Propagating Starter Cultures

[krops13]

Has any one/ is it possible to save a culture for use in another cheese. for example taking a culture from buttermilk or yogurt or just buying the culture from a commercial seller and putting it on a agar plate to grow the culture. then propagate it out for use on what ever cheese needs it. i work in a lab and have a hepa filtrated hood available so contamination wont be an issue. hoping to be able to put a culture on a plate and then just keep transferring it to a new plate when I've used most of it up. I already do this for my yeast i use for brewing beer so hoping to do it the same whey. 

[FRANCOIS]

Linuxboy would be the forum member that knows the most about lab type propogation.  The old fashioned way for commercial cheesemaking is to make a bulk culture from sterilized milk (mother culture) and just keep saving some and reculturing your bulk.  The plant I work in has one strain that has been carried forward since the early 50's.

So, the short answer is yes.

[wharris]

where do i find out more about this?  I feel too dumb to even ask questions. 

(you all think i know more than i do sometimes)

[FRANCOIS]

Wayne,
Any older cheese book will have a section on mother culture.  I think Morris's book does as well.   Most culture houses in Europe deal heavily in bulk culture, inctead of powder, as it's the traditional method there.  I had some samples of a culture mix flown in from Germany recently and, being used to direct vat powder, was surprised to open the coolels to find bulk liquid.  I inquired if I was able to get powder and was told that many cultures they hold are only available in liquid form.  Go figure I guess.

I am definately a convert now, bulk culture is pretty easy to make and propogate and the difference in cheese making is significant.  The "prime time" is very short before renneting and the curd is, I think, more uniform in density.

[FRANCOIS]

If it helps, this is how we do our trial bulk, not the stuff that makes it into actual product.  We take 1 gallon of skim milk, new never opened, put it in the lab dishwasher, which has a "sterilization" setting.  It takes about 5 minutes.  We remove the bottle and allow it to cool till warm to the touch.  Pop the top, peel back the foil and dump in about 1/2 tsp of DVS powder.  Shake it up and leave out over night.  The next morning we test the pH to be sure it's under 5.0 and pop it in the fridge till needed.

Like I said, not very scientific but it works great for us.  I use 1-1.5% bulk by volume to innoculate, but others here go up to 2%.

[wharris]

Very interesting.  That I can understand.

Why Skim milk?  This really really intrigues me..

[FRANCOIS]

You need to be able to pour it out, although it's still quite thick.  If you used regular milk and acidified that much it would be a solid block.

[wharris]

Solid advice.  I'd give you a cheese but holy mackeral, you have gazillions..

[FRANCOIS]

Yeah, I'm a hoarder I guess.  I never even noticed that "cheese" thing until yesterday.

[linuxboy]

The method Francois described is a great method for practical culture replication in a commercial setting, or if you make cheese frequently. It's actually very scientific. The only other thing I would add is to pay very careful attention to contamination and to prepare a known pure sample of bulk culture that you freeze so that if the normal culture is contaminated somehow, you can toss it and start anew. Commercially, it's also important to rotate because of phages.

If you want to use agar, I would use a broth if you want to maintain and replicate. A plate is better for isolation. Look at Ellikers lactic agar, or MRS or M17. You can agitate the broth at a slow RPM, and use a buffer if you want, and centrifuge after to concentrate. If you have a lyophizer, you can take the centrifuged mass and freeze dry it, which would form a DVI culture .

I can find some links for detailed culture prep instructions if you want something more exact. But the gist of it, sure, you can propagate on your own with agar, just watch the pH and food needs.

[Sailor Con Queso]

Can you explain "1-1.5% bulk by volume to innoculate".

Does that mean 1.5 gallons of innoculant to 100 gallons of milk? Wow, seems like a lot

[FRANCOIS]

Yup, that's exactly what it means.  It acidifies things much faster than powder.  It's consistent too.

[wharris]

Good info,  a bit over my head.  But I like stretching what I know.  I read and re-read.  I will continue to absorb this info.


What I learned quickly:
Agar
a⋅gar  /ˈɑgɑr, ˈægər/  Show Spelled Pronunciation [ah-gahr, ag-er]   
–noun 1. Also, agar-agar. Also called Chinese gelatin, Chinese isinglass, Japanese gelatin, Japanese isinglass. a gelatinlike product of certain seaweeds, used for solidifying certain culture media, as a thickening agent for ice cream and other foods, as a substitute for gelatin, in adhesives, as an emulsifier, etc.
2. Biology. a culture medium having an agar base.

bacteriophage  
/bækˈtɪəriəˌfeɪdʒ/  Show Spelled Pronunciation [bak-teer-ee-uh-feyj] 
–noun any of a group of viruses that infect specific bacteria, usually causing their disintegration or dissolution.

Also called phage.



My takeaway. 
Use freeze dried commercial cultures 'till i read more

Thanks guys...

[linuxboy]

In terms of the difference in activity between bulk starter and DVI culture, it may help to think about this from the point of view of bacterial metabolic and reproductive processes. That's most of what bacteria care about. They want to gorge themselves enough to satisfy their own respiratory needs, and take the excess to create enough parts to multiply. In this, bacteria have a need to have access to the proper nutrition, and the right environment. The right nutrition is lactose, vitamins/minerals, and proteins. The right environment is temperature, pH, and ionic concentration to aid in cell wall active and passive transport.

So for active bacteria in a bulk starter, they're awake and hungry, and looking to multiply. You can actually time the cycle (based on pH) to where the colonies are lively enough to be at the peak of their replication cycle (typically around 4-6 x10^9 CFU/g), and will very rapidly acidify. For DVI culture, their cells needs to be rehydrated first, then they wake up, then they'll do an internal check, then they'll start feeding themselves, and only then when they feel fine will the bacteria multiply and really get going with the lactic acid production. That lag time is pretty significant, 30-60 mins.

BTW, I'm happy to explain all this more detail if anyone wants. Please help me by narrowing down the scope, because I can talk for hours

[Sailor Con Queso]

Linuxboy - more is good.

What I need to know is how in the world to adjust ripening times. The Direct Set packets are "calibrated" based on activity level. Is there a way to test BASIC activity level to calculate either culture volume or ripening times?

Peter Dixon suggests a shortcut for kick starting the starter cultures while you are heating milk to its starting temp. He says you should quickly heat a much small container of milk (a glass full?) to 80-85 F and add the starter to that container. So while the main vat is heating up, the starter is already becoming very active. He says that this is a way to greatly reduce ripening time. However, he does NOT suggest how to adjust the timing. I  guess if you know what the target pH is at renneting, you could just monitor and add rennet at the right time. Without pH levels, I'm lost about how to adjust times.