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Shelf life of jam based on microbiological factors

shelf life jam challenge test microorganisms expiry date marmalade microbiology

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#1 Ismene

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Posted 10 April 2019 - 07:51 AM

Hello to everyone,

 

I've been trying to find the shelf life of a jam only based on the microbiological factors. I am trying to see how this part works first. It is my second time doing this test and I am confused!

 

So, I inoculated jam of the same lot with the same amount of microorganisms and I stored them in the same conditions. The examination lasted a month, and I analyzed the products, every 2-3 days.

 

The number of the microorganisms was stable during the whole examination process. The log phase wasn't reached. I am attaching the growth curve for the dmfit.

 

So, my question is, can I find the shelf life based on these findings?

 

Thank you

 

 

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#2 pHruit

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Posted 10 April 2019 - 08:38 AM

Are you considering the life once open, or are you expecting microbiology to be the limiting factor on shelf life of unopened packs?

I wouldn't normally expect growth to be a significant consideration for jam.

 

As for the growth curve, the usefulness of the data will surely depend on the nature of the organisms you've used for the inoculation?
You're working with a product that I'd assume has a low(ish) aw and low pH, so there are a reasonable number of organisms for which growth wouldn't be expected.

 

(Also the scale on your x-axis isn't labelled, so it's not entirely clear what sort of shelf life you're looking at - is this over 30 hours/days/weeks/months?)



#3 Ismene

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Posted 10 April 2019 - 09:23 AM

Thank you for the reply,

 

I am considering the life of unopened packs. Yes, the pH and the aw is low. The pH is 2.83 and the aw is 0.78. A few microorganisms can grow on these conditions, so I used multiple microorganisms.

Also, I wasn't sure if the conditions would affect the microorganisms, so I was monitoring the jam without inoculation too. And the number of the microorganisms that were in the jam before the inoculation, was stable too. Also, I was monitoring the pH and the aw and they didn't show any significant change.

 

The x-axis is days.

 

So, in some products with similar characteristics, I shouldn't rely on the microbiological factors to find the shelf life? Monitoring the color, for example, would have been a better choice?



#4 pHruit

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Posted 10 April 2019 - 09:51 AM

Ok, so at that aw you may still see some Aspergillus, Saccharomyces growth.

But if you're considering unopened life, then processing/packing will be a very relevant factor to consider - most jams on sale here are packed as ambient-stable products so the limiting factor is organoleptic quality, but whether this is applicable for you will depend on the specifics of the process you're using.



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#5 zanorias

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Posted 10 April 2019 - 09:59 AM

I expect mould organisms would likely be a limiting factor once open? Would it be worth running both micro & organoleptic tests? Perhaps different from ambient/conserves, but this is what I do for chilled meat products - establish use by with micro tests form an accredited lab, then run organoleptic panels along that life (within the 'safe' boundaries as established by micro ofc).

 

Anyway, I'm sure Theresa May would be happy with the jam regardless :rolleyes:



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#6 Ismene

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Posted 10 April 2019 - 10:58 AM

I expect mould organisms would likely be a limiting factor once open? Would it be worth running both micro & organoleptic tests? Perhaps different from ambient/conserves, but this is what I do for chilled meat products - establish use by with micro tests form an accredited lab, then run organoleptic panels along that life (within the 'safe' boundaries as established by micro ofc).

 

Anyway, I'm sure Theresa May would be happy with the jam regardless :rolleyes:

 

Yes, moulds are the biggest threat for jams once opened.

 

I wanted to run organoleptic tests during the life span, but I don't have the samples to do it. But now I realize that the organoleptic factors are more important for these types of products, before the opening of the package.

 

And as for the month that passed with the samples that I have, the organoleptic characteristics haven't changed. I will try to find the samples to do a "real-time" organoleptic testing. And see how it will change during the first months.

 

I just searched the Theresa May comment! :lol2: 

 

Thank you for the reply!



#7 pHruit

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Posted 10 April 2019 - 11:08 AM

Organoleptic changes are probably going to occur quite slowly - you could be looking at a shelf life of potentially 24 months.

There may be a local service that can offer some accelerated shelf life testing facilities if needed?



#8 Ismene

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Posted 10 April 2019 - 11:26 AM

Organoleptic changes are probably going to occur quite slowly - you could be looking at a shelf life of potentially 24 months.

There may be a local service that can offer some accelerated shelf life testing facilities if needed?

 

As I am trying to figure out the shelf life testing, I will work it first on my own, and probably send samples to another laboratory, to see if my results are correct. But that is when I am sure that I did the correct testing on the product. I want to work on some dairy and meat products too, which are quite different.



#9 Scampi

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Posted 10 April 2019 - 12:27 PM

I would think your expected shelf on unopened jars (sealed correctly of course) should be nothing short of 1 full year. Jam is incredibly stable due to the aw and pH AND sugar content. 

 

http://shelflifeadvi...m-and-preserves

 

https://www.edsmith.com/en/faq/

ED Smith says 18 months of storage in the home post purchase which would equate to a 2 year shelf total (including warehousing and distribution)


Because we always have is never an appropriate response!


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#10 Ismene

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Posted 10 April 2019 - 12:38 PM

I would think your expected shelf on unopened jars (sealed correctly of course) should be nothing short of 1 full year. Jam is incredibly stable due to the aw and pH AND sugar content. 

 

http://shelflifeadvi...m-and-preserves

 

https://www.edsmith.com/en/faq/

ED Smith says 18 months of storage in the home post purchase which would equate to a 2 year shelf total (including warehousing and distribution)

Thank you for the links!



#11 Charles.C

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Posted 10 April 2019 - 12:40 PM

As I am trying to figure out the shelf life testing, I will work it first on my own, and probably send samples to another laboratory, to see if my results are correct. But that is when I am sure that I did the correct testing on the product. I want to work on some dairy and meat products too, which are quite different.

 

Hi Ismene,

 

This is shelf life 101 -

 

First determine whether shelf life is to be based on safety or non-safety factors. Some older threads here have decision trees incorporating this.

 

For an ambient shelf-stable product, any textbook should give non-safety.

 

Regarding an approximate shelf-life you could simply go to a supermarket and look at some labels ?


Kind Regards,

 

Charles.C


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#12 Ismene

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Posted 11 April 2019 - 06:34 AM

Hi Ismene,

 

This is shelf life 101 -

 

First determine whether shelf life is to be based on safety or non-safety factors. Some older threads here have decision trees incorporating this.

 

For an ambient shelf-stable product, any textbook should give non-safety.

 

Regarding an approximate shelf-life you could simply go to a supermarket and look at some labels ?

Thank you,

 

Yes, I searched for the older threads on Shelf life, they are helpful!

I understand that now, I thought that all of the factors should be checked to determine the shelf life.

 

I went to a supermarket and the shelf life of most of the jams is 2 years







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