Guide · Defects and grading
Dirty eggs: what counts as dirty and where they go
A dirty egg has an unbroken shell with adhering dirt or foreign material, such as faeces, blood, soil or yolk. It cannot be Class A, which requires a clean shell. In Brazil, washing is mandatory for dirty, uncracked eggs sent to processing, and eggs that are both dirty and cracked are discarded. In the European Union, Class A eggs must not be washed.
Updated · 4 min read
What is a dirty egg?
A dirty egg has a whole, uncracked shell with dirt or foreign material stuck to it. The US definition is direct: a dirty egg has an unbroken shell with adhering dirt or foreign material (7 CFR 57.1). The usual culprits on a farm are faeces, blood, soil, stuck feathers and yolk from another broken egg.
Brazil's RIISPOA treats dirt as both a quality and a safety criterion: Class A requires a "clean" shell (art. 225), and eggs with external faecal dirt are unfit for human consumption as they are (art. 500).
Can a dirty egg be washed?
It depends on the destination and the country. In Brazil, MAPA Ordinance 612/2022 defines washing as the step that sanitises eggs and makes it mandatory for dirty, uncracked eggs going to industrial processing (art. 18, as stated in MAPA's question-and-answer guide).
Dirty cracked eggs may be neither washed nor used in egg products (RIISPOA, art. 228). MAPA is explicit: they have no use at all as human food and must be discarded immediately at the establishment.
In the European Union the table-egg rule is the opposite: Class A eggs shall not be washed or cleaned, before or after grading, except as provided for (Delegated Regulation (EU) 2023/2465, art. 4). Washing can strip the cuticle, which helps protect the shell's pores.
| Situation | Brazil | European Union |
|---|---|---|
| Dirty, not cracked | Not Class A; processing with mandatory washing | Not Class A; Class A cannot be washed |
| Dirty and cracked | Discarded immediately; banned from egg products | Not Class A |
| Clean, not cracked | Can be Class A if it meets the other requirements | Can be Class A |
What is the difference between dirt, stains and natural shell colour?
Not every dark patch on a shell is dirt. Shell colour varies from egg to egg and even within one egg, and the egg's dome creates a natural brightness gradient under any light. A grader, human or automatic, has to tell three things apart:
- Adhering dirt: material on the shell (faeces, soil, blood, yolk), usually a different colour from the shell with an irregular edge.
- Natural variation: speckles and tones of the shell itself, which are not a defect.
- Lighting effects: highlights and shadows from the dome, which change with the position of the egg and the lamp.
How do you measure shell dirt with a camera?
Comparing each pixel with a fixed brightness fails, because the rim of a clean egg is naturally darker than its centre. Vigiovo fits a quadratic shading surface to each egg and measures only what falls well below it, so every stain is measured against its own egg.
In parallel it measures colour deviation in Lab colour space, which catches stains as bright as the shell but a different colour, and it discards specular highlights. If the stains add up to 3% or more of the visible shell, the egg is graded dirty. That limit is a Vigiovo configuration value, calibrated with labelled eggs from each line, not a legal standard.
How do you reduce the number of dirty eggs?
Grading removes dirty eggs, but the cause is in the house. The factors that matter most:
- frequent collection, so eggs spend less time in the nest or cage;
- clean, dry nests and litter;
- maintained collection belts, to avoid broken eggs smearing their neighbours with yolk;
- tracking the dirty-egg rate per house and per day, which shows early when something changed.
A system that records the class of every egg, like Vigiovo, turns that last point into a daily number with no extra work.
Frequently asked questions
Can dirty eggs be sold?
- Not as Class A, which requires a clean shell. In Brazil a dirty uncracked egg can go to industrial processing, with mandatory washing. A dirty cracked egg must be discarded.
Can you wash dirty eggs to sell them as Class A?
- Brazilian rules treat washing as a processing step (MAPA Ordinance 612/2022, art. 18). In the European Union, Class A eggs shall not be washed or cleaned, before or after grading (Delegated Regulation (EU) 2023/2465, art. 4).
What percentage of dirt makes an egg dirty?
- The regulations cited here don't set a percentage: they require a clean shell for Class A. Automatic graders use a configurable limit. Vigiovo's default is 3% of the visible shell, tuned when each line is calibrated.
Sources
- Decreto nº 9.013/2017 (RIISPOA), Presidência da República (Brasil)
- Perguntas e respostas sobre a Portaria MAPA nº 612/2022 (versão de 05/06/2023), Ministério da Agricultura e Pecuária (MAPA)
- Delegated Regulation (EU) 2023/2465, marketing standards for eggs, EUR-Lex
- 7 CFR § 57.1 Definitions (Inspection of Eggs), U.S. Electronic Code of Federal Regulations
How Vigiovo helps
Vigiovo grades eggs on the conveyor as clean, dirty, cracked or unverified, in real time, with deterministic computer vision: every decision comes with the measurements behind it, on an ordinary CPU.