I used to always boil my starters for the perfunctory 10 minutes. Lately, as I see the boil rolling, I’m taking it off after 5 minutes, mainly because I feel it’s done and there is no reason to waste another 5 minutes on it.
So, what’s the issue I could be running in to? I have not seen any issue with the starter itself.
Dave
The only reason I know for the boiling is sanitation.
If your starters are turning out fine and the beer you ferment with the yeast is turning out fine, then a 5 min boil is working for you.
I boil for 10 min just because I do and its only another 5 min.
This will likely ruffle some feathers but, for sanitation it is only necessary to bring it to a boil.
I agree with zimaclone, and would add anything over 145* will make it safe. So if you think about the amount of time it takes to get it from that to boiling and then back down below you should be good to go.
i think you do want to create some hot break with the wort - bringing it up to 145 won’t do that I don’t think.
I do 10 min cause that’s what I’ve always done - no special reason other than it works. YMMV.
I agree with that too. I’m not an expert on extract or anything but I still would think you want a hot break, no?
Dave
LOL, I just clicked through. I always did 10 mins too, but after hot break I’m like: “why am I standing here?” If I make 30 starters a year and save 5 minutes on each, then I get 2.5 hours of my life back…
Dave
Why wait for the hot break if you’re not going to separate the trub anyway?
Hmmm. Good question. I thought it made it more fermentable.
Well, 145F is pasteurization temp, but it must be held for 30 minutes to be effective at that low temp. And don’t confuse pasteurization with sanitized. Pasteurization only kills most organisms, not all. That is why ultra-pasteurized milk can be stored longer than pasteurized milk. Higher temp = more dead organisms.
I would agree though that once it boils for a minute or two, you can take it off - even let it sit and cool slowly if you want. The wort is still hot with the burner off. I do like to boil for a while so the steam will also sanitize my flask and foam stopper.
This is why I boil for ~5 minutes for my starters. You could also sanitize them with starsan or something.
so tom - you of all people would know - we don’t need to wait for hot break?
I bring to a boil in the flask and set the timer for 10 minutes while I do assorted other tasks then chill and pitch. Nearly Effortless. 
Ron,
Agreed. But I’m wondering if it needs to be 10 minutes or can you get 5 minutes closer to effortless?
Dave
And what is the difference?
Just my $.02 worth but for several years now I just bring the starter up to a full boil, turn off the gas and let it sit for a couple of minutes. Then I cool it down in the sink using tap water as the water bath. I have had no issues with this method.
I have always assumed that the time spent to get it boiling and cooled down was enough to sanitize the pan/lid and liquid.
Paul
From what I understand, the fermentation process would make it safe in this scenario. Harmful bacteria, such as salmonella, wouldn’t survive it. But it would survive 145 degrees in a pot/flask and so I would guess some organisms that can spoil your beer that can survive the fermentation process might also. I believe this is why boiling wort/starters is recommended, basically no bacteria/virus/fungus is going to survive an hour of a vigirous boil.
I like Tom’s method. This says one minute is fine. #7.
I’ve always boiled 1-2 minutes. Good to see.
I used to do the ten minute boil because that’s what most/all homebrewing literature said you had to do. Now I am in the just-a-few-minutes camp. Once I see boil I let it go for a few minutes but there’s really no precision to it.
I guess it’s worth pointing out that Yeast makes the point that somewhere in homebrewing ideology came the idea that a ten minute boil equals sterilization but that is not the case because boiling water is not hot enough to sterilize. Actually I’m not sure why it’s worth pointing that out…