[bradginn]

What do you all use for potential extract from Corn Sugar when formulating your recipes?  I've always used Promash and never questioned it. Promash uses 1.046. During Teach a Friend to Homebrew Day a buddy said it's 1.037 (a number from Noonan, iirc).  I was brewing a dubbel, which had a significant amount of corn sugar.  We pulled out several books and did some web searching and didn't find anything close to a consensus.  Next day, I dissolved 1 oz corn sugar in 1 cup water (to simulate 1 lb in 1 gallon) and measured it (w/ refractometer and converted to s.g.) at 1.038.  Due to the small amounts, this little experiment is greatly affected by small measurement errors, so I'm not highly confident in the results.

Thoughts?

[a10t2]

95%, or 1.0439 - and it would have to be 1 oz dissolved in a TOTAL of 8 fl oz for your experiment to work.

[bradginn]

Not sure what you mean by 95%.  95% of the potential extract of sucrose?

The change in volume from adding 1 oz corn sugar to 1 cup water was less than the thickness of the line on my measuring cup, hence my caveat about small measurement errors.

[a10t2]

Right, potential extract is commonly given as a percentage, compared to sucrose. Pale malt, for example, will generally be around 80%.

It's interesting that your results were so different though.

[bradginn]

I see, that makes sense.  I don't recall seeing PE given as a percentage before.

I'm not sure why my result was so low either, other than measurement error.  I need a more accurate method to measure volume.  I measured the sugar to the nearest gram, which is as close as I can get w/ my scale.  I could convert the volume of water to a weight and measure it that way, but w/out knowing the density of the corn sugar I can't calculate the precise weight of water I would need to end up w/ 8 fl oz of solution.

I did a little more web searching and all I found was more different numbers.  hbd.org has a table listing corn sugar at 40 pppg.

[denny]

I've always used 45 ppg and gotten the results I expected.

[Kaiser]

Working with ppg makes the problem of figuring out the extract potential much harder and the easiest way is to take the extract potential of sucrose (47 ppg) and multiply it with the sugar content of corn sugar (95%) like a10t2 said. This gives you 44.6

I found that a lot of the priming and efficiency calculations are much easier when working with Plato. To get the deg Plato for a solution all you need to know is the weight of the water and the weight of the extract (or sugar)

Plato = 100 * m_extract / ( m_extract + m_water)

If you need to know the volume of the resulting solution just determine the specific gravity either by estimation sg = 1 + Plato / 250 or with a more precise approximation. Then you can determine the volume of the wort by dividing its weight ( m_extract + m_water) by the specific gravity which has the unit kg/l

V_wort = sg * m_wort = sg * ( m_extract + m_water)

This is also how you can calculate how much dissolved sugar expands the volume of the solution and you can reverse the calculations to determine home much weight of extract is in a wort of given volume and specific gravity.

In addition to that, the PPG based calculations are actually the result of using the simplified Plato to sg conversion: sg = 1 + Plato / 250. If that wouldn’t be close enough for most of our calculations we wouldn’t be able to use the simple PPG based methods.

Kai

[bradginn]

Thanks, Kaiser.  That Plato formula is what I need to more accurately reproduce my experiment at home, since I can measure weight more accurately than volume.

[a10t2]

extract potential of sucrose (47 ppg)

Where is that number from, Kai? I've never seen anything other than 46.21.

[Kaiser]

Where is that number from, Kai? I've never seen anything other than 46.21.

Yes, you are correct. My own article says 46. I have caculated that a wile back and copied the 47 from other  posts in this thread.

Kai

[Kaiser]

Since I always wanted to do that, I just derived the formula for PPG based on the extract potential in %.

Starting point is the equality between the two efficiency calculations that we know. Weight based and PPG based:

100* (Plato * sg * V_liter)  / (E * m_kg) = 100 * (GP * V_gal) / (ppg * m_lb)

where:

Plato = wort strength in Plato
sg = wort specific gravity
V_liter = wort volume in liter (V_liter = 3.78 * V_gal)
E = extract potential in %
m_kg = grist weight in kg  (m_kg = m_lb * 0.45)
GP = Gravity points (GP = (sg -1) * 1000)
V_gal = wort volume in gal
ppg = extract potential as ppg
m_lb = grist weight in pounds

using the aforementioned substitutions and the simplification that Plato = ( sg – 1 ) * 250 I find:

ppg = E * 0.476 / sg

You notice that the ppg number depends on the specific gravity. If you have sugar (E=100%) the ppg for a resulting wort og 1.040 will be 47.6 / 1.04 = 45.77 whereas for a resulting wort of 1.080 it is 44.07.

At home I would have to take the time to calculate this with a more precise sg to Plato conversion, but the trend will be the same: the gravity point gain you get from sugar or malt also depends on the target gravity itself.

In practical brewing this error likely gets absorbed in the efficiency of your system which is known to change with the gravity of the beer anyway and you already account for that.

Kai