coliforms in clabber culture

[justsocat]

I use homemade clabber cultures as a mesophilic starters for different kinds of cheeses more than year long. But i've faced a problem. I made analysis and they showed E.coli in Feta. I guess that my culture contains coliforms. Can anybody tell me how to get rid of coliforms in clabber culture?

[linuxboy]

Have to pasteurize the milk or have better sanitary practices when milking if using raw.

[justsocat]

Thanks, but the milk was pasteurised at 75C and all equipment and instruments boiled. There are only three possibilities: clabber culture, spices and vegetable oil. But spices and oil were taken from cans bought in store so i suspect my culture...

[linuxboy]

Oof, then you're likely right. It's either the milk was contaminated in the milk room, or sometime after while making the clabber.

Pash, is there any way you can make a new batch of clabber and have it tested? If you get a coliform-free sample, what you can do is use that clabber as the mother starter and propagate it forward. Then re-culture it using only pasteurized milk. This is similar to how it is done commercially.

[justsocat]

That's the main problem i face - all culture is in one and lonely sample divided by several portions and frozen. Somewhen earlier the culture was contaminated somehow and now, though i use pasteurized milk each time i need more culture, it is already contaminated. Pasha, I know there are microbiology labs that could separate pure culture from the mix, is that right? I don't want to loose my culture because of the very good taste and smell of the cheese it gives. And you understand, of course, that the cheese i make with my own culture is unique.

[linuxboy]

Yes, you would need to isolate the mix you have into its individual strains, and then recombine, and then reculture to try and recreate a balanced mix of bacteria. It takes time, but the equipment is basic. You can do it with agar plates, making colonies more pure each time until you can isolate the strains. There are also media out there for destroying coliform but preserving other bacteria. This may be a good option.

[justsocat]

Thank you. I never knew about media that can destroy coliform. I guess this is what i need.