Asked myself the same question last year when going to Gran Canaria. The interesting news: I've never seen such an abundance of soy yoghurt ANYWHERE. They also had all kinds of soy products even in the smallest supermarkets. Should be the same on Tenerife I'd guess. The seitan I found at a small organic store was the best I ever had. If you're self-catering there's nothing to worry about. Only going to restaurants was not exactly great in my case. Good luck!