★英語(yǔ)聽(tīng)力頻道為大家整理的大學(xué)英語(yǔ)聽(tīng)力下載：老式冰淇淋機(jī)，供大家參考。更多閱讀請(qǐng)查看本站英語(yǔ)聽(tīng)力頻道。
Old Fashioned Ice Cream Makers
Have you ever seen an old-fashioned ice cream maker? Nestled inside the wooden bucket, there’s a metal canister with a hand crank on top. Cranking the handle scrapes the sweet, creamy mixture from the sides of the metal canister, which sits in a bath of ice water and salt. But what does salt have to do with freezing?
Why not just use plain ice water?
The bath of salty ice water freezes ice cream faster than plain ice water could. And speedy freezing does more than minimize the cranking time on a hot summer’s day. A fast freezing process also yields small crystals, insuring a silky texture. Slower freezing could make big crystals with an unpleasant crunch, kind of like ice cream that’s gritty with freezer-burn.
The coldest that salt less ice water can get is 32 degrees Fahrenheit, where there’s a balance between the rates of melting and freezing. Add salt to the mix and the energy balance tips, allowing the temperature to drop below 32 without freezing.
Salty
Let’s say you toss a handful of salt into ice water, and the temperature drops to 20 degrees. At this lower temperature, salty ice water can absorb more heat from the mixture inside the canister, freezing it faster than salt less ice water could. This means you can quit cranking sooner, kick back on the porch and enjoy some good-old-fashioned ice cream.
譯文：
老式冰淇淋機(jī)
你是否見(jiàn)過(guò)冰淇淋機(jī)？這種冰淇淋機(jī)帶有木桶，而木桶內(nèi)安裝了一個(gè)頂上帶手搖曲柄的金屬罐。搖動(dòng)手柄將糖和奶油的混合物從泡在冰鹽水中的金屬罐的一邊擠出來(lái)。但是鹽在冰凍過(guò)程中有什么作用？
為什么不是只使用淡冰水？
盆中的冰鹽水能比淡冰水更快的凍結(jié)冰淇淋。在炎日的夏天，快速制冷能夠限度的減少搖動(dòng)手柄的時(shí)間。快速制冷過(guò)程也能夠產(chǎn)生微小的冰晶，確保絲滑的口感。較慢的制冷過(guò)程則形成大的冰晶體，使口感變差，似乎冰激凌表面因?yàn)槔鋬鲎冇擦恕?BR> 含有少量鹽的冰水溫度最低可達(dá)華氏32度，這一溫度是凝固和融化的平衡點(diǎn)。將鹽加到量能打破能量平衡，使得溫度低于32度而不結(jié)冰。
鹽
讓我們嘗試一下，你將少量鹽投放到冰水里，溫度降到了20度。在這種低溫里，鹽水能從金屬罐里的混合物中吸收更多的熱量，與淡冰水相比能盡快將其凍結(jié)。這意味著你能快速停止搖動(dòng)，返回走廊，享受美味的老式冰淇淋了。
Old Fashioned Ice Cream Makers
Have you ever seen an old-fashioned ice cream maker? Nestled inside the wooden bucket, there’s a metal canister with a hand crank on top. Cranking the handle scrapes the sweet, creamy mixture from the sides of the metal canister, which sits in a bath of ice water and salt. But what does salt have to do with freezing?
Why not just use plain ice water?
The bath of salty ice water freezes ice cream faster than plain ice water could. And speedy freezing does more than minimize the cranking time on a hot summer’s day. A fast freezing process also yields small crystals, insuring a silky texture. Slower freezing could make big crystals with an unpleasant crunch, kind of like ice cream that’s gritty with freezer-burn.
The coldest that salt less ice water can get is 32 degrees Fahrenheit, where there’s a balance between the rates of melting and freezing. Add salt to the mix and the energy balance tips, allowing the temperature to drop below 32 without freezing.
Salty
Let’s say you toss a handful of salt into ice water, and the temperature drops to 20 degrees. At this lower temperature, salty ice water can absorb more heat from the mixture inside the canister, freezing it faster than salt less ice water could. This means you can quit cranking sooner, kick back on the porch and enjoy some good-old-fashioned ice cream.
譯文：
老式冰淇淋機(jī)
你是否見(jiàn)過(guò)冰淇淋機(jī)？這種冰淇淋機(jī)帶有木桶，而木桶內(nèi)安裝了一個(gè)頂上帶手搖曲柄的金屬罐。搖動(dòng)手柄將糖和奶油的混合物從泡在冰鹽水中的金屬罐的一邊擠出來(lái)。但是鹽在冰凍過(guò)程中有什么作用？
為什么不是只使用淡冰水？
盆中的冰鹽水能比淡冰水更快的凍結(jié)冰淇淋。在炎日的夏天，快速制冷能夠限度的減少搖動(dòng)手柄的時(shí)間。快速制冷過(guò)程也能夠產(chǎn)生微小的冰晶，確保絲滑的口感。較慢的制冷過(guò)程則形成大的冰晶體，使口感變差，似乎冰激凌表面因?yàn)槔鋬鲎冇擦恕?BR> 含有少量鹽的冰水溫度最低可達(dá)華氏32度，這一溫度是凝固和融化的平衡點(diǎn)。將鹽加到量能打破能量平衡，使得溫度低于32度而不結(jié)冰。
鹽
讓我們嘗試一下，你將少量鹽投放到冰水里，溫度降到了20度。在這種低溫里，鹽水能從金屬罐里的混合物中吸收更多的熱量，與淡冰水相比能盡快將其凍結(jié)。這意味著你能快速停止搖動(dòng)，返回走廊，享受美味的老式冰淇淋了。