Lower of than expected before trub

Welcome to the BA site, Georgeobie, and to the homebrewing forum. A few extra things we'll need to know to figure out what happened:

Was this an extract brew?
Was it a partial boil with top-off water added?
What temp was the wort when you took the 1.04 reading?
Was the 1.07 reading taken immediately after you put the trub into the fermenter and a lot of it was in suspension?

 

^^^This. You can think of specific gravity as how “heavy” your liquid is. The mashing process takes plain water and adds dissolved sugars into it. So your wort will be “heavier” than just plain water. The more quantity of sugars that are dissolved, the “heavier” the wort, and the higher the OG reading. Alcohol “weighs” less than water. So after fermentation those sugars have been converted to alcohol, and your final beer is “lighter,” and your FG is lower.

So, long story short, when you added the trub you did indeed make the wort “heavier.” Just not necessarily with fermentable sugars.

That said, I also predict no noticeable negative effects. RDWHAHB

Carpe cerevisi!

 

This is true, but there are also as many molecules of CO2 produced as there are alcohol, so a not insignificant amount of the sugar's weight becomes CO2 and gasses off.

In fact, as I think about it, more of the gravity change is due to "lost to CO2" mass than to the difference in density between alcohol and water.

 

Okay, the wort temp was where it needed to be to take a gravity reading, and the fact that this was mostly an extract brew says that your mash efficiency was not a cause since you did not have a mash process. Extract brewing is very predictable for its original gravity reading as long as the correct amount of liquid is present. So it is either the trub in suspension, or when you added your top-off water it was not well mixed and your gravity sample had too much of the top-off water in it, thus a low reading. Either way, I think your beer will be fine.

 

It has been my understanding that floating solids (like stirred up trub) do not affect specific gravity readings. Only dissolved goodies can do that. (Or so I thought...)

https://mashmadeeasy.yolasite.com/

 

Basically true. But floating solids can act as buoys to help float a hydrometer. In practice, with a normal wort, the effect is negligible.

 

That's like saying that mud isn't thick, and I don't buy that.

 

But density is not thickness.

 

I agree with @Mothergoose03: I'm strongly suspect your original reading was so low largely because the wort and added water were not mixed well. RDWHAHB. Cheers!

 

Just listened to a Brulosophy podcast about kettle trub in the fermenter. Marshall had clean wort in one fermenter (avoiding racking trub at all costs) and another where he literally did what you did and put spoonfuls of trub into the fermenter. He didn't notice any flavor differences between the two, but the one with trub in it was unexpectedly much clearer and fermented further (lower FG) with the yeast performing a noticeably more aggressive fermentation. He did this same experiment multiple times with the same results. Here's the link:

http://brulosophy.com/2015/03/22/the-impact-of-kettle-trub-part-2-exbeeriment-results/

 

I make absolutely no effort to separate trub from wort, and I find that the yeast gobble it right up as if it was prime yeast food. Can't say that I've noticed any difference since I got tired of trying to separate out the trub, sans that I fill more bottles with beer now than I did before from the same size batches. By the end of ferment the trub is nowhere to be found, and only yeast sediment remains.

https://mashmadeeasy.yolasite.com

 

Ever since noticing the advice to not aerate wort when using Lallemand dry yeasts (as seen in their data) I have also discontinued that practice, with no noticeable difference in the results.

https://mashmadeeasy.yolasite.com