Salability and measuring external eggshell quality and strength

Cuxhaven, 26.04.2021 – Think “egg”, and the mouth immediately starts watering: Do we boil it, scramble it, fry it? Bake a cake? Stir it with sugar as a topping for a cup of coffee? It’s incredibly easy to get overwhelmed by this delicious, nutritious, and super versatile superfood. Yet mother nature would undoubtedly win any design award for the ingenuous and shapely packaging of the egg, if there ever was one for her to participate in. So, let’s focus outwards for a moment, since that’s what customers will be doing as well!

Order to test the shell’s stability, the force needed to break the egg is recorded with special devices and is expressed in Newtons. The measurement is done at the poles of the egg due to its higher repeatability. Breaking strength at the poles is more important since most of the packed eggs that get broken during transportation show damages at those areas. A breaking strength between 40 and 50 Newton is considered good to excellent. “Of course, H&N also selects for shell strength. The shell strength in H&N birds is increased around 1 Newton every generation, and this improvement is done at older ages, allowing our birds to be kept in production for longer cycles”, explained Dr. David Cavero.

Moment of crack – there can be only one

It may seem like a waste of time speaking about the waste of the egg – but that is only when it cracks at the right time. In fact, structural engineering is at work in every egg and both the breaking strength and dynamic stiffness determine the fine line between vain and value.

“We test ourselves the hardest and use several devices. In routine recordings at different ages of the birds, we combine results of conventional breaking strength devices with information about the dynamic stiffness from the Acoustic Egg Tester (Single crack-detector)”, says Dr. Cavero. He uses the Detector to measure resonance parameters that are used in a formula to calculate a quantitative value of the dynamic stiffness of the eggshell which is used to improve its stability on the genetic selection. Like large commercial egg graders, the single Crack Detector sorts out eggs with hairline cracks and other defects. “Heritability estimates for dynamic stiffness are higher than for breaking strength and genetic correlations to each other are positive but moderate, which means that both measurements are capturing different characteristics of the eggshell and complement themselves”, said Dr. Cavero.

Increasing breaking strength and the dynamic stiffness has been proven to reduce the probability and frequency of cracks during routinely handling and transportation.

Egg Shape

Simply and truly: An egg is an egg due to its unique shape. Egg Shape is routinely defined as an index where length is divided by its width. There is a negative correlation between eggshell stability and shape, which means that rounded eggs have a higher stability, thus selecting for higher eggshell strength will put the egg shape under pressure. That is why egg shape is routinely measured and monitored during selection, so that the desirable shape of the egg is maintained even when special focus is put on increasing eggshell strength.

Show the true colors!

So far, this was all mechanical and ancillary sciences. Let us look at the color that is so important depending on whether customers are in brown or white markets, in developed or saturated markets. In theory, humans can perceive five million nuances of colors. There are many different whites as there are many different browns.

The preferred eggshell color of brown H&N breeds is an attractive dark brown, which does not get paler as we approach the end of production. Consumers pay attention to color intensity and uniformity, as pale or unevenly colored eggs may be rejected. Clearly, reduced variability of eggshell color improves the presentation of eggs at point of sale. But colors can vary from dark, almost milk-chocolate brown as produced by Brown Nick, to creamy, rosy hues of a gentle nude tan of Coral, a special breed H&N offers for special interest markets such as Russia or Malaysia. “In some markets, a different color can help make your eggs stand out from the crowd and be recognized by the end consumer”, said Xabier Arbe. “That’s why we offer Coral.”

The method of choice to test eggshell color is a Minolta spectrophotometer, a compact tristimulus color analyzer that measures reflective colors on surfaces. “It’s also used in the automotive industry to measure hues and nuances in car finish”, explained Dr. Cavero smilingly. “With birds of that much adaptive potential we leave nothing to chance! And customers should not, either!”