My company manufactures a vegan seed powder that is high in protein (Hemp seed protein). It is a fairly dry product (8-10% water only, aw < 0.55)
I am trying to better understand lab results we are getting on micro during production and finished product.
We take a composite sample of each day of production (milling) by sampling each barrel produced and sending a sample from this mix to our lab, which runs a micro panel (APC, Yeast and mold, b. cereus, salm, S. aureus, coliforms and E. Coli, and C. perfringens)
We consistently get low counts for B. cereus (< 100 cfu/g), and about 30% of the time we will have a low count for c. perfringens as well (< 30 cfu/g). Which is odd because the raw material absolutely always tests negative for c perfringens.
What is a little disconcerting to me is that when we ask our lab to retest the sample for perfringens, or if we send another sample from the same batch, it will very often test negative. When dealing with low counts like that, should we expect perfect repeatability of testing?
Is it the lab that is not being consistent, or are we demanding too much?
We were told by our lab that powders often have very heterogenous distribution of micros, and therefore testing and getting a "negative" only means that in the 1g they pulled the count was below detection. They also told us that c. perfringens is the same as b. cereus in that it is impossible to get rid of the spores in vegetal derived products. in their mind counts of C. perfringens < 100 cfu/g are not something to worry about in dry products, as the aw would not support growth.
What is your take on this? Do we have a sloppy lab giving poor advice?