Challenge studies using surrogate microbes

Although I'm not intending on performing one (if I can help it), the idea of performing a challenge study to confirm the reduction in pathogens after baking came up in a number of discussions in regards to validating an oven, both in person as well as in various old discussions on this forum.  Has anyone discussed whether the challenge studies must use the actual pathogens or whether nonpathogenic surrogate indicators (quite a mouthful) are suitable?  I found an article that discusses one such test case, but I'm not sure how common (or acceptable) this practice might be.  Thoughts?

Journal of Food Protection,Vol.79,No.4,2016,Pages544–552  doi:10.4315/0362-028X.JFP-15-241  "Validation of Baking To Control Salmonella Serovars in Hamburger Bun Manufacturing,and Evaluation of Enterococcus faecium ATCC 8459 and Saccharomy cescerevisiae as Nonpathogenic Surrogate Indicators"

I'd avoid the challenge study as much as possible and see what time/temps you actually get to first. Use an irreversible temperature indicator in the middle of your fattest products at lowest time/temps and see what you have for internal temp first, then do a literature/legal review to see if it meets an existing standard.

Hi bornyesterday,

I suggest for yr peace of mind that  quantitative micro. parameters acquired via challenge studies are frequently allowed to be quoted together with their associated predictive formulae. Lethality-related characteristics/equations are a classic example, eg D/z/F₀ values-equations.

As per previous post, you likely only have to (practically) worry about process temperature/time which can often be complicated enough already.

Of course, the argument as to whether baking is a CCP, PRP, oprp, none of the previous is afaik eternally open-ended.

I suggest for yr peace of mind that  quantitative micro. parameters acquired via challenge studies are frequently allowed to be quoted together with their associated predictive formulae. Lethality-related characteristics/equations are a classic example, eg D/z/F₀ values-equations.

Yes ... I also ran across a 2013 paper (Chen) which discussed how the Weibull model might be used to predict microbial survival patterns using Bill Gates' spreadsheet software ... definitely an area for future reading for me ...

I'd avoid the challenge study as much as possible and see what time/temps you actually get to first. Use an irreversible temperature indicator in the middle of your fattest products at lowest time/temps and see what you have for internal temp first, then do a literature/legal review to see if it meets an existing standard.

Excellent idea.  What kind of calibration assurances are included with it?