"I Always Bought Number 1 Eggs for Health"...No Nutritional Difference from Number 4? [Masjal X-File]

"Inside the Eggshell": All You Need to Know About Shell Codes

"Rearing Environment Does Not Directly Affect Egg Quality or Nutrition"

Analysis of Egg Product Information on Kurly, Coupang, and Naver

Question. I'm making baby food - is it okay to use eggs with shell code number 2? Do I absolutely need to use number 1?
- Comment 1. It doesn't matter. I fed my baby number 4, and they're growing up healthy.
- Comment 2. I buy both eggs with shell code number 1 and number 3; I only use number 1 for my baby, and adults eat number 3.

A post was recently uploaded to an online mom's community, asking about which eggs to use for baby food. Specifically, the author wondered which eggs, identified by their 10-digit shell code printed on the shell, would be most suitable. This question clearly stems from the desire of parents to provide their children with eggs that are high-quality and rich in nutrients.

As the so-called "eggflation" continues, with egg prices soaring, there is growing interest in egg shell codes. Is checking the shell code enough to pick the best eggs? In this edition of the Taste Expert X-File, we'll examine what factors consumers should take into account when purchasing eggs. We'll also analyze the key information provided by major shopping platforms for those who buy eggs online without seeing them in person.

"Egg quality is judged by livestock product grading... Freshness is checked by the date of lay"

First, the shell code refers to the 10-digit number printed on the eggshell.

According to the Ministry of Agriculture, Food and Rural Affairs on the 26th, eggs distributed in Korea are stamped with a 10-digit shell code: a 4-digit date of lay, a 5-digit farm identifier, and a 1-digit code representing the rearing environment. In the mom's community post, the term "shell code" was being used to refer specifically to the last digit, which indicates the rearing environment.

The higher the final digit of the rearing environment code, the poorer the living conditions for the hens. Number 1 represents free-range, number 2 means barn-raised, number 3 indicates improved cages, and number 4 represents conventional cages. Numbers 1 and 2, which indicate relatively improved environments, are classified as animal welfare certified eggs.

Starting in 2017, following the pesticide egg crisis, Korea began mandating the display of the rearing environment code on eggshells. At that time, keeping hens in cramped spaces led to mite problems that were treated with pesticides, some of which ended up inside the eggs. As a result, from 2018 to 2019, the government made it mandatory to display the rearing environment code as the last digit in the 10-digit shell code.

So, does a lower rearing environment code mean the egg is better in terms of quality or nutrients? Experts say the rearing environment is not a direct indicator of the egg's quality or nutritional value. Even eggs with the same rearing environment number can differ from farm to farm, as management practices vary, and these differences do not necessarily lead to significant differences in nutrition.

In other words, the rearing environment mostly affects the health and welfare of the hens, not the taste or nutrition of the eggs themselves. According to a recent study by Professor Yoon Jinhyeon and his team at Chonnam National University, eggs from hens housed in narrow cages were found to have nearly double the level of stress hormones compared to eggs from animal welfare-certified farms. Therefore, the rearing environment code is important from an ethical consumer standpoint.

Experts explain that, to actually assess an egg’s quality or nutritional content, consumers should look at livestock product grading instead of the shell code. According to the Rural Development Administration, eggs in Korea are graded as 1+ grade, 1st grade, or 2nd grade according to detailed grading standards. Grades are determined by examining shell appearance, checking interior quality by candling, and assessing the yolk and white quality after cracking the egg open.

However, most eggs for sale do not carry a grade label. This is because egg grading is not mandatory, so only a small proportion of eggs are officially graded. According to the "2025 Livestock Product Grading Statistics Yearbook" by the Korea Institute for Animal Products Quality Evaluation, only 8.3% of all eggs (out of about 1.5 billion produced last year) received a grade assessment.

For this reason, consumers are advised to check the date of lay, which appears as the first four digits of the shell code, when selecting eggs. Industry sources say the freshness of an egg can influence its quality and nutritional value. The longer it has been since the egg was laid, the less fresh it becomes; therefore, the more recent the date of lay, the fresher the egg. Generally, it is recommended that eggs be consumed within a month of the date of lay if stored in the refrigerator.

What information is available for online egg purchases?

These days, many consumers buy groceries and daily essentials online. It would be ideal if you could check the shell code in person, but that's often difficult when shopping for eggs online. We checked three major online shopping channels—Coupang, Naver Shopping, and Kurly—to see how they display information such as date of manufacture (date of lay), rearing environment code, and livestock product grade for eggs.

First, Kurly listed the shell code, rearing environment, feed, and date of lay on their egg product pages. The date of lay is indicated as "within X days of lay," and for the consumption period, they specify, for example, "items will be shipped within X days of lay as of the ship-out date. Total consumption period is 30 days from the date of lay." Depending on the product, this "date of lay" can differ; for example, some products specify seven days, others ten.

Kurly explained, "For eggs with rearing environment code 1 or 2, only products laid within 7 days are shipped; for eggs with code 3 or 4, only those laid within 10 days are shipped. This is our basic quality standard." They added that livestock product grading is only listed in the product description for eggs that have actually undergone grading. Kurly also stated, "With growing interest in animal welfare and rearing environments, we’ve placed the rearing environment code in a prominent position at the top of product pages, so customers can make intuitive choices."

Coupang carries different information for Rocket Fresh products and other products. For Rocket Fresh eggs, the date of lay is not indicated separately, but the consumption period is shown, and some graded eggs specify their grading. Industry sources say that for Coupang Rocket Fresh eggs, the consumption period is based on the use-by date indicated for each item at the time of stocking. Each partner determines the consumption period based on eggs produced within 7–10 days of the date of lay.

For non-Rocket Fresh eggs sold on Coupang, information such as date of manufacture, rearing environment code, or livestock product grades may be shown differently depending on the individual product. Some product titles highlight the rearing environment code, for example, stating "shell code number 1," and product descriptions may describe them as "freshly laid eggs every morning," helping consumers identify this information.

Naver, for eggs sold through its Smart Store, has a product information section at the top of the product page where sellers are prompted to provide the rearing environment code. However, fields for date of lay, consumption period, or livestock product grade are not included by default. Like non-Rocket Fresh eggs on Coupang, some sellers highlight "shell code number 1" in product titles, or mention "laid and shipped on the same day" in the descriptions, enabling shoppers to assess egg quality using that information.

The variation in egg information from company to company is due to their different sales models. Kurly and Coupang’s Rocket Fresh service both purchase inventory and manage egg information directly, so they can offer detailed data. In contrast, other Coupang products and Naver Smart Store operate as open markets, where both sellers and buyers participate, so product sellers are responsible for entering all relevant details themselves.

Naver explained that its Smart Store platform provides an input field for sellers to enter the eggs' date of manufacture, and that sellers can voluntarily list the rearing environment code in the product name or detailed product page. Livestock product grading may also be entered if the seller has obtained official grading for their eggs, and Naver provides a system for this information to be registered.

A Naver representative stated, "Information like the shell code is useful for helping consumers make purchasing decisions, so we may consider upgrading our system to better display these details or require more detailed information upon product registration."

On average, each Korean consumes about 278 eggs per year (based on 2022 data). With egg prices rising sharply this year, even a simple fried egg may seem like a luxury for some. Now more than ever, it pays to check the details carefully when buying eggs and to choose fresh, nutritious, high-quality eggs for your cooking.

This content was produced with the assistance of AI translation services.