Confused by Nottingham yeast rehydration instructions

Can anyone help me understand the Nottingham yeast rehydration instructions:

• Sprinkle the yeast on the surface of 10 times its weight of clean, sterilized (boiled) water at 30–35°C.
Do not use wort, or distilled or reverse osmosis water, as loss in viability will result. DO NOT STIR. Leave undisturbed for 15 minutes, then stir to suspend the yeast completely, and leave it for 5 more minutes at 30–35°C. Then adjust temperature to that of the wort and inoculate without delay.
• Attemperate in steps at 5-minute intervals of 10°C to the temperature of the wort by mixing aliquots of wort. Do not allow attemperation to be carried out by natural heat loss. This will take too long and could result in loss of viability or vitality.
• Temperature shock, at greater than 10°C, will cause formation of petite mutants leading to long-term or incomplete fermentation and possible formation of undesirable flavours.
• Nottingham British Ale yeast has been conditioned to survive rehydration. The yeast contains an adequate reservoir of carbohydrates and unsaturated fatty acids to achieve active growth. It is unnecessary to aerate wort.

The bit that I'm not sure about is the second part. What are 'aliquots of wort'? I guess it's small amounts taken from the cooling wort, but how much? It sounds like it needs to be pitched within 5 or 10 minutes after the post-stir 5 minuite wait. Timing it this precise would be tricky to get it to coincide with when the wort has chilled to the right pitching temperature. I prefer minimum handling to reduce risk of contamination, so this 'aliquots of wort' business sounds like a risky proposition to me. I'll probably just play it safe and pitch dry as I usually do with Safale yeasts but I'm curious.

Wow that whole second step there, I've never seen that on any of my Notty packs. Too complicated...I do the first step, yep, and I leave it without stirring for as long as I need it - up to 30-45 minutes maybe, depending on how long it takes to cool my wort. I then stir it, let it sit a few minutes maybe, and dump it in. Sometimes I just dump after the long wait, no stir.

The re-hydration I've found does help Nottingham kick in faster, I get some pretty fast starts with it when pitching a new pack like this.

Wonder what an aliquot is....

You are likely only dropping the temperature of the rehydrated yeast by about 10°C and hence could probably do it with one addition of your wort.
You could just measure the temperature of the yeast solution as you add the wort until you reach the temperature you want. As you have mentioned sanitation is the key word.

Psych said:

Wonder what an aliquot is....

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Aliquot ! Wow haven't heard that since the Pharmacy Board exams.

Basically a fancy way of saying a portion or part of the whole.


bosco

boscobeans said:

Aliquot ! Wow haven't heard that since the Pharmacy Board exams.

Basically a fancy way of saying a portion or part of the whole.


bosco

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Hah nice, so one could also say "some" hehe

in cooking terms we call it tampering. what it wants you to do is slowly add small amounts of wort in intervals to bring the temperature of the yeast up to the temp of the wort to avoid shock

When I last rehydrated I searched this forum for the amount. I forget the amount but it is not much. I then just left the cup on the counter with sanitized tin foil covering it. I cooled the wort to about 70 to pitch, then put it in my swamp cooler. I didn't worry too much about the water amount or temperature and my fermentation started within 4 hours.

Just like tempering for cooking. You are trying to adjust the temp in stages. In cooking simply mixing to very disparate ingredients can curdle or cook one of them before it's had a chance to integrate. In this case you are simply trying to get the yeast sort of used to it's new home. It's like placing a baggie of fish in the aquarium before you cut it bag open and let the fish swim freely.

And now I have a new brewing term to bug my wife with!

Time is not an issue once you are adding the small amounts of wort because you are adding resources to keep the yeast going. The problem comes when you rehydrate then let the now active yeast sit around and starve.

I emailed Danstar about these same questions. The answer to the timing question was: “Our technical manager suggests that you don't go longer than 30 minutes after the start of rehydration before pitching the yeast into wort as the yeast needs nutrients. If there is a delay you could actually add more wort to the rehydration water to give the yeast something to eat while you are waiting to pitch it, so long as it isn't too hot.” I avoid having a delay by having the rehydration complete 10 – 15 minutes after the wort is ready for it.

I asked if it is acceptable to cool it in a cold water bath instead of adding some wort to it. The answer: “Regarding cooling, indeed you can use a cool water bath, or you could add a bit of wort to the yeast/rehydration water blend to get it closer to pitching temperature.”

Psych said:

Hah nice, so one could also say "some" hehe

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Yup. Mix 2 ounces of concentrate with 2 ounces of diluent to get 4 ounces total.
Then add 4 ounces of diluent to arrive at 8 ounces, then 8 ounces of diluent...and so on and on it goes. LOL

Tempering, like in cooking is the same thing like Homercidal stated.

bosco

Interesting information. It roughly agrees with the label on, IIRC, the Lalvin 71b packet, which says to wait no more than 45 minutes after hydrating before pitching.

I broke that rule once. It didn't kill all the yeast. They still ate all the sugar in my mead. SO IT'S ALL A LIE!

Er, no, so it's probably not the end of the world if it takes longer, but it's always good to know what the best practices are before you go violate them.

ncbrewer said:

I emailed Danstar about these same questions. The answer to the timing question was: “Our technical manager suggests that you don't go longer than 30 minutes after the start of rehydration before pitching the yeast into wort as the yeast needs nutrients. If there is a delay you could actually add more wort to the rehydration water to give the yeast something to eat while you are waiting to pitch it, so long as it isn't too hot.” I avoid having a delay by having the rehydration complete 10 – 15 minutes after the wort is ready for it.

I asked if it is acceptable to cool it in a cold water bath instead of adding some wort to it. The answer: “Regarding cooling, indeed you can use a cool water bath, or you could add a bit of wort to the yeast/rehydration water blend to get it closer to pitching temperature.”

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Thanks everyone for the explainations. They sure know how to make something more complex than it needs to be. And watch out for those petite mutants!