Yeast: Mangrove Jack's M44 - US West Coast

Yesterday I brewed an IPA recipe but had a couple of issues when it came to pitching the yeast.

The first was that I could not get the wort temperature below 23.9ºC (75F).

The second was that I cooled the re-hydrated yeast too far, to 19.1ºC (66F), as I expected to get the wort down to 21ºC-ish (70F). When I could not get the wort temperature any lower, after using the chiller for almost an hour, I decided to warm the yeast up slightly to 21-22ºC (70-72F) so I could pitch at a slightly higher than normal temperature. Mistakenly I warmed the yeast far too quick by placing the re-hydrated container of yeast in a saucepan of water on the hob. In the space of 10-15 seconds it warmed from 19.1ºC (66F) to 22.3ºC (72F).

At pitching the temps were:
Wort - 23.7ºC (75F)
Yeast - 22.3ºC (72F)

18 hours later the bucket appears to be doing nothing. The airlock is inactive and the lid is not even bulging slightly to indicate a build up of pressure. I have ordered another sachet of M44 yeast which will hopefully arrive tomorrow.


  1. Is the higher than optimum pitching temperature likely to delay the start of the primary fermentation?
  2. Will the temperature shock of quickly warming the yeast by 3.2ºC (5F) in 10-15 seconds have likely damaged the yeast?
  3. How long should I wait before determining whether I should pitch the additional yeast?
  4. If I pitch another sachet of yeast will there be any effects on the end flavour?
  • 1
    More often than not the brews I've done in buckets don't bubble. It's either a slightly fractured seal on the lid, or a bad seal on the grommet where the airlock goes in. Aug 2, 2018 at 13:36
  • @DavidLiamClayton True, I have found the buckets to be a bit rubbish with airlock activity. However, the lids have always bulged which is why I'm worried with this one.
    – joe92
    Aug 2, 2018 at 14:03
  • I'd leave it another 12 hours and see if any foam forms on top, or any other visual clues, before repitching Aug 2, 2018 at 14:07
  • What happened with your brew? Any movement? Aug 4, 2018 at 14:04
  • @DavidLiamClayton There is. I've added an answer below with an update to the situation. Your guess at a fractured seal was dead on the money for the lack of airlock activity!
    – joe92
    Aug 7, 2018 at 15:43

3 Answers 3


From my perspective, you're taking this temperature thing way too seriously. I mean, it is important to respect temperatures when brewing, (especially for mashing) but in the fermentation process, you should not see any significant differences within the range of 2-3°C.

  1. your yeast performs best in the range 18-23 degrees, a 0.9°C difference should not change anything (are you even sure that your thermometer handles that kind of precision ?)

  2. 3.2°C is not really a shock for your yeast, it is not that much

  3. Wait another day or two and test your gravity, no bubbling does not mean no fermentation.

  4. It depends on the volume of wort, for a 20L wort, 2 packages of dry yeast is not too much.

My guess is that your problem comes from somewhere else:

  • Are you sure your yeast was not expired ?

  • Did you make a starter to pitch the correct amount ?

  • Did you aerate your wort correctly ?

  • Maybe your wort is fermenting? check your SG after few days

  • I probably am taking it slightly too seriously but I had a failed fermentation a few months ago so I'm a bit sensitive to yeast issues now lol. To answer your Q's: Yeast was brand new. I did not make a starter but re-hydrated according to instructions. I did aerate. It may be fermenting with a leaky seal somewhere, I shall check the SG as you suggest.
    – joe92
    Aug 2, 2018 at 14:01

If the water in the sauce pan was hotter than 80°F. I'm thinking it was since it only took a few seconds for a few° rise.

What mostlikley happened is most of the yeast in closest contact to the pan water was instantly killed. The other yeast also would have experienced a rapid expansion damaging the cell walls.

Repitch it. This time just put your yeast next to your fermentor until they both have the same temp.


An update to my original question in case anyone stumbles across this in the future.

Around 24-36 hours after asking this question the primary fermentation began - indicated by a krausen which formed at the top. This is the slowest start to a fermentation I have had and I can only assume is down to conditions described in the OP damaging the yeast somewhat.

A further 24 hours after that the new yeast arrived. Given that the primary fermentation had begun I opted not to pitch the additional yeast.

However, there was still no build up of pressure or any airlock activity. After a much closer inspection just now - 5 days after pitching - I noticed the seal where my probe thermometer breaches the lid has split slightly with a 1mm crack on either side of the probe. I could see straight through to the wort below. I have hastily applied silicone around the gap to create a seal and have placed my other lid in sterilization fluid, and will switch them around shortly just in case the drying silicone can cause any issues.

From here all I can do is hope that the beer hasn't been contaminated and carry on as before.

To the next brew...

For the issues of cooling in hot weather I am going to look into the options of a heat exchanger / plate chiller.

  • Out of interest what is your ambient temperature, how are you currently chilling your wort, and what is your batch size? I'm in the (unseasonably hot) UK, and don't have any problems cooling 10L of wort from boil to under 20c in 15 mins using a crude home made immersion chiller made of 10M of 10mm copper pipe and some jubilee clips. I don't have any way to control fermentation temp yet so I just pick a style that's OK with the ambient temperature. Aug 7, 2018 at 16:39
  • Also in the UK (Leeds). Ambient temperature while brewing was around 21C. However, using an immersion chiller with a double copper coil I couldn't drop the temperature any lower (25L of wort) than 24C. Water temp may have been an issue with higher than normal ground temperature warming the pipes. During winter or the usual summers we get it usually takes 20-25 minutes to cool the wort to below 20. This one came as a shock. First time brewing in such temps!
    – joe92
    Aug 8, 2018 at 16:34
  • @DavidLiamClayton For controlling fermentation temp I use a brewbelt with a temperature probe to turn it on/off when the temp drops too low. Currently no means to cool the fermentation if it gets too hot.
    – joe92
    Aug 8, 2018 at 16:37
  • well I live in Kent now but grew up in Ripon, and one quality I'd never have ascribed to that part of the world is "too hot". Things have cooled down a bit here now. I brewed a wit a month ago and fermentation temp was up in the high 20s, and that turned out decent. I'm going to get a sneaky pale ale in now we're back at 20 (mashing now) and hopefully it'll heat up some time so I can get a weizen in before the end of summer. Aug 9, 2018 at 19:31
  • @DavidLiamClayton I definitely would not describe this area as too hot either! This year has been an absolute shock weather wise (pleasant shock). Just done another brew today (Black IPA) and it took 40 minutes to get the wort temp down. Thankfully I could get it down this time. The difference in temperature between last week and this week... If we get those temperatures again I'll have to try a more seasonable beer too!
    – joe92
    Aug 10, 2018 at 15:49

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