My newly bottled beer was in <40 degree weather for 6 hours; is it ruined?

Question

I went to the store where I'd taken a beer brewing class, bottled my beer, noted her instructions about keeping it at 70 degrees in my house, and then merrily went on my way for another five hours running errands and attending a meeting. There my beer sat in my car, and the outside temp was about 38. Inside the car was warmer, of course, but the beer still got cold.

It was only on my way home that I realized I hadn't even thought about the temp of the beer.

Is it ruined? Thankfully, it's only a one-gallon batch, but I struggle to believe that if the bottles of beer are too cold that the carbonation yeast will die; when I bake bread, it's only the high heat of the oven that kills the yeast, and lots of bread recipes explain how to let your bread raise in the refrigerator over night or longer. In fact, I keep my bread yeast in the freezer for years. Is beer yeast so different? Won't the cold temperatures yesterday simply slow it down, but not kill it?

So many questions; thanks!

Answer 1

You are right. Cold temperatures only slow down the yeast, not completely kill them. As long as the beer is kept at the correct temperature for the rest of the time, it should turn out fine.

Answer 2

Cold temperatures don't hurt or kill the yeast, but only slow them down. In fact at the end of fermentation of my last batch, I had my beer down to 29 F in the garage for about a week, and it's still carbonated just fine in the bottles. So it's not a concern at all. Bottle conditioning works best anyplace from about 50-65 F, or so-called "cellar temperature" like a typical basement. Most primary and secondary fermentations are best in about that range as well. Beer yeast is happiest there.

Enjoy.