I prepared a must for a mead last weekend (recipe below) and after a whole week there has been no fermentation activity. I took a pH reading and it came in at 4.4 - is it likely that the must is simply too acidic for the yeast? I added a teaspoon of CaCO3 and stirred it in - got a small fizz - so will wait and see if that works. Should I re-pitch more yeast?

16L mineral water 4kg cherry blossom honey 4kg peeled, stoned, and pasteurised lychees 11g US-05

I pitched the yeast at 20 degrees, after aerating the cooled must. There's 20L of must in 2x10L fermentors. I added 1tsp of yeast nutrient in each fermentor, along with 1tsp of pectic enzyme and 1tsp of tartaric acid. When fermentation hadn't started after 2 days I prepared a yeast starter with another 11g of US-05 and the starter was fine, so I know the yeast was healthy when I pitched.

Any suggestions gratefully received.

1 Answer 1


Try getting the must pH to greater than 5,aim for around 5.4. Then add some extra yeast.

Only do this if your addition of CaCO3 was not successfully fixed the pH.

  • Great thanks. The CaCO3 did the trick and today the pH was up to 5.2 so I pitched more yeast. The only relatively neutral yeast I had left though was Nottingham Ale yeast. Anyway, within 15 minutes of pitching the starter it's now bubbling away. Hopefully the must didn't get oxidised too much or infected while it was waiting!
    – Snowman
    Jul 6, 2015 at 10:24

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