Tuesday, January 20, 2015

Cell Density Meter Update

When the Cell Density Meter is released we want to make sure we have worked out all the bugs, smoothed all the wrinkles, and that it works seamlessly.  Our goal is straight forward operation with complex algorithms underneath to provide accurate measurements in the strenuous brewing environment.

At this point we have several working algorithms and are evaluating how they can best be implemented.  The enclosure is in its final stages of fit checks and adjustments.  

To put the Cell Density Meter though it's paces I conducted a comparative study of starter growth with and without a stir plate.  In summary the yield is about the same, but the cell growth is much faster with a stir plate.  Download the full report below.
Agitation Effects on Growth Rate and Yield of Brewer’s Yeast

Saturday, January 3, 2015

Bittering Hops in 15 Minutes

In case you wanted to isomerize alpha acids six times faster here is how to do it.  The full article is on Home Brew Talk here:

Wednesday, November 12, 2014

Extract vs All Grain

 All Grain (left) and Extract (right)
A side by side comparison of  two American Pilsners.

The cost of making beer with extract compared to making it with all-grain is occasionally debated, but when it is, it's always fierce. The goal of this comparison was to see what makes sense for me. The results here are not to say that any one is better than the other. It's really just me sharing my personal decision. If you are curious if all-grain or extract costs more for you I encourage you to perform the evaluation using your own economic factors.

These two beers were brewed as close to each other as possible with the exception that one is all grain, and the other is extract based.  Hop tea was made ahead of time to use for several batches of beer with high alpha hops and a two hour boil time.  See my book for more details.

1.5 gallon batch size
OG: 1.069
FG:  1.017
IBU: 32
SRM: 4
Fermented at 56°F

The cost of heating the water for the all grain batch was appreciable. Between the mash, sparge, and boil my burner was on full tilt for 2 hours. My last gas bill indicates that natural gas costs me $0.0139 per cubic foot.  At that rate my stove costs $1.67 per hour to run one burner at full heat.  That's $3.34 in fuel costs.  The amount of heat use to make the hop tea was trivial by comparison.

For extract brewing I use distilled water because the minerals are already in the extract. This costs $0.75 per gallon at my local grocery store which added $1.13 to the extract beer. When brewing all-grain I use tap water because the mineral content is needed for acidification of the mash, among other things. By comparison, the tap water is virtually free.

Making the extract took 12 minutes from weighing the first ingredient to pitching the yeast.  The all grain batch took 5 hours.

All grain methods typically loss 20% of the beer to trub, although with this batch it was 29%.   It is common to start with 6 gallons at the end of the boil, transfer 5.5 to the fermentor and have 5 gallons for bottling.  When brewing with extract the trub losses are lower because extract as already been boiled once.  This means that the extract has already gone through one hot break.  This batch was fairly typical at 10% trub loss.

But how do they taste? that's the real question.  To judge the verdict of taste, I selected half a dozen of my friends be the lucky ones. (Well... Really I begged and pleaded to persuaded them to compare the two beers.  Same thing right?)  In a blind tasting of these beers none of them preferred the all grain beer, and some of them preferred the extract beer! I was shocked. So I made a second beer. This time it was an IPA instead of a Pilsner, and the response was the same.

The difference in cell density was interesting.  After bottling the beer the remaining slurry was weighted. Because the two had the same starting gravity, yeast strain and fermentation conditions the total number of yeast cells produced should be nearly identical.  The all grain batch had 1,124g of slurry remaining while the extract batch measured it at only 326g.  This means that the cell density of the extract batch was about 3 times higher than that of the all grain.  This means when storing yeast, the same number of cells taken from extract beers take up about one third of the space in your fridge compared to all grain.

A recipe that used more specialty malts would have allowed the all-grain batch to shine, but with a steep or partial mash the same flavors could be imparted on the extract batch.

Monday, November 10, 2014

Another Article on Home Brew Talk

I've been busy working on another article for Home Brew Talk, "4 Tips for Making Great Beer in 15 Minutes." It's the first in a series of 15 minute beer articles that I'm working on. Check it out here, http://www.homebrewtalk.com/four-tips-making-great-beer-15-minutes.html Thanks!

Saturday, October 25, 2014

3 Common Yeast Misconceptions

Home Brew Talk asked me to write a post for them, so I wrote on what I know best: yeast.

The full article can be found here: 3 Common Yeast Misconceptions

Misconception: Yeast growth and cell division only occur at the beginning of fermentation.
Misconception: Yeast activity slows at the end of fermentation because the yeast is exhausted.
Misconception: Water washing yeast removes contamination and dead yeast.

Thursday, July 10, 2014

Cell Density Meter

A product development team that I'm excited to be part of has started design of a beer color and cell density meter. Our team is composed of engineers and scientists with over 40 years of combined in field professional experience.  Below is a summary of the feedback we have received, but we still need to hear more about what you might expect.  We are looking forward to making accurate cell counts a reality accessible to the home brewer.

What is it?

The yet to be named device is a cell density meter that also measures beer color. It provides an easy and accurate cell count of starters or yeast slurry.

How does it compare to a microscope and hemocytometer?

It’s much easier to use, faster, and considerably less expensive. Counting cells using a microscope is highly depended on the operator. If you asked three different lab technicians to count the same sample of yeast you are likely to get three different answers. Tests I have done indicate that variation in counting is 10% on average. The accuracy goal of this device is 5%. One advantage of the microscope is that viability staining can be performed. Our device may not be able to measure viability, but we do have some resources that will be listed in the manual for estimating viability of yeast throughout the brewing process.

How do you know it is accurate?

In addition to rigorous engineering analysis we will be testing the device with a set of standards. We will be using yeast standards but will also add a gradient of beer color, creating a two dimensional matrix of standards. These results will also be compared to counts using a hemocytometer.

Is it accurate in dark beers? How does it work?

Unlike other cell density meters, this device is specifically designed to compensate for beer color. Cell density meters, commonly used in laboratories, work by measuring the amount of light transmitted through the sample and correlating the measurement to cell density. This makes the device susceptible to error caused by the color of the liquid in which the cells are suspended. Our device employs additional hardware and software algorithms to compensate for beer color producing a more accurate cell count.

Can I see it work?

If there is enough interest there will be a demonstration of the device to Boston area brewers. We will also be producing a video of the device in action.

Will you be doing a Kick Starter?

Yes, without it we wouldn’t get off the ground. Many of the parts will require custom machining which can be very expensive in low quantities. Our target is to build at least 100 devices.

Can it tell the difference between yeast from trub?

The short answer is that it cannot tell the difference between yeast and trub. However, trub makes up only a small amount of the mass at the end of fermentation. The slurry from a five gallon (20 liter) batch of beer will contain about five trillion yeast cells.

Does it measure Viability?

Viability of yeast under various conditions that they may see through the brewing process is something that I have studied in length. The results may surprise you. Essentially there is very little drop in viability with refrigerated yeast even over months of time. The dominant factors effecting viability of yeast slurry harvested post fermentation is the amount of alcohol in the beer and how long it has been at room temperature.
Viability method: http://www.woodlandbrew.com/2012/11/...viability.html
Viability of Yeast in the refrigerator: http://www.woodlandbrew.com/2012/12/...viability.html
Viability of Yeast at room temperature: http://www.woodlandbrew.com/2013/01/...-on-yeast.html

How much will it cost?

Our goal is to produce a product that is accessible to the home brewer. It needs to be straight forward to use and reasonably priced. We are undertaking this effort because this is what we enjoy doing. We aren’t looking to make a profit on production, and I’m sure we aren’t going to be able to afford to “pay ourselves” for the countless hours that we are pouring into this project. We are doing our best to keep assembly labor as low as possible so the cost is mostly driven by materials. We will likely be able to produce this product for about $100 per unit.

Friday, June 13, 2014

Book Review

I'm really grateful for all of my readers who have bought a copy of the second edition of Brewing Engineering.  To date, over 200 copies of the second edition have been sold. If you have read my book, would you mind doing me a favor and leaving a review on Amazon?  Not only will it let others who are interested know what to expect from the book, but it will provide me with valuable feedback for future editions.