为什么美国人要冷藏鸡蛋？

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

“向时报提问”(Ask The Times)是“时报内情”(Times Insider)的一个子栏目，利用《纽约时报》的专业知识解答读者提出的问题。

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

一位读者问：“美国人为什么冷藏保存鸡蛋?”

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

时报美食记者金·西弗森(Kim Severson)对这个问题进行了思考。

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.

美国人喜欢冷藏东西，鸡蛋是他们从杂货店回来最着急放进冰箱的食品之一。相比之下，欧洲、亚洲和世界其他地方的人却乐于把鸡蛋用漂亮的碗装起来，放在厨房的柜台上。

So what gives?

为什么会这样呢?

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.

这主要跟清洗有关。在美国，拥有3000只或以上产蛋母鸡的鸡蛋生产商必须清洗自家生产的鸡蛋。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.

这么做的是为了控制沙门菌。这是一种附着在鸡蛋上的具有潜在致命性的细菌。据疾控中心估计，沙门菌每年导致大约120万人患病，450人死亡，不过这些病例并非都和鸡蛋有关。

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.

沙门菌可以穿过多孔的蛋壳，从外面的物质进入鸡蛋。不过，在更少见的情况下，这种细菌也可以通过感染鸡的卵巢，从体内感染鸡蛋。

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.

为什么以3000只鸡为截点呢?在大型养鸡场，爆发沙门菌疫情的情况更为普遍。在那里，鸡被养在相近的鸡舍内，通常是关在一个个摞起来的笼子里。有些大型生产商会给鸡群接种疫苗，但不是所有厂商都会这么做。因此，只能实行这种一刀切的清洗规定。

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.)

但这里有一个大问题是，清洗鸡蛋也会洗掉一层薄薄的保护皮层，这是天然产生的、从一开始就防止细菌进入蛋体的保护层(这层保护膜也能防止湿气进入鸡蛋)。

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.

如果没有了那个保护层，有一点就至关重要，即从清洗鸡蛋那一刻开始，直到准备烹饪之前，让鸡蛋保持冷藏状态。美国的法律是这么规定的。上世纪90年代爆发过一次严重的沙门菌疫情之后，日本也有了一套标准化的清洗和冷藏鸡蛋的制度。

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.

在欧洲和英国，情况正好相反。欧盟规定禁止清洗鸡蛋。其理念是保存保护膜比洗掉脏东西更重要。

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.

在大多数美国农场摊点和农贸市场，鸡蛋都是以未冷藏状态售卖。许多厨师把从小生产商那里买来的未清洗的鸡蛋储存在柜子里，在使用前才会清洗它们——如果是丢进沸水里煮，则压根不洗。

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，如果你买了冷藏的农场鸡蛋，最好把它们继续冷藏起来。如果不准备立即烹饪却把它们放置在室温下，可能会导致水汽凝结，以致破坏那个保护层或产生霉菌。不管是从哪买来，冷藏的鸡蛋保存四五周是没问题的。没有冷藏的鸡蛋则最好在一周内吃完，尽管放两周可能也没问题。

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.

撇开安全方面的考虑，室温鸡蛋做起来会更好吃。如果把低温的鸡蛋和高脂肪的物质打成糊，它们会让脂肪再次硬化，最后你只能得到像是凝结了的糊，口感会大打折扣。此外，如果你为做蛋奶酥打蛋清时想打得更蓬松些，也要用室温下存放的蛋。