Candling and quality control: air cell, spots, float test, sizing

This lesson is part of Table eggs: from nest to customer specialisation. It opens to every registered student, from free registration. Levels 1 to 5 and the tracks remain readable by everyone.

Grading looks at the outside of the egg. The customer judges the inside, and discovers it when breaking the egg in the kitchen. Between the two, someone must look through the shell before them: that is candling. A lamp, a box with a hole, a dark room, and the egg becomes transparent: the air cell tells its age in millimetres, invisible cracks appear as lines of light, spots can be seen, the yolk can be made out. This lesson teaches how to build and use a candler, how to read what it shows, how to do the float test when it is useful, how to size, and how to build a daily quality control on 50 eggs that protects the other 1,800.

• ✓Build a simple candler and candle an egg in good conditions
• ✓Read the air cell in millimetres and deduce freshness; recognise cracks, blood spots, dark spots, moulds, mobile yolk
• ✓Use the float test and the shake test wisely, knowing their limits
• ✓Size by weighing and keep a control plan of 50 eggs a day with decision thresholds

1. Why control what grading has already looked at
2. Building and using a candler
3. Reading the air cell: freshness in millimetres
4. Spots, yolk, cracks: what else the light shows
5. The float test and the shake test: useful, but not on the farm
6. Sizing: weigh, class, check the promise
7. The control sheet and the decision thresholds
8. Going further

• •Control covers a sample of 50 graded eggs a day, at random, and decides the whole batch; it looks for what grading does not see: freshness, hidden cracks, spots, size.
• •Candler: opaque box, strong lamp, 25-30 mm hole, in the dark; turn the egg; 10 seconds per egg.
• •Air cell: ≤ 4 mm extra fresh; 4-6 mm fresh; 6-9 mm to sell quickly; > 9 mm old, not at full price; mobile = ruptured membrane, withdrawal. It measures real age, not the calendar.
• •Blood spots 1 to 3% normal; dark spot or mould = withdrawal and search for wetted, washed, cracked eggs, or a humid room; the float test wets the egg: for the customer or an egg to be broken, never for an egg to be stored.
• •Sizing: scale or grading machine set at 53, 63, 73 g; 30 eggs of 60 g = 1,800 g; 'large' tray > 1,890 g net; decision thresholds written on the sheet.