Water evaporation exposed the meat - is it safe?

I’m making a brisket sous vide. When I went to bed, the meat was fully submerged. When I woke up, some of the water had evaporated and a very small portion of one corner of the meat was above the water level. I brought the water level back up, and the meat has another 10 hours to cook.

Is the meat ruined? Is it necessary, and sufficient, to cut off that corner before serving?

I too am cooking a brisket right now. I would say no, you don’t have a problem. If it was just a small corner, it was probably getting heat by conduction through the meat and convection from the warm air above the water. Assuming it had already come up to your full set temperature (assuming between 145 F and 180 F), the meat had been pasteurized and as long as it stays sealed no pathogens are going to get in.

Good luck with your cook. I’m going with 167 F (75 c) for about 24 hours after 2 hours of cool (~100F) smoke from frozen.

Thanks for the comment Jim. I’m actually doing 137° for 24 hours, for something between medium and medium rare. It should have come up to temp before I left it overnight, as it isn’t that thick just an inch and a half or so. I was wondering about how much conduction I could count on within the meat. It sounds like as long as it stayed above 125 nothing should be growing.

Those are interesting temps and times?  I just received my Precision today.  And having already just thawed a 4 lb brisket from our frozen stock of organic side of beef, decided to look up a recipe for brisket.  I only came across one recipe on the Anova web site.  135 deg F for 48 hours, with liquid (pale ale beer) in the bag (in addition to the spices and onions).  

Q1) Why so low for so long when I see you mentioning higher temps at shorter time? 
Q2  Why liquid i the bag, even if it is alcahol?  

@JayDPiii  The temperature you cook the meat at is all about how you want the finished product to turn out. Do you want a more traditional well done brisket or a medium rare one?  A while back I made these short ribs and only went up to 136° F. http://community.anovaculinary.com/discussion/590/beef-short-ribs#latest
With the tougher cuts of meat you want the collagen to break down to make it tender. I am sure someone has done a time versus temperature study on this. If you look at the ribs I did they show something you can’t do any other way. Medium rare short ribs that were tender and juicy. Going to a higher temperature would shorten the time and your results while delicious would be more like traditional braising.

With tender cuts I normally cook them in the 130° to 135° F range just long enough for them to heat through, I think this keeps the meat as juicy as possible.