The Roving Brewer: Episode 2

November 10, 2006 at 12:00pm

Author(s): Eric Watson

This is the second installment in a series of discussions with our roving brewing expert, Eric Watson. Episode 1 of The Roving Brewer caused quite a stir and brought up a number of questions. We will address some of those question in the next few episodes.

Q: Those are some very new ideas to me especially the one about dextrin. I mean, a doppelbock with a FG of 1025 definitely tastes thicker and richer than a pils with an FG of 1007. Would you say then that the melanoidins could have something to do with it?

A: Well... it is possible that this is a contributor, but as they stated, they don't quite know yet. I do know, in the case of you r bock, a portion of the viscosity impression is due to the residual sugar. In this case there would be a slightly measurable increase in viscosity, but in humans, sugar is also known as a psychological trigger for an increase in this perception due to the building upon childhood memories of syrups. It is not the only causal factor though as they pointed out. The dextrin study was just concluded a recently. Knowing that the dextrin study took 2 years, I'll bet the next one takes alot longer since there are so many variables involved instead of 1!

Q: Thanks for the info, could you please tell us what mash thickness is recommended?

For example, I'm using around 3L per kg and can't get conversion @ 68C in 20min based on an Iodine test.

A: As long as you are using fresh, fully modified malt the conclusions I reach are that 1) Your mash thickness may be too thin to maintain an appropriate temperature to achieve complete conversion via such a short rest, or/and 2) You need to raise your dough in temperature and insulate your mash tun.

Thickness: You need to be between 1.23 L to 1.33 Liters per .45Kg grain. (Equates to 1.3~1.4 Qts per Lb. grain). I would mash in between these amounts... say 1.28L water to .45Kg grain.

Mash Tun: One of the difficulties of instituting this concept in a home-brew setting is that home-brew mash tuns tend to be much deeper and narrower than commercial ones. This geometry creates a greater convection effect which can create a substantial temperature differential between the top of the mash and the bottom, so mash thickness becomes the controllable variable in this situation.

In your case, dough in to achieve a target mash temperature landing on the higher side of the temperature range (69~70C). Make sure to cover the tun and then insulate it if possible. A thick blanket should do the trick. (Another way of maintaining mash temperature is to place the covered tun (IF METAL!!!) into an oven on the warm setting. I used to do this when I home-brewed.)

If you still get an iodine negative reaction, warm the first runnings (slowly or it may scorch!) to 75.5C and perform the vorlauf until clear. Try the iodine test after the runnings are clear. If it is negative, sparge at 75.5C until your runnings are at 2.5P/1.010SG and top up to volume for the boil.

Hint: To assure that you don't get false positives via iodine tests, run the test sample through two back-to-back coffee filters to eliminate the possibility that grain particulate is in the sample when tested.

If this doesn't work, your only choice is to extend the mashing time.

Q: First, are you saying that it would be better, if we have a good starter, to not have ANY oxygen at all in the wort? In other words, not only NOT use an airstone in wort, but should we take steps to avoid ANY form of aeration, such as splashing the wort into the fermenter or otherwise causing foaming of the wort before pitching?

Second, for those of us who don't currently have an airstone and have only aerated by shaking the vessel, will that create a sufficiently large starter to follow your recommendation, above? If so, what size should the starter be for a 5 gallon batch?

Third, if the answer to you question #2, above, is no, and the starter is therefore not of an _ideal_ population, then how advisable or detrimental is aeration of the wort using the common methods of splashing/shaking/mixing/aggitating the wort in the fermenter? It would seem almost a necessity if we want a quick and vigorous start. Is the difference in results likely to be noticeable enough that you would recommend switching methods to an airstone aerated starter and no aeration wort? ... and how much would you stress that recommendation (slight? ... highly?)

A: Yes, as I stated, it is best to only aerate the starter if you are so equipped to do this. The reason is that once the yeast has all the oxygen it needs to build strong cell walls and reproduce, it does not need any more. Any additional oxygen beyond that point will cause them to stay in a reproductive state rather than begin a fermentative state. If you can do this, you will notice a refined smoothness to your beers due to a reduction in ester production and therefore your beer will condition faster.

Since shaking a starter vigorously only produces large bubbles, it is an inefficient and inconsistent practice. I assume if you would do it for a LONG time... say 30 minutes, it would probably be sufficient, but 1) who wants to shake a starter for 30 minutes? & 2) since the air is not sterile, you would definitely risk contamination.

The cost for a pump, tubing, filter and stone shouldn't be more than $35 and the stone can serve as device to force carbonate in kegs that would only take 20 minutes or so. But if this investment is not in your future, go back to the splashing method in the carboy.

Starter sizes are actually cell count/viability dependent. The best practice is to pitch 1 million cells per ml wort per 1 degree plato for ales and 1.5 million cells per ml of wort per degree plato of wort with a cell viability of 96% or more.

Since most home-brewers can't measure cell counts or don't viability tests, The best practice otherwise is to step the yeast culture up one day at a time to 100 ml, 200 ml, 400 ml, 800 ml and finally to 1,000 ml (5 total days of stepping) using a 5 deg. plato hopped wort (remember you want REPRODUCTION not fermentation, this is why the wort gravity is low.) While doing this, aerate 24 hours a day (builds strong cell walls/keeps yeast in a reproductive state) using the air pump/sterile filter method. For a 5 gallon batch, this should be adequate. If you do this, there is absolutely no need to aerate the wort.

The discussion continues! We will pick up with more questions in the next installment.

Here are more articles from The Roving Brewer:

The Roving Brewer: Episode One
The Roving Brewer: Episode Three
The Roving Brewer: Episode Four
The Roving Brewer: Episode Five

Comments on this article?