To Protein Rest or not to Protein Rest?

I've collected and edited slightly some postings that George Fix made in August, 1994, on the topic of whether and when a protein rest is appropriate or should be avoided.

Date: Thu, 18 Aug 94 10:24:46 -0500
From: gjfix@utamat.uta.edu (George J Fix)
Subject: Yield

I have found that the two most important operational variables affecting yield are the mash pH and the time/temperature program used.

For infusion mashes I have found that it is highly advantageous to keep the mash pH at 5.4 or lower. Decoction mashes appear to be more forgiving in this regard. The negative effects of a high mash (and wort) pH are numerous, and I plan to treat this subject in great detail in my new book.

It appears that yield (which is a measure of the extent we dissolve grain carbs.) is strongly influenced by the lower temperatures used, while the composition of the carbohydrates dissolved (i.e., % fermentability) is influenced by the higher temperatures. The following batch is typical of the results I have been getting with highly modified malt.

   Data
         brew size = 15.5 gals
         total water = 9.5 gals in mash + 9.5 gals for sparging
         grain bill : 24 lbs. D-C Pale Ale malt
                       2 lbs. D-C Caravienne
                       1 lb.  D-C Aromatic

   Temperature Program

         40C (104F) - 30 mins.- 24 lbs. base malt + 6.5 gals. water
        
         Transition 40 to 60C - add 3 gals. of boiling water - add
             adjunct malts at the end as a brake - less than 5 mins.
             is needed

          Note - I now feel (with Narziss) that the time spent in the
             range 45-55C should be keep below 15 mins. if highly
             modified malt is used.

          60C (140F) - 30 mins.

          Transition 60 to 70C - external heat is needed and this can
             be done in 15 mins.

          70C (158F) - 30 mins.

Mash Data

          Vol = 9.5 gals.
          % extract = 22P (i.e., 22 grms extract per 100 grams mash)
          SG =1.092

Converting to wt/vol and US units the % extract comes out to 62.24 lbs/bbl. (~2 lbs/gal). This means that the mash has

          62.24*9.5/31 = 19.1 lbs. extract.

Yield in commercial units is

          19.1 * 100/27 = 70.7%.

Yield in homebrew units is

          92 *9.5 /27 = 32.3 pts/(lbs/gal).

The value of the rest at 40C can not be understated. The rise in SG in this mash is almost 3 times faster than what I get when this rest is omitted. The final mash yield is ~20 % higher. Clearly there is a lot of favorable activity going on including preparation of the enzyme systems, beta glucanase activity, and highly favorable enzymatically assisted grain liquefaction.

This wort clears up very quickly (for European malts), and after ~2 gals. of recirculation it will change from a milkly turbidity to a moderate see through clarity. The 1st wort is then run into the kettle until 1 inch of liquid covers the grain surface. At this point sparging is started with the inflow and outflow rates adjusted to ~1/3 gals/min. It is of course very important to maintain the liquid cover of the grain bed. After ~30 mins. the sparge water is depleted, and the outflow is increased to ~1 gal/min. The following is typical data at kettle full:

                   Vol = 17 gals.
                   % extract = 12.3 P
                   SG = 1.050.

Repeating the above calculations, this means that 18.3 lbs. of extract was carried over to the kettle. The losses in sparging were


                   water = 19 -17 = 2 gals.
                   extract = 19.1 -18.3 =.8 lbs.

By using a slower runoff and a higher fraction of sparge water it is likely one could leach most of the residual extract out of the grains. I choose not to do this because this is not the way I brew. The finished wort in the fermenter typically cames out as follows:

                   Vol = 15.5 gals.
                   % extract = 13.3 P
                   SG =1.053

This means that a final yield of 30.4 pts was obtained. With a single temperature mash (or 60-70 combo) this would have dropped into the 26-28 pts/(lbs/gal) range.

The % fermentability as determined by a liter sized forced fermentation at 30C usually gives an ADF near 79% (RDF = 65%). This means that FG limit is 1.011. The ale strain that I am using does not completely ferment maltotriose, so I usually wind up a 1.012 to 1.013 in this context. The ADF is greatly influenced by the times spent at 60 and 70C. E.g., 15 mins. at 60 followed by 45 mins at 70 will typically drop the ADF into the low 70s. The reverse will increase it into the mid 80s. For my ale strain spending at least 15 mins. at 60C is crucial for it greatly increases the maltose/maltotriose ratio.

I strongly prefer moderately modified malt for lager beer, and I have found that a protein rest at 50C (122F) has numerous advantages. I have done test brews with a 40-50-60-70 schedule, but little is gained in yield over a 50-60-70 program. I personally am going to stick with the latter since among other things half of the 3 gals of transition water can be used to go from 50 to 60, while the other half can be used to go from 60 to 70. Thus very little external heat need be applied to the mash. Another point I have noticed is that most lager yeast are insensitive to maltose/ maltotriose ratios. W-34/70 for example starts taking in maltotriose at the same time it takes in maltose, and metabolizes both sugars at approximately the same rate. Thus the rest at 60C can be used with such strains simply to adjust ADF.

George Fix

Posting 7: Extracted from file:  1511
Date: Tue, 23 Aug 94 16:28:05 EDT
From: cem@cadre.com (Chuck E. Mryglot)
Subject: George Fix  yield posting

I found the yield posting by George Fix very interesting. However, I wonder if someone (George?) could clarify something for me.

At the end of the post is:

>      I strongly prefer moderately modified malt for lager beer, and I have
>      found that a protein rest at 50C (122F) has numerous advantages. I have
>      done test brews with a 40-50-60-70 schedule, but little is gained in
>      yield over a 50-60-70 program. I personally am going to stick with the
>      latter since among other things half of the 3 gals of transition
>      water can be used to go from 50 to 60, while the other half can be
>      used to go from 60 to 70.

The example given in the post was a 40-60-70 schedule with a comment to minimize the time in the 45-55 range. In the above snipet the 50-60-70 schedule is recommended. Is there some contradiction here? and/or am I misunderstanding.... (won't be the first time...). Also, if I use the 50-60-70 schedule, should I rest at 50 for 30 minutes (as a replacement for the 40 in the example) or should I stay under 15 minutes as noted.

Or is this the difference for highly vs moderately modified malt.

Zum Wohl
ChuckM
Posting 8: Extracted from file:  1514
Date: Fri, 26 Aug 94 13:56:41 -0500
From: gjfix@utamat.uta.edu (George J Fix)
Subject: References, Indices, New D-C Maltings

I been asked for specific references on Dr. Narziss' work on malt and mashing. IMHO the most informative are the following:

  1. "Comments on some taste factors in Beer", Brauwelt, Vol.IV, 1992.
  2. "Qualitative and Quantitative aspects of Mashing ", Brauwelt, Vol. III, 1993.

The first discusses (among other things) the negative effects on a beer's malt flavor arising from excessive protein modification. The second discusses his ideas on how malt with a high degree of protein modification is best mashed.

I have been asked about the comment in M+Br. Sci. (p.260) that malt whose Kolbach index is in the range 37-40% is overmodified. It is my belief that this is possibly a typo. The German malts I have been playing around with (Durst, Irek, and the new one from Stuttgart) range from 36-38%, and the original D-C Pils malt (according to the Siebel data) came in at 38%. For these a protein rest is highly advantageous. Narziss is taking about malts whose Kolbach indices are in the 40s. BTW this index is virtually the same as soluble protein as % of total protein (which is sometimes shortened to the "S to T ratio").

I have also been getting some e-mail from people expressing some disappointment with the malt flavors they are getting with lagers made using D-C Pils malt. Terms like "dull" and "neutral" have been used to describe the effect. I personally have been busy comparing the ones from Germany, and have not brewed with the D-C version for some time. I got a copy of Schreier's new malt analysis sheets to see what changes might have occurred over the original version with which I have the most practical experience. The assortment data looks terrific (those using floor maltings always always seem to get nice uniformly plump kernels!). The protein level is at 10%, which is in the dead middle of DeClerck's preferred range of 9-11%. The bad news is seen in the modification data. As far as starch modification is concerned, just about all brewers (lager or ale) prefer a high degree. One index that is used for this is the fine/coarse grind extract difference. The D-C Pils comes in at 2.2%, which is a tad high and indicates a slight undermodification of grain starch. The other D-C malts come in at 1.5 or lower which is ideal. The original version of the D-C Pils malt came in at 1.7, which also gets good marks. Perhaps this change may explain some of the yield problems with the new version which have been communicated to me. (In general, the lower the f/c grind difference, the higher the degree of starch modification and the easier it is to extract carbohydrates).

The protein modification is exactly the reverse, and the S/T of the new D-C malt of 48.6 is the highest I have ever seen for commercial malt of any type. E.g., domestic malts and malts from Canada typically are in the range 40-43%. The D-C ale malt comes in at 43%, which is close to values I have seen for H-B and M+F's pale ale malts. Values I have seen for Maris Otter range from 42-43%. Even British maltsters would regard anything over 45% as undesirable overmodification.

I promptly called Arthur Spurlock at Schreier, who BTW was very helpful and friendly (Schreier is indeed a great company!). His own measurements indicate that the Kolbach index is lower than the values quoted, but still in the mid 40s. The references cited above have hinted than many of the new spring 2 rowed varieties (e.g., Alexis) are displaying a tendency toward a high degree of protein modification even with continental Pils malting procedures. This means that the current situation with the D-C Pils malt may soon be typical of most lager malt from Europe. The practical significance of this for us is unknown to me, and I have no way of telling if this is the real problem behind the complaints. Current research points clearly to the desirability of having a high degree of starch modification without protein overmodification, and these new varieties seem to displaying the reverse. Narziss (reference 2) says in effect that not to worry for altered mashing schedules can overcome any difficulities. I for one need to get some of the new D-C pils and brew with it.

BTW Alexis is a hybrid from Triumph (I believe it called Trumpf on the continent) and wild barley. Triumph made some great malt in its day, but now appears to be on the way out. It never displayed a tendency to protein overmodification, and many feel this property in the new varieties (all Triumph hybrids) may be coming from genetic material in the wild barley.

George Fix

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Edited by

Spencer W. Thomas (spencer@umich.edu)