Explainer · Defects and grading
How to identify a misshapen egg by its shape
A misshapen egg has a shape outside the normal range. Class A requires a shell of normal shape (RIISPOA, art. 225, I), but the rule sets no numeric value for shape. A camera measures the outline by solidity, fit to an ellipse, the ratio between the axes and area. When the outline falls outside that pattern, Vigiovo gives the egg no grade and sends it to manual review.
Updated · 4 min read
What is a misshapen egg?
A misshapen egg is one whose shape departs from a normal egg: flatter or longer than usual, with one end irregular or an outline that is bent. Normal shape is one of the requirements for Class A: the shell and cuticle must be of normal shape, smooth, clean and intact (Decree 9.013/2017, art. 225, I).
The EU rule uses the same idea: shell and cuticle of normal shape, clean and undamaged (Delegated Regulation (EU) 2023/2465, art. 3). Neither fixes a number for shape. The line between normal and abnormal shape is therefore a judgement that each grading line has to calibrate.
How does a camera measure the shape of an egg?
The camera measures each egg's outline against three references. Solidity is the ratio between the egg's area and the area of the smallest convex shape that encloses it, so an outline with a notch or dent has lower solidity. Fit to an ellipse shows whether the outline looks like an egg. The ratio between the axes shows whether the egg is too long or too flat.
The table summarises Vigiovo's shape criteria. The values are configuration settings, not standards.
| Measure | What it indicates | When the egg goes to unverified |
|---|---|---|
| Solidity | Concave outline, a sign of overlap or a dent | Solidity below 0.90 |
| Fit to an ellipse | An outline that does not look like an egg | The outline does not look like an ellipse |
| Ratio between the axes | An egg that is too long or too flat | Ratio above 1.8 |
| Area | A size very different from a typical egg on the line | Area outside 0.35 to 2.5 times that of a typical egg |
An egg cut off by the edge of the image is also not graded, because its outline is incomplete. The full measurement is described in how it works.
Why does an off-shape egg get no grade?
An egg whose shape fails these tests is marked unverified and is never graded. A grade given to an uncertain outline could be a made-up grade, so Vigiovo prefers to send the egg to manual review.
This path also avoids false defects. Two touching eggs form a concave outline that, without the test, would look like a misshapen egg. With the test, the case goes to review and not to the list of defects.
Is an abnormal shape the same as Class B or unfit?
Not necessarily. Art. 500 lists the cases that make eggs unfit for consumption, and shape is not among them. For Class A, an abnormal shape rules the egg out. A harmless egg of abnormal shape is, in principle, Class B, for industrial processing (art. 226, I and sole paragraph).
So the camera should not decide the fate of a misshapen egg on its own. It sets the case aside for review, and the review decides whether the egg leaves Class A and where it goes. Fissured eggs and soft-shelled eggs are different defects, with their own rules.
How do you calibrate the shape limit on your line?
The values in the table are a starting point. Calibration adjusts the limits to the egg type and the camera on your line, using eggs your team has already labelled. The full method is in calibrating with labelled eggs.
- Gather eggs labelled by the team, with normal and abnormal shapes.
- Measure those eggs with the current configuration and compare the results with the labels.
- Adjust the limits for solidity, ellipse fit, proportion and area until the results match the labels.
- Record the final configuration and the batch used in calibration, for audit.
Frequently asked questions
Can a misshapen egg be Class A?
- No, if its shape departs from normal. Class A requires a shell of normal shape, smooth, clean and intact (RIISPOA, art. 225, I). The rule gives no numeric shape index, so the judgement limit should be calibrated with eggs labelled from your own line.
Is an egg with an odd shape always unfit for consumption?
- No. Shape is not among the unfit cases in art. 500 of RIISPOA. An egg with an abnormal shape but an intact shell and sound contents is, in principle, Class B, for industrial processing (art. 226, I). It is unfit only if it shows one of the cases in art. 500.
How does Vigiovo know an egg has an abnormal shape?
- It measures each egg's outline by solidity, fit to an ellipse, ratio between the axes and area, compared with fixed limits. If the outline falls outside that pattern, the egg is marked unverified and sent to manual review, instead of receiving a grade.
Sources
- Decreto nº 9.013/2017 (RIISPOA), Presidência da República (Brasil)
- Delegated Regulation (EU) 2023/2465, marketing standards for eggs, EUR-Lex
- Como o Vigiovo classifica ovos sem IA / How Vigiovo grades eggs without AI, Vigiovo
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.