科學實驗室：自制雪糕樂無窮

As summer comes rolling in， you might be thinking more and more about cooler sweets to eat， namely[也就是] ice cream. Or maybe you think about ice cream all the time， no matter what the temperature is. Regardless[不管]， ice cream is definitely one of the most delicious treats[宴饗] you can have， but did you know you dont only have to buy it at the store？ You can make it yourself！

Water has three states： solid[固體]， liquid and gas. Water changes into its solid state when it reaches 0 °C， but if there is Sodium Chloride[氯化鈉] （NaCl）， otherwise known as salt， then that temperature drops. Thats because salt lowers waters freezing point[凝固點]. Have you ever noticed how when the sidewalk is icy they put salt on it to melt the ice and make it safer for walking？ Thats the same principle[原理]. The salt they put on the sidewalk mixes with the ice and because its freezing point is lower than the temperature of the unsalted ice， the sidewalk melts.

When youre making ice cream the lower temperature of the ice and salt mixture[混合物]， which surrounds the cream and sugar mixture， is cold enough to change the state of the cream from a liquid to a solid. So lets get started！

隨著夏天的熱浪撲面而來，你也許會愈發(fā)渴望吃點更涼快的甜食，也就是雪糕。又或者不管氣溫高低，你一年到頭都惦記著雪糕呢。不管怎樣，雪糕絕對是最可口饞人的美食之一，但你知道雪糕并不是只能在商店買到嗎？你完全可以自己動手做喔！

水有三種形態(tài)：固態(tài)、液態(tài)和氣態(tài)。水達到零度就會轉化成固態(tài)，但如果有氯化鈉（NaCl）——也就是我們常說的鹽參與反應，水的結冰溫度就會變低。這是因為鹽會降低水的凝固點。你留意到了嗎？每當人行道結冰的時候，人們總會在路上撒鹽，將冰塊融化，才能安全通行。那也是出于同樣的原理。撒在人行道上的鹽會與冰融合，由于其凝固點比沒撒鹽的冰塊要低，人行道（上的結冰）就會融化。

在你制作雪糕的時候，奶糖混合物周圍的冰鹽混合物溫度更低，足以讓液態(tài)的奶油凝結成固態(tài)。讓我們這就來試試吧！

Materials 材料

1/2 cup milk

1/2 cup whipping cream[生奶油] or heavy cream[多脂奶油]

1/4 cup white sugar

1/4 teaspoon vanilla extract[香草精]

1/2 to 3/4 cup table salt[精制食鹽]

2 cups ice

quart Ziploc bag[封口袋]

gallon Ziploc bag

Thermometer[溫度計]

Measuring cups and spoons

Bowls， cups， spoons or cones[錐形蛋卷筒] to serve your ice cream treat

半杯牛奶

半杯生奶油或多脂奶油

1/4杯白糖

1/4茶匙香草精

1/2到3/4杯精制食鹽

兩杯冰塊

夸脫封口袋

加侖封口袋

溫度計

量杯和量匙

用來享受美味雪糕的大碗、杯子、勺子或者甜筒等

Procedure 步驟

1. Add 1/4 cup sugar， 1/2 cup milk， 1/2 cup cream， and 1/4 teaspoon vanilla to the quart Ziploc bag. Zip that bag up so nothing leaks[泄露]！

2. Put the 2 cups of ice into the gallon Ziploc bag.

3. Use the thermometer to measure the temperature of the ice in the gallon bag. Make sure to record this number so you can remember.

4. Add 1/2 to 3/4 cup salt to the gallon Ziploc bag of ice.

5. Place the sealed[密封的] quart bag inside the gallon bag of ice and salt. Seal the gallon bag securely[牢固地].

6. Rock the gallon bag from side to side. Hold it at the seal so that the cold ice doesnt freeze your hands instead of your ice cream. You can also use gloves[手套] or a cloth to protect your hands， just remember it will be colder than 0 °C！

7. Continue to rock the bag for 10-15 minutes or until the contents of the quart bag have solidified[凝固]， or until you cant wait for ice cream anymore.

8. Open the gallon bag and use the thermometer to measure and record the temperature of the ice and salt mixture. Notice how much colder it is than the ice on its own.

9. In bowls or cones serve and most importantly enjoy your homemade[自制的] ice cream！

1. 將1/4杯糖、半杯牛奶、半杯奶油和1/4杯香草精加入夸脫封口袋。袋子的封口要封好，可別漏出來哦！

2. 將兩杯冰塊倒入加侖封口袋中。

3. 用溫度計測量一下加侖袋里的冰塊溫度，將數(shù)值記錄下來，以防忘記。

4. 將1/2到3/4杯鹽倒入裝有冰塊的加侖袋中。

5. 將密封的夸脫袋放入裝有冰塊和鹽的加侖袋中，確保加侖袋密封好了。

6. 左右搖晃加侖袋。手抓封口，以免低溫冰塊在雪糕做好之前就將你的手給凍傷了。你也可以用手套或者一塊布保護好手部，要記住這溫度是在零度以下哦！

7. 繼續(xù)搖晃10到15分鐘，或者等到夸脫袋里面的東西已經凝固，又或者到你已經迫不及待要吃雪糕才停止。

8. 打開加侖袋，用溫度計測量并記錄袋中的冰鹽混合物溫度。注意對照這個溫度和冰塊本身的溫度相差多少度。

9. 裝到碗里或者甜筒里，最重要的是盡情享受你的自制雪糕！

Toppings 澆頭

Theres always the possibility to add all different types of toppings： chocolate sauce， sprinkles[糖屑]， caramel[焦糖]， strawberries， chocolate chips！ Feel free to add these ingredients[作料] to the quart bag before you mix everything， but know that your mixture will turn to ice cream much faster if you hold these special treats and add them as toppings.

雪糕上面總是可以澆上各種各樣的配料：巧克力醬、糖粒、焦糖、草莓，甚至巧克力棒！你也可以在混合之前往夸脫袋里隨意加入這些東西，但你得知道，如果將這些特殊配料留到最后作為雪頂澆頭，你的混合物凝固成雪糕的速度會更快喔。

Ice Cream Maker 雪糕機

This is a very easy way to make some delicious ice cream！ If you are interested in making your own homemade ice cream all the time， you may want to look into an actual ice cream maker. It still uses the ice and salt mixture to freeze the cream， it just provides an easier and higher volume[量] way to make ice cream at home.

這能讓你輕而易舉地制作出美味的雪糕！如果喜歡隨時自制雪糕，你也許該考慮買臺真正的雪糕機了。雪糕機也是靠冰鹽混合物將奶油凍結，不過它能為你在家里自制雪糕提供一種容量更大的便捷方式。

你知道嗎？

夸脫（quart）是容量單位，主要在英國、美國及愛爾蘭使用。1夸脫于英國和美國代表的是不同的容量，而美國更有兩種夸脫：干量夸脫及濕量夸脫。

英制：1夸脫= 1136.5225 毫升

美制：1干量夸脫= 1101.220 毫升

1濕量夸脫= 946.352946 毫升

而1加侖（gallon）=4夸脫，1品脫（pint）=1/2夸脫。