Harbertson-Adams assay debate.

December 11th, 2008



Wines and Vines wrote today about some growing debate over the validity of the Adams-Harbertson assay.

In short, this is an assay that gives winemakers real-time quantitative and qualitative information about the tannins in their wines. However, the validity of the test is being challenged by winemaker Larry Brooks, Leo McCloskey and Doug Mckesson of Enologix and Marshall Sylvan – a University of California Santa Cruz mathematician and consultant to Enologix.

The assay was developed by two scientists at U.C. Davis: professor Dr. Douglas Adams and Dr. James Harbertson who was a UCD student at the time and is now affiliated with Washington State University. According to the Wines and Vines Article, the assay “has been adopted by several wineries and at least one commercial lab in California“.

The assay may serve winemakers by giving information necessary for tannin management, color stability and blending as well as age worthiness. A winemaker familiar with the assay (which requires an approximate $5,000 start-up layout for equipment – according to him) said it does not offer a specific indicator of a wine’s flags of ageability. Rather, the panel is analogous to a metabolic panel done in hospitals. It gives multiple parameters and data points. Observing any patterns in these indicators and seeing how they correlate with a wine’s evolution over time may yield hallmarks of age worthiness.

The Brooks paper challenging the validity of the assay cites “significant variation in results from trials at five labs“. The trials were conducted by a third party: Vinquiry Inc., a commercial enology lab. Vinquiry, however, has declined to comment on the results of their trials.

This variation may be intrinsic to the method or it may be operator-dependent. Training, competency or skill of the person performing any test impact its accuarcy. I see this in medical diagnostic imaging on a daily basis. But design flaws can doom the validity of a test as well.

One winemaker told me, off-line, that based on what they heard at a UCD seminar and read in a letter form an enologic laboratory, they believe that the Adams-Harbertson assay measures “tannins in juice but it could [not] correlate it with how much tannins you would end up in the wine” – which raises real questions of the test’s utility.

On the other side of the fence, a comment posted on the Wine and Vines article raises a possibility of a conflict of interest for the authors of the paper.

I invite all interested and informed on the matter to contribute to the discussion but request civil discourse.

[Larry Brooks has provided a copy of the paper in question.]



Winebusiness.com reports on Thursday Dec 18th that UC Davis V&E Chair Andrew Waterhouse released a statement asserting the department’s support of the Harbertson-Adams assay.


Email & Share


28 Responses to “Harbertson-Adams assay debate.”

  1. NRC Says:

    The Harbertson-Adams assay is sort of an approximation of the tannin level in a wine. That is like trying to measure the fruit in a supermarket with one number. HPLC on the other hand counts each phenol species ie: how many apples, how many oranges, how many watermelons, etc… and gives the total that way. Of course they are totally going to be different.

    In trying to understand what is happening at a phenolic level in the wine, HPLC should be the standard. Because of the complex ways that phenols interact with one another and with other substances in the wine, it doesn’t do a lot of good to just use the H-A to try and draw conclusions.

    H-A and the somewhat more reliable Methyl-Cellulose methods are most accurate at correlating to ‘how tannic’ a wine is going to seem on the palate. This is because we perceive the astringency of tannin because of the way that tannin interacts with salivary proteins (proline) in our mouths. But you could just taste the sample too – not sure if anyone has run the correlations on a large scale. The main advantage of a lab method might be to eliminate the day to day subjectivity and order of tasting prejudices that cloud production scale sensory evaluation. But both H-A and Methyl Cellulose are difficult and time consuming to perform in a production laboratory, even with trained techs. I know many top wineries that have tried and basically threw their hands up after a season of hundreds of tech hours and little correlation to reality.

    If I want to understand color stability, degree of polymerization, and the trajectory of a wine, or if I am using analysis to make judgments about a scientific trial, HPLC is really the only way to go. If I want to know which fining agent will most likely be effective in correcting a wine, or to understand which wines will do well to blend together, HPLC is the way to go. If I am trying to understand if I have sufficient extraction in a fermentor, HPLC is the only thing that can cut through the clutter and give a good result.

    I think that one really needs (as always) to understand the right measure to use for the problem at hand. It is no good using a kg scale to measure how tall someone is, and it is crazy to expect a precipitation method to tell you what species of tannin are present or to quantify them.

  2. Clark Smith Says:

    Dear Arthur:

    I’ve written a lot about this assay, but let me boil down the essentials for you.

    First some background on phenolic assays. Phenolics are a class of substances in grapes (especially red grapes), oak and wine which contribute much to the flavor, aroma, color, bitterness, astringency and texture of wine. Some of these are potent antioxidants and thus contribute to wine’s life energy. A subclass of phenolics (the vicinyl diphenols) can gobble up oxygen and in the process daisy-chain into polymers which form a red wine’s macromolecular structure. Think of them as oxygen-hungry legos.

    These oxidative daisy-chains and others formed in berries without oxygen are called tannins. When they get to be four units long or more, they start to be able to react with proteins in your saliva and precipitate in clumps that feel grainy. We call this astringency or harshness.

    Chemists would love to be able to characterize these polymers, but the normal approach of discrete analytical chemistry doesn’t work. In a thousand ways, chemists can pull a sample apart into its pieces and analyze how much of each substance you have. But when you start to make polymers, that doesn’t work, because every combination is a unique arrangement, like snowflakes – no two alike. So instead, we have to look for ways to characterize the behavior of a group of similar but non-identical arrangements. We’re humans, and we really just want to know how the arrangements affect our senses.

    The other challenge is that winery labs don’t have much of a budget. Most can do pH, TA, SO2, alcohol and VA for around $10,000. It’s not too difficult to persuade them to upgrade to an oxygen meter for $1,000, but serious instrumentation in the six figure range ain’t happening. Fancy assays like HPLC have also never justified their stratospheric price tags (six figures or better) because polymers come out in a big undifferentiated blob. HPLC is absolutely great for monomers, but practically useless for differentiating tannin fractions.

    So in 1976, an Australian named Chris Somers devised a general wine phenolic assay that used a fairly cheap instrument called a spectrophotometer ($2-4K). The assay had problems which were corrected by Roger Boulton, and we now have a simplified version of Boulton-Somers on our website.

    The Boulton-Somers assay has some blind spots of its own. Geeks like me are interested in the concentration of color molecules in a young red wine, and Somers only shows the visible portion. Most of the color is invisible, so it’s not much help. More important, Somers tells us nothing about texture. What we needed was a way to analyze astringency: how much of the total phenolics was precipitated in the mouth by salivary protein or something like it?

    In the late 1980’s the famous French enologist Yves Glories offered an addition to Somers – a Gelatin Index.. In this assay, you add gelatin to the sample, settle out the precipitate and look at the difference before and after. This innovation swept through Europe and is still the standard today.

    However, American enologists rejected the analysis because gelatin itself, which closely resembles salivary mucin, varies a lot and makes a lousy analytical standard. Doug Adams proposed to use Bovine Serum Albumin, the Gold Standard of analytical proteins instead. In my opinion, although BSA doesn’t resemble mucin, he was right in his choice. Adams decided to use the strong reactivity of red pigmented anthocyanins to measure the fractions of tannins.

    BSA isn’t perfectly consistent. Leo McCloskey and Larry Brooks of Enologix are vocal on the web picking nits about its failure to measure up to the stringent peer review parameters established for discrete analyses – a ridiculous position considering that Enologix refuses to reveal ANY details about the nature of its competing black box analysis. Still, I frankly I think UCD deserves all the flack they are getting from Leo for their arrogant handing of him, refusing to let him speak, contribute or even fund their research, frequently branding him a charlatan for no greater crime than proposing to occupy their own sacred ground. A plague on both their houses.

    With his brilliant and hardworking slave Jim Harbertson, Adams accumulated piles of data about how his assay worked. A debate has emerge about what the Adams actually measures. UC Davis sacred doctrine has held for decades that astringency is a simple function of polymer size. Therefore, protein adherence must directly relate to polymer. The terminology Doug coined for tannins assumed that the ones that didn’t precipitate protein were shorter, and he called them SPP – Short Polymeric Pigment, while the ones which were removed by addition of BSA protein were called LPP – Long Polymeric Pigment. We later found out that skilled treatments of wines with oxygen and lees can result in increases of SPP, thus the names are probably erroneous.

    In my opinion, LPP probably relates more to sensory astringency than degree of polymerization. Lunkhead scientists claim that Pluto isn’t a planet because it doesn’t conform to their theories of planetary formation. Well, guys, your theories are obviously wrong or incomplete, right? In the same way, LPP is a very useful number for total astringency which has nothing to do with chain length or form.

    The weakness of the Adams assay and the whole Davis approach is that they steadfastly refuse to acknowledge different forms of astringency. Perfectly made young reds like Chateau Latour are loaded with sheet-like grippy “hard” tannin atop the tongue which over time will soften and expose aged flavors, while equally obnoxious grainy dry tannins from excessive hangtime Zinfandel will worsen in the cellar as the underlying, unprotected wine oxidizes and falls apart. These distinctions are critical to collectors and the Adams assay does nothing to illuminate this distinction. You just have to taste.

    A cleaned up version of Adams-Harbertson exists on the Vinovation website. I think its best use is in the vineyard. It gives an excellent assessment of total tannin and I’m betting it can shine some light on when field oxidation is getting out of hand. A nice side benefit of Adams’ assay was solving the problem I care about of determining how much color – including the invisible portion – is in young red wine. Now I know how many bricks and how much mortar I have to build a structure.

    What we really need is for a group of winemakers to collaborate in testing a combination of Somers and Adams. Unfortunately, few winemakers have succeeded in wading through the politics of their development and the complexity of the technical issues in order to mount such a study. Maybe some day.

    Clark Smith

    [hyperlinks placed by Arthur to complete the original email communication from Clark]

  3. Larry Schaffer Says:


    First off, thanks for posting the information above and starting a discussion / debate about this issue. One thing I hate about ‘press releases’ is that you do not have the opportunity to ‘interact’ with them!

    Second, I’d like to add my $.02 to the discussion. To NRC, I don’t disagree that HPLC’s are cool and provide interesting info, but please, let’s get real – how many wineries, including very large ones, can afford an instrument like this, much less staff it with someone who can understand how to use and maintain it AND interpret its results? In addition, just because you know the minutae of phenolic components does NOT mean that you have a better understanding of the organoleptic qualities of the wines being analyzed – and, at the end of the day, shouldn’t the results be ‘practical’ and ‘useful’ for the winemaking team?>!?!?!?

    Clark, thanks for the history of where tannin analysis has been and where it is at present. That said, I’m really not sure where you come off with some of the statements that you make. Yes, Davis has had a reputation of being an ‘ivory tower’, but speaking from a very objective person who graduated from there less than 5 years ago and has stayed in contact with many folks within the department, I just don’t see that being the case these days. The Dept seems to be very interested in enthusiastic about outreach to the winemaking community and providing them with current research information AND listening to their ideas for future projects. I also think it’s unfair to categorize their ‘relationship’ with Mr. McCloskey – I don’t think he has been, nor will he ever be, completely forthright in his conversations about his company and his ‘tactics’ . . . Yes, many people, including you and I most likely, are ‘suspect’ when someone brings something new to the tabel – this is not a bad thing in and of itself. It’s only when these ideas are panned outright without discussing/investigating further than I feel problems arise, and I do not feel that is the way the folks at Davis work. You are certainly entitled to your opinion, but it is not one shared by all.

    Now onto the Assay itself. We’ve had this discussion on your blog as well, but it’s worth repeating here – you still seem to be misunderstanding some of the findings that the Adams lab came up with in regards to the MicroOx study and some of the terminology itself. The analysis was used to compare/contrast wines that had been subjected to micro ox treatments vs. the same or similar wines that were not subjected to these treatments. The results showed an increase in both Long Polymeric Pigments (LPP) and Short Polymeric Pigments (SPP). The important factor from an organoleptic standpoint was the LPP – this increase does happen over time as a wine ages, but not as quickly as it did with micro ox involved. Further analysis in the lab showed that the total tannin levels were not changed – just that the percentage of tannins that now had anthocyanin molecules bound to them (this is what an LPP is) had increased. The lab looked at these LPP molecules and noticed something very intersting – these ‘tannin’ molecules had a much lower binding affinity to salivary proteins than the same tannin polymer withOUT an anthocyanin attached. This then shows objectively that as a wine ages, one of the main ways it softens is by this combining of anthocyanins and tannins – AND THAT THIS ANALYSIS COULD OBJECTIVELY TRACK THIS. Though neither Doug nor Jim H. have ever pushed this concept to the forefront, it is VERY important from a winemaking standpoint – it marries the objective ‘numbers’ with the somewhat ‘subjective’ organoleptic interpretations of wines . . . And as far as SPP goes, these are NOT tannins – they are other phenolic materials that are are color-stable – they may be a single catechin monomer that has an anthocyanin attached but they do NOT ppt with BSA and are therefore NOT tannins. They very well may impact ‘astringency’, but my educated guess is that they most likely impact ‘bitterness’ more . . .

    I could go on, but I’ll leave that for my response to the next person (!) . . . but I also do want to comment on Clark’s statement about Davis not recognizing different ‘types’ of astringency – I think the folks at Davis, include Dr. Adams, certainly agree that there are different ‘types’ . . . but these ‘types’ generally boil down to different quantitative amounts or chain lenghts of specific tannins . . . THIS is generally what they have found is the cause of semantic differences observed by others . . .

    Looking forward to continuing this discussion – without name calling . . .


  4. Larry Brooks Says:

    Hi Arthur,
    Bit of a storm over what is a fairly straightforward validation study of one aspect of Adams Harbertson. We used accepted scientific protocols of validation which should have been done, of course, by UCD before they touted this analytical method. Our study was peer reviewed and published by the leading journal in the discipline which speaks volumes. The Davis controlled AJEV would not even have looked at this paper which also says volumes about who has an agenda and who doesn’t in the area of wine analysis.
    There seems to be a bit of over reaching all around. We are not comparing HPLC and HA in this study. That has been done before and the superiority of HPLC is well accepted by research scientists in the field. We were simply trying to validate an analysis that many of my clients were attempting to utilize without reliable results. We found that the tannin portion of this analysis may be the problem as we saw unacceptable variation both by commercial and competent well equipped winery labs.

  5. Larry Schaffer Says:


    Thanks for taking part in the discussion. Would you mind providing a bit more information regarding a few things:

    (1) You mention that many of your ‘clients’ were attempting to utilize the HA Assay without reliable results. Care to mention whether these were clients of Brooks Consulting or Enologix? Also, can you provide a little background on these clients – how long did they attempt to run the analysis, did they seek out assistance with inconsistencies after they occurred?

    (2) Share to talk about the ‘well equipped’ winery labes that were used here in the study . . . what specific types of centrifuges were used? How old was the FeCl used? How well trained were the individuals involved? Were all samples run in duplicate?

    This is NOT a simple assay to run, unlike VA’s. / Free SO2′s, etc, and therefore proper training is of utmost importance.

    There are many other potential questions to be asked and I’m hopeful you will be frank and forthcoming in your responses . . .


  6. Arthur Says:

    Larry Brooks has shared his article with me. With his permission, I am linking to it at the bottom of the original post and here: the paper in question

  7. Wes Hagen Says:

    Assays, lab stuff, etc. is not all that important to me as a winegrower.

    If I find one of my wines is soft and gutless, I look to improving my cultural practices in the vineyard.

    Labs are for a problem I find with my nose and mouth. Of course I do panels for unfiltered bottlings, etc., but understanding everything about the chemical structure of my wines just sucks the passion right out of it for me.

    Now if a barrel start stinking or spitting or tasting funky, I go right to the lab.

    Knowing too much about wine chemistry is like having a PhD in film and trying to lose yourself in a movie: it’s possible, but chances are you’ll be second guessing every edit.

  8. Larry Schaffer Says:


    I agree that lab stuff should not and cannot replace good old fashioned tasting and smelling . . . That said, good lab data CAN help illuminate ‘problems’ or highlight ‘positives; what may have been missed along the way . . .

    My whole point in this disucssion is not that any one lab procedure should be run by everyone and anyone – certainly not the case .. . But this Assay, which I am very knowledgable about, is being slammed for being unpredictable AND not relevant – just not the case . . .


  9. Wes Hagen Says:

    If I came across as contrarian that wasn’t my only intent.

    Tools and science have carried California winemaking a long, long way. Those who dedicate their lives to the study of wine chemistry, etc have my respect and support–I’m just glad it doesn’t have to be me.

    I want to be a poet winegrower until a problem arises–then I want every test, assay, plating, etc to be available to me when I drop my samples off.

  10. Larry Brooks Says:

    [in response to Larry Scahffer]:

    [1]: Some were “clients” of one, some of both, some of neither. One had been running this assay in parallel with HPLC for a full year and was not able to get the precision desired. Talking to this client got me wondering what was going on.

    [2]: If you’ll read the paper you’ll see that the commercial lab did not do any better than the winery labs so I don’t think that this is an issue of equipment or expertise. Also in the paper our method is described – 9
    duplicates of 3 wines were run by each lab. They were all blind coded so
    none of the labs know what they were analyzing beyond 27 red wine samples by the HA method as published on UCD website. All chemicals fresh, equipment to specification in method.

    [re: "This is NOT a simple..."]: I would have to say based on our validation study that not only is it NOT simple, even when run correctly it is NOT valid. All labs involved had experience with the analysis.

    [re: "There are many other potential..."]: It’s science so it pretty much goes without saying that facts are of the essence. I think the question that needs to be answered frankly is why a validation study similar to this was not done sooner and by the very academics using and promoting it.

  11. larry schaffer Says:


    Mind explaining the definition of a ‘validation study’ and what specifically was being ‘validated’ in your paper?


  12. Leo McCloskey Says:

    A valid measurement allows wine farmers and winemakers, to create interoperability, for a vineyard or winemaking process, which means easy exchange of information. Validity is to chemistry what spelling is to language. Valid measurements are a language to communicate between winemakers.

    All industries use the same formal processes to test a chemistry’s validity, which is defined by the Association of Official Analytical Chemists. Statistically, validity is the percent recovery of a one measurement to the reference measurement, which can be both a commercial laboratory’s results or standard from the American Standard Testing Materials. A perfect result is 95% to 105% recovery of a reference measurement. When an assay produces 95% to 105% recovery it can be used as an industry standard, since users can create interoperability between wineries. By example, Federal regulatory agencies demanded and created validity for wine alcohol measurements used to approve California wine labels. In the case of alcohol measurements the validity is better than ±5%. Validity testing for tannin is of greater importance than for alcohol.

    Tannin is economically important to wine companies. This is because tannin is linked to taste scores, which are linked to bottle prices. A valid tannin measurement allows California winemakers to match their tannin concentration to the benchmarks by which we all judge wines, which are those from the great European and New World appellations such as Bordeaux and Napa Valley.

    It makes business sense to validate any assay that has economic value to fine winemakers.

  13. Brad Kitson Says:

    Please help me I’m a little confused. Some people here have said the assay wasn’t validated at UC Davis. My assumption is that would have represented the major work of Jim Harbertson’s PhD thesis. Is it being said here that he didn’t statistically analyze the precision and accuracy of the assay in his thesis? Numerous master’s students have utilized the assay in the vineyard and winery. Are you saying that none of these studies represent any level of validation of the assay? My assumption is that these studies would have a lot to say about precision with real world data and could have something to say about accuracy.

  14. Anthony King Says:

    Larry and Leo,

    Glad to see that you are both participating in this conversation. You are right that validation studies are key to feeling confident that the data is meaningful. The question is whether the assay was performed correctly at these various facilities.

    Many things can go wrong in a laboratory setting. This is why CONTROL SAMPLES are key. Measurement of the same wine in each lineup of samples allows you to check for repeatability. Also, it is helpful to include benchmarks in each run; for instance, how do the tannins of these fermenting samples compare to last year’s blend?

    The truth is that your paper does not include enough information to properly assess what might be going on? Other than Vinquiry, did these labs have any experience with the assay? Do they own microbalances for measuring the catechin standards? What were the R2 values of the catechin standard curve? If that R2 value was unacceptable, was the data still included in your validation study? Were the micropipettes properly calibrated? Did the operators know how to properly use a micropipette?

    The raw data would be helpful in understanding the details of the situation. Can you please post the raw data used for this experiment?

    Thank you.

    Anthony King
    Lemelson Vineyards
    Carlton, Oregon

  15. adam Says:

    Thank you Wes! Science is sucking the soul out of the domestic wine culture!

  16. Larry Schaffer Says:


    I agree that ‘science science-sake’ should not get in the way of creating an artistic product such as wine . . . but that said, we all depend upon science in this industry . . . including YOU!

    And this assay, though not intended for all wineries, certainly is very practical and provides objective, practical information that winemakers can AND do use to help with fermentation regimes, pressing decisions, blending, and more . . .


  17. larry schaffer Says:

    Arthur et al,

    Here is the UC Davis Dept of Vit and Enology’s response to the current research papers from Mr. Brooks et al:


    As everyone can see, there are many differing opinions about the results from the Brooks et al study . . .


  18. Arthur Says:


    Winebusiness.com reports on Thursday Dec 18th that UC Davis V&E Chair Andrew Waterhouse released a statement asserting the department’s support of the Harbertson-Adams assay.

  19. Leo McCloskey Says:

    We scientists can thank or discredit winemakers for reporting on our work.

    University of California’s chair of Department of Viticulture & Enology discredits Brooks et al’s publication in the December 18 letter.

    I recommend thanking Brooks’, afterall his work was published in the prestigious J Assoc of Official Analytical Chemists, which required high precision research, and peer review processes. When was the last time any of us published in this journal?

    Thanks Brooks, too, for using commercial laboratories accredited by the International Standards Organization (ISO). The chair reports the winery laboratories were not accredited. The fact is the chair does not know whether the laboratories are accredited or not. Two commercial laboratories accredited by ISO were used by Brooks, one for finding the error within the Adams-Harbertson and another for finding the error between HPLC and the Adams-Harbertson. When was the last time the American Society of Enology and Viticulture performed a validity study?

    Winemakers such as Brooks et al could get the impression that there is a culture of the cover-up in California if we do not thank them whenever they want to report from the vineyard or and winery. Winemakers should be encouraged to report problems they find, whether they are as innocuous as co-pigmentation and tannin or as econmically important as black-goo, Primitivo, rootstocks, and TCA.

    Thanks Larry.

  20. wine sooth » Blog Archive » Electrifying wine. Says:

    [...] or ionization. The polyphenols in the wine might then react with those metal ions. After all, the recently debated Harbertson_Adams tannins assay takes advantage of the fero-reactive tnature of some polyphenols to precipitate [...]

  21. Linus Says:

    I know it late to add my two cents but I just stubbled on this thread and there is something I would like to say as a reader of the Brooks JAOAC 91(5) paper and a soon-to-be-former AOAC member (having declined to renew my subscription after this gross disappointment in their publishing standards): this paper, is not a validation study at all. The laboratories used were not all certified labs,which is fine but in the absence of that condition (non standard conditions) other mention of equipment calibration and uniform training should have been given (which it was not). I equate this excercise to someone exclaiming “Clocks found useless,” after asking multiple people the time and getting different answers. I’m sure the statistics were preformed to utter mathematical precision but its a case of: garbage in = garbage out, as the study design is embarassingly bad.

  22. Larry Brooks Says:

    Actually, Vinquiry which participated in this study is an accredited lab. They were sent the same blind samples as the winery labs. The precision of this accredited lab was no better than the winery labs so I think we can concluse that the winery labs performed as well as the accredited lab. It is also worth noting that this assay was released and promoted by UCD specifically as a winery lab analysis. We were testing it in the environment that it was supposedly designed for. I would stick with my original conclusion, garbage analysis, garbage results.

  23. Brad Kitson Says:

    I appreciate that the study was done. I did a “quick” review of the paper itself.

    The most useful data in the paper are the CV numbers. CV is a very good measure of precision. In Table 4, the pinot noir no.1 CV is 14.1%. That means there’s 14.1% variation in testing this wine. Not so good. When at a later date the lab tested this wine again (Pinot noir #2), they got CV numbers of 2.8%. Wow, that’s pretty good! If you look at the CVs for the Merlot and Cab, the same trend of better precision was observed. What we are seeing here is a CLEAR indication of the lab getting better at the analysis.

    A further look at Table 4 shows a trend of higher recovery for all three of the wines. This a CLEAR indication that as the lab got more precise, the lab also got more accurate.

    My conclusions from the DATA are that one commercial winery has learned to run this analysis with much better than AOAC-approved precision. It appears that the commercial lab also got more accurate. How accurate can’t be determined from the data. The study lacked a standard, as specified by AOAC guidelines, to measure accuracy. The conclusions contained in the paper are NOT supported by the DATA.

    Larry’s last post doesn’t agree with the DATA. The commercial lab’s results were by far the best after they learned the analysis.

    Brad Kitson
    Assistant Winemaker
    Farella-Park Vineyards

  24. Larry Brooks Says:

    Brad, With all due respect I don’t believe that you’ve understood the data presented. If as you state that the cv data are the most important you will see in tables 1,2,&3 that indeed the commercial lab had higher cv than the winery labs involved in this study. Table 4 does not show sequential analyses and improvement in technique by the commercial lab. This accredited lab was already using this assay and selling it to its customers and had done hundreds if not thousands of these analyses. What it shows is unacceptable variation in recovery and other analytical aspects of two different wines sent in multiple samples.
    You have a good point about the “standard”. There was no standard used in the original presentation of this assay by Adams and Harbertson. Our validity study was focused on variation between wines. This does not require a “standard”. The variation is unacceptable with or without a standard.

  25. Brad Kitson Says:

    Larry, Would it be possible to stick to the paper and, more specifically, Table 4? What exactly did I misunderstand? Are you saying the results for Pinot#2, Cab#2 and Merlot#2 aren’t precise, in terms of CV?

    Are you saying Pinot noir #1 and Pinot noir #2 are not the same wine? (I assumed they must be because of the data was used to compare recovery and this comparison would be meaningless between different wines.)

    Are you saying formula 2b doesn’t have first result divided by second result? That implied sequential to me.

    The analysis put forth in the paper in regards to Table 4 missed the point completely. It compares recovery between precise data and imprecise data. IT”S PROBABLY A GOOD THING THAT PRECISE DATA DIDN’T COMPARE WELL WITH IMPRECISE DATA! Though, the paper says it’s a bad thing. The IMPORTANT analysis is why is the SAME lab on the SAME wine consistently imprecise then consistently very precise?

    My conclusion was learning. How do you explain the 5x improved precision between Pinot noir #1 and Pinot noir #2? And, how do you explain similar improved precision for Merlot #2 and Cabernet #2? If not by learning, then how?


  26. Larry Brooks Says:

    Dear Mr. Kitson,
    I strongly suggest that you read the paper more carefully before attacking it’s conclusions. The tables 1,2, and 3 deal with interlaboratory results and as I said they show that the commercial lab was if anything less precise than the winery labs despite performing this assay many more times. Table four as is clearly stated on page 1092 of the paper addresses intralaboratory precision. To qoute, “The commercial laboratory served to measure intralaboratory precision by performing analyses on the same wines on 2 different occasions.” There were issues with all labs on yeild and some labs with precision. None of this is acceptable performance for an assay as far as I’m concerned.
    I’d also like to remind you that using CAPITAL letters in communication of this sort is the text equivalent of yelling. In the interests of civility why don’t you tone it down?
    Larry Brooks

  27. Brad Kitson Says:

    The Intralab (Table 4) data:
    (1) Indicates this study had operator problems and
    (2) The problems were most likely related to sample recovery technique.

    The authors of the paper missed these two very important points. You should have dug deeper when you saw the Table 4 data. There’s a source of error not explained by limitations of the assay. It’s in your table 1-3 data, too. These tables are full of the imprecise commercial lab data.

    In tables 1-3, at a minimum, all data from the commercial lab should be ignored and all analysis using the commercial lab data should be ignored.

    I question whether the authors are qualified to comment on what is a useful assay for a winemaker. More importantly, I question the conclusions of this paper. I’ve already shown operator issues. When operator issues are involved, its very hard to rationalize any other problem. When the authors don’t recognize it, it’s even harder to rationalize any other problem.

    Your previous comments calling the assay garbage were rude, mean and unwarranted.


  28. Winemaker29 Says:

    Naturally we assume that all science is good. The goal of science, like journalism, is about shedding light where there is darkness. Yet, science and journalism can be wrong quite often when no one is chekcing the scientists and journalists. Just because a scientist produces science does not guarantee the science works in the hands of trained scientists. Brooks et al, highly experienced winemakers, could not replicate the science. Thanks.