15 replies to this topic

[Qldboo5]

Hi,
Just wanting to do a finished product spec for some yoghurt. What would you suggest as target/marginal/fail limits for yeast & mould? It seems like there is a lot of different numbers floating around. I would like to know for beginning & end of shelf life.
Also, what routine micro testing is standard?
Thanks in advance
:)

[Charles.C]

Hi,
Just wanting to do a finished product spec for some yoghurt. What would you suggest as target/marginal/fail limits for yeast & mould? It seems like there is a lot of different numbers floating around. I would like to know for beginning & end of shelf life.
Also, what routine micro testing is standard?
Thanks in advance
:)

 

Hi Qldboo,

 

Thanks for yr query and Welcome to the Forum !

 

See this post and go to the 5th pic. down -

 

http://www.ifsqn.com...ge-2#entry40662

(ingredients) (not inc.starter culture)

 

and USDA spec for yoghurts -

 

 USDA spec yoghurt.pdf   20.93KB   230 downloads

(Pg 3)

[Charles.C]

addendum

 

bit more data -

 

 yoghurt standards.pdf   43.98KB   201 downloads

[Qldboo5]

Thanks Charles, these numbers are pretty low compared with some I have seen. In your opinion are they low to keep the quality of the product rather than for public safety/regulations?
I just started working in a small business and there are no other food techs to bounce ideas off. This forum is great.
Thanks

[Charles.C]

Hi Qldboo,

 

Should state that Dairy products not my main area of expertise but the data is from  standard references.

As you can see there was a certain range of opinion regarding max. Y&M in my quotes.

 

What sort of numbers are you regarding as non-low ?.

 

Here are 2 more paraphrases –

 

Yoghurt, at the point  of  sale, should  preferably contain  < 100  viable  yeast  cells/ml. Above  10(^3) cfu/ ml implies a serious risk of deterioration for, although serious gas production and off-flavour development may not be apparent until the yeast population reaches 10(^5)cfu/ ml, such counts can be readily achieved within a 2–3 week shelf life.

 

The presence of yeasts or moulds at > 10 cfu/ ml of starter is likely to  lead  to  spoilage  during  the  shelf  life  of  the  retail  product.

[Qldboo5]

Thanks Charles, I saw some at <1000, which I thought was not very low. I will post link when I remember where I saw it....
I'm thinking I'll spec <10 as satisfactory, <1000 as marginal and >1000 as unsatisfactory, but I'll do a bit more research. Pathogens are easier to set limits for due to legislative requirements, but indicator microbs seem to be a bit more subjective.
FYI the product is non dairy yogurt. So I am using dairy guidelines, but not strictly correct I guess.
Appreciate your help,

Also, does anybody know about mycotoxin testing? When would you use that? Just considering my corrective actions if product was marginal. Cheers

Thanks

[Charles.C]

Hi Qldboo,

 

AFAIK, the HTST pasteurization step  in dairy yoghurts theoretically "eliminates"  yeast/mould (vegetative cells and spores)  so problems in the finished product typically relate to subsequent  stages, eg added ingredients, hygiene control.

 

I noticed this condensed comment from a project to optimise the output from a yoghurt manufacturing line –

 

It is important to note that the mean yeast and mould count decreased from log 4.66/ml before HACCP to < 1/ml after HACCP implementation. The absence of coliforms and yeast and moulds is an indication of efficient plant hygiene and sanitation

.

 

For dairy yoghurt, mould problems  have occasionally been reported due various genera (see attachment below). The limits shown in my previous post were proposed as a  trigger for this.

The toxigenic species Penicillium frequentans has been reported (1984) as a contaminant  in  a  commercial  yoghurt  sample.

 

Document below seemed quite informative regarding the occurrence/control of Y&M in dairy production. It includes the comment -   

 

Fruit purees added to yoghurt – usually the main source of moulds and yeasts

 

 Moulds and Yeasts in the Dairy industry (2014).pdf   2.58MB   250 downloads

 

There are a few “dairy” professionals on this forum who may have further comments.

 

More detail  regarding yr product/ process may increase the likelihood of relevant comments.

[Qldboo5]

Thanks again Charlie. A few more details: I'm drafting a micro spec for a finished product which is nondairy yoghurt with fruit purée at the bottom in different flavours. I want to also draft a corrective action for when results indicate marginal. This way action can be swift. I found pathogens easier because if detected you go straight to recall plan. I am having more difficulty drafting the action if micro on indicator microbes is marginal/unsatisfactory. Specifically Y&M, when would you test for mycotoxins?
Thanks

[Charles.C]

Hi Qldboo,

 

My guess is that yr query is not readily answerable in an absolute sense because mould is not a species and not all genera of moulds produce mycotoxins.

 

http://www.mycotoxin...info/qanda.html

An additional factor is that the scope and official tolerance limits for specific mycotoxins globally vary, eg  –

http://services.leat...heet.aspx?ID=79

 

The most conservative viewpoint (ie highly Risk Averse) would  presumably adopt a "zero tolerance" type logic and test any detection. This is equivalent to the strictest  limit  in my previous post or the (parenthesis) limit in example No.2 in this attached file.

 

 dairy specs-controls.doc   316KB   102 downloads

 

I have yet to see any opinion or detailed analysis  of a specific “safety” relationship between a positive “mould count" and “mycotoxins”.

 

Nonetheless, there do seem to have been very few reported instances of proven mould-related mycotoxins causing health-related incidents for dairy yoghurts. For mould growing on the surface of yoghurt this (2009) observation might be an explantion but it looks a bit too convenient IMO  –

 

since mycotoxin production would be expected to coincide with visible growth, and visibly spoiled products are unlikely to be consumed, this does not seem to be a serious hazard.

(the comment does not exclude the possibility of  direct toxin contamination via the original milk, or later additions.

 

It is obviously crucial to control any items added post-pasteurization, eg see the puree comments in No.(3) of attached file.

 

As a possible caveat to assuming mold on yoghurt has only non-safety significance,  this later (2013) incident has become globally well-known  –

 

http://www.usatoday....h-risk/2788405/

http://www.foodquali...nsumers-or-not/

 

Further speculation over Yoghurt X welcomed.

[Charles.C]

addendum

 

Hi Qldboo,

 

Here is one opinion from a safety POV -

 

 toxins.pdf   6.76KB   68 downloads

 

Just as a historical sampling  - 

 

 Yogurt-Aspergillus.pdf   373.67KB   91 downloads

[Tony-C]

Thanks to Charles for the numerous useful attachments, I have used inhibitor cultures and they do have some impact.

 

Yoghurt should have minimal yeast & mould contamination so a typical specification is < 10/g target, maximum 50/g. If you consistently find contamination then you need to work on improving control in the processing and packing environment.

 

There are many factors that need to be considered here such as the shelf life, cooling after packing and storage temperatures. At end of life you would not want to see significant numbers so < 100/g target, maximum 500/g.

 

Regards,

 

Tony

[Qldboo5]

Thanks for all the input, I eventually settled on target <10, Marginal 100-1000 & unsatisfactory >1000 for Yeast & Mould.  I also agree that presence of Y&M is to do with post-pasteurisation contamination & plant hygiene is key to low numbers.  After looking into it & asking a lab, I don't think I would do Mycotoxin testing, as if numbers were unsatisfactory, the product would not meet its shelf life, so my corrective action would be to withdraw the product whether it is hazardous or not.

Thank you again for such a great forum

:)

[Charles.C]

Hi Qldb,

 

There should be a 10-99 in yr post somewhere.

[Qldboo5]

Sorry that should be <100 for satisfactory. That is the lowest we can get back from the lab who do a rapid method.

[Aliali]

Hi 

 

Do you mind I ask the shelf-life of your products please?

 

I am establishing a yeast and mould limit for yoghurt products as well. 

 

Thanks

[Qldboo5]

Hi,
Just to update, I arranged for the lab to do another dilution so limits are now:
Target <10
Marginal 10-100
Unsatisfactory >100
Our shelf life is 5 weeks