Yeast & Mould Limits in yoghurt
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,
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 219 downloads
(Pg 3)
I just started working in a small business and there are no other food techs to bounce ideas off. This forum is great.
Thanks
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 ?. :smile:
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.
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
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 246 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.
Thanks
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 100 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. :smile:
addendum
Hi Qldboo,
Here is one opinion from a safety POV -
toxins.pdf 6.76KB 66 downloads
Just as a historical sampling -
Yogurt-Aspergillus.pdf 373.67KB 88 downloads
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
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
:)
Hi Qldb,
There should be a 10-99 in yr post somewhere.
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
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