Coliforms in Spray Dry Product

 

We are a manufacturer of spray dry products. Before we send it to the customer, we have tested our product for MPN coliform with <3 results. However, when it was received by our export customer, according to our customer, the product was coliform positive. 

Does anyone here have the same experience? How do coliforms appear in powdered products? How to reduce the number of coliforms in powder products?

 

Thanks before

 

Hi Ciegel,

I hope yr result not based on one sample.

I suggest the first thing to do is to check is whether the sampling(eg No.samples)/analytical  (eg BAM MPN/VRB count) procedures are (a) reliable and (b) equivalent.

Do you have an agreed specification ? eg nmMc ?

Yes, we check with the BAM MPN method. For the analysis method, our customers instead use test liquid of ISO 4831:2006 they used Pre-Enrichment test liquid (sample 25g/Lauryl Sulfate Tryptose Broth 225mL). Did the method have that much effect on the result?  Does anyone know how to reduce the coliform? Do the humidity control of the customer's storage warehouse, the use of UV light, and dehumidifier have an effect?

Yes, we check with the BAM MPN method. For the analysis method, our customers instead use test liquid of ISO 4831:2006 they used Pre-Enrichment test liquid (sample 25g/Lauryl Sulfate Tryptose Broth 225mL). Did the method have that much effect on the result?  Does anyone know how to reduce the coliform? Do the humidity control of the customer's storage warehouse, the use of UV light, and dehumidifier have an effect?

Hi Ciegel,

I'm a little confused.

Afaik BAM uses LST broth in 1st stage which yields presumptive coliforms tubes where positive.. The latter tubes then have to be confirmed using BGLB broth.

ISO 4831 contains 2 procedures for coliforms, namely (1) detection of coliforms, (2) MPN method for enumeration. Offhand (2) looks similar to BAM although the temperatures used may/(may not) be the same.

So which Procedure is yr customer using ? (Should be matched to your own).

Regardless  a single negative (ie <3 MPN/g) sample for coliform obviously does not preclude a further sample having a positive result.

Does yr specification require nil detection of coliform (eg <3MPN/g) for say n=5 or similar ?. This would be unusual IMEX since 'coliforms" is not usually considered a safety-related group.