蘋果點解會氧化??? ( 英文答 )

CHIN:

蘋果氧化是因為 蘋果內所含的鐵質氧化了的關係，
蘋果本身的鐵質被空氣中的氧，氧化形成氧化鐵的顏色。

如果沒有接觸到空氣中的氧，是不會氧化的。
去皮的蘋果，如果放入水中，就能停止變色。
有的人會在水中加入少許的鹽，這也能阻止蘋果變色。
鹽水具有溶出細胞中氧化酵素(多酚酶)的作用，如此便可延緩蘋果變色。
ENG:
The apple oxidation is because in the apple contains ferroguinous has oxidized the relations,
apple itself ferroguinous by the air in oxygen, the oxidation is formed the ferric oxide the color.
If has not contacted in the air the oxygen, cannot oxidize.
Goes to the skin the apple, if puts in the water, can stop the color deterioration.
Some people can join the little salt in the water, this also can prevent the apple color deterioration.
The salt water has dissolves in the cell the oxydase (multi-phenolase) the function, so then may delay the apple color deterioration.

Q:鐵質會變質??



A: 這是個極度錯誤的觀念.有人以為蘋果在削皮後會變色﹐是鐵質氧化的結果﹐所以蘋果可以補鐵﹐這個認知是錯誤的。削皮後變色是氧化的結果沒錯﹐但不是鐵的氧化﹐而是一種叫多酚的有機物質在酵素的促成下氧化的結果。



http://www.healthhouse.com.tw/info/confuse/apple.htm





(一)蘋果氧化原理:



蘋果切開後，接觸到空氣會變色，是因為水果含有酵素和多酚類基質，而多酚類基質受到酵素的氧化後，便會使顏色產生變化。切開的水果要變色，必須同時具有酵素、多酚類基質和氧氣三個條件。不同水果所含有的多酚類基質和酵素，含量各不相同，所以變色的情況也有時間和深淺的差異。



有些水果甚至不含有多酚類基質和酵素，因此即使長時間暴露於空氣中，顏色也不會改變。加熱時會破壞酵素的活性，食鹽也有抑制酵素活性的效果，利用此種方式能有效防止切開的水果變色。一般多以抹食鹽或浸泡食鹽水來保持水果的新鮮顏色。市面上所購得的水果罐頭，在製作封罐之前都會經過蒸煮過程，以保持水果的原味，並防止變色現象。當蘋果切開時，會立刻接觸到空氣，所以要盡快浸泡在食鹽水中，才能避免直接在空氣中造成變化。浸泡食鹽水的時間不需太長，大約３～５分鐘即可明顯的看出浸泡食鹽水與直接暴露再空氣中水果切片顏色的差別。水果、蔬菜種類不同，其變色程度和變色所需要的時間也有差異，如牛蒡削皮或切開後，立即可見變褐色現象，而蘋果則須約半小時左右。



要防止蘋果變色，最容易的方法就是將蘋果與空氣隔開，不過也可以用加熱方法來破壞蘋果中的酵素，可使酵素無法產生氧化作用，或者是利用低溫來抑制酵素氧化，也可用維生素Ｃ或檸檬汁來抑制酵素氧化。而日常家庭裡面，常常將切好的蘋果浸泡鹽水，以防止蘋果變色，那是因為鹽水也可用來抑制蘋果中的酵素進行氧化，因為鹽非常易於取得，所以大家就常用此法來保持蘋果的色澤。



(二)食得太多會唔會有害??
食物暴露於空氣中氧化變色後，其營養價值也會隨著改變，這是因為當“變色”反應在進行時，其他一些營養物質也會被氧化，其中維生素C流失最為嚴重。這就令營養大打折扣,故多吃亦不會有益.



因此已被削皮或切開之蔬果必須立即做好處理工作，避免產生褐色反應，而影響人體的健康。





http://wf66.com/page/20066/127933A16A.htm

http://hk.knowledge.yahoo.com/question/?qid=7006090905335

http://w2.tpes.tc.edu.tw/nine/nine7/nine727.htm

This article is about the tree and its fruit. For the technology corporation, see Apple Inc.. For the record company, see Apple Records. For other uses, see Apple (disambiguation).
iApple



Botanical origins

Wild Malus sieversii apple in KazakhstanThe wild ancestor of Malus domestica is Malus sieversii. It has no common name in English, but is known in Kazakhstan, where it is native, as 'alma'; in fact, the region where it is thought to originate is called Alma-Ata, or 'father of the apples'. This tree is still found wild in the mountains of Central Asia in southern Kazakhstan, Kyrgyzstan, Tajikistan, and Xinjiang, China.

For many years, there was a debate about whether M. domestica evolved from chance hybridisation among various wild species. Recent DNA analysis by Barrie Juniper, Emeritus Fellow in the Department of Plant Sciences at Oxford University and others, has indicated, however, that the hybridisation theory is probably false. Instead, it appears that a single species still growing in the Ili Valley on the northern slopes of the Tien Shan mountains at the border of northwest China and the former Soviet Republic of Kazakhstan is the progenitor of the apples we eat today. Leaves taken from trees in this area were analyzed for DNA composition, which showed them all to belong to the species M. sieversii, with some genetic sequences common to M. domestica.[citation needed]

Some individual M. sieversii, recently planted by the US government at a research facility, resist many diseases and pests that affect domestic apples, and are the subject of continuing research to develop new disease-resistant apples.[citation needed]

Other species that were previously thought to have made contributions to the genome of the domestic apples are Malus baccata and Malus sylvestris, but there are no hard evidence for this in older apple cultivars. These and other Malus species have been used in some recent breeding programmes to develop apples suitable for growing in climates unsuitable for M. domestica, mainly for increased cold tolerance.[citation needed]


Apple cut horizontally, showing seedsThe apple tree was perhaps the earliest tree to be cultivated, and apples have remained an important food in all cooler climates. To a greater degree than other tree fruit, except possibly citrus, apples store for months while still retaining much of their nutritive value. Winter apples, picked in late autumn and stored just above freezing, have been an important food in Asia and Europe for millennia, as well as in Argentina and in the United States since the arrival of Europeans.[citation needed]

The word 'apple' comes from the Old English word æppel, which in turn has recognisable cognates in a number of the northern branches of the Indo-European language family. The prevailing theory is that 'apple' may be one of the most ancient Indo-European words (*abl-) to come down to English in a recognisable form.[citation needed] The scientific name malus, on the other hand, comes from the Latin word for apple, and ultimately from the archaic Greek mālon (mēlon in later dialects). The legendary placename Avalon is thought to come from a Celtic evolution of the same root as the English 'apple'; the name of the town of Avellino, near Naples in Italy is likewise thought to come from the same root via the Italic languages.

Linnaeus assigned the apple to the genus Pyrus, along with pears and quinces. Philip Miller subsequently separated the apple into its own genus, a division repeatedly ratified over the years.

Apple contains iron which will be oxided when exposed in oxygen.