Mash Conversion experiment

[cyberwollf]

Just finished building a 3 vessel all electric system and am getting much worse efficiency than i used to on my BIAB setup. Im really careful about my batch sparging so I had a hunch it was a conversion problem. After reading all of Kaiser's stuff here: http://braukaiser.com/wiki/index.php?title=Troubleshooting_Brewhouse_Efficiency

I wanted to setup a conversion experiment:

1 lb of Rahr 2-row. The 50lb sack i have states 81% from the lab.
3lbs of RO water (= 1.43 quarts if i did that math right)
0.4g of Calcium Chloride (puts my RO water around ~50ppm, if i calculated that right)

I mashed in at 150F
@15mins in, the SG was 1.057 and the pH was 5.0 (at 150F on cheap test strips)
@30mins in, the SG was 1.068
@45mins in, the SG was 1.075
@60mins in, the SG was 1.079
@mashout 165F, the SF was 1.083
According to the table on Kaisers page, that is close to 100% conversion eff.

Really interesting to know, I usually just wait 60 mins at rest and then start the sparge (with no idea where my mash should be SG-wise)

Knowing this I will not even start a sparge until I know im 100% convered instead of just waiting for time.

I think i can easily blame this for my low brewhouse effiecencies. I know my last 1.5q/lb mash i was only at 1.060 when i started to sparge, Had i known I would have tried to fix the problem at that point at least this takes away one more parameter on loss of inefficiencies. If you are having a problem, I urge you to check your mash SG to ensure close to 100% conversion otherwise all the sparging in the world wont help. Also Kaiser notes that an iodine conversion test can indicate full conversion, when in-fact there is still starch within the grist

 

[ajdelange]

If you put 1 pound of grain in 3 pounds of water and got 100% conversion you would have a 25 °P wort. Even the lab only got 81% which implies 20.21 °P or SG 1.084. You say you got 1.083 IOW you did as well as the lab's Congress mash which, given that it was 81% was probably a fine grind dry basis number. It is virtually impossible that you would get extract equal to the FGDB value using real malt in a normal mash unless the malt were dried first and fine ground i.e. unless you followed the Congress mash procedure. Also many malt spec sheets list a conversion time which is seldom more than 10 - 20 minutes. It is, thus, suspicious that your gravity continued to rise for an hour.

If you used a typical home brewing hydrometer I would look to that as the source of the error. If you used narrow range brewing hydrometers or a digital density meter I would have no explanation. Perhaps loss of water from evaporation - in the Congress procedure the funnel is covered during the filtration process. Or perhaps you didn't filter as you don't say anything about that.

 

[cyberwollf]

Yea 81% from the congress. What I meant was i got near 100% eff according to kaisers charts (which is set at 80% I think)

I used a refract, but temp kept falling lower than 150. Hard to keep 1 gallon of water at a set temp on stove. So I suspect lower temp lead to slow convert

Really I just wanted to be sure my crush, my water profile, and basic process was capable of getting a good convert vs just a simple iodine test. And now I know what to expect/test for durring mashing so I don't blame my lautering for low numbers when it was actually my convert.

 

[ajdelange]

I used a refract,

OK - that explains the error.

...just a simple iodine test.

Nothing wrong with an iodine test if it is done properly. This is part of the Congress mash. One puts a drop of liquid on a white porcelain plate and then puts a drop of iodine next to it. Where the two run together one reads the color. If it stays yellow conversion is complete. If it is redish then some starch is still present (may be in the form of dextrines) and, of course, if it is blue then raw starch is present. Yes, grain particles do contain some starch even after conversion. That's partly why efficiencies are not 100% and that's why one takes care to exclude particles when doing the test.

 

[ArcLight]

>>I used a refract,

>OK - that explains the error.

Why would a refractometer be inaccurate if the wort is first cooled to room temperature?
There is no alcohol present.

Is a hydrometer a lot more accurate?

 

[ajdelange]

Refractometers are built to measure the refractive index of sucrose solutions in water at a particular temperature. Hydrometers are built to measure the density of sucrose solutions at a given temperature. Wort contains very little sucrose so both instruments produce readings that are only approximate. But the hydrometer is much more robust i.e. it doesn't respond to the differences between sucrose and the actual wort sugars to the extent that the refractometer does. Even so, refractometers are 'close enough' most of the time. The problem is that sometimes they aren't. In trying to determine whether I wanted to use one or not I took both hydrometer and refractometer readings on several brews. Most of the time the agreement was within a couple tenths of a Plato degree. But sometimes the refractometer is off by more than 1 degree. That's certainly enough error to be a reasonable explanation as to why OP saw what he saw. When measuring extract the gravity of the wort should be determined with at least a narrow range hydrometer if not a digital density meter. As the °P reading appears in the efficiency formula in 2 places an error in it can have a pretty big effect on the calculated efficiency. A 1 °P error at 15 °P can put the efficiency estimate off by a factor of 1.3.

 

[ArcLight]

Thank you for the detailed explanation!

>> But sometimes the refractometer is off by more than 1 degree.

Might you remember when this occurred? (high temperatures? High Gravity? Low Gravity? High Altitude?)

 

[ajdelange]

I could probably find it in my log but my log is 600 mi away and I won't be back south until probably Oct. I'm guessing it would be higher gravity beers but I really don't want to assert that until I check. Even 1 °P is only 0.004 SG and people probably don't get much better than that using inexpensive wide range hydrometers, not temperature correcting etc.

 

[dstar26t]

I track conversion using a refractometer every time I brew. It may not be the most accurate way to measure wort strength but it works good enough and it's very easy. In my brewing spreadsheet, I input the FGDB and moisture from the malt analysis sheet(s) provided by the maltster(s). Usually, 75-80% of the conversion is done after 20 minutes but I let it go for 45 where it's usually 85-90% converted. Then I ramp up to a glyco-protein rest (72ºC) and the rest of conversion happens pretty quick. A quick stir can help speed along conversion as well.