Portable yogurt maker with precise thermo regulation (by 1 step per °)

[Free_WiFi]

I need some kind of portable thermoregulated cup to make yogurt.
For now i didn't spot something of good,by good i mean "precise digital controlled heat cup ... "
By the way i do spot this cup here some time ago and i'm wondering if this toy could be actually very precise regarding the thermal regulation and viewing the precise thermal output.
Deerma DEM-DR035
https://www.banggood.com/it/Deerma-DEM-DR035-300W-350ml-Portable-Electric-Kettle-Cup-from-Water-Constant-Temperature-304-Stainless-Steel-Liner-p-1593203.html?utm_source=googleshopping&utm_medium=cpc_organic&gmcCountry=IT&utm_content=minha&utm_campaign=minha-it-it-pc&currency=EUR&cur_warehouse=CN&createTmp=1&utm_source=googleshopping&utm_medium=cpc_bgs&utm_content=xibei&utm_campaign=xibei-ssc-it-all-0508&ad_id=347257067887&gclid=CjwKCAiAuoqABhAsEiwAdSkVVOKq8eRu1sc5WaC2voZnRMEX-YyiK7qND9Y4v3ekeDEqw5QSabS2phoCCOUQAvD_BwE

[pardo-bsso]

Is that really needed?

Here after an initial warmup in a cheap electric oven set to minimum we just let the milk overnight inside a big and old (belonged to my grandmother) glass thermos and that works fine.

[coppercone2]

I think it is warranted if you want to take yogurt into your diet in a serious amount rather then as a treat/snack. I know some people that literary eat yogurt every single day. I would probobly try freezing vacuum sealed bags of milk and cook it with a sous vide cooker.

[GlennSprigg]

When I worked as a Tech in a large Dairy Plant years ago, I remember them having to accurately control
the temperature to within .5 deg C. They said that this is to maintain the required temperature for the
'desired' and introduced bacteria to thrive, and to inhibit undesired ones!  Evidently, it can be that critical,
otherwise you will get a sour taste, although some people might not object to that.

[Free_WiFi]

I need an accurate thermal cup to make my yogurt,because the bacteria which i bought require this kind of environment.
I'm spending money on these medicine,so yes !!!
for me is very critical to don't fry my bacterias,i need to grow them in ideal environment which is absolutely required.
In my specific case i need an cup which can precisely stand 38C° +1/-1 (39C° or 40C° would optimal)