sulfate and hop perception

[slugsly]

Is anyone a member of this site and able to read this article. It seems like they collected data on sulfate levels and hops additions:

http://www.mbaa.com/publications/tq/tqPastIssues/2010/Abstracts/TQ-47-2-0623-01.htm

"We were able to show that process variables in terms of time and manner of hop addition had statistically significant effects on the perception of bitterness, hop aroma, hop flavor, citrus character, fruit character, grassy character, and malt. We also found a statistically significant negative correlation between the intensity of hop flavor and level of sulfate in the brewing water."

 

[ColoHox]

The article was more focused on the timing of hop additions, but they did measure sulfate in the water.

They found that: "highly hopped beer might be better made using brewing liquors with lower sulfate concentrations."

 

[PlinyTheMiddleAged]

I wouldn't call that linear fit to the data "statistically significant". There is a heck of a lot of scatter of the data relative to that line. I wonder what the conclusion would be if a different function were fit - perhaps it would conclude that moderate sulfate levels are beneficial. Of course, I could be totally wrong since I'm only looking at one figure taken out of a paper.

Interesting, nonetheless.

 

[ajdelange]

It is statistically significant but the significance here means that it is unlikely that the correlation coefficient is 0. Now 0.44 (the value for Pearsons r) that goes with Fig. 10 isn't a very impressive correlation coefficient by any means. It indicates that 20% of the variation in hops perception is attributable to sulfate and the rest to 'noise' by which here we mean things other than sulfate. Also, clearly, if you take out the 750 and 1200 mg/L points the correlation (and r) go down. I wouldn't hang too much significance on two data points but I wouldn't dismiss them out of hand either.

 

[PlinyTheMiddleAged]

Just out of curiosity (and too much free time), I took a crack at reviewing the data in that figure. I replotted the data in Excel and fit a line to it - I got an R^2 value of 0.20. Then I tossed out the two values at 760 and 1200 ppm (I dismissed them out of hand) and the resulting R^2 drops to 0.08. So, as AJ says those two points have a strong effect. When I fit a second order polynomial, the R^2 jumps back up to (nearly) 0.20.

I think all of this is a weak relationship, but this does lead to the tenuous conclusion that hop flavor is supported by moderate levels of sulfates - the second order polynomial peaks at around 150 ppm. In other words, I pretty much baked the interpretation of the data to fit my a priori conclusion!

 

[zwiller]

Interesting. Not really scientific compared to the study, but now and then I do a low SO4 IPA to see if my attitude toward sulfate loading changes and it always is a step backward and I go back to 300ppm.

Although I've not visited each location, I have gone to at least 3 Rock Bottom Breweries and as a BJCP I think their beer is mediocre at best and this unfortunately distorts my interpretation of the study. That said, OT but I am curious about the results of the timing studies.

 

[mabrungard]

It's interesting that the researchers explored very high sulfate levels. I have to wonder if the water taste would have influenced the results at the every high levels?

An interesting anecdote came from Colin Kaminski when we were helping with the Water book. He pointed out that he had explored fairly high sulfate levels (I think it was in the 600 to 800 ppm range) and he said he liked the beers, but his customers didn't. As AJ points out, sulfate is definitely an ion that some tasters prefer at differing level.

Along with that advice, I like to point out that you can't understand what your preference is without going over the limit. With the ease of dosing gypsum in your glass of beer, you can at least explore changes in flavor and perception without 'ruining' a whole batch of beer. My palate says that 300 ppm is nice in a hoppy beer. Find your level!

 

[slugsly]

Thanks for the responses. The person who told me about this study implied it was definitive proof sulfate levels in hoppy beers dont matter. Hardly seems to be all that definitive and I also wonder what other variables were in play.

I've done what Martin B suggested, putting a pinch of gypsum in a beer I was drinking and thought I preferred it after the small addition but it could've just been in my head. I'll have to try some sort of blind taste test.

 

[zwiller]

An argument could be made for placebo affect. That said, nearly all the recipes in the book IPA (provided by the brewery) have the sulfate bump.

Although dosing a pint works with many things, I recall the interaction of sulfate and hops is through boiling, so not entirely sure you'll get the same results.

 

[ajdelange]

Keep in mind that Fig. 10 shows correlation between sulfate level and perceived hop flavor. Indeed the plot shows that there is only a weak correlation between the two and that it is negative. No correlation between perceived bitterness and sulfate is presented but data is presented correlating perceived bitterness and measured at r = 0.39. This is a weak correlation. The author says "There must be something else that affects the perception of bitterness than maeasred IBU since the measured IBU cannot account for all the differences observed for perceived bitterness." Indeed there must and I suspect it is the makeup of the panel. I wouldn't take this paper too seriously.

 

[zwiller]

AJ, since you have read this, can you provide any insight as to what their results were relating to most citrus and fruit character? This is extremely interesting to me. As of now, the best results I have achieved were a 30m hopstand above isomerization temps.

 

[Hermit]

Indeed there must and I suspect it is the makeup of the panel. I wouldn't take this paper too seriously.

I know a handfull of people whose palate I trust and I know will give me honest answers. None of them were on this panel.

Seriously, I can only read the abstract but they lost me on the first sentence. "Craft brewers face the challenge of creating beers with high levels of bitterness and hop flavor and aroma from an extremely limited supply of aroma hops." On second thought I guess it is chanllenging to get "high levels of bitterness" from aroma hops. But, I suppose that is why most of us using bittering hops. (And they thought they were brewing identical beers except for the one hop addition and the sulfate levels varied that much? It's after midnight so I'm probably missing something here. We won't even go into what might have been in the various waters at the different breweries.....)

The bit I have access too seems to be written to impress, not inform.

 

[spenghali]

The real thing to take home is that everyone's palate is different due to genetics. Small sample sizes from sensory panels may not be representative of the population. Heck, some people cannot even perceive certain bitter compounds while others can (such as caffeine). It is a complex science and a complicated chemical system that leads to perception of "hoppiness" or bitterness.