Is it a myth that water removes an egg's bloom?

[quackingdom]

A lot of people seem to think that rinsing an egg with plain water will wash the protective bloom/cuticle off. I've always thought so too, but then a post on Instagram questioning this caught my attention and I decided to research it. Now I'm not so sure.

There are various studies researching washing eggs with various chemicals and detergents. I only found one that actually tested with plain water (albeit on quail eggs, not chicken eggs):

https://europepmc.org/article/med/32731973

Click to read the full text and look at Table 2. You'll see that water and sodium hypochlorite didn't seem to remove the cuticle. Both seemed to affect it slightly, with sodium hypochlorite having more of an effect, but neither removed it. All the other substances used did remove the cuticle.

Here's another study:

https://www.sciencedirect.com/science/article/pii/S0362028X22115528?via=ihub

In this one, eggs were washed with a mix of water and detergents. It didn't seem to affect the bloom/cuticle. This was their conclusion:

"We could find no evidence to suggest that the washing procedure used in this study irreversibly changed the cuticle quality of eggs from the end of lay, which inherently had poor cuticle coverage (worst-case scenario). This conclusion was valid for both brown and white eggs and was based on the assessment of the cuticle coverage, using a dye, and on the cuticle quality criteria as assessed by SEM. Moreover, within each group of eggs, a lot of variation in cuticle coverage and quality naturally occurred."

A third study:

https://www.sciencedirect.com/science/article/pii/S0032579119495928

This had a variety of findings:

1. Cuticles vary by hen. Some hens lay eggs with very little to no cuticle. Other hens lay eggs with a cuticle covering most, but not all of the egg.
2. Hen age didn't seem to make a difference. (Which was interesting, because the study I linked to first contradicted this.)
3. Brushing/scrubbing eggs can damage the cuticle.
4. The cuticle deteriorates naturally with age.
5. Spraying eggs with chlorine dioxide did not affect the cuticle.
6. Manure did affect the cuticle.

So, based on that, if you try to scrub dirt/poop particles off with a brush and without water, there's a chance you might be damaging the bloom more than if you washed the egg.

An article (not a study):

https://www.cfsph.iastate.edu/thelivestockproject/eggs-is-washing-and-refrigerating-necessary/

This says, "Using a chlorine-based sanitizer between 50-100ppm protects the cuticle of the egg while sanitizing." Not sure what their source is. It also says, "Warm water allows the egg to expand and push bacteria out, but cold water pulls the bacteria in."

Hatching & Brooding Your Own Chicks (Gail Damerow) says:

"You don't want to wash the eggs, for fear of removing the protective bloom, but you might dip them into a sanitizer. Some poultry keepers routinely sanitize all hatching eggs, which does not affect the bloom and does improve the hatch rate. . . . Never use water that's cooler than the eggs, because it can force contamination through the shell. Dip the eggs in the sanitizer for at least 1 minute but no more than 3 minutes, then set them on a clean towel to air dry; do not rub them dry, which would rub off the bloom."


What do you think? Is it a myth that washing eggs with water removes the bloom? Am I misunderstanding something? What if the protective quality of the bloom is compromised by water even if the bloom isn't removed? (Guess I could try to research that too.)

 

[aart]

I 'wash' eggs under warmer than the egg water and using my hands 'scrub' every part of the egg. I can feel the bloom, it feels kinda slimy. Some have much more than others, but pretty sure it all comes off. I only wash 'dirty' eggs immediately before using for myself,I do not wash eggs I sell.

 

[TRALALARA1]

Interesting. I did something different this last hatch when I set the eggs. I took a warm damp paper towel and gently wiped off dried poop on the eggs. Just on the dirty ones which was quite a few. I was worried it could affect my hatch rate but I also didn’t want to introduce bacteria into the eggs by leaving the poop on. I had 27 of 30 eggs hatch and survive. Quite healthy actually. If we have much rain my hens can bring in a lot of mud on their feet and sometimes poop. I feel like wiping the eggs down had no effect on the chicks.

 

[FunClucks]

I wash eggs to sell using the Mana Pro egg wash and a microfiber cloth and lots of warm water. The microfiber cloth gets all the bloom off.

I recently hatched some formerly dirty/muddy chicken eggs. I scrubbed them using a microfiber cloth while drenching them with hydrogen peroxide, then laid them on a paper towel to mostly air dry. All 24 developed, and 21/24 hatched. 20/24 were healthy chicks (one I culled due to a defect I think due to improper egg turning). I washed my hands before going into the brooder to turn or candle.

I don't know that washing with hydrogen peroxide helped increase my hatch rate, but it sure doesn't look like it hurt anything. The chicks were super healthy and have grown well.

 

[Perris]

What if the protective quality of the bloom is compromised by water even if the bloom isn't removed?

I don't think it is.

According to S. SAMIULLAH and J.R. ROBERTS 'The eggshell cuticle of the laying hen' World's Poultry Science Journal, Vol. 70, December 2014, the "cuticle layer of the eggshell is composed of inner calcified and outer non-calcified water insoluble layers" (emphasis added). This makes sense, as in nature an egg would be exposed to rain and dew, and if water in that form was harmful, the chick inside would fail to survive, so selection pressure must favour a cuticle not adversely impacted by exposure to rain. Another function of the cuticle is to keep "the water and electrolyte levels of the egg contents in balance by preventing evaporation", again suggesting impermeability.

They add that the cuticle is less effective as a microbial barrier when fresh and moist than when mature and dry, and that "Washing has the potential to damage the cuticle although manufacturers of modern egg washing equipment aim to reduce the impact on the cuticle".

Incidentally, noting the inconsistency in reports on the effect of age, they conclude that "Further research needs to be conducted to determine the effect of flock age on functional cuticle cover and such studies should involve vertical surveys of the same flocks at different ages". That was in 2014; I don't know if any more has been done on it yet.

 

[Perris]

The studies I read only used staining if I remember right.

the 2011 paper you cited used SEM, not the 1975 one.

What do you think would be different? Many people's backyard hens are more than a year old, so they might have less cuticle coverage. Would free-range hens tend to have better or worse cuticle coverage than a commercial production hen? More variability or less variability?

Cuticle quality may decline with age, but I'm not going to generalise it to all hens on the basis of studies that used birds only 23-70 weeks old, who were all production hens, fed commercial feed, in confinement. One of my 5 years olds is laying stronger eggs now than she did when she was 1-2 years old.

I assume hens that are not restricted to commercial feed would have better cuticle coverage, because they get a diet that nourishes all of them, not just the bits required for maximum egg production at minimum cost. Free range hens get in addition fresh air, exercise, and probably a much better social life, all of which contribute to better health, I think. I imagine there is a lot of variability between them too; at least, I see a lot of variability in each single hen's eggs, depending on what she ate recently, and how good her health is.

 

[Yardmom]

When I think of washing an egg I think of scrubbing the dirt off and this clearly damaged the bloom coverage. May rethink how I wash eggs.

 

[quackingdom]

I don't think it is.

According to S. SAMIULLAH and J.R. ROBERTS 'The eggshell cuticle of the laying hen' World's Poultry Science Journal, Vol. 70, December 2014, the "cuticle layer of the eggshell is composed of inner calcified and outer non-calcified water insoluble layers" (emphasis added). This makes sense, as in nature an egg would be exposed to rain and dew, and if water in that form was harmful, the chick inside would fail to survive, so selection pressure must favour a cuticle not adversely impacted by exposure to rain. Another function of the cuticle is to keep "the water and electrolyte levels of the egg contents in balance by preventing evaporation", again suggesting impermeability.

They add that the cuticle is less effective as a microbial barrier when fresh and moist than when mature and dry, and that "Washing has the potential to damage the cuticle although manufacturers of modern egg washing equipment aim to reduce the impact on the cuticle".

Incidentally, noting the inconsistency in reports on the effect of age, they conclude that "Further research needs to be conducted to determine the effect of flock age on functional cuticle cover and such studies should involve vertical surveys of the same flocks at different ages". That was in 2014; I don't know if any more has been done on it yet.

Interesting.

I also found this...

https://www.petersime.com/hatchery-...-when-incubating-waterfowl-eggs-with-cuticle/

"Due to the increased degree of biological challenges experienced by the vulnerable embryo in its natural ‘wet’ environment, waterfowl eggs have a thicker ‘coating’ or cuticle compared to chicken eggs. This coating protects the eggs from contamination. In nature, the cuticle of waterfowl eggs gradually erodes during incubation due to the nest activity of the parent bird. This results in more exposed pores and, consequently, an increasing rate of gas exchange that provides the developing embryo with sufficient oxygen and creates an air cell big enough to facilitate hatching. To replicate the interaction between parent bird and incubating waterfowl eggs, two approaches are traditionally used. Some hatcheries actively remove the cuticle by washing the eggs before incubation. Others spray the eggs with water during incubation."

 

[ChickNanny13]

Interesting, will be checking out those links ... My girls (thankfully) lay clean eggs, so I just refrigerate & wash before I use them (sometimes I get lazy). I inform those I give/sell eggs to that they're not washed, some say not necessary.

Thank you for sharing

 

[quackingdom]

We also inform people we sell to that they're not washed, and they're fine with it, but sometimes I feel bad because there are quite a few that have visible dirt on them. It's often very wet where I live and a lot of the birds lay on the ground. I've always shied away from washing them for fear of washing off the bloom. Now I'm reconsidering, but wanted to see what other BYCers thought.