Is it safe to heat active dry yeast to make a substitute for nutritional yeast?

Question

Nutritional Yeast isn't available at my location so i'm looking for alternatives.

While searching Seasoned Advice i've found this question How can I make nutritional yeast?. But i don't want exactly to grow nutritional yeast. It's too difficult to it and i need something more practical and less risky in terms of sterelization.

So i've came across this page. Basically it says i can use active dry yeast and toast it to make something that tastes like nutritional yeast. In this The Fresh Loaf post this heating the yeast technique is also mentioned.

Well, i did tried it at home and the result was very very tasty! First time i made it i've dropped a little yeast in a cup with water and sugar and it didn't started fermenting, but the second time i've tried it was still alive.

1. There is any way to make sure that all the yeast is uniformly dead?
2. Even if manage to kill all the yeast, let's say, by heating in the oven, is it still safe to eat it? I've read a lot of disquieting stuff on the web about yeast and botulism. (but there might be other factors to consider)
3. (I must use Saccharomyces cerevisiae as the main ingredient because i want something similar in terms of protein content (about 45g on 100g of yeast)

Answer 1

Right, so, there are basically 2 ways of killing micro-organisms: chemistry and heat, and heat can be divided in moist heat and dry heat. Dry heat is more straightforward, although generally less efficient in killing things than moist heat (and also not appropriate for lots of surfaces, etc.)

Now onwards to your questions:

1 - Sterilization efficiency depends mainly on a few parameters: contact surface (meaning that the more your surface is in contact with the heat, the better), contact time x temperature (so, if you use lower temperatures, you need more time to kill everything). For practical applications you should a) spread your yeast on the largest surface available with the thinnest layer possible to maximize your contact surface and b) be patient and let it toast well - I don't know the temperature, but it should stay for at least 5 minutes in order to have everything killed

2 - Botulism is caused by Chlostridium botulinum which is a bacteria that sprouts in low-oxygen moist environments and when it sprouts, it releases the toxin that causes botulism. Dry active yeast is a fungus called Saccharomyces cerevisae and they need medium to high oxygen environment to grow and be viable, and they usually out-compete bacteria, to the point of being used to treat bacterial diarrhea so it is very very improbable that your package of active dry yeast will be contaminated with Chlostridium spp and that it will be able to sprout while you handle it. Bottomline: it is safe.

3 - Yes. And also it is the most viable option if you want to just buy it and kill it later (both for price and reliability).