Tell if a culture is still good?

[Thewitt]

I have stumbled on a local supplier of Mesophilic DVS culture, however his supply is just sitting on the shelf and is at least a year old. It is marked as "shelf stable" however it's not been stored in the freezer.

The brand is Mad Millie and it's packaged in the UK, sold in the US.

How can I tell if it's any good?  He has a small case of this and wants to know if he should trash it or not.

I don't know how I can tell, but I thought perhaps measuring PH would be one way since this is an acidification stage.

TIA

[RayJ]

Put some in a cup of warm milk and incubate it at room temp. It should set up into yoghurt like consistency in a few hrs. Length of time to set would depend on how viable it is.

[Thewitt]

I put 1/64 tsp in 1 cup of 2% milk (no whole milk here today) and let it sit at 72 degrees overnight.  There is some coagulation, but I would not call it "yogurt-like" at all.  I'm going to let it sit for a few more hours, but without comparing this to a fresh culture I'm not sure how this would work.

[RayJ]

I use direct set meso for cream cheese. I add it and incubate overnight. In the morning I have light yogurt consistency and a buttermilk like flavor. You can use pH if you have a meter but without knowing how fast it should acidify when new all you can tell is that it does acidify just as the incubation test will do.