Impact of Boiling Time & Temp & Trub on Fermentability

[biertourist]

A Master's Thesis on the myriad impacts to a beer on increasing wort boiling temp and duration. http://dalspace.library.dal.ca:8080/bitstream/handle/10222/15434/Mishra%2c%20Ankita%2c%20M%20Sc%2c%20PEAS%2c%20August%202012.pdf?sequence=1


Points:
[list bull-blackball]

• There IS such a thing as "too vigorous" of a boil; an overly vigorous boil exerts shearing forces that break trub into small flocs instead of large flocs and makes them less likely to properly coagulate and fall out of solution.
  
• Some of the precursor chemicals involved in malliard reactions (5-hydroxymethyl furfals(HMF) & furfals) inhibit yeast's ability to produce CO2; young yeast cells will take these chemicals up and convert them to non-ethyl alcohols if there's not too much of it; too much HMF or furfals and the yeast just can't get rid of them (much like the diacetyl problem)
  
• Generally small peptides, amino acids, and vitamins in the solution can reverse the impact of the previously mentioned chemicals
  
• To summarize the previous two points, although melanoidins generally taste good and increase stability of beer, in high concentrations they reduce wort fermentability (dark bocks being the stereotypical example here)
  
• Increasing yeast nutrient loads in wort lead to a reduction in final beer PH (FAN is a major post-boiled wort ph buffer)
  
• Normal gravity all malt worts contain MORE than enough yeast nutrients; using yeast nutrients here will likely increase diacetyl, ester, and fusol alcohol production
  
• The exact mechanism by which a lack of yeast nutrients may lead to a stuck fermentation has been thoroughly documented
  
• An increase in Zinc concentration increases fermentation speed without increasing cell growth (so it doesn't increase diacetyl or ester production)
  
• Hot break trub is primarily made up of large molecular weight proteins that degrade head formation and would later lead to chill haze formation (when combining with polyphenols
  
• Cold break trub is primarily protein-polyphenol based and includes carbohydrates, too
  
• Although some studies have shown that trub has a stimulatory effect on yeast growth some new studies have suggested that this is because trub acts as a nucleation site for CO2 which decreases the dissolved CO2 in solution and this is what increases the yeast health; traditional German lagering practice of adding boiled beech wood chips perform the same function.  Another study showed that the presence of trub leads to faster yeast autolysis
  
• Most zinc in the boil gets pulled out of solution with proteins in the break (it may be better to add zinc in the fermenter)
  
• Higher temp boils and longer boil durations resulted in fermentations with a slower uptake in sugar and a high finishing gravity (lower fermentability)
  
• The turbidity test shows that there was less yeast in suspension in the beers that were boiled longer and hotter; it appears that the increased presence of malliard constituents and a decrease in yeast nutrients (FAN) are ultimately responsible
  
• The longer and hotter boiled worts also saw faster yeast flocculation which also contributes to the increase in finishing gravity (flocculation likely occured faster because lower levels of yeast nutrients mean that the yeast depleted their reserves before consuming all fermentable sugars)
  
• It's also SUPER important to point out that this test measured the concentration of each of the major sugars in each heat-treated wort and showed no significant change; the increased final gravity is NOT due to the "carmelization of sugars"/ the formation of unfermentable sugars.  We really need to get away from this language.  We know that sugar carmelization at boiling temps, ph and concentration is simply NOT going to happen.
  

When taking this study and the previous one on the fermentability of crystal malts into account its becoming clear that high temp and long boils result in more residual sugars than adding a small percentage of low color crystal malts... Interesting....


Also interesting is that this study really is starting to show a pretty strong coorelation between malliard products and a higher finishing gravity; I think we're finally getting some evidence for why decoction mashed beers taste maltier; it's not just the TASTE of the malliard products but also the impact that they have on the yeast, which has an impact on the fermentation.  -AWESOME!

I hate to say it because I've been really anti-90 minute boil for a while but a 90 minute boil definitely might be a good way to go to get a maltier and slightly sweeter finish.

It's also important to note that long boiled beers should probably have yeast nutrient added back at the end of the boil and the longer and hotter you boil, the lower the FAN content of your wort.



Adam

[biertourist]

This study also validates that the German tradition that says that trub is bad for a fermentation and that you want to carefully avoid getting trub into your fermenters is correct.

Trub is BAD for yeast; not good for it.

They covered this from many angles and reviewed the existing literature on both sides of the argument. Trub is bad; decreased CO2 levels during fermentation are good.

Adam

[Ciderhead]

Fantastic! proof of what I have been saying for years, well except I drew the analogy of my kids sitting in shitty nappies, but proof never the less!
But dammit I am just coming into 90 min boils, and they have been too vigorous, coupled with too much oxygenation and hey presto Wurthers original.
Remind me what FAN is again?

ok Wiki

Free amino nitrogen (FAN) is a measure of the concentration of individual wort amino acids and small peptides (one to three units) which can be utilised by yeast for cell growth and proliferation. For vigorous fermentation, a sufficient quantity of FAN must be present in the wort. An excessive concentration in the wort is not desirable however, as this may cause production of a significant quantity of fusel alcohols, or spoilage of the finished beer by other organisms.

[M3talDave]

Decoction mash may make a beer taste maltier (or not), but I doubt this is due to any Maillaird reaction in the mash tun.  From Harold McGee's (1984) work, I understand that higher temps than those used in mash tuns are required to get this maillard reactions going.  If d-mash adds maltiness, it's more likely (in my opinion) because part of the mash time is at higher temps - temps at which conversion is less effecient.

The 90-minute boil resulting in maltier beers makes 100% perfect sense to me.  Looking at he historical record, we see extremely long boil times in medieval English brewing.  Given the maltiness of trad English beers, I would have expected a correlation between the two. This study, I suppose, shows a causal relationship, which is nice to know.

[DEMPSEY]

Just being watching the mega factories series,the current one is the Corona Brewery in Mexico. They do a 90 minute boil and after the wort was passed through the heat exchanger at 80C with 2C water coming in the other side,the wort reaches the fermenter at 10C.

[biertourist]

Decoction mash may make a beer taste maltier (or not), but I doubt this is due to any Maillaird reaction in the mash tun.  From Harold McGee's (1984) work, I understand that higher temps than those used in mash tuns are required to get this maillard reactions going.  If d-mash adds maltiness, it's more likely (in my opinion) because part of the mash time is at higher temps - temps at which conversion is less effecient.

I'm confused by this comment.
You do understand that decoction mashes involve taking a decent proportion of the grain out of your kettle, then boiling it (at 100C, a temperature much higher than normal mash temps and a temp at which malliard reactions certainly DO occur), then adding the boiled portion back to the main mash and doing this again another 2 or 3 times.

-You're boiling your mash 2-4 times; boiling in the presence of simple proteins and sugars -the exact conditions in which malliard reactions occur.


(Are you possibly thinking of Step Infusion mashing where you mash at multiple temperatures either by increasing the mash temp via direct heat or hot water infusions?)

Adam

[biertourist]

Just being watching the mega factories series,the current one is the Corona Brewery in Mexico. They do a 90 minute boil and after the wort was passed through the heat exchanger at 80C with 2C water coming in the other side,the wort reaches the fermenter at 10C.

Many, many, many micro and big breweries do 90 minute boils but this is mostly to boil off the DMS precursors.  -The surface to volume ratio of large commercial brew kettles is VASTLY different to home brew kettles.  Home brew kettles have significantly increased evaporation rates.  -10% is plenty to get rid of DMS; even 6% can be ok depending upon  your basemalt selection.  I was getting over 20% with my 5.5kw electric elements on full blast in a 5 gallon batch; if I could get decent hop isomerization out of a 30 minute boil I'd actually be ok from the perspective of DMS.


The study is also interesting in that it points out that really strong beers should actually only be boiled for 60 minutes if you want to maximize attenuation and dry that bad boy out to get a lower finishing gravity; a long boil actually works against the attenuation of those barley wines!

Adam

[biertourist]

hey presto Wurthers original.

I just had my beautiful oatmeal stout turn into wurther's original!  -But it wasn't there at the beginning nor for a long time after.  -That means the culpret is: 

Pediococcus in the beer line with the tap as the infection vector!

I just got a keggerator and now I have a tap head exposed to the outside air; it's also got a crappy non-Perlick tap that gets clogged up with beer sugars and I haven't been giving it a squirt of starsan after each days use so I was really asking for it.

Its nice to know that diacetyl can be yeast pitching / fermentation related OR it can occur post fermentation / at serving because of pedio infection.  -If I had that nice microscope that I've been oogling, I could validate it for sure, but alas, I don't have one currently..    


Adam