What does this mean? (Advice about splitting culture)

[tobyw]

Hi all - I have bought a packet of mesophilic culture from a really helpful website. However I am hoping for some help with how to work out how much to use for the small quantities I make.

The manufacturer's instructions for the pack I have bought say that 6.5DCU is enough for 100 litres of soft or semi-hard cheese, and the packet contains 25 DCU. Presumably that means the packet is enough to culture 400 litres of milk - which matches what the website says too.

So that suggests that for the small quantities of cheese I am able to make at a time (4 litres) I need to use exactly 1/100th of the pack. I was planning to use some precision scales I have ordered to help here, but the website has a book with some advice which says to halve it and halve it again until you have the relevant number of packs - which sounds like it might be easier than fiddling about with the scales trying to measure out 1/100th of 6.5g one hundred times.

Now comes the bit which has me stumped. The book says this

Divide up the culture into half, then quarters, etc. etc. until you have a bundle of tin-foil wrapped cultures. Fold them up and quickly put them in an air-tight container in the fridge or freezer (depend- ing on the culture). Note: If one culture is good for 100 gallons, you won’t get 100 packets for 100 separate gallons. That’s because at volume the growth of the bacteria in the milk is exponential, literally feeding itself at the vat level. Aim for about two thirds of that.

Can anyone help me understand what that means? So I can't actually expect to get 100 'doses' from my original volume? And if not, what does it mean about aiming for 'two thirds of that'?Does it mean 1/100th of the original volume would only be sufficient for 2/3rds of a litre? If so, it still seems like I would get a decent number of doses from my original dose.

If anyone could help me understand, that would be grand. Or just general advice on how to split the original dose as accurately and effectively as possible.

Thanks as always

[cats]

As they say you will have to split the culture in two, then each in two again and so on.
You will reach about 2/3 of 100 packets = 66. Means that you'll need to split the content of the package in 66 equal parts.
This is if you split for 4 liters at a time.

Many recipes here call for 1/16, or 1/8 teaspoon of cultures each time, or a pinch...
That's what I use, but I might put too much at start as they will multiply anyway.
So I pour the culture in my measuring spoon and I spread over the milk.

Even with a low level of starter culture, they will multiply in the milk.
1 will split in two, then 2 in 4 and so on, so they rapidly grow.
The more you start with, the faster the ripening should be, but due to the cost and to better control the acidification, you use just a small amount.

If you decide to split your 25DCU in pre-measured doses, I think it would be better to work in a sanitized environment and to light a burner in the area you will be working in order to kill the nasties around.
When I work with yeast for beer this is what I do to prevent contamination by other yeast or bacteria.
Well, I might be wrong for cheese culture as I'm not into biology at all, but I prefer to be on a safe side

[tobyw]

Thank you cats. I'm thinking maybe to avoid having to make 66 packets to start with, I could leave one half of each split as I go, so I would end up with 1/2, 1/4, 1/8, 1/16, 1/32 in the freezer and 1/64th to use for my first batch - only needing to make 6 splits to start. And then splitting the smallest remaining pack each time i need to make a batch. I can't decide if that's clever or flawed logic.... who would have thought making cheese required so much maths?

[cats]

You're more clever than I am.
I would have splitted the whole pack in 66 but would have failed because it's not a power of 2   That's my autistic part.

I read in a book that as the content is not by weight but by units ( DCU ) you can weight the packet full, then empty and note them down.
And for that batch of culture, you can use a precision scale to weight your needed culture each time.
 
I saw some that use plastic jars with screw lid to hold the cultures, and I think I will also go hunting for some as storing already opened packets in a zipper seal bag in the freezer is not the most convenient.

Well, let us know how your experiment turns out

[Andrew Marshallsay]

Like a lot of home cheesemakers, I use the mini measuring spoons and find them quite satisfactory and easy to use. There are a couple of things which I do which might be worth thinking about if you decided to go that way.
1. It's worth checking mini spoons as they are not accurate but once checked you can allow for that.
2. I always use the dosage recommended by the retailer of the culture rather than that quoted in recipes as you don't know the source of the culture used in writing the recipe.
I did note that the site which you gave the link to did not give quantities for small recipes but I am sure that a quick search would turn up small scale dosages for Danisco MM100.

[awakephd]

I'm with Andrew - to me it is not worth the effort to try to split the pack up; much easier just to use mini-measuring spoons. As you gain experience with a package of culture, you can adjust as needed (e.g., if a batch acidifies too quickly or too slowly).

[tobyw]

Thanks all - I invested in some scales, and some miniature measuring spoons. I quickly found that one of the smallest measures equals pretty much the unit of starter I calculate to be required for 4 litres of milk, and in turn, that scales up to about half of the recipe I have for 8l.

That makes scaling the starter culture easy from now on. B.lines and p.candidum will not be quite so neat, because they weigh much less, and even the smallest spoon is way more than called for according to my calculations. Advice seems to vary between the need for absolute accuracy (often in books) and doing it by eye... i've had success and failure both ways.