Maltase Rest Hefeweizen Experiment

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Mr. No-Tip

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Back in November I attended the concise course at the Siebel Institute in Chicago. It was a super intense two weeks and a learnt a lot of useful information about the transition from homebrewer to commercial brewer.

One key piece of information stuck out to me though, and it’s arguably a more homebrewer level technique (simply perhaps because it’s way too much of a PITA to achieve commercially): the maltase rest.

So I tried writing up a quick and dirt rub, but I think Kai Troester of braukaiser.com can say it much better than I:

Maltase converts maltose into glucose. It is therefore an important enzyme for the yeast. But it is also present in malt. But since its temperature optimum is between 95ºF (35ºC) and 104ºF (40ºC) [Narziss, 2005] and it is being deactivated above 115ºF (45ºC), this enzyme does not play any significant role in most mashing schedules since higher temperature rests are necessary to genate glucose for this enzyme.

It is however used in a mashing schedule developed by Markus Hermann from the Weihenstephan brewing school in Germany. This mash converts half the mash to get a large amount of glucose. After that conversion is complete, it is mixed with the remaining mash to achieve a rest temperature of 95ºF (35ºF) where the maltase converts the now existing maltose to glucose. After that the whole mash is again run through a regular mashing schedule to convert the remaining starch to matose and dextrins. The result is a wort with a very high glucose content (about 40% of the fermentable sugars). Yeast fermenting such a wort will generate more esters, a property that can be used to produce German wheat beers with a high ester content.

- Braukaiser

Late last year, I produced two consecutive batches of hef during a 14 hour brew day - one of my standard AABC winning hef and one using a pre-mash and maltase rest much like the above, but with maybe about 33% 'glucose' – 1/3 of the mash was maltase rested.

I bottled a bunch of the beers (I am a firm believer that bottle conditioning heavily enhances a hef) and sent them out to a bunch of Canberra Brewers who I have previously involved in my experiments (Hef three way and Belgian sugar orgy).

Participants were given two beers, differentiated by lid colour – red and black. No further indication was given. Responses were sought on aroma, flavor, BJCP score, and ‘other comment’s.

So…onto the results. You can see the unadulterated comments attached (sorry about the bad format), but here’s a summary:
Bar one participant who got some fairly problematic bandaid phenols in one of the beers, (sorry about that), and some apparent bottle conditioning inconsistencies (perhaps some early tasters), comments were pretty consistent across both beers. Both were rated well, but the red beer was rated a better hef.

In terms of guessing which was which, the consistency was at a rate of 70/30. 70% of participants thought the first ‘red’ beer was the maltase rest (largely due to perceived higher esters), and it also rated much higher.

The black lid beer rated lower, but looking at the comments is interesting – there are fairly split and carrying opinions on the presence of banana, the dominance of clove (or lack thereof). Only the score seems to differentiate the beers consistently.

So which was which?

Most people (70%) thought the (generally considered) more estery red lidded beer was the maltase rest beer. That makes sense if this whole experiment is to prove anything. But here’s the rub….the black lidded beer was the maltase rest beer. The one that largely scored lower, was often viewed as more subtle, and even watery by some participants.

So why?

I am intrigued as to why the experiment effectively disproved the value of the maltase rest, but I have a couple ideas why…

Pitch Size

My reading of the popular belief among homebrewers is that ester production is inversely related to pitch size. In fact it’s the opposite! In a nutshell, the same coenzyme is used for yeast growth and ester production, so if the yeast has to grow more, there’s less potential for esters. If you don’t believe me, check out: http://www.danstaryeast.com/articles/yeast-growth

I have always underpitched my hef, originaly out of the same misperception I am trying to correct above - I never do a starter for my hefs and have pitched a 'just in date' vial in 20+l with no issue. WLP300 is a virulent *******. Learning more about esters though (see the articles above) perhaps this was more of a coinkydink than anything else. Perhaps a 3l starter for your hef could be a trick for some hardcore ester production - perhaps a candidate for a future experiment.

Fermentation Temperature

As you will see if you check out the Hef three way experiment, I do a low and slow ramp to fermentation – pitch at 13 and rise up to sub 20s. This technique has served me well in recent years.

This is a stressful proposition for yeast. Growth is slowed and it’s always been an only somewhat provable point of mine that this increases esters.

In the context of the extra glucose, my current and unprovable thinking comes from the homebrewers mantra that yeast will go for the simple sugars first… that the extra simple glucoses made available by the maltase rest were first consumed in the temperature ramp…while the Co-a was busy making yeast (due to my low pitch) and couldn’t readily make esters. What remained, at proper fermentation temperatures approaching 20c was a thinner, maltose wort that simply had less to give to ‘ester ready’ production.

This is my main working theory as to why a beer that theoretically should have produced more esters produced less.

Oxygenation

I oxeganate my hefes the same as any other beer. It’s widely viewed that low oxy environments will produce more esters. I can’t see a way that this is different between the two methods, but may be a factor in the context of the two differentiators above.

So there you go. I’d love input on anything above!


The following PDF has some issues. Refer to post #3 below for the corrected version.

View attachment Hefeweizen Maltase Rest Experiment 2015 - Google Drive.pdf
 

Mardoo

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:wub: Totally dig your experiments. Breathless fan you might say.

Slightly off topic question. Do you reckon "naturally" carbonating in the keg would have a similarly positive effect to bottle conditioning for these beers?
 

Dave70

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Hey Mr Pink, will that award winning recipe of yours get you something like Weihenstephan heffe?
I might pinch your recipe and method for this weekends brewing.
 

Mr. No-Tip

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Mardoo said:
:wub: Totally dig your experiments. Breathless fan you might say.

Slightly off topic question. Do you reckon "naturally" carbonating in the keg would have a similarly positive effect to bottle conditioning for these beers?
Interesting. I think it would - if there really is an appreciable difference (a blind test of a forced and conditioned sample probably required to test I am not kidding myself) then it's surely a result of refermentation regardless of vessel.

Dave70 said:
Hey Mr Pink, will that award winning recipe of yours get you something like Weihenstephan heffe?
I might pinch your recipe and method for this weekends brewing.
To be honest I've never really done a side by side against commercial hefes. To me it's not a huge banana nose, but I know I am not as sensitive to isoamyl acetate as some people. Feedback tends to be that it's a balanced pretty evenly between banana and clove with neither really dominating. This is probably reliant on the ability to do the step mash.
 

Mardoo

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I often think it is possible to get an additional ester hit from bottle conditioning, ones where you don't lose any to oxidation. I haven't run taste tests yet as I've only just started kegging However, according to my reading, fermenting under pressure suppresses ester production so there may not be any appreciable ester production in bottle or keg conditioned beers. My speculation is that is part of what accounts for the flavour difference in bottle conditioned beers.

Thanks for sharing that great little insight into mashing, and your experiment. I've been wanting to go to Seibel for a very long time now. You may have tipped me over from dreaming into planning.
 

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