Eggs shells and diseases

ngrrsn(7)October 29, 2012

I told a friend I use egg shells in my garden. I rinse and save the shells, then after a while when I have enough I crush and bake them at 350 degrees until they start to turn brown...just before buring.

A friend said egg shells can have diseases like salmonella and botulism bacteria and be transferred to the vegetables I am raising. She said egg shells should never be added to compost and she questioned whether baking at 350 degrees was sufficient to kill the dangerous bacteria.

I can't find any qualified answers online --- you know, real scientific evidence, not just garden gossip. Does anyone know of a source or that has learned evidence whether she is all wet? I don't want to kill my family or guests with "bad eggshells".

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RpR_(3-4)

She is all wet.

    Bookmark   October 29, 2012 at 4:59PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

There are all sorts of claims made about the use of egg shells in gardening - both pro and con. Claims about how dangerous it is to use them in gardening and composting are no more reliable than are all the claims about the things they supposedly cure and wonderful things they do.

But your friend's particular claim seems to ignore the fact that salmonella and c. botulinum spores (as well as many other fungi and bacteria) are already in the soil anyway. And in the air and all around and even inside us.

It is the toxins they produce when given the ideal growing conditions that pose the threat, not the bacteria themselves and they are a normal part of life. Assuming good gardening and food hygiene practices they pose no threat to us.

Dave

    Bookmark   October 29, 2012 at 5:21PM
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rhizo_1 (North AL) zone 7

She's a germiphobe. Lots of those around these days.

    Bookmark   October 29, 2012 at 9:34PM
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buckyz4

I throw raw egg shells into the garden without thinking twice about it. Is she is concerned, yes baking would kill anything she could be worried about, that is why we cook eggs prior to eating them, although I do miss eggnog with raw eggs!

    Bookmark   October 29, 2012 at 9:40PM
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cheapheap(7a)

Salmonella information from the USDA:
http://www.fsis.usda.gov/factsheets/salmonella_questions_&_answers/
See the last question on the page (the rest of the information is worth reading)

Botulism information from the USDA:
http://www.fsis.usda.gov/FACTSheets/Clostridium_botulinum/index.asp#10
See the last question on the page (the rest of the information is worth reading).

I don't think you have anything to worry about. Like digdirt said, these things are everywhere.

Hope this helps but some beliefs are not swayed by reason - just because you are right does not mean that you will win the argument.

    Bookmark   October 30, 2012 at 12:02AM
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planatus(6)

If anything, the eggshells will suppress nematodes and other diseases in the soil, because they are a rich source of chitin.

    Bookmark   October 30, 2012 at 9:02AM
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rhizo_1 (North AL) zone 7

Planatus, I think you're confusing egg shells with the outer 'skin ' of other creatures. Egg shells contain no chitin. Crustaceans, insects, and other arthropods all have exoskeletons made of chitin.

    Bookmark   October 30, 2012 at 12:10PM
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ngrrsn(7)

Thanks! Cheapheap's link to the USDA shows that "... Only a pressure cooker/canner allows water to reach 240 to 250 ðF, a temperature that can kill the spores...."

Therefore, baking crushed shells at 350 degrees (100 degrees higher temp than pressure cooking) will surely kill any spores. Whether raw eggshells or not added to the garden could cause issues, and whether I even need to do this, certainly this is proof that I am not putting my family or anyone else at risk!

    Bookmark   October 30, 2012 at 5:38PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Therefore, baking crushed shells at 350 degrees (100 degrees higher temp than pressure cooking) will surely kill any spores.

No, sorry but dry heat temps and wet heat temps aren't comparable. And wet heat under pressure is even less comparable. They all work very differently on micro-organisms.

But as has already been mentioned by many, you have no reason to be concerned anyway.

Dave

    Bookmark   October 31, 2012 at 11:11AM
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ngrrsn(7)

(sigh) Thanks Dave. I am not going to worry about it; you and lots of people say it isn't an issue. But I would think some Ag student out there looking for a graduation term paper would have done a research paper on this! LOL!

    Bookmark   October 31, 2012 at 2:42PM
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albert_135(Sunset 2 or 3)

I've been away from the lab for awhile. I do recall that Salmonella is everywhere and some are harmful. I do recall that it takes more dry heat to kill spores than moist heat. Moist heat under pressure is the best.

How long does it take to kill spores in a common household kitchen pressure cooker?

    Bookmark   October 31, 2012 at 3:27PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

How long does it take to kill spores in a common household kitchen pressure cooker?

Frequent question over on the Harvest forum here - the food preservation forum.

Answer is the time varies depending on the density and the pH of the food and the amount of pressure used. And if canning, the volume in the container(s) inside the pressure canner.

Dave

    Bookmark   October 31, 2012 at 3:49PM
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Beeone(4 N. Wyo.)

Think about it this way. Once upon a time those eggs had white and yolks in them. Chances are many of them were eaten for breakfast. When you cook an egg for breakfast, do you cook it to 350 degrees until the entire egg starts to turn brown? A soft yolk hasn't even been heated to 200 degrees. So while we eat the egg, people are worried that the shell it came from, placed in the garden, is going to transfer salmonella and such to the vegetables even though the egg that was in the shell was heated to a relatively low temperature with no ill effects?

The point of a pressure cooker is to heat the food in the jar to the lowest possible temperature for the shortest time to maintain food quality while assuring that all pathogens are killed as the sealed jar, sitting on the shelf for months, forms an ideal place for a few pathogens to multiply and create a toxic soup. Eggshells in the garden don't have that kind of environment.

    Bookmark   November 1, 2012 at 2:06AM
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PlantsAndYarn(5)

I put the crushed eggshells in my compost without rinsing or baking them. No one has gotten sick off the garden.

    Bookmark   November 1, 2012 at 7:05AM
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cheapheap(7a)

I personally bake eggshells sometimes - it helps in crushing them finely - I believe this to be the reason why many bake them, the internal membrane gets dried out or burned off and makes pulverizing them much easier. Mostly, I would just add them to the compost just how they were right after cracking them into the pan and I personally would not have any problem putting them right into the garden..

It is true that there does not seem to be any research entirely specific to your friend's concerns. I personally would not assume from that the claims have any merit. Perhaps it be more likely that your friend's concerns are so off base that they are not worth researching?

As an aside - To clear it up, since it has been mentioned above a couple of times, and for my own curiosity, can someone explain the difference between a "wet" and "dry" temperature in regards to sterilization?

I had always assumed that pressure canning was a way to transmit heat using a common, easily obtained and easily worked with liquid (water) that just happened to have the flaw of only being able to be heated to 212 F at sea level. With additional pressure the maximum temperature that water can reach is increased to a point at which all botulism spores can be destroyed with an additional margin added for safety. Time in cooking (I had assumed) is needed only to overcome the insulative value of the material being processed, with an additional amount of time added for safety as well .

I would be interested in knowing how pressure kills botulism spores other than its effect on the boiling temperature of water.

Thanks.

    Bookmark   November 2, 2012 at 2:35AM
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albert_135(Sunset 2 or 3)

Suggested by digdirt above, the Harvest Forum is a very interesting forum. Much of the information reads well, that is to say seems reasonable to someone who has studied these things.

Consider How to kill botulism spores? for example; says Temps of 240ðF. I believe we used Temps of 250ðF in the hospital laboratory.

    Bookmark   November 3, 2012 at 2:15PM
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alan290

cheapheap,

The reason wet heat is better at killing spores than dry heat is probably due to the fact that the specific heat of water is greater than that of air. For example, if you put your hand in an oven that is at 250 degrees, it would not burn you right away, but if you stuck your hand in boiling water that is 250 degrees, it would burn you instantly. The boiling point of water is 212deg F.

    Bookmark   April 8, 2014 at 11:48PM
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seysonn(8a WA/HZ 1)

Beeone made a good point about eating eggs for breakfast to be ok but how come composting it becomes harmful ? we are not eating the compost :) hehe

About the pressure -tempeature, wet and/or dry relationship.

What kills the bacteria is the temperature not pressure. Inside your car's tire there is twice as much pressure as in pressure cooker/canner but bacteria will/can live in it fine and produce spores too.

By pressurizing on heat we raise the boiling temperature of water ( aqueous medium). It does not matter wet or dry, solids or liquid parts. Given enough time temperature will be stabilized inside the vessel.

    Bookmark   April 9, 2014 at 3:07AM
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