“酵母粉”常见的英文表达是 yeast powder 或 baking yeast powder(更强调用于烘焙的酵母粉)。
Add some yeast powder to the flour to make the dough rise.
(在面粉中加入一些酵母粉,让面团发酵。)
I bought a packet of baking yeast powder for my bread-making.
(我买了一包烘焙用的酵母粉来做面包。)
Active dry yeast(活性干酵母,常见于烘焙)
Instant yeast(即发干酵母,发酵速度更快)
根据具体语境选择即可,但 yeast powder 是最通用的说法。