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The educated materials presented here were developed
这里展示的教学材料
by students and faculty of
由爱荷华州立大学食品科学
the Department of Food Science and Human Nutrition
及人类营养学系的
at Iowa State University.
师生完成
Funding for this project was provided by grants from
此项目由
the American Cancer Society
美国癌症协会
Midwest and the Lance Armstrong Foundation.
中西部和兰斯阿姆斯特朗基金会赞助支持
The materials are intended for educational use
此材料仅作教学使用
and are not meant to provide medical advice.
而非医疗咨询
We welcome your feedback about these materials.
我们希望收到你对于这些材料的反馈
Please use the evaluation survey link on the homepage
请通过首页上的评估调查链接
to provide your comments and suggestions.
给我们提供评价和建议
As we get started examining this topic
在我们开始研究这个话题之际
here's a question for you to think about.
请你们思考一个问题
How much tea do you consume daily?
你们每天喝多少茶?
Why do you drink tea?
你们为什么喝茶?
All tea comes from the plant Camellia sinensis.
所有的茶都来在于野茶树这种植物
The types of tea that can be found are
已发现的茶的种类有
white, green, oolong, and black.
白茶，绿茶，乌龙以及红茶
All the teas from the grocery store
食品杂货店里所有的茶
are derived from these types and flavor is added.
都是这几种，并添加了口味
The type of tea is determined
茶的种类
by when the tea is harvested
由茶叶的收获季节
or the time the tea is picked.
或采摘时间决定
The amount of oxidation that occurs also plays a role.
茶叶的氧化程度也是其中一个因素
Oxidation occurs when the picked leaves
当采摘下来的叶子暴露在空气中时
are exposed to the air.
它就会开始被氧化
The leaves then react with the oxygen in the air
叶子与空气中的氧气反应
and start to turn brown. This is similar to
开始变成褐色，这类似于
what happens when leaves fall from a tree.
叶子从树上落下时发生的变化
Another determining factor of the type of tea
另一个决定茶叶类别的因素
is the processing that it goes through. Tea is grown in
是茶的处理过程，茶叶的产地有
China, India, Japan, Sri Lanka, and Taiwan.
中国，印度，日本，斯里兰卡以及台湾
White tea is picked before leaf buds fully open
白茶是在叶芽完全张开之前
and are still covered with fine silky hairs.
表面依然长着柔滑细毛的时候采摘的
The white tea leave buds are air dried
白茶的叶芽在空气中晾干
preserving more of its antioxidant properties.
其含有的抗氧化成分很大程度被保留了下来
White tea is said to have three times
据说白茶含有的
more antioxidants than green tea.
抗氧化成分比绿茶的多三倍
Green tea is tea leaves that
绿茶是
have undergone minimal oxidation during processing.
在加工过程中氧化程度最低的茶叶
Oxidation is a chemical reaction that takes place
氧化是一种在茶叶被采摘后
when tea leaves are picked and begin to wither and die.
并开始枯萎凋零时发生的化学反应
After tea leaves are picked
茶叶采摘后
they are left in a climate controlled room
会被放置在一间环境可控的屋子里
where they turn darker as time progresses.
并且随着时间的推移颜色逐渐变暗
This is due to the enzymatic breakdown of chlorophyll.
这是由于叶绿素在酶的作用下被降解了
Green tea is only 5 to 40% oxidized.
绿茶的氧化程度只有5%到40%
It is heated immediately through steam
一旦到了那个氧化程度，它会立刻被放在蒸汽
or dry cooking pans once it reaches that level.
或者干炒平底锅里加热
It is usually processed within 1 to 2 days of harvesting.
并通常在采摘后的一到两天内进行处理
Oolong tea is oxidized between green tea and black tea.
乌龙茶的氧化程度介于绿茶和红茶之间
It is oxidized for 2 to 3 days before being processed.
在处理前，会对它进行两到三天的氧化
Black tea is formed
当茶叶完全氧化时
when the leaves are allowed to completely oxidize.
就成了红茶
This creates the deep rich flavor.
这能产生一种浓重的口味
They are oxidized between 2 weeks and 1 month.
它们要氧化两周到一个月的时间
Again the composition of tea is affected by
总而言之，茶叶的成分会受
growing season, strain or variety,
生长季节，品种或类别
storage and brewing conditions.
贮存及煮制条件的影响
Herbal teas such as chamomile, ginger tea
像野菊花，姜茶或薄荷茶这样的草药茶
or peppermint are really not tea at all.
实际上根本不是茶
This is because herbal tea is not made
这是因为草药茶不是
from Camellia sinensis. It is made from seeds, roots, flowers,
从野茶树上采摘得来，而是用植物和草药的种子，根，花
or other parts of plants and herbs.
或者其他部位制成的
As a result herbal teas are nearly always caffeine free.
因而草药茶一般几乎不含咖啡因
