Mobile Softee ice cream X Science / 追雪糕車食雪糕 X科學

If anyone of you are traveling to Hong Kong, one of the most signature thing you can find is the ice cream truck: Mobile Softee, or the Mister Softee.
如果大家到香港旅行，其中一樣最重要試的事就是雪糕車!!

There are only limited number of those running around in Hong Kong, due to the Hong Kong Government stopped issuing new license in the 1978, so only those trucks that can still run are allowed to continue as vendors. Therefore they are part of Hong Kong history and might be gone in short coming future.
由於香港政府在一九七八年停止發牌，所以只有那些仍然可以運作的雪糕車才可以繼續賣雪糕，他們剩下的數目已不多了。他們是香港歷史的一部分，同時也可能會在短時間內消失。

Only 4 products were sold from the ice cream trucks, but the vanilla soft ice cream was always the most popular one. And that’s the one I am getting~
雪糕車只售出4種產品，但是香草軟雪糕總是最受歡迎的。我也是買這個~

The driver will also serve as the ice cream seller.
司機也將作為雪糕賣家

Freshly made ice cream for you everyday.
每天新鮮製作的雪糕

Previously some of my Steemian friends left this comment on my post: @nanosesame: I would like to see how he ties food/ travel to science
以前我的一些Steemian的朋友把這個留言寫在了我的帖子上： @nanosesame ：我就想看他如何把美食旅遊之類拉到科普

This post is not going to end right there, I love vanilla ice cream but I will not be giving reviews on the food. The only review that I will be giving is science review.
這個帖子不會在那裡結束，我喜歡香草雪糕，但我不會對食物給予評論。我唯一的審查是科學。

The challenge is on, let’s move to the science part XD
我來挑戰，讓我們轉到科學部分XD

Ice cream!! Ice cream are basically frozen dairy product, the base is usually milk or cream. The dairy product is cooled below the water freezing point while stirring, this stirring process will prevent the formation of big ice crystals during the freezing of the dairy product. The presence of large ice crystal will affect the overall smoothness of the ice cream. And because the use of refrigerators during ice cream production are usually requiring a long time, which favors the formation of big ice crystal.

雪糕！！雪糕基本上是冷凍的乳製品， 通常是牛奶或奶油。在攪拌的同時，將乳製品冷卻到水凝固點以下，這種攪拌過程將防止在乳製品冷凍期間形成大的冰晶體。大的水冰晶的存在將影響雪糕的整體口感平滑度。而雪糕生產過中使用過的通常需要很長時間，這有利於大冰晶體的形成。

Stirring of the dairy product during the refrigerating process will help disperse the ice crystal, preventing them to form a big piece of dairy ice due to the slow cooling process of the dairy product. Apart from stirring, the rate of the dairy product being cooled is also important to note. Rapid cooling of the dairy product will greatly reduce the time for the ice crystal to grow to bigger size, thereby making the ice cream with a smoother texture. This rapid cooling can be achieved by liquid nitrogen and thus spring off the liquid nitrogen ice cream. Liquid nitrogen has boiling point of -196 degrees Celsius, while water freezes at 0 degrees Celsius. Using proper amount of liquid nitrogen can instantly turn the dairy product into ice cream, therefore preventing formation of large ice crystal, and as they claim, the ice cream produced in this way will be much smoother. Similar use of dry ice can also serve this purpose.

在製冷過程中攪拌乳製品將有助於分散冰晶，防止由於乳製品緩慢冷卻過程而形成大塊乳製品。除了攪拌外，被冷卻的奶製品的比例也很重要。乳製品的快速冷卻將的時間大大減少,防止冰晶體長到更大尺寸，從而使雪糕具有更平滑的質感。這種快速冷卻可以通過液氮來實現，從而開發出液氮雪糕。液氮的沸點為-196攝氏度，而水分在0攝氏度時凍結。使用適量的液氮可以立即將乳製品變成雪糕，從而防止形成大的冰晶體，正如他們所說，以這種方式生產的雪糕將會口感更加平滑。類似的干冰也可以用於同樣目的。

Reference:
http://physicsbuzz.physicscentral.com/2014/06/the-science-of-ice-cream.html
https://en.wikipedia.org/wiki/Mobile_Softee
https://en.wikipedia.org/wiki/Ice_cream
https://www.acs.org/content/acs/en/education/resources/highschool/chemmatters/past-issues/archive-2013-2014/ice-cream-chemistry.html

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