All grain gravity readings

Was thinking about this the other day. I've noticed that when i take a sample of the boiled wort and cool it down to 20C i get high hydrometer readings. But when i let the same sample sit overnight which allowed the trub to completely fall out of suspension the reading was way down, is it possible that we are kidding ourselves about the gravity/fermentables in our beers.

There is ceratinly a lot of proteins in solution when coming out of the mash which will raise the gravity at that point, after boiling there is lots of insoluble proteins floating about to raise the gravity. After pitching there is lots of yeast in suspension to raise the gravity. Surely the boiled sample left overnight to allow trub to fall out is giving the real gravity from sugars ie quite a lot lower???

I haven't noticed that. When mine sit overnight they tend to stay almost exactly the same. Just my experience though.

seefresh said:

I haven't noticed that. When mine sit overnight they tend to stay almost exactly the same. Just my experience though.

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That surprises me i can't imagine the trub settling out not affecting the gravity to some extent. Do you have quite a lot of sedimented debris at the bottom of the trail jar? Maybe its something im doing thats producing excessive amounts of proteins that are giving me 'falser' gravity readings. Thing is i use british 2row as my base grain which is famed for its low nitrogen/protein levels.

I usually have quite a bit of debris... but honestly, 45 minutes to an hour after I've cooled it down and let it sit, lots of trub has already settled to the bottom.. that's when I take my reading.

Plus the trub is suspended in the wort, not dissolved in the wort so it should not affect SG. A log floating in water does not affect the density (SG is a measure of SG).

Matt

seefresh said:

I usually have quite a bit of debris... but honestly, 45 minutes to an hour after I've cooled it down and let it sit, lots of trub has already settled to the bottom.. that's when I take my reading.

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Yes mine would be very similar at that stage, it seems to be it that it has to be left overnight to produce the big fall (there must still be lots of much smaller proteins in solution which take longer to fall out keeping the gravity high at about 45-60 mins).

clayof2day said:

Plus the trub is suspended in the wort, not dissolved in the wort so it should not affect SG. A log floating in water does not affect the density (SG is a measure of SG).

Matt

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Stick your hydrometer in porridge see what sort of reading you get even with the oats not dissolved in the milk!! Im guessing it would be pretty high .

clayof2day said:

Plus the trub is suspended in the wort, not dissolved in the wort so it should not affect SG. A log floating in water does not affect the density (SG is a measure of SG).

Matt

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Hydrometers are used routinely to measure suspensions (ie the amount of clay in silt etc) so i don't think particles need to be dissolved/solvated to cause an increase in the hydro readings.

Also you could argue that the larger trub clumps (those likely to fall out out much quicker) are less likely to keep the reading high as apposed to the much smaller particles which truly are in suspension and therefore take a long time to come out of it (overnight).