To make a bacterial culture you will need an incubator – fermenter. There are a number of these which you can buy, such as –
Davis & Waddell:
With this fermenter you can set the temperature & the time.
The containers can be supported by 3 coins.
You can make your own using a Chilly Bin (Eski):
Lamp Fermenter:
You will need a chilly bin.
Bolt a lamp holder (screw thread) onto a plastic lid (marmite jar). Screw the lid onto a block of wood. Drill power cable hole into the side of the lid & near the corner of the chilly bin, just above the bottom.
A 12W CFL bulb may do.
Incubator:
You will need a chilly bin, plus – heating pad, controller, plastic box, power cable, bolts.
Racks are useful – I made mine from aluminium. You could make a wooden frame. The plastic containers need to be above the bottom of the bin, so hot air can circulate.
Heat Distribution:
Without a container support in the D & W Fermenter, bottom heating will distribute heat by convection and the temperature variation would be minimal. When the milk sets, convection stops, & conduction through the bottom occurs, so the bottom of the milk will be hotter than the top.
If the container is supported so that there is a gap underneath, hot air will circullate & the temperature will be more even.
Bacteria to Culture:
Lactobacillus reuteri – DSM 17938 and ATCC PTA 6475 strains)
Lactobacillus gasseri – BNR17 strain
Bacillus coagulans – GBI30,6086 strain
Lactobacillus casei – Shirota strain
Kefir
Capsules containing the first 3 bacteria can be bought from iHerb.
The Shirota bacteria is found in Yakult bought from your supermarket.
Kefir – you wil find this at your supermarket – preferably not containing yeast. In New Zealand, “The Collective” brand is ideal.
Temperatures Needed:
If you search on the internet, you will find some variation. I have taken into account what Dr. Davis suggests & research papers that I have seen.
L. reuteri: 38 C
L. gasserei: 43 C
B. coagulans: 48 C
Shirota: 38 C
“The Collective” Kefir: 2 batches – 30 C & 38 C
I found temperatures for all 13 bacteria & 2 different temperature batches covers all 13.
Note: You can keep on reculturing the first 4 bacteria. However, if there is a mixture of bacteria, some may dominate with reculturing. After, say, the 2nd batch, you could make Kefir ice cubes to be used as future starters.