Hello, I used to make my own steamed bread and play with bread at home, and it turns out that there are two main reasons:

1: If it is fresh yeast, it is particularly easy to expire, so the noodles are sour.

More importantly, the yeast must be melted with warm water, and then mixed with this yeast warm water, which is not only uniform, but also can activate the yeast. If it is cold water or boiled water, it will fail. As you said, I also appeared, and the yeast expired that time.

3. How much yeast is put affects the fermentation time of flour, which has little effect, but it is not easy to put too much flour at 250G, and the product tastes too bad and smells uncomfortable.

4. It is also very important that when fermenting, one noodle should be placed in a warm place. I usually put it in a microwave box with a lid, and then put it in the oven for fermentation at 50 degrees. In that case, the time will be shortened a lot.

The reasons I said should include all the key points of fermentation, which I summed up myself. What is said online is part of it, and what is important is practice. I hope it is useful to you, and I wish you success ~