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  • Why do humans drink so much milk?

    為什麼人類喝那麼多牛奶?

  • And given that all mammals lactate,

    所有哺乳動物都會泌乳

  • why do we favor certain types of milk over others?

    但人們為何喜歡某些牛奶 勝過其他種類?

  • Milk is the first thing we drink,

    奶水是我們最先喝到的東西

  • and thanks to developments in the production and variety of dairy products,

    多虧了製造業的發展和奶製品的多樣

  • it can take on countless forms for our dietary and sensory well-being.

    它可以呈現許多 有益於我們飲食及感官的形式

  • Milk's primary function is as a complete source of nutrition for newborns.

    奶水最主要功能 是為新生兒提供全面營養

  • In fact, since it has all of the vital nutrients for development and growth,

    實際上,它含有 所有成長所需的重要營養

  • proteins,

    蛋白質

  • carbohydrates,

    碳水化合物

  • fats,

    脂肪

  • vitamins and minerals,

    維他命和礦物質

  • and water,

    以及水分

  • milk is the only thing a baby even needs to ingest

    奶水是新生兒 6 個月大之前

  • for the first six months of life.

    唯一需要攝入的

  • The unique makeup of milk can vary depending on factors like species,

    它的獨特成分取決於多樣的因素

  • diet,

    比如物種

  • and location.

    膳食習慣

  • Reindeer of the Arctic Circle, for example,

    和地理位置

  • make energy-dense milk that's about 20% fat,

    比如,北極圈馴鹿

  • roughly five times more than human or cow's milk,

    其奶水是能量密集型 含有 20% 的脂肪

  • to help their young survive the harsh, freezing climate.

    大概比人奶或牛奶多 5 倍

  • So how is milk made?

    以保證小馴鹿在嚴寒之地可以生存

  • In the uniquely mammalian process of lactation,

    奶水是怎樣產生的呢?

  • a special class of milk-secreting cells known as mammocytes

    在哺乳動物獨特的泌乳過程中

  • line up in a single layer around pear-shaped alveoli.

    有一種泌乳細胞稱為「乳腺細胞」

  • Those cells absorb all of the building blocks of milk,

    它們沿著梨狀濾泡排成單層的一排

  • then synthesize tiny droplets of fat

    這些細胞汲取所有製奶的基本成分

  • on structures called smooth endoplasmic reticula.

    然後在「平滑內質網」組織 製造微小的脂肪滴

  • The droplets combine with each other and other molecules

    脂肪滴與脂肪滴 及其他分子互相結合

  • and are then expelled and stored in spaces between cells.

    然後排出並儲存在細胞之間的空間中

  • Mammary glands eventually secrete the milk through the breasts, udders,

    乳腺最終經由乳房、乳頭排出乳汁

  • or, in the rare case of the platypus, through ducts in the abdomen.

    或在鴨嘴獸的罕見案例中 經由腹部的管道

  • Although this process is typically reserved for females,

    雖然這個過程通常發生在雌性

  • in some species, like dayak fruit bats,

    但在一些物種,如棕櫚果蝠

  • goats,

    山羊

  • and even cats,

    甚至貓

  • males can also lactate.

    雄性也能泌乳

  • Milk drinkers worldwide consume dairy from buffalo,

    全世界的牛奶飲用者 飲用的牛奶是取自水牛

  • goats,

    山羊

  • sheeps,

    綿羊

  • camels,

    駱駝

  • yaks,

    犛牛

  • horses,

    馬匹

  • and cows.

    和乳牛

  • Almost all of these species are ruminants,

    幾乎所有這些物種都是反芻動物

  • a type of mammal with four-chambered stomachs

    一種四室胃的哺乳動物

  • that yield large quantities of milk.

    能產生大量的奶水

  • Of these, cows were the most easily domesticated

    其中,乳牛是最容易馴養的

  • and produce a milk that is both easily separated into cream and liquid

    可生產易於分離成奶油和液體的奶

  • and has a similar fat content to human milk.

    並具有與人乳相似的脂肪含量

  • In their natural environment,

    在自然環境中

  • mammals secrete milk on call for immediate consumption by their young.

    哺乳動物分泌乳汁 隨時供牠們的幼仔使用

  • But with the demands of thirsty consumers,

    但隨著消費者的大量需求

  • the dairy industry has enlisted methods to step up production,

    乳製品產業 已經採取了提升生產的方法

  • enhance shelf life,

    增長保質期

  • and provide a variety of milk products.

    並提供各種奶製品

  • In the dairy, centrifugation machines spin milk at high speeds,

    在乳製廠,離心機高速旋轉牛奶

  • forcing less dense fats to separate from the liquid and float up.

    迫使較低密度的脂肪 與液體分離並浮起

  • After being skimmed off,

    脫脂後

  • this fat, known as butterfat, can be used in dairy products

    這種脂肪,稱為乳脂 可以用於乳製品

  • like butter,

    像黃油

  • cream,

    奶油

  • and cheese.

    和奶酪

  • Or it can be later added back to the liquid in varying proportions

    或稍後以不同比例加回到液體中

  • to yield different fat content milks.

    以產生不同的脂肪含量乳

  • Full fat milk, sometimes referred to as whole milk, has 3.25% butterfat added

    全脂牛奶──有時稱為全脂奶 添加了 3.25% 的乳脂

  • compared to 1-2% for low and reduced fat milk,

    相比之下,低脂和減脂牛奶為 1-2%

  • and less than half a percent for skim milk.

    脫脂乳則是少於 0.5%

  • To stop reseparation of the fat from the water, or creaming,

    為了防止脂肪與水的再分離 ── 即「乳狀液分層」

  • the mixture undergoes the high-energy pressurized process of homogenization.

    混合物經過高能量加壓的 均質化處理 (homogenization)

  • Before milk hits the shelves, it's also typically heat treated

    在牛奶送上貨架之前 它通常也經過加熱處理

  • to reduce its level of microbes,

    以減少其微生物含量

  • a government-sanctioned process

    這是政府批准的製程

  • that raw milk enthusiasts argue may reduce milk's nutritional worth.

    但生奶愛用者認為 這會降低牛奶的營養價值

  • Milk spoilage is started by microbes,

    牛奶腐敗始自微生物

  • which consume and break down the nutrients in milk.

    它會消耗和分解牛奶中的營養物質

  • That process causes butterfat to clump together,

    這會導致乳脂聚集成塊

  • leading to a visually unpleasant product.

    形成看起來令人不快的物質

  • And the byproducts of the microbes' consumption

    而且微生物消耗後的副產品

  • are compounds that taste and smell nasty.

    是味道和氣味令人作嘔的化合物

  • But there's a bigger problem.

    但是有一個更大的問題

  • Raw milk can carry microbes that are the sources of deadly diseases,

    生奶含有致命疾病來源的微生物

  • so in order to kill as many of those microbes as possible,

    因此為了盡可能殺死微生物

  • and keep milk fresh longer,

    並使牛奶保鮮更久

  • we use a technique called pasteurization.

    我們使用一種稱為 「巴氏殺菌」的技術

  • One version of this process involves exposing milk

    其中一個方法是讓牛奶 處於高溫下約 30 秒

  • to about 30 seconds of high heat.

    另一個方法稱為 「超高溫消毒法」(UHT)

  • Another version, called ultra-high temperature processing,

    或「超巴氏殺菌」

  • or ultra pasteurization,

    以相當高溫加熱牛奶數秒鐘 (用 135~150°C 加熱 2~3 秒)

  • blasts the milk with considerably higher temperatures over just a few seconds.

    UHT 牛奶有更長的保質期

  • UHT milk boasts a much longer shelf life,

    不放冰箱也可保質 12 個月

  • up to twelve months unrefrigerated,

    而巴氏殺菌的牛奶 放冰箱則可保質兩週

  • compared to pasteurized milk's two weeks in the fridge.

    這是因為溫度較高的 UHT 處理

  • That's because the higher temperatures of UHT processing

    消滅更多的微生物

  • inactivate far more microbes.

    然而,較高的加工溫度

  • Yet the higher processing temperatures

    可能不利於牛奶的營養和質感

  • may adversely affect the nutritional and sensory properties of the milk.

    最終,這種選擇在於消費者的口味

  • Ultimately, that choice lies in the consumer's taste

    與便利性的需求

  • and need for convenience.

    幸好,這個每年超過 8.4 億噸產品的商業

  • Fortunately, there are many choices available

    提供了很多的選擇

  • in an industry that produces in excess of 840 million tons of products each year.

    翻譯:Yue Chen

Why do humans drink so much milk?

為什麼人類喝那麼多牛奶?

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B2 中高級 中文 美國腔 TED-Ed 牛奶 脂肪 微生物 哺乳動物 營養

牛奶的科學 - 強納生.歐蘇立文 (The science of milk - Jonathan J. O'Sullivan)

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    卓子鈞 發佈於 2018 年 07 月 25 日
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