pre-boil wort contamination?

[maltman]

This weekend I made a hefe-weizen over a 2-day period. Conducted the mash and lautered on Saturday. Collected the runnings into my boil kettle and set it aside for boiling on Sunday. I have done this before and it has worked out for me in the past when time is short.
When I came home on Sunday, I immediately checked on the unboiled wort and noticed what appeared to be a krausen on the surface of the wort. I thought it was strange but was in a rush to start the boil so I didn't think too much of it. That is until it started coming up to temp. Once I began heating it, I noticed a sharp, sour smell coming from the kettle. I continued with the boil anyway. I was certain that the wort was contaminated but when I tasted it, it didn't seem sour at all. I pitched the yeast anyway out of curiosity more than anything else.
My question is can wort become infected within 24 hours to the point where there is a krausen-like foam present on the surface? It seemed to me that whatever was going on in the unboiled wort was very active.
The unboiled wort never got below 100 deg F and was covered the whole time I was away.
Anyone have any experience with this?

Your help is greatly appreciated.

 

[Yooper]

Yes, it can become infected that quickly. That's how "sour mashes" are done. Warm wort is full of lactobacillus and will quickly spoil. It's like leaving milk out on the counter overnight.

90-140 degrees is a real sweet spot, so that would make the wort especially vulnerable. As an example, food is supposed to be left out only for 2 hours if over fridge temps and under 140 degrees.

If you want to mash one day and boil the next, I'd suggest bringing the wort to a boil briefly before sticking it in the fridge. That would kill the lactobacillus and other bugs and keep it ready to go for the next day.

Or do an overnight mash, and then boil in the morning.

 

[ron,ar]

How did you keep it at 100F+ overnight and why?
"The unboiled wort never got below 100 deg F and was covered the whole time I was away. "

 

[maltman]

Thanks Yooper. In the past, I haven't had this problem when I've done this, but I'm thinking now that may be because I usually only let about 12-14 hours pass between sparging and boiling. This time it was more like 26 hours!
So, you mentioned lactobacillus. That would fit with the sharp sour smell I suppose. If that's the case, can I call this a berliner weisse instead of a hefe-weizen? (I'm only half joking)

 

[maltman]

How did you keep it at 100F+ overnight and why?
"The unboiled wort never got below 100 deg F and was covered the whole time I was away. "

Hi ron'ar. not sure why I wanted to keep the temp up, that's just what I've done in the past and everything turned out fine. Just brought the kettle inside, didn't insulate the kettle or anything.