After I have a chance to take a look about Microbiota  from University of Utah  genetic science learning center, one picture of new born baby cover colonized by microbiota remind me about one. I used to curious about  why eggs in USA need to be refrigerated? When I was young, I always saw eggs store at room temperature in the kitchen cabinet. But after moving to USA, I get used to keep eggs in fridge with no doubt. Just one day that I was surfing online and found out that eggs are stored  in room temperature in European country and most of the countries around the world except USA, Japan and Australia.

How Eggs Been Handled

The United States Department of Agriculture (USDA) regulated that eggs must be washed with water at a minimum temperature of 90°F and at least 20 degrees warmer than the internal temperature of the egg at the time of washing. (If it were colder than the egg, this could result in a very slight contraction, sucking in contaminated water through the shell’s pores).

The eggs will also be washed with some form of detergent and chemical sanitizer like chlorine, then are rinsed again and thoroughly dried- the latter further helping make sure pathogens can’t easily find their way through the egg’s thousands of pores. After this, the eggs are often sprayed with some form of protective coating like mineral oil. Finally, the eggs are taken into a room where they are stored at temperatures at or below 45°F. The processing of cleaning egg is the salmonella problem with eggs by concentrating on preventing the bacteria from entering through the shell.

While  European  prohibits egg producers from washing their eggs, shells have natural protection from salmonella and other contaminants via a waxy substance known as the cuticle. The cuticle coats the shell initially as a liquid when a hen lays the egg and then dries within minutes of being exposed to the air. Egg washing may eliminate surface contaminants, but it also washes away the cuticle and its natural protection that  allowing bacteria to get into the egg via its pores or hairline cracks. So no wash and clean eggs in farm is encouraged in European country, but eggs should be kept suggested that eggs are stored at an ambient temperature of around 17 to 23 °C (62 to 73°F).


There is no definite study showing that fridge or non fridge egg is better but we can take a look of the case of Salmonella in in USA and in England.

On average, there are approximately 142,000 cases of egg-related salmonella poisoning in USA  every year according to the U.S. Department of Agriculture. This is approximately 1 in 2,200 people infected every year (give or take depending on whether an individual is a repeat offender in a given year).  In contrast, in England and Wales in 2009, there were just 581 cases of egg-related salmonella poisoning, or about 1 in 95,000. Notably, before the British started vaccinating their chickens in the late 1990s in response to a major egg-induced salmonella outbreak, in 1997 there were 14,771 cases of egg related salmonella poisoning in England and Wales, or 1 in 3,700.  

This article can clear my picture of natural newborn baby and non washed eggs, both are natural protected by very first microbiota.

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