微波爐
在現在追求快速的時代；生活步調也隨之加快，食物的烹煮也是儘可能的方便快速，因此微波爐的使用在現今社會已是非常普遍的，微波爐的微波也是輻射的一種，它是利用頻率為2450MHz的輻射使水分子相互磨擦生熱；進而加熱食品，現在我們就來了解微波爐原理與構造及使用微波爐的注意事項。
一、微波爐的原理與構造
１、原理
傳統的烹飪方式是利用熱的傳導、輻射等原理來加熱，所以必需先將容器、介質加熱後，才可使食物加熱。微波加熱的方式和傳統由外而內的方式不同，微波是每秒數一次的電磁波震盪，形成一電磁場。因此將具極性物質（如食品中之水、脂肪、蛋白質）置於磁場中，分子會隨著磁場的振盪而來回碰撞，互相摩擦而產生熱。
微波爐中產生微波的元件稱為磁控管(magnetron)，它發射的微波頻率為2450 MHz，功率約介於500 至100 Watts 之間。微波爐的磁控管將電能轉化為微波能，當磁控管以2450MHZ的頻率發射出微波能時，置於微波爐爐腔內的水分子以每秒鐘24.5億千次的變化頻率進行振盪運行，分子間相互碰撞、磨擦而產生熱能，結果導致食物被加熱。微波爐正是利用這一加熱原理來進行食物的烹飪。
圖3-1 微波爐的構造圖與各部分動作流程
２、構造
微波爐之右上方有一磁電管（磁控管），受到電流衝擊後就會產生微波振動；所以磁電管可說是微波發生源。此振波振動透過金屬管傳至 金屬扇葉形攪拌器，在透過攪拌器將微波均勻的散發至微波爐內金屬內壁上，不斷反射，直至食物將此波動吸收轉為熱能。
二、微波爐的潛在危害
我們可以將微波爐所產生的危害細分為二類：
１、微波洩散所造成的人體危害：
人體是由大部分的水、蛋白質、脂肪所構成，微波本身顯然對人體產生危害。
雖然微波對人體所造成確實的影響，現在尚未完全研究出來，但科學家目前大都同意會有以下的非累積性危害：
(1)眼部的危害：眼睛部分水分極為豐富，極易受微波影響；加上眼球許多部分（如角膜、水晶體）之血流量極有限， 散熱能力較差，所以一旦受到微波的侵襲，無法有效於短時間熱量驅散，而造成熱的殘留。長期暴露可能會有發生白內障的危險。
(2)生殖器官的危害：主要是指男性的睪丸而言。男子睪丸若受微波之熱，容易溫度升高而傷害到精子的產生。所以使用微波爐時，要將它放置在妥當的地方，且避免鼠蹊部直接暴露於微波可能洩漏之處。如果微波爐久失維護，有洩漏可能時，那麼孕婦也不適合接近，以免可能影響胎兒。
(1)皮膚與皮下組織：一般說來，微波所具的危害性與頻率高低成反比，頻率越高（波長越短），穿透力越弱，傷害層面通常越小。
２、包裝容器不當：
被加熱的物品中如含有金屬膜、金屬板之類，不但不能使裡面包裝物熱起來，如果有細長的金屬存在，則可能會發生火花。繪有金、銀絲線之碗碟，可能會由於接受磁波，發出火花使這部分掉下來。而飛散下來的金屬屑片會散在食物內，有被食入的可能。
三、微波爐的注意事項
１、微波爐內不可使用金屬器皿
其理由有：
(1) 由於微波會在金屬表面產生電流，因此電流產生的熱如果發生在較厚的金屬 (如湯匙) 則可輕易的驅散，但若是發生在薄層的金屬 (如鋁箔及鍍有金屬表層) ，則可能會因為過熱而發生起火現象。
(2)金屬邊緣可能會因為蓄積過多電荷，當接觸其他金屬 (如湯匙) 時，產生火花而破壞微波爐。
(3)因為金屬會反射微波，因此包於鋁箔內的食物可能需要數倍的能量方能完成烹調，當與其他食物共同烹調時，食物會有不均衡的烹調程度。
２、防止微波外洩
微波爐的設計大抵均能使微波僅出現於微波爐內，但由於設計不良或微波爐老舊外洩的原因，微波輻射也有可能因此外洩。但目前的數據顯示，微波爐發生微波外洩的量，大多遠低於法規所規範的程度。過去研究顯示，微波對於一些對熱敏感的器官例如眼球、大腦、以及睪丸會造成熱的傷害，但這些都發生在長時間暴露於高強度微波的族群身上，而此暴露量也都遠高於微波的外洩。使用微波爐時應在微波爐內放置被烹調食物，主要原因是，若無食物吸收微波，則微波便會而在微波爐內反覆散射，而增加微波外洩的機會。
３、防止燙傷
因觸摸烹調食物而產生的燙傷，是微波爐另一個安全上的問題。烹煮液體食物時更容易發生這種傷害，那是因為過熱(super-heated)而造成的。這是因為微波爐加熱水時，若是均勻靜止的水，因沒有熱對流，使水均勻加熱致超過沸點，此時如果晃動液體，或以餐具攪動液體，即可能產生瞬間沸騰，以致沸水溢出而產生燙傷事件。
４、消滅食物中的微生物
微波爐烹調食物的速率與食物中含水量、食物量以及食物密度有關。較厚的食物可能會因為烹調時間不夠，熱在食物中可能分布不均而未能完全消滅其中的致病微生物。因此，若烹煮時能達到足以殺菌的溫度，也要在食物烹調完畢之後，讓食物在爐中停留一段時間，使熱在食物中傳開，而讓各部份都達到殺菌所需的溫度。
壹●前言
目前台灣地區家庭微波爐普及率已達 55%至 60%，每年並以 5%的成長率逐年增
加中，而調查新竹以北的企業則發現高達 6 成的辦公室，已備有冰箱和微波爐。 微波爐這種不需火就可加熱的電器真的很方便，但是它的原理究竟是什麼呢？廣 義的說法應是，利用微波（高能量的光子）破壞水分子間，氫鍵（hydrogen）的
鍵結．但是由於氫原子與氧原子，對於電子親和力的不同，水分子之間的氫原子
與氧原子又產生鍵結的現象，隨著氫鍵的破壞與重組，使得水分子不斷地在擾動
（在微觀上水分子的平均動能隨時間擴大），故在宏觀的觀察下，水分子重新排
列的結果以熱的形式放出能量，使得水分子的溫度隨時間增加，進而達到烹煮食
物的效果。
貳●正文
一、關於微波
微波是一種具有很大穿透力的高頻電磁能量，可以自由地在空間中傳播，遇到金 屬面會反射，可在介電質中轉換成熱能，加熱介電質，就是所謂的微波加熱。微 波是由稱為磁控管的微波產生器產生出來，微波一般是 300MHz~300GHz 周波數
的電磁波。微波的利用常見於一般家庭使用之微波爐及業務用之微波加熱裝置 等。加熱的材料隨著接觸定在波位置不同而產生加熱不均的現象，因此為了要避 免加熱不均勻的現象，將材料放置在旋轉盤上或用金屬製的攪波扇在箱內旋轉，
使接觸到材料的定在波改變，防止加熱不均勻的現象產生。
二、關於微波加熱
微波加熱與傳統加熱最大的不同在於熱源的供應方式不同，傳統加熱屬於間接加
熱，主要靠熱媒的熱傳導，微波加熱屬於整體加熱，主要靠微波的熱輻射。
微波加熱的優點包括高速加熱、高速對應、均一加熱、選擇加熱、高熱傳導效率、
操作簡便及作業環境整潔等；微波加熱的缺點為不適合誘導電體物質或金屬加熱 用、加熱物質的大小、形狀受限於電的性質與設備費比較高等。
由於微波特性的影響及其物質的交互作 ，常會造成微波加熱有特殊的加熱現 象。微波是一種以光速前進的電磁波，其行徑方式受電場與磁場的影響，受到電
磁場的作用會有極化現象，因此在加熱過程首先要考慮因介電性質差異所引起的
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選擇性加熱現象。
三、微波加熱原理
01. 水與微波加熱
微波加熱是利用什麼原理？這就要談到水。水是一個很奇特的分子，在吸收電磁
波時，竟然在可見光頻段有那麼一個大峽谷。同樣神奇的是，水一直冷縮到攝氏 四度，然後在攝氏四度以下開始膨脹，這又是少有的。假如水在攝氏四度以下繼
續冷縮，水面結成的冰就會沈到水底，明年夏天來時，因為隔了那麼深的一層水，
水底的冰無法融掉，然後冬天來了，又有一堆冰沈下去，大概幾十年後整個湖都 是冰，即使夏天也一樣。生物是從水裡發展出來的，如果水沒有這個特性，可能
就不會有生物，也沒有人類。
為什麼水和微波爐的關係這麼密切？因為水分子另外還有一個特性：它天生就有 電偶極。在水中，水分子的電偶極通常排列很紊亂，微波爐作用時，作用腔內就
有電場產生，水分子在電場中受到力矩作 ，電偶極就會朝著電場方向排列，電 場方向不斷改變時，水分子的方向也就一直跟著改變，不斷地打轉。
02. 能量與微波加熱
是否每打 個轉就增加一點能量呢？這倒不見得。例如船在水波上面，每來一個
波峰，船就上升一點，波峰過後船又下降，下一個波峰來了，又做相同的動作，
一再重複相同的動作，船的能量並沒有一直增加。這個道理運用到水分子的轉動
上也是一樣，能量不會一直增加，所以並沒有加熱。要加熱，水分子周圍必須要
有東西，這樣才能在轉動的同時，因彼此之間碰撞而加熱。
比如一塊肉，電磁波讓裡面的水分子轉動，去擠動旁邊肉的組成分子，這時就能
加熱。如果全是一杯水也可以，只要水分子之間互相擠動就會變成熱能。我們都
清楚，熱能就是亂無次序的動能，在空氣裡頭的熱能就是如此。風的動能就不叫
熱能，因為風是往同一個方向吹，是有序的動。水分子在電場裡一起有序的動，
也不是熱能，能量還可以再回傳給電場。可是當水分子和其他分子擠在一起動的
時候，相互擦撞，這時大家的方向就亂了，變成了熱能，這就是微波爐的加熱原 理。
03. 微波加熱的頻率
微波加熱不但要使微波能進到食物裡面，還要能被吸收。頻率太低，大部分都穿
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透過食物，頻率太高，在食物表面上就被吸收，進不到裡面，微波加熱的頻率（大
都是 2.45GHz）就是在這個條件下所選擇的，這是微波爐專用的頻率，所以不會
干擾通訊。由於微波能進到食物裡面，同時加熱各處，所以加熱速度快。此外，
金屬作 腔壁吸熱慢，溫度不高，散熱少，這種加熱方法效率高達 50％ 左右，
比傳統烤箱加熱效率（約 10％）大得多，所以也省電。
四、影響微波加熱的因素
01. 微波頻率。
02. 微波的輸出功率。
03. 食品的質量。
04. 食品的密度。
05. 溫度。
06. 食品的形狀。
07. 食品的熱傳導係數。
08.食品的比熱。
五、微波爐
01. 構造
微波爐是大家最熟悉的，和我們的關係也很密切。也許大家還沒想到，跟各位關
係最密切的不是微波爐裡的微波，而是自己身上射出的微波。由我們體溫所放射 出的熱，就是電磁波，其中微波的成分還蠻高的。微波爐的主體是一個作 腔，
是個用金屬封閉的箱，微波射進去加熱食物。箱上有一個可看進去的視窗，可是 微波漏不出來。
其他的機械構造還有
A. 高壓電源（將電力輸送至微波產生器）。
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B. 磁控管（將供給的電力轉換為微波能）。
C. 耦合裝置（控制能量由微波發生器至加熱部，減少逆向傳送的危害）。
D. 微波輸送裝置（主要為同軸線與波導，用來傳送能量至加熱部）。
E. 加熱部（食品在此進行加熱）。
F. 密封或截波裝置（防止微波外洩）。
G. 感測與控制裝置（感測被加熱物之溫度、水分等品質變化以進行回饋控制）。
02.磁控管
磁控管是微波爐裡面最主要的器件，它是一個微波發射器。因為磁控管可應用在 家用的微波爐中，產量動不動就是幾百萬個，這裡面的商機就很多，而最尖端雷 達所使用的磁控管通常賺不了錢，因為需要量常常只是一兩個，所以微波爐才是
商家真正在追逐的利基產品。加速器也是一樣，要找人做還得四處拜託，因為量
太少沒利潤。現在為了競爭，磁控管可以做到一個不到十元美金，量產能使價格
便宜到這種程度，相當不可思議，而太空偵測用的微波管可能一個要價百萬美
金，簡直不成比 。
六、微波加熱的使用
微波加熱技術具有大體積快速加熱、易控制與調整、能源轉換效率高、自動化、
特殊區域加熱能力強、減少污染等特性，是工業製程上不可或缺的重要設備之
一，微波加熱之能量密度較紅外線加熱為高，應用面極廣，它可應用於食品、紡
織、造紙、化工、電子及醫藥等產業方面。
微波加熱依照使用者的不同而區分為家庭用及業務用，雖然設備規模、操作方式
與機械構造有所 別，但是包括電源供應器、磁控管、波導、控制器及加熱腔等
基本單元皆大致相同。家庭所使用的微波爐之功能較簡單，通常只要設定微波的
功率及處理時間即可；至於業務用微波裝置，一般會和熱風併用，而且能進行溫
度的測定，因此加熱效果更佳。
其應用大致上如下
01. 烘焙。
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02. 濃縮。
03.烹調。
04.硬化(主要用在塑膠)。
05.乾燥。
06.殺菁。
07.最後乾燥。
08.冷凍乾燥。
09.加熱。
10.巴斯德殺菌。
11.膨發和發泡。
12.去除溶劑。
13.滅菌。
14.調溫。
15.解凍。
參●結論
隨著工業化的腳步，微波加熱其選擇性加熱、加熱迅速均勻、產品品質高、節省
能源等優點，使微波爐漸漸普及化。
基本上，微波爐可用於烘焙、烤及殺菁、殺菌等，且不用靠水為熱媒，能提高蔬
菜營養素的保存，非常適合家庭用。而微波加熱節省操作空間、能源及可快速升
降溫度控制，非常適合食品工業界使用。
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微波在食品工業較重要的應用可分為殺菁、蒸煮、乾燥、殺菌、滅菌及解凍回溫
等六項。
此外，微波加熱也可應用在種子處理及蟲害控制方面。總而言之，微波加熱不只
在食品加工的應用可以廣泛應用，在未來還有可能會有更多的發展。
肆●引註資料
註一、http://www.ccsh.tp.edu.tw/board/show.asp?no=2380
註二、
http://www.nsc.gov.tw/_newfiles/popular_science.asp?add_year=2005&popsc_aid=125
註三、http://www.phy.ntnu.edu.tw/demolab/phpBB/viewtopic.php?topic=7871
微波爐目前已是許多家庭必備的用具。那麼微波究竟是怎麼作用的？怎麼發現的？有關微波的一些問題，像微波燒的菜是否比較不好吃？微波會致癌嗎？微波加熱的牛奶是否對嬰兒不好？本篇就要簡單地回答這些疑問。
微波簡介
微波是一種電磁波，波長比可見光或紅外光的波長要長，但比無線電或電視波的波長短，頻率在每秒三億週到三千億週之間。（每秒十億週的頻率單位簡寫為GHz）。目前所有家用微波爐都是用2.45GHz的微波，因為這個波長對水的加熱，效率最高。
微波最早是在1939年第二次世界大戰時，偵測納粹軍機的雷達所使用的一種電磁波。工作人員發現冷掉的咖啡，放在微波雷達附近會變熱，因而得知微波可以加熱。然而這種微波產生器需要用水來冷卻，體積很大，而且昂貴，所以無法普及到家用。目前一般家用微波爐所使用的微波產生器（magnetron）則是日本人Keishi Ogura所發明的，便宜、耐用又無需冷卻。微波爐與微波產生器的構造如圖所示：陰極在中間，陽極包圍在外圈，外圈呈不規則形狀。上下端是磁場。電子由陰極射向陽極，而磁場使電子圍繞著陰極轉圈，這些繞圓圈加速的電子會產生電磁波。家用微波爐的設計就是產生頻率為2.45GHz的微波。這個微波沿著導波管通到轉動返射器，以各種角度射到微波爐中，使食物加熱。
電磁波中的紫外光可破壞分子鍵，可見光可激發分子中的電子，紅外光可使分子振動，而微波則可以使分子旋轉。當微波遇到極性物質，會使極性物質旋轉而變熱。所謂極性物質就是該物質分子中的電荷分布並不平均，有的地方電子比較多而稱為負極，另一邊則電子較少稱為正極，水就是一個極性物質。水分子H2O中，氧的一端屬負極而氫的一端屬正極。因此用微波加熱蔬菜、魚肉、水果時，就是其中所含的水分被加熱所致。然而並非所有的水分子都可以吸收微波。如果水分子被固定住，無法旋轉，就無法吸收微波而被加熱。例如，冰塊中的水分子就無法用微波加熱。你可以同時加熱一杯水與一杯冰塊90秒的時間，你會發現水已沸騰而冰尚未溶化。（做此實驗時需使用直接由冷凍櫃取出之冰塊，否則有一層水熔化在冰塊的表面上，效果就不明顯。）
微波爐應用在家庭烹飪和化學實驗室
微波爐所用的波長為12.24公分，這表示在微波爐內有的區域能量高，有的區域能量低。物體若是放在低能量的節點處，就不會被加熱，因此有些微波爐就靠轉盤，使得食物能均勻地照到高能量微波。
微波爐可加熱但無法使食物焦黃，這是微波爐不如傳統烤箱的地方，但若使用具有「加熱強化區」的食品袋，就可以達到焦黃的效果。這種加熱強化區乃是在紙袋上塗一層金屬薄膜。如此可以使爆玉米花以及比薩等食物的表面酥脆。例如在微波爆玉米花的袋中，金屬的加熱強化區可使溫度達到250℃，這就是為什麼爆玉米花的紙袋在爆過之後，會有燒焦痕跡的原因。（用微波爆玉米花時，不要離開微波爐太遠，以防紙袋起火！）
雖然食品調理袋中有加熱強化區的金屬層，但是一般金屬絕不可放入微波爐中，因為金屬會造成電流，產生火花。石墨也會導電，在微波爐中發白光。而金屬氧化物會熔化，例如取五克的氧化銅或氧化鋅等樣品放入微波爐中加熱，每秒可上升10℃，所以不消一分鐘金屬氧化物就熔化了！
用微波燒煮食物只是微波多項功用之一。微波還可用在空中與海上交通的控制、衛星信號的傳送與工業用途。美國懷俄明州的一座火力發電廠就發現該廠所排放出的廢氣，用微波照射後，可使二氧化硫變成硫，二氧化氮變成氮氣。另外，《科學月刊》1993年9月號第711頁也有以微波製造半導體材料的報導。
至於微波在化學反應方面的用途，直到1988年加拿大的化學家發現有些反應用微波爐可以加快很多，才使化學家對微波做化學反應有興趣。例如要合成一個化合物氰苯苯甲醚（cyanophenyl benzyl ether），用微波只需12秒就完成了，若用其它的方法則需12小時。然而用微波做化學反應，仍有些問題需要注意，因為有些實驗可能會爆炸，必需使用鐵氟龍（teflon）做的瓶子。此外，溶劑的選擇也很重要，極性越高的溶劑加熱越快﹔非極性溶劑，像己烷則根本就無法用微波加熱。而在分析實驗室中，常用微波加熱，讓煤炭、油及生物樣品溶於硫酸及硝酸中，以便分析其中所含的微量金屬。
早期曾有微波爐之微波外洩的例子。例如某一分析實驗室用微波爐加熱硝酸中的樣品時，由於酸的蒸氣腐蝕掉自動斷電系統，因此當爐門開著的時候，樣品加熱仍繼續在進行，而操作員站在一旁並不知情。結果有一天他站在微波爐附近，又因站得過久，結果因為熱休克而昏倒！至於家用微波爐中的微波則不會逃逸出來，因為微波無法穿過金屬壁，以及鑲有金屬網的玻璃門。即使是因為爐門有裂縫而逃逸出的微波也是非常少量，你不會有感覺的。
微波爐的疑惑
那麼有關微波爐的一些通俗說法，又是否正確呢？
一、用微波燒煮出來的菜，其滋味是否不同？答：是不同的。
美國加州大學戴維斯分校曾研究煮過食物所產生的香味。以傳統燒烤方式煮的食物，放出 （thiazole）、 喃（furan）及 （pyrazine）等令人垂涎的香味。若用微波則會放出 （oxazole）， 吩（thiophene）及 咯（pyrrole）等的味道，較不會令人喜歡。他們認為是因為燒煮食物的時間較短，溫度較低的緣故。
二、用微波加熱牛奶，對嬰兒會不好？答：錯。
用微波加熱是會使其中某些氨基酸，像左旋－ 咯（L-proline）變成嬰兒不會消化的右旋－ 咯。然而根據佛羅里達州邁阿密大學的研究發現，用一般的加熱板（hot plate）加熱牛奶，同樣也會使左旋變成右旋。
三、微波會致癌嗎？答：不會。
事實上，微波可以殺死癌細胞。例如，在胸部、頸部及頭部的癌細胞，可以用微波加熱，而使癌細胞熱死的方式治療。因為癌細胞沒有正常細胞的血管網絡，微波加熱後，熱無法散出而導致細胞死亡。多年前，曾有實驗指出實驗室的小鼠長期曝露於低能量微波下，其染色體的受損比例較高。然而，該實驗結果在1984年發表之後，其他的科學家做同樣的試驗則並未得到相類似的結論。
數年前，也有實驗室發現某些塑膠製容器或保鮮膜，經微波加熱後會釋放出易被脂肪物質吸收的化學物質，而其中有些化學物質可能會引起癌症。從此以後製造商改變了塑膠的處方，以防止此類事件再發生；此外，在塑膠中所添加的成分，以使塑膠具彈性、色澤及抗火性的化合物也都必須經過測試無害後才准上市使用。
Microwave
In the present era of rapid pursuit ; also will accelerate the pace of life , the food is cooked quickly and easily as possible , so the use of microwave ovens in today's society is very common , microwave oven radiation is one, it is the use of frequency for the 2450MHz radiation friction between the water molecules and heat ; thereby heating the food , and now we come to understand the construction and use of microwave theory and microwave precautions.
A microwave oven works and construction
1 , the principle
The traditional way of cooking is the use of heat conduction, radiation and other principles to heat , so must the first container , dielectric heating only after heating the food . Microwave heating methods and traditions from outside to inside in different ways, the microwave is once per second shock wave to form an electromagnetic field . Therefore a polar substances ( such as food in the water, fat , protein ) in a magnetic field, the molecules with the magnetic field oscillating back and forth impact , friction heat is generated with each other .
The microwave oven magnetron for generating microwaves element is referred to (magnetron), which emits the microwave frequency of 2450 MHz, power of about between 500 and between 100 Watts . Magnetron microwave energy into the microwave energy , when the magnetron frequency to 2450MHZ emit microwave energy when the microwave oven cavity water molecules to 2.45 billion thousand times per second change in the oscillation frequency of operation, intermolecular collisions, friction generates heat , resulting in food is heated. This principle is the use of microwave heating for cooking food .
Figure 3-1 microwave oven parts of the structure and operation flow of FIG.
2, Structures
The top right there is a microwave magnetron tube ( magnetron ) , by the current shock will produce microwave vibration ; therefore magnetron can be said microwave generating source . Discovering this vibration transmitted through a metal tube -shaped metal blade agitator , agitator in the microwave evenly through the dissemination to microwave metal wall, constantly reflecting , until this fluctuation absorbing food into energy .
Second, the potential hazards of microwave
We can microwave hazards arising subdivided into two categories:
A microwave leakage caused by scattered human hazards:
Most of the human body is composed of water , protein, fat composition, microwave itself clearly cause harm to humans .
Although the microwave does to the human body caused by the impact of , and now it has not been fully studied , but most scientists now agree that there will be the following non- cumulative hazards:
( 1 ) Eye hazards : the eyes of the water is extremely rich, highly susceptible to microwave effects ; plus many parts of the eye ( eg cornea, lens ) of a very limited blood flow , cooling capacity is poor, so once the invasion by the microwave , can not effectively dissipate heat in a short time , causing the residual heat . Long-term exposure may be risk of cataracts .
( 2 ) reproductive hazards: mainly refers to the male testicles terms . Men 's testicles if by microwave heating , the temperature rises easily hurt sperm production . Therefore, when using a microwave oven , to place it in the proper place , and avoid direct exposure to microwave groin may leak place . If the microwave oven for so long maintenance, there is a leak possible, so not suitable for pregnant women approaching , so that may affect the fetus.
( 1 ) Skin and subcutaneous tissue : In general, with the dangers of the microwave frequency is inversely proportional to the level , the higher the frequency ( shorter wavelength ) , the weaker penetration , damage levels are usually smaller .
2 , improper packaging container :
Heated articles which contain metal film , metal plates and the like, not only can not heat up the inside of the packaging , if there exists an elongated metal , sparks may occur . Painted with gold and silver thread of dishes, may be due to accept the wave , spark to make this part of the fall. The sheet metal debris scattered down will be scattered in food , there is a possibility of ingestion .
Three , microwave Precautions
1, the microwave oven can not use metal utensils
The reasons are:
( 1 ) As the microwave current in the metal surface , so the heat generated by the current in the case of thick metal (e.g. spoons ) can easily disperse, but if it is place in a thin layer of metal ( such as aluminum foil and coated with a metal surface ) , overheating may occur because of the fire phenomenon .
( 2 ) metal edges may be due to excessive accumulation of charge, when contact with other metals ( such as spoons ) when sparks and damage microwave.
( 3 ) Because the metal will reflect the microwave , so the food wrapped in aluminum foil of energy may be required to complete the cooking times , when cooked together with other foods , the food cooking level will be uneven .
2, to prevent microwave leakage
Microwave microwave design probably all can only appear in the microwave , but due to poor design or microwave leakage causes aging , may also be a result of microwave radiation leakage . However, the current data show that the amount of microwave leakage occurs microwave , mostly far below the level of normative regulations . Past studies have shown that the microwave for some heat-sensitive organs such as the eye, brain and testicles can cause heat damage, but these have occurred in the prolonged exposure to high intensity microwave ethnic body, and this exposure are also much higher than the microwave leakage. Use the microwave should be placed in a microwave oven cooking food , mainly because , in the absence of food absorption of microwave , the microwave will be repeated in the microwave scattering , and increase the chance of microwave leakage .
3 , to prevent burns
Caused by touching the cooking food burns , is microwave safe on another issue. Cooking liquid food more prone to such injuries , it is because of overheating (super-heated) caused. This is because the water is heated in a microwave , even if the still water , because there is no thermal convection , the heated water evenly over the boiling point caused by this time, if the liquid shake or stir the liquid in order to tableware , which may produce instant boiling , boiling water overflow, the resulting scald events.
4 , to eliminate microorganisms in food
The rate of microwave cooking food in water content, the amount of food and food density. Thicker foods may be because the cooking time is not enough , the heat in the food may not completely eliminate the uneven distribution among pathogenic microorganisms. Therefore, if the cooking time can be enough to sterilization temperature , but also in food cooking is finished, allow the food to stay for some time in the furnace , the heat in the food spread, and let each part has reached the desired temperature sterilization .
One ● Introduction
Currently Taiwan families microwave penetration rate has reached 55-60% , and the annual growth rate of 5% yearly increase
Canada , and the survey found that enterprises in Hsinchu , north of up to 6 percent of the office, had a refrigerator and microwave. This microwave oven can be heated without fire appliances really convenient, but it is the principle of what is it ? Argument should be generalized by microwave ( high-energy photons ) destruction of the water molecules , the hydrogen (hydrogen) in
Bond . However, due to the hydrogen atom and oxygen atom , the electron affinity of the different between the hydrogen atoms of water molecules
With oxygen atoms bonded phenomenon has produced , along with the destruction of hydrogen bonds and reorganization , making the water molecules constantly disturbed
( Sheung Shui in the microscopic average kinetic energy of molecules expand over time ) , so the macroscopic observation , the water molecules rearrange
The results listed in the form of heat energy is released , so that the temperature of the water molecules increases with time , thus achieving the cooked food
Material effect.
II ● Text
I, on the microwave
Microwave is a great penetrating power of high frequency electromagnetic energy that can be freely spread in space , across the metal surface will be reflected in the dielectric is converted into thermal energy , dielectric heating , microwave heating is called . Is called a magnetron microwave generator generated microwaves , microwaves generally Frequency 300MHz ~ 300GHz
Electromagnetic waves. Microwave use is common in general home use and business use of the microwave oven microwave heating devices. Contacting the heated material with a different fixed position in the wave phenomena arising from uneven heating , so in order to avoid the phenomenon of uneven heating , the material is placed on the rotating disc or metal wave mixing fan rotates in the box ,
The contact material is fixed to the changes in the wave , to prevent the phenomenon of uneven heating .
Second, on the microwave heating
Microwave heating and conventional heating biggest difference is that the supply of heat in different ways, conventional heating is indirect plus
Heat, mainly by thermal conduction heat medium , microwave heating is overall heating , mainly by microwave radiation .
The advantages of microwave heating speed , high-speed mapping, uniform heating , select the heating , heat transfer efficiency ,
Easy to operate and clean working environment , etc. ; disadvantages of microwave heating is not suitable for inducing electrode material or metal , heating, heating material size, shape limited by the electrical properties compared with higher equipment costs .
Because microwave properties of its material interactions , often resulting in a special microwave heating phenomenon . Microwave is a forward speed of light waves , which acts by way of electric and magnetic fields , by the power
The role will be polarization field , so the first thing to consider because of the heating process dielectric properties caused by differences
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Selective heating phenomenon .
Third, the principle of microwave heating
01 Water and microwave heating
What is the use of microwave heating principle ? It is necessary to talk about water . Water is a very strange molecules in the absorption of electromagnetic
Wave, even in the visible light spectrum so a Grand Canyon. Also amazing is that water has been shrink to four degrees Celsius , four degrees Celsius in less then began to swell , which in turn is rare . If the water following the below four degrees Celsius
Continued shrinkage , the water formed ice will sink to the bottom , next year when the summer comes , because every so deep layer of water ,
The bottom of the ice can not melt away , and then winter comes, there are a bunch of ice sank , probably a few years later the whole lake is ice , even in summer , too. Organisms are developed out of the water , if the water does not have this feature , you may
Not have biological , nor humans.
Why is the relationship between water and microwave so close ? Because water molecules in addition to a feature : it is born with the electric dipole . In the water, the water dipole molecules are often arranged a disorder, microwave effect, the effect of the cavity on the
Generating an electric field , the water molecules in the electric field as being moment , dipole field will be arranged in the direction towards , changing the electric field direction , the water molecule also been followed in the direction changing and spin.
02 . Energy and microwave heating
Does every turn to make a little more energy? This inverted necessarily. For example boat above the waves , each to a
Crest , the ship goes up a little , crest after the ship has dropped , the next wave came, it did the same action ,
Repeated the same action , the ship's energy has not been increasing . This principle applied to the rotation of water molecules
The same is true on the energy would not have been increased , and there is no heating . To be heated , the water molecules surrounding must be
Something , so as to rotate at the same time , due to the collision between the heating .
Such as a piece of meat , so that electromagnetic waves inside the water molecules rotate , move side to squeeze the molecular composition of the meat , then you can
Heating . If all the glass of water can be, as long as the water molecules move between each squeeze becomes heat. We all
Clear energy is the kinetic energy of the order without chaos , the heat in the air inside is so . Kinetic energy of wind is not called
Energy, because the wind is blowing towards the same direction , is orderly move. With the water molecules in the electric field in an orderly move,
Nor heat, electric energy can also return pass . But when the water molecules and other molecules move huddled together
Time , mutual collision , when everyone's direction into chaos , into heat , which is the principle of microwave heating .
03 microwave heating frequency
Microwave heating is not only to make the inside of the microwave energy into the food , but also can be absorbed . Frequency is too low , the majority of wear
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Through food , the frequency is too high, the food is absorbed on the surface , not get into the inside, microwave heating frequency ( large
Are 2.45GHz) is selected in this condition , which is the frequency of microwave ovens , it will not
Interfere with communications . As the microwave energy into the food inside, while heating throughout , the heating speed . Furthermore ,
Metal wall heat for slow , the temperature is not high , less heat , the heating efficiency of the method of this up to 50 %, and
Heating efficiency than conventional oven (about 10% ) is much larger , so it is power.
Fourth, the factors affecting microwave heating
01 microwave frequencies.
02 microwave output power.
03 . The quality of food .
04 . Food density.
05 Temperature .
06 the shape of the food .
07 . Thermal conductivity of the food .
08. Specific heat of the food .
Five , microwave
01. Structure
Microwave ovens are the most familiar , and our relationship is very close . Perhaps we have not thought of , to tell you off
Department most closely microwave microwave oven is not , but his body emitted microwaves. Emanating by our body heat , is an electromagnetic wave , wherein the microwave components quite high . The subject is a microwave oven for the chamber ,
Is a closed metal box , microwave radiation into heat food . Box has a window looking into , but not out of microwave leakage .
Other mechanical construction as well
A. high voltage power supply ( the power delivered to the microwave generator ) .
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B. magnetron ( the supplied electric power is converted to microwave energy ) .
C. coupling means ( control energy from the microwave generator to the heating unit , to reduce the harm reverse transmission ) .
D. microwave conveying means ( mainly coaxial with the waveguide for transmitting the energy to the heating portion ) .
E. heating section ( heated food on this ) .
F. sealing or clipping device ( to prevent microwave leakage ) .
G. sensing and control device ( sensing the temperature to be heated , water quality changes , etc. for feedback control ) .
02 . Magnetron
A microwave oven magnetron inside the main device, which is a microwave transmitter . Because magnetron can be used in household microwave oven, production at every turn is a few million , and there's a lot of business opportunity , and the most sophisticated radar uses a magnetron usually losing money because the requirement is often just one or two so is the microwave oven
Businesses in the pursuit of true niche products. Accelerator is the same, please find someone to do have four , because the amount of
Not too little profit . Now in order to compete , the magnetron can do a less than U.S. $ 10 , with volume production to make the price
Cheap to such a degree , quite incredible, and the space used for microwave tubes may detect an asking price of one million United States
Gold is simply disproportionate .
Sixth, the use of microwave heating
Microwave heating rapid heating with a large volume , easy to control and adjust the energy conversion efficiency, automation,
Special district heating ability, reduce pollution and other characteristics, is an industrial manufacturing process indispensable equipment
First, the energy density compared to microwave heating Infrared heating is high, very wide application , which can be used in food , textile
Weaving, papermaking , chemical, electronics and pharmaceutical industries .
Microwave heating varies according to the user's divided into household and business use , although the device size, mode of operation
And mechanical construction has not , however , including the power supply , magnetron, waveguide , the controller and the heating chamber , etc.
Basic units are roughly the same. Families are using microwave function relatively simple, usually just set the microwave
Power and processing time can be ; For business use microwave devices , generally , and hot air and use , and can be warm
Determination , so the heating effect is better.
Substantially below their applications
01. Baking .
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02 . Concentrated.
03 . Cooking .
04 . Sclerosis ( mainly used in plastic ) .
05 drying .
06 blanching .
07 and finally dried.
08. Freeze-dried.
09 . Heating .
10 pasteurization .
11 leavening and foaming .
12 the solvent was removed .
13 sterilization.
14 thermostat .
15 . Thaw.
Participation ● Conclusion
With the pace of industrialization , its selective heating microwave heating , heating quickly and evenly , product quality , saving
Energy , etc., so that microwave oven gradually popular.
Basically , a microwave can be used for baking , baking and blanching , sterilization , etc., and do not rely on water as a heat medium , can improve vegetable
Preservation of food nutrients , ideal for family use . The microwave heating operation saving space, energy and can quickly rise
Lowering the temperature control , ideal for food industry use .
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Microwave in the food industry is more important applications can be divided into blanching , cooking, drying , sterilization, sterilization and thawed back to temperature
Other six .
Moreover , microwave heating may also be used in seed treatment, and pest control . In summary , the microwave heating only
In food processing applications can be widely used in the future there may be more developments.
Four citations ● Data
Note a , http://www.ccsh.tp.edu.tw/board/show.asp?no=2380
Note two ,
http://www.nsc.gov.tw/_newfiles/popular_science.asp?add_year=2005&popsc_aid=125
Note three , http://www.phy.ntnu.edu.tw/demolab/phpBB/viewtopic.php?topic=7871
Microwave oven has been essential appliances for many families . So how exactly is the role of the microwave ? How discovered ? Microwave on some of the issues like whether to compare microwave cooking can not taste ? Microwave cause cancer? Microwave heating of milk is not good for babies ? Benpian will simply answer these questions .
Microwave Introduction
Microwave is an electromagnetic wave , the wavelength of visible light or infrared light wavelength is longer , but less than the radio or television waves wave length , the frequency of three hundred billion weeks per thoughtful between three hundred million . ( One billion weeks per unit of frequency abbreviated GHz). At present, all of 2.45GHz microwave oven microwaves are used , because the wavelength of water heating , the highest efficiency .
Microwave was first developed in 1939 during World War II , the Nazi military radar detection uses an electromagnetic wave . Staff found that the coffee cools down , placed near the microwave radar becomes hot , so that you can microwave heating . However, this microwave generator requires water for cooling , the volume is large, and expensive , so it can not spread to the home . It is generally used in domestic microwave oven microwave generator (magnetron) is invented by the Japanese Keishi Ogura , cheap , durable and without cooling . Microwave oven and microwave generator constructed as shown: in the middle of the cathode , the anode surrounded by outer , outer irregular shapes. Upper and lower ends is the magnetic field . Electrons from the cathode toward the anode , while the magnetic field the electrons circling around the cathode , the electrons accelerated in circles will produce electromagnetic waves. Domestic microwave oven design is to produce a frequency of 2.45GHz microwave . The microwave waveguide pass along to turn back emitter , at various angles onto the microwave , heating the food .
Wave ultraviolet light can damage the molecular bonds , visible light can excite electrons in the molecule , the infrared light allows the molecular vibration , while the microwave you can make molecules rotate . When the microwave encounters polar substances , polar substances causes the rotation becomes hot . The so-called polar molecule substance is the substance of the charge is not evenly distributed , but some places are more known negative electron , the other side is called the cathode electron less , water is a polar substances. H2O water molecules , the oxygen and the hydrogen end of an end of the negative electrode is a positive electrode . Therefore, the microwave heating vegetables, fish , fruit , that the water contained therein is heated due. However, not all the water molecules absorb the microwave . If the water molecules are fixed and can not rotate , it can not absorb microwaves and is heated. For example , the water molecules in the ice will not be able to use microwave heating . You can heat a cup of water with a cup of ice 90 seconds of the time, you will find that the water has boiled and the ice has not melted . ( Do this experiment will be used when taken directly from the freezer to the ice, otherwise there is a layer of water on the surface of the ice melting in the effect is not obvious . )
Microwaves used in home cooking and chemistry laboratory
Microwave wavelength used 12.24 cm , which means that some areas in the microwave energy is high, some low energy region . If an object placed in low-energy node , it will not be heated , so some rely on microwave turntable , so food can be evenly shine high energy microwave .
Microwave oven can be heated but can not make the food brown , which is not as good as conventional microwave oven place , but if having a " heat strengthened Area" food bags , we can achieve the effect browned . This heating enhancement area but in a paper bag coated with a layer of metal film . This can make popcorn and crispy pizza and other food surfaces . For example, in the microwave popcorn bag , heating the metal to strengthen the zone enables the temperature reaches 250 ℃, which is why the popcorn bag off after the blast , will cause burn marks . ( Microwave popcorn , do not leave the microwave too far to prevent the paper bag on fire ! )
Although enhanced food conditioning bags with heating zones of the metal layer, but generally the metal must not be in a microwave oven , because the metal will cause current to produce sparks. Graphite is also conductive , white hair in a microwave oven . And the metal oxide will melt, such as to take five grams of copper oxide or zinc oxide sample was placed in a microwave oven , can be increased per 10 ℃, so that the metal oxide on one minutes Needless melted !
Microwave microwave cooking food just one of a number of functions . Microwave can also be used in the air and maritime traffic control , satellite signal transmission and industrial use. Of a thermal power plant in Wyoming found the plant out of the exhaust gases emitted by microwave irradiation, can become sulfur dioxide , nitrogen dioxide becomes nitrogen. In addition, " Science Monthly ," September 1993 No. No. 711 but also to microwave semiconductor materials reported.
As for microwave use in the chemical reactions until 1988 Canadian chemist found that some of the reactions can be accelerated with a microwave oven a lot , just make do on microwave chemistry chemists are interested . For example, to synthesize a compound benzonitrile anisole (cyanophenyl benzyl ether), a microwave just 12 seconds to complete , if using other methods need to 12 hours. However, to do with a microwave chemical reaction , some issues still need to pay attention , because some experiments may explode , it is necessary to use PTFE (teflon) do bottle. Moreover , the choice of solvent is also important , the faster heating polar solvents higher ; non-polar solvent , such as hexane and then simply unable to microwave heating . In the analytical laboratory , the commonly used microwave heating , so that the coal , oil, and biological samples dissolved in sulfuric acid and nitric acid in order to analyze the trace metals contained therein .
Early had microwave microwave leakage examples. For example, an analytical laboratory microwave nitric acid sample, because the acid vapor etching away automatic power system, so when the door is open when the sample is heated continued progress , and the operator did not know standing situation . Results One day he was standing near a microwave oven , because of the stand too long , the results because the heat shock and collapsed ! As for the domestic microwave oven will not escape out of the microwave because microwaves can not pass through metal walls , and glass doors inlaid with metal mesh . Even as the door a crack and escape out of the microwave is very small , you do not have feelings .
Microwave doubts
So some popular argument about microwave ovens , and whether the right thing to do ?
First, the use of microwave cooking out of food , its taste is different ? A: is different.
University of California , Davis, has studied the smell of cooked food produced . The traditional way to cook barbecue food , release (thiazole), furans (furan) and (pyrazine) and other mouth-watering aroma. If using the microwave will emit (oxazole), thiophene (thiophene) and cough (pyrrole) and other flavor, less likely likeable . They think that because of the short time cooking of food , because of the lower temperature .
Second, the use of microwave heating milk, the baby will be bad ? Answer : False.
Microwave heating is make some amino acids , such as L - slightly (L-proline) becomes baby will not digest dextral - slightly. However, according to researchers at the University of Miami, Florida found that , with the general heating plate (hot plate) heating the milk , also will become a right-handed left-handed .
Third, the microwave cause cancer? Answer: no .
In fact , microwaves can kill cancer cells. For example, in the chest, neck and head cancer cells , you can use the microwave heating , leaving the way dead heat treatment of cancer . Because cancer cells do not normally vascular networks , microwave heating , the thermal shed which can lead to cell death. Many years ago, there have been experiments indicate that laboratory mice exposed to long-term low-energy microwave , its higher proportion of chromosomal damage . However, the results published in 1984 , other scientists to do the same test is not been a similar conclusion.
A few years ago , there are lab found some plastic containers or plastic wrap, by microwave heating will release fatty substances easily absorbed chemicals , some of which chemicals may cause cancer. Since then manufacturers have changed the plastic prescription to prevent such incidents in the future ; addition, the added ingredient of plastic to make the plastic flexible , color and fire resistance of the compounds must be tested before quasi harmless listed use .
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