Ending kettle efficiency mismatch between recipe and brew session when brewing with sugar

[jeronim0]

When using simple sugars (e.g. Cane sugar) in your fermentables, there is a mismatch between the ending kettle efficiency defined in your recipe vs. a perfectly executed brew session. The calculated ending kettle efficiency in the brew session will be much lower than what you put into the recipe, even if your OG is spot on.

I believe I found the reason but it's very confusing. The brew feature removes the expected contribution from the raw sugars from the actually measured ending kettle gravity before doing the efficiency calculation. This way, the efficiency figures pre and post boil can be compared.

The recipe ending kettle efficiency just adds all the fermentables together and applies the efficiency figure to that. Hence, if you're recipe contains a lot of cane sugar, you will also need to set a higher ending kettle efficiency than you normally would, to correct for the fact that cane sugar is actually 100% efficient. This is undesirable IMO, because the efficiency should be a characteristic of the setup, not recipe, as much as possible (I know efficiency will drop for very high gravity brews but that's an entirely different story). It also means I cannot correct my recipes with the results from the brew session, because the definitions are different!

An option would be to add a checkbox or third option when choosing between brewhouse efficiency and ending kettle efficiency in the recipe editor? A checkbox like "exclude raw sugars from efficiency"?

 

[BOB357]

Not sure I fully understand what you're saying. At what point are you physically adding the simple sugars?

 

[jeronim0]

During the boil. So in pre boil gravity there is no sugar yet, post boil gravity includes it, but the ending kettle efficiency in brew log corrects for it (this is mentioned as a corner case in the docs). But this correction / corner case is not taken into account in the recipe editor in the ending kettle efficiency field.

 

[Pricelessbrewing]

Just to make sure I follow, you're adding sugars during the boil and getting a inflated kettle efficiency because the efficiency is not subtracting the sugar additions from the equation?

Lets say you're making a SMASH with 12 lbs of 2 row, and a lb of succrose.

If you add the sugar during the boil, you should check the "late additions" checkbox in the fermentables section.
(Side note: Kinda confusing terminology, I would recommend changing that to "boil addition". And likewise changing "Boil gravity to "Pre-boil Gravity").

Let's say you have a measured preboil gravity of 1.046 (mash efficiency of 72%), and OG of 1.066 (brewhouse efficiency of 72%).

|                    | W/ Sugar | W/o Sugar |
|--------------------|----------|-----------|
|  Preboil Gravity   | 1.044    | 1.044     |
|  Kettle Efficiency | 71       | 471       |
| OG                 | 1.057    | 1.066     |
| Brewhouse          | 71       | 71        |

The table above is the result from going through the brew sessions between the two recipes posted above. Note that the potential of sugar for a 5.5 gallon volume is roughly 8.4 SG which is the difference between the 1.057 and the 1.066 OG (rounding differences account for the remaining 0.001 SG).

Doesn't look like I'm getting the same bug. Can you be more specific?

 

[BOB357]

Glad it's not just me

 

[jeronim0]

@Pricelessbrewing thanks for taking the time of making an example.

You are absolutely correct, but my point was about the efficiency field in the RECIPE editor, which I thought did not match the ending kettle efficiency of the brew session (that you posted). However, it turns out I was wrong about this! It was a completely different bug that led me to believe the efficiency was wrong.

I hope the devs read this: I found 2 different bugs:
1. If I set Target to Kettle in my recipe, next time I edit the same recipe it reverts to Fermentor (but the efficiency keeps mentioning "Ending Kettle") (Chrome browser)
2. In the Brew Log Entry for Boil Complete, the "Expected:" value (see screen) is lower than the ending kettle volume mentioned everywhere else. The difference seems to be the contribution "Volume increase from sugar extract", which is erroneously subtracted from the total volume! Late or Early addition does not matter, the difference is always there. In this case I expect 21 liter, but there is 1.2 liter of sugar that is not taken into account.

 

[Pricelessbrewing]

Gotcha. Yeah that looks like a bug in the brew log boil complete event kettle volume, the expected volume should account for the sugars, which will carry through to the efficiency calculation.