Beersmith for Extract Brewing. Accurate or not?

[TanMan15]

So, I've just started using Beersmith, but I've only used it for some extract brews. So far, I've done 2 recipes and both seem a fair amount off from what Beersmith estimates. First, the FG of a Coconut Cream Porter either seems off, or I vastly underpitched my yeast. Here's the recipe...

Fermentable:
9 lbs of Amber Malt Extract
1 lb Lactose

Steeping Grains:
4 oz Black Patent Malt
4 oz Chocolate Malt
8 oz Crystal Malt - 40L
8 oz Roasted Barley
8 oz Special B Malt

Hops:
1 oz Galena

Secondary:
1.25 lbs of toasted coconut

Yeast: Wyeast 1968

I only have a 5 gallon brewpot, so it's about a 3.5 gallon boil for a 5 gallon batch size.

Beersmith predicts a FG of 1.017 while Brewer's Friend predicts an FG of 1.28. Three weeks into primary fermentation, I've got a gravity of 1.032. That's not too far off from Brewer's Friend, but why the discrepancy from Beersmith? My big concern is that I underpitched my yeast, so I'm trying to determine if I did, or if my FG is in range of appropriate.

I also have a Kolsch that I have fermenting, and without getting into the recipe, Beersmith predicts a OG of 1.48 but the actual OG came out to 1.60. I'm sure it's an input error, but if so, I'm trying to find the variable that caused the error, but this one doesn't bother me so much, because who doesn't enjoy a little extra alcohol content?

 

[kh54s10]

FG estimates are just that - estimates. Many factors contribute to either reaching, exceeding or falling short of the predicted FG. An underpitch will contribute to missing high. The BS prediction seems low and to me the Brewer's Friend seems high. But then again they are only predictions.

At 3 weeks you should have been at FG for over 2 weeks. 1.032 seems high. I would swirl the wort a little, allow the temperature to rise to about 70 degrees and see if fermentation continues - about another week.

On your Kolsch, I suspect that your OG was closer to the BS prediction. That your wort was somewhat stratified and you sampled a stronger area. Unless you made a serious over addition of some fermentable you shouldn't be able to be that far high.

 

[TanMan15]

FG estimates are just that - estimates. Many factors contribute to either reaching, exceeding or falling short of the predicted FG. An underpitch will contribute to missing high. The BS prediction seems low and to me the Brewer's Friend seems high. But then again they are only predictions.

At 3 weeks you should have been at FG for over 2 weeks. 1.032 seems high. I would swirl the wort a little, allow the temperature to rise to about 70 degrees and see if fermentation continues - about another week.

On your Kolsch, I suspect that your OG was closer to the BS prediction. That your wort was somewhat stratified and you sampled a stronger area. Unless you made a serious over addition of some fermentable you shouldn't be able to be that far high.

That makes sense. Thanks for the clarification. I'm fairly certain that I drastically underpitched the yeast and that it stalled out. The next question, is would it be worth creating another starter and pitching it, or should I just accept that it's going to be a very sweet beer?

 

[TanMan15]

I took another gravity reading today and it's stuck at 1.032. I also took a taste and man, is it sweet! Do you think I could get that gravity down any more with another yeast starter or is that even worth it? At about 4.5%, already, would the new yeast even be able to live? I'm leaning towards racking it into the secondary onto the toasted coconut, like I intended, and calling it a desert beer, because this mother trucker is going to be sugary.

 

[kh54s10]

What yeast are you using? Check it's alcohol tolerance. Most go close to 10% I would try to get it down a little because you say it is really sweet. I would try the swirling and raising the temperature first but if that doesn't work I would pitch more yeast. Maybe a neutral, strong attenuating, alcohol tolerant strain. But the lactose that you used will not ferment out.

 

[stodds]

Are you using a refractometer for your FG readings? If so, you need to run it through a calculator, as alcohol affects the reading (it will read high). If you are using a hydrometer, you may forget I said anything.

Cheers!

----edit------

Never mind. ~1.080 OG. No way you are down to 1.009 on ~70% attenuation yeast.

 

[chickypad]

In Beersmith make sure the Not Fermentable box is checked for lactose (shows in the pop up window when you double click on the grain in your recipe). I think the default was that it is not checked, as this option was added in a later update. May be fixed in BS3, I haven't downloaded it yet.

 

[BrewnWKopperKat]

Beersmith predicts a FG of 1.017 while Brewer's Friend predicts an FG of 1.28. Three weeks into primary fermentation, I've got a gravity of 1.032. That's not too far off from Brewer's Friend, but why the discrepancy from Beersmith?

Going back to the original post, could it be that there is a incorrect value / setting in your installation of BeerSmith?

The equations for estimating OG and FG are basic math and lookup tables (PPG, attenuation, ...).

Is there a way that you can get BeerSmith and Brewer's Friend to show the calculations at each step along the way?

If the OG values are similar between the two, check the estimated attenuation (or attenuation range) for the yeast that your using.

My big concern is that I underpitched my yeast, so I'm trying to determine if I did, or if my FG is in range of appropriate.

Wyeast 1968 is described as a low attenuating, high flocculation yeast (https://www.wyeastlab.com/yeast-strain/london-esb-ale). As I understand yeast, low attenuating yeast can leave maltotriose behind. All-grain brewers will often mash at a lower temperature (producing less maltotriose) when working with low attenuating yeast.

I've read that high flocculation yeasts can drop out early (leaving a couple of gravity points behind). The book Yeast could be a good starting point for learning more in this area.

In general, with DME/LME, since the mash has already been done, the amount of maltotriose has already been determined. So it may be that your FG will finish a little higher than the estimate. Amber DME/LME, which is believed to be a base malt with crystal malts (to get to that amber color/flavor) is also believed to be slightly less fermentable than light / extra light LME/DME. A fast (forced) fermentation test would be the process for getting more insights into the fermentability of specific LME/DME & yeast combinations.

 

[wepeeler]

I entered your recipe into my Beersmith, and I got an estimated OG of 1.087 and estimated FG of 1.029. Looks like you did fairly well if you're getting 1.032.