Couple Questions About boil and Gravity?

[Djanvk]

What might cause my original gravity to be .010 points lower than a predicted gravity?

Also when you do a boil is there a temp I would aim to hit or am I looking for a actual rolling/bubbling boil?

My last brew was .010 points lower than it was supposed to be with the OG and I did my boil with temps over 175F but never really achieved a actual "Boil".

Thanks for the help.

 

[kevmoron]

If you are doing extract, the lower expected gravity could result if you end up with greater than the expected volume. Is this the case? The same could be true if doing all grain, or you could have poor efficiency from your sparge.

175F is nowhere near a boil. Your boil will be 212F unless you are at high elevation. There is no other temp to go for. A strong boil is important to drive off unwanted malt volatiles, such as s-methyl methionine (SMM), which leads to formation of dimethyl sulfide (DMS).

 

[Djanvk]

So will my beer be messed up now?

 

[kevmoron]

Only one way to find out. In the future, just make sure you have a good solid boil. besides boiling off unwanted volatiles (for which a rolling boil is necessary), actually hitting 212 F is necessary for several other things:

- extracting and isomerizing hop alpha acids; without a good boil, your hop utilization will suffer
- sterilizing the wort (though you probably killed most everything off)
- stopping enzymatic activity (probably fine here)
- precipitating proteins and polyphenols (hot break - your beer might be really really hazy)
- boiling down to the correct volume for fermentation and concentrating the wort (it sounds like this was the reason your gravity came out low - normally you lose a gallon or so to evaporation and the post-boil gravity is higher)

So yeah, your beer might come out a little weird, or it might not. Don't dump it, though. See it through to the end; it could come out fine.