Introduction

According to EU regulations, eggs reach the market classified by quality category, size, and rearing method.

Depending on their age and consistency, eggs are categorised into Classes A, B, and C.

Regarding weight categories, there are eight classes:

• Class 1: eggs weighing 70g or more each, minimum 870g per dozen
• Class 2: less than 70g and up to 65g each, minimum 810g per dozen
• Class 3: less than 65g and up to 60g each, minimum 750g per dozen
• Class 4: less than 60g and up to 55g each, minimum 690g per dozen
• Class 5: less than 55g and up to 50g each, minimum 630g per dozen
• Class 6: less than 50g and up to 45g each, minimum 570g per dozen
• Class 7: less than 45g and up to 40g each, minimum 510g per dozen
• Class 8: eggs weighing less than 40g

A key indicator of egg quality is freshness:

The egg white loses carbon dioxide through the shell’s pores. Since this CO₂ is in equilibrium with HCO₃^–, the pH of the white increases. This pH rise acts as a defence mechanism against microorganisms.

Eggs also lose water through the pores, causing the air cell at the top to enlarge. A popular test for freshness is to submerge the egg in water: if it sinks, it is fresh; if it floats, it is old.

Over time, the white becomes less viscous. Fresh eggs are more compact, while older ones spread out more. A displaced yolk (not centred) when cracked is another sign of ageing. The elasticity of the vitelline membrane also decreases.

Time causes both the white and yolk to become more fluid.

There is also the risk of bacterial and fungal contamination and eventual putrefaction. This can originate from the birds’ intestinal tract, the environment, facilities, or improper handling.

Egg Classification

According to legislation, eggs are classified as:

• Fresh eggs: those with characteristic smell and flavour, which have only undergone dry cleaning.
• Chilled eggs: whole eggs stored in cold rooms for over 15 days but no longer than 30 days from laying, at temperatures not exceeding 4ºC.
• Preserved eggs: stored in cold rooms at 0ºC for more than 30 days but less than 6 months.
• Defective eggs: cracked or partially broken but with intact membranes; those that, without being spoiled, have off-odours or flavours.

Additives in Eggs

The use of carotenoid colourants in animal feed is permitted. Therefore, yolk colour is no longer a reliable indicator of free-range farming.

In liquid egg and yolk products, some preservatives are allowed, such as benzoic acid (E-210) and sorbic acid (E-200), in very high concentrations (10 g/kg).

Fresh eggs, thanks to their shell, are almost germ-free. To extend shelf life, treating agents such as fats, paraffins, or fatty acid emulsions may be applied to the shell.

Toxic Substances

Toxic residues are usually found in the yolk, as most are fat-soluble. Contaminants that may appear in eggs include:

• Medicine residues: used in intensive farming to prevent intestinal diseases (coccidiosis), helminths, and infections.
• Aflatoxins: can appear in poorly stored feed, although hens tend to stop laying if the feed contains more than 10 mg/kg of aflatoxins.
• Heavy metals: often found in fishmeal given to animals, which may be contaminated with mercury or arsenic.

Egg Derivatives

These are products wholly or partly made from shell-free hen’s eggs, intended as raw materials for food preparation.

Advantages:

• Greater versatility and variety of products
• Easy to use and dose
• Improved bacteriological safety
• Simplified handling
• Convenient for distribution and trade

For industrial purposes, egg derivatives are prepared in various forms:

• Frozen eggs: primary derivatives made from fresh, chilled, or defective eggs, homogenised and strained.
• Powdered eggs: dry derivatives obtained by removing water from eggs using authorised technology.
• Dehydrated egg yolk: dry product made by removing water from yolks.

Nutrition

To conclude, it is important to mention one of the most debated topics regarding eggs: their relationship with cholesterol.

While egg yolk is high in cholesterol, it has been shown not to directly raise blood cholesterol. Cholesterol content in food is not the only factor affecting plasma cholesterol levels. Saturated fats have a stronger impact on cholesterol production than the cholesterol from yolk, which also contains lecithin, a substance that helps regulate cholesterol.

There is no justification for removing or restricting a single food to manage cholesterol levels. Eggs contain many essential nutrients that support health and proper body function.

What matters most is that the overall diet is balanced, rather than eliminating specific foods.

It’s important to note that some people are allergic to eggs, especially children under 3. These allergies often disappear over time. When they persist, it’s crucial to read labels carefully to avoid any products that may contain egg or traces of it.

Finally, how many eggs can we eat per week?

If you are healthy, one egg per day is perfectly fine—even for athletes.

For children, the recommendation is 2–3 eggs per week.

For those with cardiovascular conditions: 3–4 eggs per week.

So don’t hesitate to include eggs in your regular diet – they are a high-quality and delicious food.