Egg shells are semipermeable, this means only certain size particles can pass through its pores. How many pores does an average egg have?

As eggs age, gases and moisture are lost through the pores. Let’s ‘Candle’ the egg (illuminate the interior with light) to find out how these losses change the air cell inside the egg!

Question: How do you ‘peek’ inside an egg to determine its freshness?

Hypothesis: Candling eggs reveals air cell size that: increases or decreases as eggs age.

Materials: • E.G.G. Kit*, Small LED Flashlight, USDA Official Egg Air Cell Guage, Lanyard *No Kit - use small LED flashlight or cellphone & find dime, nickel & quarter • Eggs - try to obtain eggs of various ages for this demonstration (white eggs are easier to candle) • Dark or interior room with little natural light

Method: 1. Hold your egg with large end up - this is the ‘Candling End’ 2. Shine light on top of this large end 3. The circular area at the top of the egg is the Air Cell 4. Now let’s grade this egg! Look at the concave cutouts at the bottom of your Air Cell Gauge card and hold them on the large end of your egg (you may need assistance to hold gauge card and flashlight) Smaller air cells indicate fresher eggs.

Discussion Questions

1. Students with Good Grades have what letter grades? How about Eggs with good grades? Is an egg with an AA or B Grade better? 2. Without an Air Cell Gauge card, the size of a dime, nickel, and quarter is a way to estimate the size of an egg’s air cell. Do you think an Egg with an air cell the size of a dime or quarter is better? 3. If you are selecting good eggs for hatching, how is it similar to picking fresh eggs for food consumption?

Learn more or how to order an E.G.G. Learning Kit: go.ncsu.edu/Embryology-E.G.G.