Repitch? 1032 down from 1045 after 72 hours

Doing my 2nd batch (after a break of 20 years :) ). Its a LME / DME porter attempt. It all went according to plan and the OG = 1045. It started fermenting more or less on time, but was sluggish from the start. From what I can see, it only built up a krausen of max 1cm. It was blubbing nicely for a few days but has slowed down now at 72 hours. Just took a sample (have a tap on the fermentation vat, so no disadvantage to doing so) and it's still at 1030. I haven't found any info or rules of thumb indicating where it should be. The yeast was a M42 New World Strong Ale Yeast. Should I repitch, or will I hit 1010 - 1015 with a few weeks of fermentation + bottle conditioning?

Topic porter fermentation homebrew

Category Mac

1
answered at

Firstly, welcome back to the world of home brewing.

Dried yeast during re-hydration are sensitive, but a little gentle shaking will not ruin the viability.

I would leave it for about 7 days from pitching if you are no where near FG by then, then make a small starter and pitch that. Once there is alcohol in the mix you really want to make a starter to ensure your dried yeast are most importantly re-hydrated when re-pitching. As if they are not the alcohol can diffuse quickly through the dehydrated cell walls and damage the cells. This is less critical with liquid yeasts.

There are a few things that may be affecting the fermentation:

  • is the wort sufficiently aerated?
  • was the yeast nice, fresh and well stored?

My guess would be either the yeast had been poorly stored (got too hot) before you purchased it or the wort was not sufficiently aerated.

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