Yeast Cell Density Meter

[stoneBriar]

Sounds very interesting. I think $100 is pricy, but I'm a cheapskate. That said it would certainly go on my wishlist.

Stuff that you probably don't have answers to at this phase of the project but:
I'm guessing such a system works based on turbidity. How do you differentiate yeast from trub? Turbidity measurements are also affected by opacity of the liquid and dark solutions usually need a standard, so how can you compensate for liquids of varying color?

 

[Leithoa]

Turbidity is correct.
Automatic cell counters work by shining a certain color light through the solution and measuring how much makes it. Then using some empirical data you convert percent transmitted to cell density.
This is meant to be used on starter wort which is typically unhopped pale malt. You can account for any SRM interference by using wort as your calibration blank.
As far as trub, again this is meant to be used with unhopped wort that has been sitting for a few days. Anything bigger than protein or yeast will have settled out during fermentation, and protein will get zeroed out.

SRM would probably have to be done prior to bottling to avoid yeast/protein interference. It is also a pretty fault tolerant scale so I imagine if you took the reading as you siphoned to your fermenter it wouldn't be too much different.
IMO SRM is something even judges are going to eyeball so a paint swatch for the style is just as effective as a reading to the nearest tenth of a unit.

 

[WoodlandBrew]

I don't want to go into too much technical until we are closer to completion, but guys are very close.

I've been tossing around different ideas on detecting viability, but so far don't have a solution that we could deliver.

 

[mtnagel]

I would need viability measurements to be useful to me. It's one thing to know there are 100 billion cells, but it's quite a bit different to know that only 25% are viable.

 

[Hermit]

"When" in the process of counting could be important here. It doesn't take much sugar to get the live cells back into solution. Feed, stir, wait an hour and check.

 

[Leithoa]

I would need viability measurements to be useful to me...

A simple addition and brief exposure time to methylene blue prior to measurement will give you what you want.
http://link.springer.com/article/10.1007/BF01568802

If you've got the time, and glassware(that +/-5% cylinder you have won't cut it) you can make your own yeast standards. http://www.phys.ksu.edu/gene/d2.html If you keep track of dilutions you should be able to calculate your original density. Likewise you would be able to make any dilution from the initial density on down.

 

[WoodlandBrew]

I've created a summary of the questions and answers below. Let me know if I missed any questions that you still have.

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/counting-yeast-cells-to-asses-viability.html
Viability of Yeast in the refrigerator: http://www.woodlandbrew.com/2012/12/refrigeration-effects-on-yeast-viability.html
Viability of Yeast at room temperature: http://www.woodlandbrew.com/2013/01/abv-effects-on-yeast.html
How much does 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.
Wow, that’s a lot of money is there another option?
There may be a DIY option available that would include just the sensor assemblies and programmed micro controller. This will likely cost less than $30. The rest would be up to you including the enclosure, power supply, sample vessel, and a few other things that are available commercially. We would provide the best instructions that we can, but support beyond that will be very limited.

 

[Shockerengr]

How much does it cost?
We will likely be able to produce this product for about $100 per unit.
Wow, that’s a lot of money is there another option?

Considering I've thought about buying a microscope and hemocytometer for counting cells (and many homebrewers have), $100 sounds like a great deal if it's decently reliable.

Looking forward to hearing more.

 

[jbaysurfer]

Woodland, I agree w/ Shockerengr, that's cheaper then the current alternative homebrewers have. I wouldn't bother with that 30 dollar setup. Those customers are going to be your biggest service drain and your lowest profit margin...and I know you said "support beyond that will be very limited" but I think the vast majority of your support calls will be exactly those product purchasers.

K.I.S.S. is my recommendation. sign me up right now. I'll prepay.

 

[pricelessbrewing]

So basically this is a power or intensity measurement of the reference laser, then compare it using the scattered diffuse light reflected by the yeast in the wort?

Wouldn't this also be affected by the protein in the wort as well? Not sure of relative size or reflectivity.

Trying to remember from my optics lab, but won't there be an upper limit on the accuracy as well? Or is it beyond the range of typical starters?

 

[WoodlandBrew]

So basically this is a power or intensity measurement of the reference laser, then compare it using the scattered diffuse light reflected by the yeast in the wort?

Wouldn't this also be affected by the protein in the wort as well? Not sure of relative size or reflectivity.

Trying to remember from my optics lab, but won't there be an upper limit on the accuracy as well? Or is it beyond the range of typical starters?

Yes, that is the basic theory of operation.

Great questions! Yes, accuracy will be limited to a range. With a hemocytometer count you normally do dilutions until you have about 100 cells per box. 20-200 cells per box is pretty much the reasonable limit with a microscope. From our initial testing I think we can beat the microscope in that range. Also, I expect that it will be able to operate beyond that range.

It will be thrown off by protein in the beer. We will do you best to adjust for typical scenarios. This is where comparison to hemocytomer counts will be very useful.

 

[pricelessbrewing]

Good to know, looking forward to product launch!

If nothing more this will be wonderful for giving more accurate estimates and a range of # of cells to expect.

 

[stoneBriar]

Sounds awesome, thanks for the Q&A. Keep us posted on your website also since I've got that in my RSS feed!

 

[WoodlandBrew]

Thanks everyone for your feedback so far! It has been very helpful.

We are looking at different options to power the unit. What are your thoughts on USB, wall power and battery power? What would you want, and what would you expect?

 

[Ben58]

Battery as portability is handy.

 

[Shockerengr]

Battery power is nice if the batteries are replaceable or common.

Otherwise USB is handy because the cords and chargers are so ubiquitous nowadays that finding one is easy...they sell piles at the checkout in the gas station even.

 

[Hermit]

I like the idea of a rechargeable unit. That way you could still go USB.

 

[pricelessbrewing]

Don't go battery unless it's replaceable or a household battery like AA or AAA and not some expensive replaceable one ala laptop or watches. Usb with rechargeable eneloop AA batteries would be pretty nice.

 

[jbaysurfer]

Definitely battery. I'd prefer the USB rechargeable if you were able to get a good quality LI battery in there. But I do have concerns about replacing said battery when it eventually runs out, which, brewery work like this can be kinda hard on batteries IME.

 

[Leithoa]

if you go the USB route for either charging or main power it'd convenient to be able to collect readings over USB.
Optional serial output might be easier to implement at a hardware level though.

 

[passedpawn]

Here's a great model for a device like this. Adding a Li battery, USB port, etc just doesn't make sense here; I don't want to pay more to make it rechargable. I want it cheap, and I'll supply the AA or AAA battery, no prob. I don't think there's much advantage in serial data from the thing since it's a one-time measurement. If it was a process measurement, like measuring ABV or gravity during fermentation, yes, USB or wireless would be cool.

This company, Hanna, has a bunch of identical instruments (the calibration and colorimetry agents are different, but the package is the same).

Measuring SRM is a simple absorbance test through a cuvette. 430nm LED. Photodiode. Simple microcontroller to do the A/D conversion and display something. The package below would be perfect. I have a couple of these types of things at home.

 

[tagz]

Subbed.

 

[WoodlandBrew]

Thanks for all the feedback! We'll do our best to meet your expectations.