為什么美國人要冷藏雞蛋？

Ask The Times, a Times Insider feature, draws on New York Times expertise to answer questions submitted by you, our readers.

“向時(shí)報(bào)提問”(Ask The Times)是“時(shí)報(bào)內(nèi)情”(Times Insider)的一個(gè)子欄目，利用《紐約時(shí)報(bào)》的專業(yè)知識(shí)解答讀者提出的問題。

A reader asks: “Why do Americans refrigerate their eggs?”

一位讀者問：“美國人為什么冷藏保存雞蛋?”

Kim Severson, a food reporter for The Times, considers the question.

時(shí)報(bào)美食記者金·西弗森(Kim Severson)對(duì)這個(gè)問題進(jìn)行了思考。

Americans love refrigeration, and eggs are high on the list of items we rush to get into the refrigerator after a trip to grocery store. Meanwhile, our culinary compatriots in Europe, Asia and other parts of world happily leave beautiful bowls of eggs on their kitchen counters.

美國人喜歡冷藏東西，雞蛋是他們從雜貨店回來最著急放進(jìn)冰箱的食品之一。相比之下，歐洲、亞洲和世界其他地方的人卻樂于把雞蛋用漂亮的碗裝起來，放在廚房的柜臺(tái)上。

So what gives?

為什么會(huì)這樣呢?

Mostly, it’s about washing. In the U.S., egg producers with 3,000 or more laying hens must wash their eggs. Methods include using soap, enzymes or chlorine.

這主要跟清洗有關(guān)。在美國，擁有3000只或以上產(chǎn)蛋母雞的雞蛋生產(chǎn)商必須清洗自家生產(chǎn)的雞蛋。方法包括用肥皂、酶或氯。

The idea is to control salmonella, a potentially fatal bacteria that can cling to eggs. The Centers for Disease control estimates that salmonella causes about 1.2 million illnesses a year, resulting in 450 deaths — though not all of those cases are traced to eggs.

這么做的是為了控制沙門菌。這是一種附著在雞蛋上的具有潛在致命性的細(xì)菌。據(jù)疾控中心估計(jì)，沙門菌每年導(dǎo)致大約120萬人患病，450人死亡，不過這些病例并非都和雞蛋有關(guān)。

The bacteria can be passed through the porous shell to the inside of the egg from material on the outside, though in rarer cases it can infect the ovaries of a chicken and infect the eggs from the inside.

沙門菌可以穿過多孔的蛋殼，從外面的物質(zhì)進(jìn)入雞蛋。不過，在更少見的情況下，這種細(xì)菌也可以通過感染雞的卵巢，從體內(nèi)感染雞蛋。

Why the 3,000-hen cutoff? Salmonella outbreaks are more prevalent in large operations where the chickens are kept in close quarters, often in cages stacked on top of one another. Some large-scale producers vaccinate their flocks, but not all. Thus, the one-size-fits-all washing regulation.

為什么以3000只雞為截點(diǎn)呢?在大型養(yǎng)雞場，爆發(fā)沙門菌疫情的情況更為普遍。在那里，雞被養(yǎng)在相近的雞舍內(nèi)，通常是關(guān)在一個(gè)個(gè)摞起來的籠子里。有些大型生產(chǎn)商會(huì)給雞群接種疫苗，但不是所有廠商都會(huì)這么做。因此，只能實(shí)行這種一刀切的清洗規(guī)定。

But — and here is the big piece of the puzzle — washing the eggs also cleans off a thin, protective cuticle devised by nature to protect bacteria from getting inside the egg in the first place. (The cuticle also helps keep moisture in the egg.)

但這里有一個(gè)大問題是，清洗雞蛋也會(huì)洗掉一層薄薄的保護(hù)皮層，這是天然產(chǎn)生的、從一開始就防止細(xì)菌進(jìn)入蛋體的保護(hù)層(這層保護(hù)膜也能防止?jié)駳膺M(jìn)入雞蛋)。

With the cuticle gone, it is essential — and, in the United States, the law — that eggs stay chilled from the moment they are washed until you are ready to cook them. Japan also standardized a system of egg washing and refrigeration after a serious salmonella outbreak in the 1990s.

如果沒有了那個(gè)保護(hù)層，有一點(diǎn)就至關(guān)重要，即從清洗雞蛋那一刻開始，直到準(zhǔn)備烹飪之前，讓雞蛋保持冷藏狀態(tài)。美國的法律是這么規(guī)定的。上世紀(jì)90年代爆發(fā)過一次嚴(yán)重的沙門菌疫情之后，日本也有了一套標(biāo)準(zhǔn)化的清洗和冷藏雞蛋的制度。

In Europe and Britain, the opposite is true. European Union regulations prohibit the washing of eggs. The idea is that preserving the protective cuticle is more important than washing the gunk off.

在歐洲和英國，情況正好相反。歐盟規(guī)定禁止清洗雞蛋。其理念是保存保護(hù)膜比洗掉臟東西更重要。

At most American farm stands and farmers’ markets, eggs are sold unrefrigerated. And many cooks store unwashed eggs from small producers on their counters, washing them just before they use them — or not at all, if they are getting dropped into boiling water.

在大多數(shù)美國農(nóng)場攤點(diǎn)和農(nóng)貿(mào)市場，雞蛋都是以未冷藏狀態(tài)售賣。許多廚師把從小生產(chǎn)商那里買來的未清洗的雞蛋儲(chǔ)存在柜子里，在使用前才會(huì)清洗它們——如果是丟進(jìn)沸水里煮，則壓根不洗。

However, if you buy farm eggs chilled, it’s better to keep them chilled. Bringing them to room temperature if you’re not going to cook them right away can cause condensation, which can damage the cuticle or encourage mildew. A refrigerated egg, no matter the source, will be good for four or five weeks. Unrefrigerated eggs are best used within a week, though they may be fine for two.

然而，如果你買了冷藏的農(nóng)場雞蛋，最好把它們繼續(xù)冷藏起來。如果不準(zhǔn)備立即烹飪卻把它們放置在室溫下，可能會(huì)導(dǎo)致水汽凝結(jié)，以致破壞那個(gè)保護(hù)層或產(chǎn)生霉菌。不管是從哪買來，冷藏的雞蛋保存四五周是沒問題的。沒有冷藏的雞蛋則最好在一周內(nèi)吃完，盡管放兩周可能也沒問題。

Safety concerns aside, room-temperature eggs perform better in the kitchen. If cold eggs are worked into batters with a high fat content, they can reharden the fats, and you’ll end up with batter that looks curdled and whose texture could be impacted. Also, if you want more volume when you whip egg whites for meringue or soufflés, use room-temperature eggs.

撇開安全方面的考慮，室溫雞蛋做起來會(huì)更好吃。如果把低溫的雞蛋和高脂肪的物質(zhì)打成糊，它們會(huì)讓脂肪再次硬化，最后你只能得到像是凝結(jié)了的糊，口感會(huì)大打折扣。此外，如果你為做蛋奶酥打蛋清時(shí)想打得更蓬松些，也要用室溫下存放的蛋。