I was delighted to be given a couple of litres of full fat milk last weekend, and planned to turn at least half of the bounty into yoghurt (which I’m still eating, day in and day out, on my morning muesli). Sadly, it turned into my first ever yoghurt failure. After culturing, it did not seem to have set up at all. I popped it in the fridge anyway, as it usually thickens up a bit more as it cools down, and went to bed.
By morning, it was still very, very runny. I tasted it, and whilst it did taste like yoghurt, it felt horrible in my mouth – slimy and mucus like. I left it out at room temperature (because I planned to throw it out), and it did thicken up rather over time, but it remained slimy. I’ve never experienced slimy yoghurt before, ever, so I tried to video its behaviour:
The gloopiness isn’t very evident in this video, but I wish it was in touch-o-vision: this stuff was just weird.
I wondered what I’d done wrong: was the milk still too hot when I added the culture? Had my frozen yoghurt culture gone ‘wrong’? Contamination of the containers?? (Pretty darned unlikely) – or could it possibly be the milk itself?
I almost always use organic milk for my yoghurt (and everything else too, for that matter), and I have heard some people say they have difficulty getting good, thick yoghurt from regular milk. But this was something different: Tesco ‘Pure’, which has supposedly been extra-finely filtered so it will stay fresh for longer (up to seven days!). And I’m wondering if it is altered in some other way, too – possibly as a side effect of the filtering, possibly some unclaimed additional process – so that it doesn’t behave like ‘regular’ milk any more. I did notice that the bottle said it was ‘not suitable for home freezing’ – why not??
I am now 100% sure that the problem was not the heat of the milk when I added the culture, nor the culture itself, nor any kind of contamination. I’m sure of this because I made a second batch of yoghurt using my regular milk – and used part of the failed batch as the starter for the new batch. The new batch is 100% fine: good texture, tastes as delicious as ever – so the microbes must be OK. Which, really, only leaves the milk.