达食材,因此它的加热速度快,即可把剩饭快速变暖。而这种电能转换成micro wave使得food内“极性分子”高速震动独特加热原理,也使得microwave面临不均匀加热的问题。microwave内,每次从固定位置以固定形式发射出电磁wave,它们在inside wall之间反射,并产生相互作用。这导致microwave总是出现固定的模式驻Wave,所以只能在固定的位置进行加热,不同位置效果截然不同。

为了解决这个问题,一些设计加入了turntable,它可以让food在heat时不断更换位置,让它们接触到的electric field环境变得平均,从而实现受heat均匀,而避免出现部分凉一些部分烫的情况。但有些没有turntable,是因为turntable不是改善additive heat loss唯一手段。一种常用的方法是在microwave内安装特殊形状金属扇叶虽然没有改变food position,但旋转扇叶可以持续改变electromagnetic field in microwave interior,从而搅拌原本固定的pattern,使不同的position都有相同强度,这些metallic fans被称为mode stirrers,他们通常位于glass或cramic material bottom下方或者塑料罩里不可见处,有时候也同时具备stirrer和turntable功能。

从实验数据看来,stirrers and turntables都能够显著改善heating uniformity,没有明显优势和劣势。不过,它们各有局限性。(1) Stirrers' limit: 即便不断打乱waves, inside the oven, the microwave intensity still cannot be completely uniform. Even if fan design is reasonable, "averaging" effect may not be as good as directly changing food location.(2) Turntables' limit: while turntables are limited because center and edge of rotation always have temperature differences. This is because food at central part of rotation cannot effectively change position during heating.

除去这些因素,加热不均匀还与food composition and geometric shape related to this point even improved microwave design can't avoid it. For example, under same micro wave strength, water and fat in food heat differently. In micro waving meat we often find that fatty parts become hot first-this is because oil has a lower specific heat capacity than water but needs less energy to raise more temperature.

Therefore, to make sure that dishes are truly heated evenly, it's best to pause mid-heating and flip the food over for a moment.