A Homebrewing Perspective on Mash pH III: Distilled-Water pH and Buffering

Capacity of the Grist∗

D. Mark Riffe† and Mick Spencer
(Dated: May 10, 2018)
We have determined the distilled-water mash pH (pHi ) and buffering capacity (Bi ) of a number of
different specialty grains used in beer brewing; our measurements have focused on flaked grains and
19 to 130 ◦ L noncrystal malts. Our simple technique, which any homebrewer with a pH meter and
temperature controller (plus some common kitchen equipment) can replicate, is to measure the pH
of precise mixtures of each test grain with a fiducial grain (for which Bi is assumed to be known).
Owing to a variety of processes used in the manufacture of noncrystal specialty malts, the pH and
(especially) the buffering capacity of these malts exhibit much less correlation with malt color than
is observed with similarly colored crystal malts. Flaked grain pH and buffering capacity varies quite
dramatically among the different grain types. In addition to results specific to flaked and specialty
grains, we have obtained two other general results: for a given grain (i) pHi and relative values of
Bi are largely independent of mash thickness (in the range of 2.5 to 8 L/kg), and (ii) batch to batch
variability of pHi can vary upwards of ±0.05.

1. INTRODUCTION pHi or Bi printed on the bag.

The good news is that a number of experimental stud-

The pH of a brewer’s mash depends upon three broad ies have been carried out that inform us about pHi and Bi
inputs: (i) the composition of the grist, (ii) the ions pre- for a variety of brewing grains. The most extensive work
dissolved in or added to the brewing liquor, and (iii) to date is that of Kai Troester (KT), who has made mea-
the concentration of strong acids or bases added by the surements on no fewer than 22 grains [1, 4]. A. J. deLange
brewer [1].1 Factors that tend to make the mash more (AJdL), another brewer with a keen interest in mash pH,
acidic – driving the pH down – are darker grains, the has carried out careful measurements on 10 different grist
divalent ions Ca2+ and Mg2+ , and acids. Conversely, components [3, 5, 6]. The maltsters at Briess have gotten
factors that tend to make the mash less acidic – driv- into the act: experimental results on a variety of Briess
ing the pH up – include lighter colored malts, carbonates products have been obtained by Bies (8 grains) [7] and
(H2 CO3 in one of its ionic states), and bases. Geurts (18 grains) [8]. Fairly recently, Joe Walts, a pro-
Each type of grain that composes the grist affects the fessional brewer with an analytical bent, has made pHi
pH through two properties. The first is the pH that re- and Bi measurements on 17 different grains [9]. All of
sults when the grain is mashed in distilled water. This these studies have focused on base malts, caramel (crys-
is known as the distilled-water pH (pHi ) for that par- tal) malts, and dark roasted grains.
ticular grain [1].2 The second property is the resistance
that each type of grain has to other influences that effect Here we build upon this previous experimental work
changes in the pH. This quality can be characterized by in several ways. First, we have developed a simple ex-
a quantity known as the buffering capacity (Bi ) of the perimental technique for determining pHi and Bi values.
grain [2, 3]. If one knows both pHi and Bi for each com- Briefly, our technique consists of measuring pH values of
ponent of the grist (i = 1 to N , where N is the number a set of precise mixtures of a test grain and a fiducial
of components), then one can readily estimate the grist grain (for which Bi is already assumed to be known).
pH (pHG ), which is the pH when the entire grain bill is For a typical homebrewer this technique is much simpler
mashed using distilled water. Knowing these quantities than the standard acid/base titration experiment typi-
also allows one to predict the pH shift from any other pH cally used to determine Bi . Second, we have measured a
changing ions that may already be present in a typical variety of brewing grains from two categories that have so
water supply or added by the brewer. The bad news is far been largely neglected: (i) noncrystal (but not dark
that malts do not arrive from the malting company with roasted) specialty malts and (ii) flaked grains. Third, we
discuss the relationship of various aspects of the malting
process to trends in pH and buffering capacity.

∗
c D. M. Riffe and M. Spencer (2018). The authors can often
Our paper proceeds as follows. In Section 2 our exper-
be found hanging out on the Beeradvocate Homebrewing Forum as imental technique is described. In Section 3 we present
utahbeerdude (Riffe) and VikeMan (Spencer). a precise definition of Bi and discuss how pHi and Bi
† URL: http://homebrewingphysics.blogspot.com/
determine pHG . This theory provides the basis for the
1 OK, so strong acids and bases do simply alter the ionic com-
analysis of our experimental data. In Section 4 we dis-
position of the water, but most brewers typically think about
acids and bases as distinct from other ions important to brew- cuss our data and its subsequent analysis before looking
ing; hence, our distinction. at the larger context of our work in Section 5. A brief
2 Here i is an index that generically labels a particular grain. summary concludes the paper.
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

2. EXPERIMENTAL DETAILS R = 4 L/kg mashes.

In order to obtain reasonable accuracy with our tech-

nique, the test grain must have a pHi value that is not 3. HOW pHi AND Bi DETERMINE pHG
too close to that of the fiducial grain. To ensure this con-
dition is met with all of our test grains, we had to find
two fiducial grains with disparate pHi values. Owing to In this section we discuss a theory that allows us to
extensive prior data on Briess Caramel malts, we chose calculate the expected pH when a mixture of grains is
Briess Caramel L10 (pHi ≈ 5.3) and Briess Caramel L120 mashed in distilled water. The underlying principle is
(pHi ≈ 4.6) as the fiducial grains. As is evident in the the conservation of charge associated with the absorption
following discussion, in each experiment the test grain is and release of H+ ions by constituents in the mash. We
mixed with one of these fiducial grains. begin with an in-depth discussion of the meaning of the
buffering capacity Bi of a single malt. From there we
Each individual mash comprises a total of 12.5 g of
are able to discern the pH when two or more malts are
grain and 31.25, 50.0, or 100.0 g of water, which results
mashed together.
in mash thicknesses R = 2.5, 4, and 8 L/kg, respectively.
In any given experiment each specific mash condition is When a single grain type is mixed with distilled water
carried out in three independent mashes. the resulting mash pH is invariably acidic, typically in the
Grains are pulverized by processing 1/4 cup at a time range between 4.5 and 6. This acidity can be attributed
for 12 seconds in a Braun Type 4041 Coffee Grinder. to malt-derived acidic buffers comprising phosphates and
Pulverized grain samples are then weighed using a Jscale organic acids [10, 11]. In addition to setting the pH, this
JS-100xV scale. buffer system resists the ability of other added acids or
bases to change the pH of the mash. This resistance to
A warm water bath is used to both pre-heat the jars
changes in pH occurs because the malt buffer system is
and to maintain samples at 145 F. The warm water bath
quite efficient at (i) absorbing H+ when a acid is added
consists of a Corningware Electrics Model SC0-150 slow
and (ii) releasing H+ (which neutralizes OH− ) if a base
cooker (crock pot) and a braising rack to keep the jars
is added. In fact, without too much error we may assume
from making contact with the crock pot bottom, filled
all the H+ ions provided by an acid are consumed by the
with water to a depth of approximately 2 inches (just low
buffering system. Likewise, we may also assume all OH−
enough that jars do not float). The steeping temperature
provided by a base are neutralized by the buffer-system
is pre-set and maintained with a Johnson A490 controller
donated H+ . This assumption is, of course, not quite true
with its temperature probe placed in a thermowell in the
as the number of free H+ in solution (as indicated by pH)
bath. The crock pot lid is in place on top at all times,
does change when an acid or base is added.3 However,
except when transferring jars in/out.
this change in the number dissolved H+ ions is typically
Distilled water is heated on a stove to the required
far smaller than the number of H+ either consumed or
strike temperature. In order to achieve a consistent mash
donated by the buffer.
temperature, the strike water temperature for each mash
is varied with R: 158, 153, and 150 F for R values of 2.5, In Fig. 1, using data from AJdL [5, 6], we illustrate
4, and 8 L/kg, respectively. Water for each steep sample these the two key properties of any given grain. First,
is weighed on a Sunbeam Model SP5 scale and added to a notice when each grain is mashed in distilled water (in-
preheated Mason jar, to which the pulverized preweighed dicated by zero acidity on the vertical axis), a particular
grain sample is immediately added and stirred. Each jar pHi results. As the figure shows, the Maris Otter and Pils
is then immediately lidded and placed in the warm wa- malts both have pHi values close to 5.85, while pHi for
ter bath for 10 minutes. After 10 minutes in the warm Roasted Barley is close to 4.70.4 Figure 1 also illustrates
water bath, each jar is removed and a liquid sample is what happens if a strong acid or base is added to the
poured off from the steeping jar through a strainer into strike water: the amount of acid or base added [which
a clean jar. The liquid-sample jar is immediately lid- is quantified in terms of mEq of H+ (positive acidity)
ded and placed in an ice water bath until cooled to 77 or OH− (positive alkalinity = negative acidity) per kg
F. Once cooled, pH measurements are performed with a of grain] vs the resulting change in pH is often well de-
calibrated Milwaukee MW101 pH meter. scribed by a linear function. For the grains in Fig. 1
a linear least-squares fit of the each data set yields the
Over time our protocol evolved. In the early trials all
straight lines shown in the figure. Under some circum-
three value of R were used with fiducial-grain fractions
stances deviations from linearity are noticeable (as is the
of 0, 0.5, and 1. These experiments led to the discovery
case for the roasted barley data in Fig. 1). Even in these
that pHi and (relative) Bi values are largely independent
of R. Later trials were thus modified to emphasize the
determination of Bi : we fixed R at 4 L/kg, but increased
the number of mixtures to six, with fiducial-grain frac- 3 Of course, any buffer system can be overwhelmed if too much
tions of 0, 0.2, 0.4, 0.6, 0.8, and 1.0. In the later trials acid or base is added.
with flaked grains R = 8 L/kg was instead utilized, owing 4 As we discuss in more detail below, pHi for a particular grain is
to excessive water absorption by the flaked component in largely independent of the mash thickness R.

2
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

We are now ready to consider what happen when two

Muntons Marris Otter different malts are mashed in distilled water. As we
60 Weyermann Floor Malted Pils now describe, pHG is determined by the condition of
Mash Liquor Acidity (mEq/kg) Briess Roasted Barley charge conservation. For the sake of this discussion we
40 (i) imagine we initially have two individual distilled wa-
ter mashes, one with malt 1 at pH1 and one with malt
2 at pH2 , and (ii) assume pH1 < pH2 . Let’s say we now
20 mix the two individual mashes, which produces a mash
comprising both malts. As far a malt 1 is concerned malt
2 is a base, and as far as malt 2 is concerned malt 1 is an
0 acid. Therefore malt 1 releases H+ ions which are then
absorbed by malt 2. There is only one pH value where
the number of H+ released by malt 1 equals the number
-20
of H+ absorbed by malt 2; this pH is pHG . Of course,
as pHG reflects an equilibrium condition, this same pHG
-40 will result if we simply start out with the grains mixed
together before any water is added.
Using this idea of the conservation of charge, we can
4.8 5.2 5.6 6.0 derive an equation that determines pHG when any num-
pH ber of malts are mixed together. As Bi is the amount of
charge Qi per mass mi of malt per pH change,6 the total
FIG. 1: Single-malt mash pH values vs mash liquor acidity, amount of charge taken up or released by a given malt
obtained from AJdL titration data on three different grains as the pH changes from pHi to pHG is simply
[5]. The data points (open symbols) are obtained from AJdL’s
cubic fits to his experimental data. The straight lines through Qi = (pHG − pHi ) Bi mi .
the symbols are our linear fits to the cubic-fit derived data
points. The vertical dashed line indicates a typical mash-pH In passing, we note Qi > 0 indicates a particular malt has
target of 5.4. taken up positive charge (in the form of H+ ). Conversely,
Qi < 0 indicates the release of positive charge.7 Because
the sum of all charge released and consumed by all malts
cases, though, the linear function is usually a reasonable in a given mash must equal zero, we have
approximation to the data. X
This observation of near linearity leads to the defini- (pHG − pHi ) Bi mi = 0, (2)
tion of the buffering capacity Bi of a malt: the buffering i

capacity is simply the slope of the straight line that best which is readily solved for pHG as
fits the added acidity A− vs resulting pH. Based on the P
fits to the three grains in Fig. 1, the buffering capacities i pHi Bi mi
pHG = P . (3)
are −51, −34 and −59 mEq/kg for the Maris Otter, Pils, i Bi m i
and Roasted Barley grains, respectively.5
With this property of a given malt we can estimate the A slightly friendlier version of this equation is obtained
pH for any given amount of acid added using by recognizing the fraction fi of a given grain in any
particular mash is simply
A− mi
pH = pHi + . (1) fi = P ,
Bi
i mi

For example, if we mash the Maris Otter malt of Fig. 1 which allows us to rewrite Eq. (3) as
using water with A− = 20 mEq/kg, then Eq. (1) tells us P
the resulting pH should be i pHi Bi fi
pHG = P . (4)
i Bi fi
20
pH = 5.85 − = 5.46. With this equation we can readily predict pHG when
51
any number of malts (with given pHi and Bi values) are
Notice this value is quite close to the pH indicated in mashed together in distilled water.
Fig. 1 for Maris Otter when A− = 20 mEq/kg.

6 Mathematically, Bi = Qi /(mi ∆pH), where ∆pH is the change

5 In some sources the units utilized for Bi are mEq/(kg pH). How- in pH.
ever, as pH is not really a unit, we feel it is better to simply use 7 Because Qi and pHG − pHi have opposite signs, Bi is always a
mEq/kg for the units of buffering capacity. negative number.

3
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

Equation (4) is the basis for our experimental determi- 6.5

nation of Bi values. Let’s say we have a mash made up Briess Aromatic Dingemans Aromatic
6.0 pH=5.39, rL10=0.95 pH=5.38, rL10=1.36
of just two malts, malt 1 (a test malt, say) with fraction
f1 and malt 2 (perhaps a fiducial malt) with fraction f2 . 5.5
Then Eq. (4) can be written (using f1 = 1 − f2 ) as
5.0
pH1 r (1 − f2 ) + pH2 f2
pHG = , (5) 4.5
r (1 − f2 ) + f2
6.5
where Briess Victory Crisp Amber
6.0 pH=5.19, rL10=0.77 pH=5.10, rL10=0.74
B1
r= (6)
B2 5.5

is the ratio of the buffering capacity of malt 1 to that of 5.0

malt 2. If a set of measurements of pHG as a function of
4.5

Grist pH
f2 is made, then the data can be least-squares analyzed
in order to determine best-fit values of pH1 , pH2 , and r. 6.5
If one has knowledge of the fiducial-grain buffering capac- Wey. Melanoidin Gambrinus Honey
ity B2 , then the unknown buffering capacity B1 can be 6.0 pH=4.93, rL10=1.44 pH=4.82 rL10=2.00

inferred from B2 and the value of r determined from the

5.5
data. As there are three unknown parameters in Eq. 5, at
least three data points are required to determine values 5.0
for all of them. As mentioned above, our first protocol is
distinguished by the minimum of three f2 values, while 4.5
our second protocol increases the number of f2 values to 6.5
six. Briess L10 Briess Extra Special
6.0 Briess L120 pH=4.55, rL10=1.23
rL10=1.57

4. RESULTS AND ANALYSIS 5.5

5.0
4.1. pHi and relative Bi values
4.5

The data obtained using our first protocol are summa- 2 3 4 5 6 7 8 2 3 4 5 6 7 8

rized in Fig. 2. Each panel plots pHi for a test grain, Mash Thickness (L/kg)
pHi for a fiducial grain, and the pHG for a 50/50 mix-
ture of the two grains. For most experiments data were
FIG. 2: Grist pH vs mash thickness for fiducial-grain fractions
obtained at mash thicknesses of 2.5, 4.0, and 8.0 L/kg. of 0, 0.5, and 1.0. Data were obtained for mash thicknesses
Data at 2.5 L/kg for 100% Briess Victory and Crisp Am- of 2.5, 4.0, and 8.0 L/kg. The green triangles are the data for
ber were unobtainable, as both both of these grains ab- 50/50 mixed mashes. The pH values reported in the legends
sorbed nearly all of the mash liquor, turning these two are averages from all data obtained on a given grain (including
attempted mashes into solid bricks. any data obtained using our second protocol). Here rL10 =
Our very first data set is shown in the bottom-left Bi /BL10 , where Bi and BL10 are the test-grain and Briess-
panel, which is a comparison of the two fiducial grains Caramel-L10 buffering capacities, respectively.
used in all subsequent experiments, Briess Caramel L10
and L120. Even without any analysis, these data are
quite revealing. First, we see that pH is rather indepen- another direct comparison of Briess L10 and L120 using
dent of mash thickness (which is more-or-less true for all our second protocol. These data (discussed in detail be-
malts we have measured). Second, because the 50/50- low) yield BL120 /BL10 = 1.57. Owing to (i) the L10-L120
mixture mashes have pH values closer to the L120 pH comparison in Fig 2 being the first data we collected (thus
values, we immediately know that the buffering capacity likely making those data relatively less precise) and (ii)
of Briess L120 malt is larger than that of Briess L10. our belief that our second protocol is generally a more re-
As we have used both L10 and L120 malts as fidu- liable method for determining buffering-capacity ratios,
cial malts, we require a reliable value for the buffering- we have used BL120 /BL10 = 1.57 in order to to deter-
capacity ratio BL120 /BL10 for these two malts. From mine the buffering capacity ratio rL10 = Bi /BL10 of all
our initial data shown in Fig. 2 we initially inferred a test malts with respect to Briess Caramel L10.
buffering-capacity ratio BL120 /BL10 = 1.97. However, There are other observations of the data in Fig. 2 worth
data later collected on several malts using our second pro- noting. First, Briess and Dingemans Aromatic malts
tocol suggest this ratio is a bit high. We therefore made have fairly similar properties: their pH values are nearly

4
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

5.6 6.2
Briess Special Roast Briess White Wheat
5.5
Briess L40 6.0 Briess L10
Gambrinus Honey Briess Carabrown
5.4
Briess L80 Briess L20
Briess RB 5.8
5.3 Briess L40
Briess L120
5.2 5.6

5.1 5.4
pH

pH
5.0
5.2
4.9
5.0
4.8

4.7 4.8

4.6 4.6

4.5
0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0
Briess L10 Fraction Briess L120 Fraction

FIG. 3: Grist pH of various grains vs Briess Caramel L10 FIG. 4: Grist pH of various grains vs Briess Caramel L120
fraction. All malts labeled Briess LX are Briess Caramel fraction. All malts labeled Briess LX are Briess Caramel
malts, where X represents the color of the malt in ◦ L. malts, where X represents the color of the malt in ◦ L.

identical, and their buffering capacities are not wildly dif-

ferent. Second, Briess Victory and Crisp Amber – two
examples of biscuit malt – have very close values of pHi 6.6 Flaked Rye
and essentially identical values of Bi . Finally, we point Flaked Wheat
out our comparison of Gambrinus Honey malt with L120 6.4 Flaked Oats
was ill advised, due to their similar values of pH when Flaked Corn
mashed in distilled water.8 Using our second protocol 6.2 Flaked Barley
we compared Gambrinus Honey malt with L10, which
6.0
produced the value of rL10 shown in the legend.
Figures 3 through 5 present data collected using our 5.8
second protocol. Figure 3 plots pH data for mashes con-
pH

sisting of test grains mixed with Briess Caramel L10, 5.6

while Figs. 4 and 5 plot pH values mixtures with Caramel
L120. The curve through each data set is a least-squares 5.4
fit of the data to Eq. 5, from which we deduce pHi for
each test and fiducial grain, as well as the buffering- 5.2
capacity ratio rL10 or rL120 . The orange circles in Figs. 3
5.0
and 4 represent the same data set obtained from mixtures
of Briess Caramel L10 and L120. As discussed above, 4.8
these data yield the buffering capacity ratio BL120 /BL10
= 1.57, from which we have deduced rL10 for test grains 4.6
that have been mashed with Briess L120. The results for
pHi and rL10 for all grains are presented in Table I. 0.0 0.2 0.4 0.6 0.8 1.0
We point out a few features regarding the data in these
Briess L120 Fraction

FIG. 5: Grist pH of flaked grains vs Briess Caramel L10 frac-

8 tion.
Based on its color, Honey malt has an unexpectedly low pH; why
this is the case is discussed in detail below.

5
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

5.5
TABLE I: Experimental results for pHi , rL10 , and Bi of grains
measured in this study. As indicated, rL10 and (hence) Bi of
5.4
Crisp Brown malt were not determined.
Grain Color pHi rL10 −Bi 5.3
(◦ L) (mEq/kg)
Flaked Rye 3 6.65 0.59 29.8 5.2 Briess L10
Flaked Wheat 2 6.57 0.63 28.2
Flaked Corn 1 6.24 0.20 9.6 5.1
Flaked Oats 2 6.21 1.01 48.2 2.5 L/kg

pH
Flaked Barley 1 5.46 1.09 51.8 5.0 4.0 L/kg
Briess White Wheat 2 6.10 0.48 36.4 8.0 L/kg
Dingemans Aromatic 19 5.38 1.36 64.7 4.9
Briess Aromatic 20 5.39 0.95 45.5
Briess Victory 28 5.19 0.77 36.8 4.8
Crisp Amber 29 5.10 0.74 35.5 Briess L120
Briess Carabrown 55 5.19 0.66 31.4 4.7
Crisp Browna 65 4.97
Gambrinus Honey 25 4.82 2.00 95.4 4.6
Weyermann Melanoidin 27 4.93 1.44 68.9
Briess Special Roast 40 4.91 2.08 99.1 4.5
Briess Extra Special 130 4.55 1.23 58.8
4 8 12 16
Briess Caramel L10 10 5.34 1.00 47.7 Run Number
Briess Caramel L20 20 5.07 1.20 59.7
Briess Caramel L40 40 4.90 1.51 72.2
Briess Caramel L80 80 4.70 1.52 72.3 FIG. 6: Measured pHi values for Briess Caramel L10 and
Briess Caramel L120 120 4.63 1.57 75.0 L120. Lines between data points are guides to the eye.
Briess Roasted Barley 300 4.67 1.41 67.5
a We measured the pH of this malt before embarking on our

buffering-capacity experiments. pHi value at 4.0 L/kg compared to the other two mash
thicknesses, but even if this is true, the pH difference is
well under 0.1, and the difference is approximately of the
three figures and the results in Table I. First, that nearly same size as typical fluctuations in the measurements.
all of the the curves are concave up is a result of the grain From these data we extract pHL10 = 5.34 ± 0.05 and
with the lower pH having a relatively higher buffering ca- pHL120 = 4.63 ± 0.03. Our observed variations in pH are
pacity. The only exception to this is the slightly concave similar to those in measurements of Briess caramel malts
downward data from mixtures of Briess L40 and Briess made by Geurts [8].
L120, which indicates the buffering capacity of L40 is
slightly larger that that of L120 (rL120 = 1.10). This
result is slightly at odds with the data from mixtures
of Briess L10 and Briess L40, which suggest the buffer- 4.2. Absolute Bi Values
ing capacity of L40 is ever so slightly smaller than that
of L120 (rL120 = 0.96). We also note only four data
points are shown for mixtures of Briess Roasted Bar- While values of pHi and rL10 are sufficient for predict-
ley and Briess L10; data at L10 fractions of 0.6 and 0.8 ing the distilled water pH for any mixture of grains, the
were collected, but were judged to be outliers, and so are rL10 values are insufficient for predicting pH changes in-
not shown. Perhaps most surprising are the results for duced by acid (or mineral) P additions. This is because the
flaked rye, wheat, and corn, all of which have remark- average buffering capacity i fi Bi of the grist is required
ably high values of pHi and low values of Bi (see Table to know exactly how a given acid addition will change
I). These data suggest the hot-roller mill processing of the pH of the mash. To this end we made measurements
rye and wheat does not develop the acidity that occurs on a spectrum of Briess Caramel malts, as this was the
when these grains undergoes traditional malting. The most widely measured group of malts in prior studies
spectacular curvature of pH vs L120 fraction for flaked [1, 3, 5, 7–9]. Our initial thinking was that these prior
corn is due to its extremely low buffering capacity, which data would allow us to straightforwardly determine the
is ∼14% of the buffering capacity of the L120 malt. value of Bi for Briess Caramel L10, which would in turn
An ancillary bonus of our study is an extensive set of allow us to determine Bi values for all of our measured
measurements of pHi for Briess Caramel L10 and L120, malts.
which are displayed in Fig. 6. As these data illustrate, As it turns out, the final gameplan was not as simple
the mash thickness is rather inconsequential as far as as we initially envisioned. This is because there are sys-
pHi is concerned. The data do suggest a slightly lower tematic differences among the sets of Bi values derived

6
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

from the data of the various researchers.9 This is evi- measured malts.
dent when groups of Bi values from different researchers When we apply these multiplicative factors to all other
are compared. Such data are displayed in Fig. 7(b) and data by each researcher, the Bi values are found to align
parts (b), (e) and (h) of Fig. 8. From the data displayed nicely for all malts types, as we show in parts (c), (f), and
in these graphs we can conclude the Bi values of Troester (i) of Fig. 8. Quite clearly, Bi values for all grain types
are systematically the lowest, followed in order by values are much better aligned after our normalization process.
determined from the data of Bies, deLange, and Walts. Perhaps most striking is the much smaller variation in Bi
The data of Geurts, while appearing to be self consistent values for Briess Roasted Barley (RB), which has been
within a given malt group, do not have a clear systematic measured by all researchers. Before the normalization the
relationship with the data from other researchers. standard deviation of the RB data of Bies, KT, Walts,
To what can we attribute these systematic differences? and deLange was 19.9 mEq/kg; after normalization the
There are three possibilities, all of which may have some standard deviation dropped dramatically to 6.3 mEq/kg.
contribution. First, a systematic error in the strength of We emphasize only Briess Caramel malts were used to de-
the acid/base solution used in titrating the mash would termine the normalization factors. The good agreement
necessarily lead to a systematic multiplicative error in across all grain types confirms the validity of our proce-
the assessed values of Bi . Second, it is possible that dif- dure.
ferences in malt grinding might lead to variation in the
measured buffering capacity. Indeed, a dependence on
malt preparation was observed by KT, who made mea- 5. DISCUSSION
surements on mashes with not only pulverized grains but
also roller-mill crushed grains [1]. KT’s data indicate pul- 5.1. Comparison of Measured pHi Values
verized grains have a buffering capacity that is ∼1.4 times
that of crushed grains. As the grains in all the experi- Our measured values of pHi are completely in line with
ments discussed here appear to have been at least finely values from other researchers. This result is illustrated in
ground, the contribution from this effect is likely mini- Figs. 7 and 8. Perhaps the best quantitative comparison
mal, but is perhaps worthy of future experimental inves- is provided by the data in Fig. 7(a), which shows pHi
tigation. Third, it is possible that mash thickness might for Briess crystal malts measured by us and others.11 As
affect the buffering capacity of a given grain. Again, KT’s shown there, versus the logarithm of the malt color we
measurements indicate buffering capacity increases by a find a decrease in pHi that is quite quite linear, as is also
factor of ∼1.25 as the mash thickness increases from 2 observed by Geurts [8]. All other researchers observe a
L/kg to 5 L/kg. This effect might account for some of general decrease in pH with increasing color, even if their
the systematic differences among researchers. data are not monotonic.
As nearly all researchers have measured at least two A second quantitative comparison is afforded by mea-
different Caramel malts manufactured by Briess, we surements of 300 ◦ L Briess RB. Data from all researchers
chose to use these data to normalize Bi values among for this grain are plotted in Fig. 8(g).12 All measured pH
all researchers. This, of course, requires a choice of a values for this grain fall between 4.62 and 4.75; our value
particular researcher’s data as the standard. Impressed is 4.67. Taken together, the six measurements on Briess
by deLange’s careful, sophisticated approach to his titra- RB can be summarized by a pH value of 4.69 ± 0.05.
tion protocol [6], we have chosen his measurements as
this standard. We determined the multiplicative factor
to apply to each other researcher’s Bi values (as well 5.2. Trends in pHi and Bi Values
as our rL10 values) by adjusting each researcher’s Briess
Caramel malt Bi values by a single multiplier until the So what can we learn from the totality of pHi and Bi
minimum average standard deviation was achieved across values? Here we discuss trends in both of these quantities
all Briess Caramel malt data. The multiplicative factors for each distinct category of grain. As we shall see, the
that resulted from this process are 1.62, 1.42, and 0.86 for behavior of (i) pHi and Bi vs malt color and (ii) Bi vs
the data of Troester, Bies, and Walts, respectively.10 For pHi provide insight into the properties of different types
our data this process sets the value Bi = −47.7 mEq/kg of malt.
for Briess L10, from which we determine Bi for all of our As is well known, different malt products largely re-
sult from differences in the processing steps used in their
manufacture; we thus naturally focus on these differences
9
in our discussion. All barley seed that eventually ends up
Where titration data have been reported as the amount of
acid/base added vs pH change, we have derived Bi by assum-
ing a linear relationship between pH and amount of acid/base
added (as discussed above).
10 For the data of Geurts we have determined multiplicative factors 11 All values were either measured near room temperature or cor-
of 1.08 for wheat and crystal malts, 1.33 for dark roasted malts, rected to reflect room-temperature values.
and 1.90 for base and noncrystal specialty malts. 12 Briess RB is the only 300 ◦ L grain represented in this graph.

7
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

the large variety of products available to the brewer.

5.6 Bies As will become obvious from the pHi and Bi data,
Walts malted barley naturally fall into four distinct categories:
5.4 Geurts
(i) dark roasted grains, (ii) caramel/crystal/dextrin
deLange
Troester
malts, (iii) base malts, and (iv) noncrystal specialty
5.2
this study malts. We now discuss in turn the pHi and Bi properties
pH

of grains in each of these categories. We also discuss the

5.0
properties of wheat malt and flaked grains.
4.8

4.6 5.2.1. Dark Roasted Grains

(a)
4.4 We start with dark roasted grains as the results for this
category are the simplest: both the pHi and Bi values are
90
(b) rather independent of the color of the grain (see Fig. 8).
With only two exceptions (Briess Dark Chocolate and
-Bi (mEq/kg) [not adjusted]

80
Briess Black Malt [8]), all pHi values lie between 4.5 and
70 4.8. Overall, these malts are among those with the lowest
pHi values. Similarly, Bi values exhibit a fairly narrow
60 range, between −60 and −80 mEq/kg. These values are
towards the high end of the range of all malts. The data
50
can be characterized by pHi = 4.64 ± 0.13 and Bi =
40 −68.7 ± 6.6 mEq/kg [as indicated in Fig. 9(b)]. The
data from Geurts for the two darkest Briess malts weakly
30 suggest some dependence of pHi on malt color, although
90
this observation is unique to this particular study [8].
A plot of Bi vs pHi for these malts [see Fig. 9(a)] ex-
(c) hibits a clear lack of correlation between these two quan-
80 tities, especially if the two darkest grains measured by
Geurts are ignored.
-Bi (mEq/kg)

70 Dark roasted malt is produced from green malt by pro-

cessing in a roaster: the temperature is slowly increased,
typically reaching a final temperature in the range of 350
60 to 450 ◦ F [12]. Roasting time is typically between 2 and
4 hours [13]. Higher temperatures and/or longer process-
50 ing times result in darker grains. Because roasted barley
(which is not malted before being roasted) exhibits the
same pHi and Bi values as dark roasted malt, we can
40 2 3 4 5 6 7 2 infer the initial malting stages are not crucial to proper-
10 100
ties of the end product. Evidently, the acidity of dark
Malt Color (ºL)
roasted grains is largely developed in the roaster by the
time a color of 300 ◦ L is reached.13
FIG. 7: Briess Caramel malt pHi and Bi values from our data
as well as measurements reported in the literature. Dotted
lines in (a) and (b) are guides to the eye. Straight lines in (c)
are least-squares fits. See text for further details. 5.2.2. Caramel/Crystal/Dextrin Malts

We have grouped caramel, crystal, and dextrin (CCD)

malts together owing to their properties being character-
as malt undergoes two initial processing steps. First, the ized by common trends. While the case can be made for
grain is steeped in water to increase its moisture con- the distinctness of these three malt types, there is def-
tent. It then undergoes a germination phase in which inite overlap among them, especially insofar as all pro-
the seed begins to grow. Malt at this stage is known as vide unfermentable dextrins and fermentable sugars to
green malt. After hydration and germination all malt the wort without the need for an enzymatic mash. The
undergoes further processing at elevated temperatures in
either a kiln or roaster, with the path through parameter
space defined by time, temperature, and moisture content
(largely) determining the state of the final product. The 13 An excellent review of the chemistry involved in the production
myriad of possible paths allow the maltster to produce of dark roasted malts is provided by [14].

8
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

6.5
Caramel / Crystal / Dextrin Base / Specialty (g) Dark Roasted

6.0

5.5
pH

5.0

4.5
(a) (d)

4.0
100 Bies
(b) (e)
Walts
-Bi (mEq/kg) [not adjusted]

Geurts
80 deLange
Troester
this study
60

40

(h)
20
100
(c) (f) (i)

80
-Bi (mEq/kg)

60

40

20 2 4 6 8 2 4 6 8 2 2 4 6 8 2 4 6 8 2 2 4 5 6
10 100 10 100 3x10
Malt Color (ºL)

FIG. 8: pHi and Bi values from our data as well as measurements reported in the literature. Dotted lines are guides to the
eye. Straight lines are least-squares fits. See text for further details.

lightest of the group are known as dextrin malts, which malts that provide not only body but also caramel-like
are touted as providing body and head retention, but character. Some have a glassy interior (the true crys-
very little in the way of flavor. Some dextrin malts have tal malts, such as those from Briess), while others have
glassy interiors (Briess Carapils is one such example), a mealy interior (caramel malts from Cargill, for exam-
while others have interiors that are quite mealy (Weyer- ple).15
mann Carafoam, for example). Some examples (such as
Dingemans Cara 8) appear to be no more than lightly col-
ored crystal malt.14 The term caramel malt encompasses
15 Curiously, Briess is careful to point out that Carapils is not a
crystal malt, even though it has a glassy interior. The reason
for Briess’ distinction is not readily apparent, as the maltster
14
does not share the exact steps in the processing of any of their
Dingemans Cara 8 was previously marketed as dextrine malt. specialty malts.

9
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

100 Wheat
Base
CCD
Specialty
80 Dark Roasted
Briess ES

60

40
(a)
-Bi (mEq/kG)

20

100
G Honey Br SR (b)
C140
C120
80 C80
Wey Mel

Dk Roast C20
60 C60 Aro Mun V/PA/M
Br ES C40
P/L/2-R
C10
40
B/A/B
C2 Wheat

20
4.2 4.6 5.0 5.4 5.8 6.2
pHi

FIG. 9: Bi vs pHi values from our data as well as measurements reported in the literature. In (a) individual data points are
plotted. In (b) average and standard deviations of values from malts in particular categories are indicated, as well as individual
data points for several malts (Gambrinus Honey, Briess Special Roast, and Briess Extra Special). Solid lines are guides to the
eye. See text for further details.

In contrast to dark roasted malts, the properties of directly shows the inverse correlation of −Bi and pHi :
malts in the CCD group are highly correlated with malt the buffering capacity magnitude −Bi decreases as pHi
color. As is clearly illustrated in Fig. 8, these malts ex- increases. As Fig. 9(b) demonstrates, if the CCD malts
hibit (i) a striking decrease in pHi and (ii) an equally are grouped by color,16 then the average values of Bi vs
striking increase in −Bi with increasing malt color. The average values of pHi follow a smooth curve with a clear
lightest malts (Weyermann Carafoam [5] and Crisp Dex- decrease (increase) in pHi (−Bi ) as the color increases.
trin [9]) have pHi values in the range of 5.5 to 5.9, while
the darkest malts typically exhibit values as low as 4.5.
With increasing malt color the values of Bi trend from
∼ −35 to −80 mEq/kg, with Weyermann Caraaroma [1] 16 The designation C40 (for example) includes all crystal malt that
coming in at an exceptional −100 mEq/kg. are closer to 40 ◦ L than any of the other color designations on
the graph.
A plot of Bi vs pHi for these malts [see Fig. 9(a)]

10
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

As is the case for dark roasted malts, CCD malts are these malts endure processing that is as minimal as is
usually produced in a roaster.17 The essential character possible: (i) germination occurs at the lowest tempera-
of true crystal malts – the hard, glassy, candy-like in- tures with the least amount of water uptake, (ii) kilning
terior – arises from a combination of (i) internal starch is characterized by relatively low humidity in the dry-
saccharification during a prolonged rest near 150 ◦ F while ing phases, and (iii) curing occurs at the lowest possible
the malt is still moisture laden and (ii) roasting at a fin- temperatures.18 The second lightest malts – Vienna/pale
ishing temperature in the range of 250 - 320 ◦ F [15]. As ale/mild malts – differ in their processing (compared to
the color of a particular caramel malt is developed during the lightest malts) by having a higher curing tempera-
roasting, it is clear that compounds responsible for the ture, which results in the development of slightly more
pHi and Bi values of these malts are also developed dur- melanoidins and other Maillard-reaction products, and
ing this stage of processing. The darkest crystal malts thus slightly more color and malt character. The in-
have pHi and Bi values that overlap significantly with tense malt character of Munich and aromatic malts is due
dark roasted malts, even though crystal-malt color tops to a combination of processing differences: (i) germina-
out at ∼150 ◦ L. For example (as is evident in Fig. 3 and tion occurs at relatively higher temperature and moisture
Table I) the pHi and Bi values for Briess Caramel 80 content (which enhance the development of melanoidin
and Briess Roasted Barley are nearly identical. The uni- precursors), (ii) during the drying phases the grains are
formity of the pHi and Bi results across the spectrum kept at relatively high moisture content (which further
of maltsters represented (Briess, Weyermann, Simpsons, promotes melanoidin precursor development), and (iii)
Crisp, and Cargill) is likely due to the utilization of rather curing takes place at higher temperatures yet. The dif-
similar steps in CCD production [16]. ference between aromatic and Munich malts largely lies
in the curing phase; as Table II indicates, aromatic malts
are typically cured at temperatures 10 to 15 ◦ F higher
than Munich malts.
5.2.3. Base Malts
The values of pHi and Bi for malts ranging from
pils/lager/2-row to aromatic, which are indicated by the
There is not a sharp demarcation between base malts
orange circles in Fig. 9(a), lead us to classify all of these
and noncrystal specialty malts (discussed in the next sec-
types as base malts. The one potentially questionable
tion). This is partially due to the fact that one cannot
type is aromatic malt.19 Although aromatic malt rarely
readily identify a single distinguishing factor that deter-
composes a large fraction of a beer’s grist, the pHi and Bi
mines whether a particular malt belongs in one category
values are fairly close to values for Munich malts. In addi-
or the other. One might argue that diastatic power is the
tion, aromatic malts typically have just enough diastatic
distinguishing parameter, with base grains being able to
power to be able to convert themselves.20 As Fig. 9(a)
at least convert their own starches in the mashing pro-
shows, for the base malts pHi values range from just un-
cess. In this case Gambrinus Honey malt would qualify
der 5.4 to just above 5.8, (with one outlier at 6.0), while
as a base malt even though it is predominately (if not
Bi values are typically between 40 and 60 mEq/kg. The
exclusively) used as a specialty grain [17]. In addition,
solid-line fit to these data show a slight correlation of pHi
there are some malted grains that are sometimes used
and Bi .
as a base malt and sometimes used as a specialty malt.
For example, in some beers Munich is a true base grain Further insight into the properties of these four base-
(when it provides substantial gravity and drives the char- malt categories is provided by the average values of pHi
acter of the beer), while in other beers it can justifiably and Bi that are plotted as orange circles in Fig. 9(b).
be considered a specialty malt (when it is used in quan-
tities typical of a specialty grain to provided nuance to
the beer’s flavor). In our discussion to follow we do offer
18 Malt kilning is typically characterized by three distinct phases:
a distinction; perhaps not surprisingly, our distinction is
(i) The first stage is free drying (also known as withering) in
partially based on a combination of pHi and Bi . which moisture is driven from the grain at relatively low tem-
In order to make sense of pH and buffering capac- perature. The moisture content of the grain typically drops from
ity values of both base and noncrystal specialty malts, ∼45% to ∼24% during this stage. (ii) The second stage is known
it is helpful to consider both the germination and kil- as forced drying, in which the grain temperature rises as the
moisture further drops to ∼10%. (iii) The third stage is known
ning/roasting processes [10, 12, 15, 18–27]. Differences as the curing stage, in which the higher temperatures develop
in these processes among major groups of malt types are melanoidins and other Maillard-reaction products from precur-
indicated in Table II. The lightest (in color) of the base sors that are formed during germination and earlier stages of
malts are pils/lager/2-row malts. Grains that become kilning [15, 18].
19 In Fig. 9 the three orange-circle data points with pH values
slightly less than 5.4 are from aromatic malts (from Briess and
Dingemans).
20 Briess and Dingemans Aromatic malts are reported to have di-
17 Some caramel malts are produced in kilns rather than roasters. astatic powers of 20 and 30 ◦ Linter, respectively. The rule–
Differences that arise due to kilning vs roasting are discussed in of-thumb minimum for self-conversion is often taken to be 30
[15] and [16]. ◦ Linter.

11
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

TABLE II: Typical processing details of base and noncrystal specialty malts. Here T represents temperature, and H represents
humidity.
Malt Typical Color Germination Moisture content Curing
(◦ L) features while drying T (◦ F)
Pils/Lager/2-Row 1.4 - 1.8 low T, low H low 176 - 185
Vienna/Pale Ale/Mild 2-5 low T, low H low 195 - 215
Munich 6 - 12 high T, high H high 212 - 221
Aromatic 17 - 21 high T, high H high 220 - 239
Biscuit/Amber/Brown 20 - 75 low T, low H low 280 - 350
Melanoidin/Honey/Brumalt 20 - 30 high T, high H, O2 restricted high 195 - 221

For these malts increased melanoidin development is cor- Briess Victory and Crisp Amber have Bi values close to
related with both pHi and Bi ; the correlation with pHi −36 mEq/kg (see Table I). Our results of pHi = 5.19 and
appears to be the stronger of the two. Bi = −31.4 mEq/kg for Briess Carabrown malt clearly
place it in this category, despite the presence of “Cara”
in its name. Consistent with our assessment, Briess
5.2.4. Noncrystal Specialty Malts states “Carabrown malt was developed on the light side
of the brown malt style in order to retain some residual
sweetness while still delivering an assortment of lightly
We now move on to noncrystal specialty malts. Many toasted flavors.” [28] Biscuit malt measured by KT has
of these malts fall into one of two categories: (i) Bis- pHi = 5.08 and Bi = −52.8 mEq/kg [1]. While this value
cuit/Amber/Brown or (ii) Melanoidin/Honey/Brumalt. of pHi is consistent with other malts in this category, the
There are, however, a number of noncrystal specialty Bi value is significantly larger in magnitude than these
malts made by various manufacturers that do not clearly other three malts. Unfortunately KT did not know the
fall into either of these categories. An example is Briess manufacturer of this malt, and so further assessment of
Extra Special, which we have measured (see Fig. 2) and this difference is not possible.
discuss below. Malts referred to as Melanoidin (Weyermann’s prod-
Malts designated biscuit, amber (Briess Victory is per- uct is perhaps the most common), Honey (a Gambrinus
haps the most ubiquitous example), and brown are pro- Malting product), and Brumalt (a generic German term
cessed exactly like the lowest color base malts aside from for these malts) have the most extensive processing of any
one crucial difference: as indicated in Table II, curing noncrystal malts [12, 19]. They are produced much like
temperatures typically range from 280 to 350 ◦ F, well Munich and aromatic malts, but with one additional step:
above the maximum curing temperatures of any base near the end of germination the malt is oxygen deprived
malts [12, 23]. Several manufacturers (Crisp, Fawcett, at temperatures close to 120 ◦ F. This step encourages the
and Bairds, e.g.) produce both amber and brown malts; development of even more melanoidin precursors. These
the brown malt is invariably the darker malt, and so is conditions are also prime for encouraging lactobacillus
cured at higher temperatures or for longer times than the bacteria that is naturally present on the grains to pro-
corresponding amber malt. It should be no surprise that duce lactic acid.
the high-temperature curing stage is responsible for the The results of this extra germination step are evident
well known toasty/bread-crust notes of these malts.21,22 in Fig. 9(b), which displays results for both Weyermann
So what is the impact of the high curing temperatures Melanoidin and Gambrinus Honey malts. Both of these
on pHi and Bi ? As the point labeled B/A/B in Fig. 9(b) malts exhibit pHi values in the range of 4.8 to 5.0, well
shows, these malts have a significantly lower pHi than below the values for any of the Munich or aromatic malts.
any of the base malts.23 The buffering capacity Bi of It seems likely this sharp drop in pH is at least partially
these malts also tends to be lower than the base malts: due to the action of lactobacillus bacteria during the last
stage of germination.
Although Briess does not advertise their Special Roast
21
malt as a Melanoidin type of malt, its pHi and Bi val-
Apparently the high curing temperature is also responsible for
the ability of these malts to absorb more water than other malt,
ues place it very close to Gambrinus Honey malt. Briess
as discussed above. characterizes this malt with the statement “Proprietary
22 In addition, the high curing temperatures destroy alpha and beta malting process intensifies toasty and biscuity flavors, de-
amylase enzymes, so these malts cannot convert themselves in velops noticeable bran flake notes, and creates its distin-
the mash. guishing bold sourdough/tangy flavor.” [28] The sour-
23 This point in Fig. 9(b) is the average of the four lowest-buffering-
capacity specialty-malt points in (a) of Fig. 9. These malts are dough/tangy flavor is not inconsistent with the low pHi
Crisp Amber, Briess Victory, Briess Carabrown, and biscuit malt value for this malt. However, Special Roast has a dry-
of unknown origin. toast character that both Melanoidin and Honey malt

12
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

lack. We note the buffering capacities of Honey and Spe- 6.0. The variations in Bi are quite large, ranging from
cial Roast malts are among the highest of all malts that −9.6 mEq/kg for flaked corn to −51.8 mEq/kg for flaked
have been measured. barley. As can be ascertained from the results in Table
As can be ascertained from Fig. 9, our results for Briess I, there is clearly no correlation between color and pH
Extra Special (ES) malt are not consistent with any malt or buffering capacity for these grains. Hence, color can-
category we have so far discussed. While it is closest to not be used as a surrogate for either pHi or Bi for these
malts in the dark-roasted category, its color is only 130 flaked products. Owing to the minimal processing – as
◦
L, much less than any of the dark-roasted grains. Briess compared to malted grains – it seems likely the differ-
gives some insight into this malt. They state “A propri- ences in pHi and Bi among the different grains are due
etary drum roasting process develops both caramel and to the inherent nature of the unprocessed grains.
dry roasted flavors.” [28] Additionally, in a presentation
at the Pacific Northwest Homebrewers Conference 2017,
Aaron Hyde of Briess states “ES has a shorter starch
conversion in roaster prior to roasting. This yields its 6. SUMMARY AND CONCLUSIONS
unique flavor profile, with some biscuity notes, but also
fig/prunes/dates compared with Caramel malts.” [29] It We have presented distilled-water mash pH (pHi ) and
seems this malt is designed to compete with Dingemans buffering capacity (Bi ) measurements on two classes of
Special B. We note Patagonia malting makes a malt des- grains that heretofore have been largely neglected: non-
ignated Especial with a color of 140 ◦ L. We judge all crystal specialty malts and flaked grains. As opposed
three of these malts to have very similar flavor profiles. to crystal malts, simple correlations between grain color
It would thus be interesting to make measurements on and these two measured quantities does not exist. For
both Special B and the Patagonia Especial. the specialty malts this result is not terribly surprising,
as processing of these malts is rather varied. For the
flaked grains, the variations in pHi and Bi are large even
5.2.5. Wheat though all products are relatively light in color.
We have also considered previously acquired data on a
The malting process for pale wheat malt does not sub- number of malted grains (and roasted barley). Interest-
stantially differ from that for the palest barley malts ingly, there are study-dependent systematic differences
[12, 26, 30]. It is thus no surprise that pHi and Bi values in Bi values extracted from these data. Nonetheless,
are close to those for pilsner/lager/2-row malts, as can we have been able to normalize all of the data and thus
be seen in Fig. 9. The slightly higher pHi and slightly present a coherent picture of pHi and Bi trends across
lower −Bi values are likely attributable to inherent dif- the various categories of malted barley.
ferences in the wheat as compared to barley. The four On the theoretical side, we have discussed how pHi
measurements shown in Fig. 9(a) are characterized by and Bi values can be used to predict the distilled-water
pHi = 5.97 ± 0.14 and Bi = −34.2 ± 1.9 mEq/kg. pH (pHG ) of a mixture of grains. Simple put, pHG is the
average of the pHi values weighted by the product of the
grain fraction fi and buffering capacity Bi .
5.2.6. Flaked Grains Unfortunately, the data presented here are not suffi-
cient to reliably predict the pH of a mash made with
There are four basic steps in the production of flaked other than distilled water. This is because we do not
grains: (i) infusion of moisture, (ii) cooking, (iii) rolling, know whether the Bi values presented here are valid in a
and (iv) cooling [31]. For some grains (corn and rice typical homebrewer mash setting. In fact, as the Bi val-
are examples) the grains are degermed before the flaking ues were all normalized to the experimental conditions
process begins. Moisture infusion and cooking take place of AJdL, it is highly unlikely they are valid for a typical
simultaneously when the cooking agent is steam. If in- homebrewer’s mash. It is thus likely that a multiplicative
frared radiation is used to cook the grains, then they are correction factor to our normalized Bi values is required
steeped beforehand to raise their moisture content. in order for our result to be applicable to a homebrewer’s
Our results for flaked grains are shown in Table I. mash. More experimental data are required to ascertain
Aside from flaked barley, pHi values are all well above what this factor might be. Something for the future!

[1] K. Troester, The Effect of Brewing Water and [3] A. J. deLange, Some Observations on Mash pH Pre-
Grist Composition on the pH of the Mash (2009), diction/Control (2013), URL http://www.wetnewf.org/
URL http://braukaiser.com/documents/effect_of_ untitled.html.
water_and_grist_on_mash_pH.pdf. [4] K. Troester, Mash Titration (2010), URL
[2] A. J. deLange, Estimating Mash pH (2013), URL http: http://braukaiser.com/blog/blog/2010/11/29/
//www.wetnewf.org/pdfs/estimating-mash-ph.html. mash-titration/.

13
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

[5] A. J. deLange, Post on Homebrewtalk Brew Science Berlin, 2004).

Forum (2016), URL http://www.homebrewtalk.com/ [20] D. E. Briggs, C. A. Boulton, P. A. Brookes, and
showpost.php?p=7354522&postcount=2. R. Stevens, Brewing Science and Practice (CRC Press;
[6] A. J. deLange, Predicting and Controlling Mash pH Boca Raton, FL, 2004).
Using Simple Models of Mash Component Acid/Base [21] P. Rajotte, Belgian Ale (Brewers Publications; Boulder,
Characteristics (MBAA Technical Quarterly 52, 3 - CO, 1992).
12, 2015), URL http://www.mbaa.com/publications/ [22] D. Richman, Bock (Brewers Publications; Boulder, CO,
tq/tqPastIssues/2015/Pages/TQ-52-1-0302-01.aspx. 1994).
[7] J. K. Palmer and C. Kaminski, Water, A Comprehensive [23] G. Noonan, New Brewing Lager Beer (Brewers Publica-
Guide for Brewers (Brewers Publications, Boulder, CO, tions; Boulder, CO, 1996).
2013). [24] G. Fix, Principles of Brewing Science (Brewers Publica-
[8] R. Hansen and J. Geurts, Specialty Malt Acidity tions; Boulder, CO, 1999).
(2015), URL http://www.mbaa.com/meetings/archive/ [25] J. D. Hertrich, One Brewer’s Observations on Malt
2015/proceedings/Pages/38.aspx. Flavor (American Malting Barley Association, Inc.:
[9] J. Walts, Brewhouse Water and Mash pH Con- 2015 Barley Improvement Conference, 2015), URL
trol (Midwest Regional Brewers Conference, Minoc- http://ambainc.org/media/AMBA_PDFs/Conferences/
qua, WI, 2016), URL https://sites.google.com/site/ 2015_BIC/11-2015-BIC.pdf.
republicbrewpub/. [26] Castle Malting, Belgian Malts That Make Your
[10] J. De Clerck, A Textbook of Brewing (Volume One) Beer So Special (Castle Malting, 2018), URL
(Chapman and Hall LTD; London, 1957). http://www.castlemalting.com/Presentations/
[11] C. W. Bamforth, MBAA Technical Quarterly 38, 1 CastleMaltingBrochureENG.pdf.
(2001), URL https://www.mbaa.com/publications/tq/ [27] J. Mallett, Malt (Brewers Publications, Boulder, CO,
tqPastIssues/2001/Abstracts/tq01ab01.htm. 2014).
[12] R. Mosher, Mastering Homebrew (Chronicle Books; San [28] Briess Malt and Ingredients Co., Briess Web Site (2018),
Francisco, 2015). URL http://www.brewingwithbriess.com/Products/
[13] D. Richter, Kilned Versus Roasted: Do You Really Know Roasted.htm.
Your Specialty Malts? (AHA National Homebrewer’s [29] A. Hyde, Sensory & Flavor of Different Specialty Malt
Conference, SanDiego, CA, 2015), URL http:// (Pacific Northwest Homebrewers Conference 2017, 2017),
www.brewingwithbriess.com/Assets/Presentations/ URL https://www.pnwhc.com/sites/default/files/
Briess_David_Richter_KilnedVsRoastedMalt.pdf. slides/PNWHC17_SpecialityMalts_AaronHyde.pptx.
[14] S. Coghe, G. Derdelinckx, and F. R. Del- [30] Viking Malt, Wheat Malt in Brewing (2015), URL
vaus, Monatsschr. Brauwiss 57, 25 (2004), URL http://www.vikingmalt.com/wp-content/uploads/
http://www.lowoxygenbrewing.com/wp-content/ 2015/06/Wheat-Malt-in-Brewing-2015.pdf.
uploads/2017/04/Coghe0604.pdf. [31] W. J. W. Lloyd, Journal of the Institute of Brewing 92,
[15] J. D. Hertrich, MBAA Technical Quarterly 50, 131 336 (1986), URL https://onlinelibrary.wiley.com/
(2013), URL https://www.mbaa.com/publications/tq/ doi/pdf/10.1002/j.2050-0416.1986.tb04420.x.
tqPastIssues/2013/Pages/TQ-50-1-0331-01.aspx.
[16] T. Foster and B. Hansen, Is it Crystal or Caramel
Malt? (2014), URL http://www.brewingwithbriess.
com/is-it-crystal-or-caramel-malt/.
[17] S. Graydon, R. Ryan, M. Scanzello, W. Thompson, APPENDIX
S. Frechette, H. Kuester, B. Krueger, and J. Dutter,
Cargill Specialty Products Group (2014), URL http:
//www.cargillfoods.com/wcm/groups/public/@cseg/ In the following tables we tabulate all pHi and Bi data
@food/@all/documents/document/na3051727.pdf. from this study and the previously published studies of
[18] M. J. Lewis and T. W. Young, Brewing (Kluwer Aca- KT [1, 4], AJdL [3, 5, 6], Bies [7], Geurts [8], and Walts
demic / Plenum Publishers; New York, 2002). [9]. All Bi values are normalized to the data of AJdL, as
[19] W. Kunze, Technology Brewing and Malting (VLB; discussed above.

14
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

TABLE III: Values of pHi and Bi for flaked grains and wheat malts from previous studies and this study (TS). Malt-color
values are generally taken to be the midpoint of published values, although the value in parenthesis is that reported by Geurts
for his sample. Where appropriate for a given malt or group of malts the average value (Ave) ± 1 standard deviation (SD) is
indicated.
Grain Color pHi −Bi Study
(◦ L) (mEq/kg)
Flaked Grains
Flaked Rye 3 6.65 29.8 TS
Flaked Wheat 2 6.57 28.2 TS
Flaked Corn 1 6.24 9.6 TS
Flaked Oats 2 6.21 48.2 TS
Flaked Barley 2 5.65 39.5 AJdL
1 5.46 51.8 TS
5.55±0.13 47.2±10.9 Ave ± SD
Wheat Malts
Briess White Wheat 3 5.89 31.9 Geurts
6.10 38.5 TS
Briess Red Wheat (3) 5.80 34.1 Geurts
Weyermann Wheat 2 6.07 34.6 Walts
5.97±0.14 34.8±2.8 Ave ± SD

TABLE IV: Values of pHi and Bi for dark roasted grains from previous studies and this study (TS). Malt-color values are
generally taken to be the midpoint of published values, although values in parenthesis are those reported by Geurts for his
samples. Where appropriate for a given malt the average value (Ave) ± 1 standard deviation (SD) is indicated. The overall
Ave ± SD for the whole group of malts is also indicated.
Grain Color pHi −Bi Study
(◦ L) (mEq/kg)
Briess Roasted Barley 300 4.62 68.6 Bies
4.75 73.1 Walts
(292) 4.73 66.3 Geurts
4.70 59.0 AJdL
4.68 62.9 KT
4.67 67.5 TS
4.69±0.05 66.0±6.3 Ave ± SD
Briess Black Barley 500 4.60 61.6 Bies
(561) 4.61 78.9 Geurts
4.62 67.2 KT
4.61±0.01 69.2±8.8 Ave ± SD
Briess Chocolate (416) 4.66 64.9 Geurts
Briess Dark Chocolate (581) 4.43 62.7 Geurts
Briess Black (629) 4.24 59.8 Geurts
Crisp Chocolate 600 4.70 78.7 AJdL
Simpsons Chocolate 444 4.55 77.2 Walts
Simpsons Black 625 4.57 77.0 Walts
Weyermann Carafa I 340 4.71 68.7 KT
Weyermann Carafa I Special 340 4.73 77.5 KT
Weyermann Carafa II Special 431 4.70 68.7 Walts
Weyermann Carafa III 525 4.81 64.4 KT
Overall Ave ± SD 4.64±0.13 68.7±6.6

15
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

TABLE V: Values of pHi and Bi for base malts and noncrystal specialty malts from this study (TS) and previous studies.
Malt-color values are generally taken to be the midpoint of published values, although values in parenthesis are those reported
by Geurts for his samples. Where appropriate for a given malt or groups of malts, the average value (Ave) ± 1 standard
deviation (SD) is indicated.
Grain Color pHi −Bi Study
(◦ L) (mEq/kg)
Pils/Lager/2-Row
Briess 2-Row 2 6.00 57.2 Bies
5.55 46.2 Geurts
Rahr Pils 2 5.80 42.4 Walts
Weyermann Pneumatic Pils 2 5.62 47.2 AJdL
Weyermann Floor Malted Pils 2 5.85 34.4 AJdL
5.76±0.18 45.5±8.3 Ave ± SD
Pale Ale/ Vienna/ Mild
Rahr Pale Ale 3 5.67 49.7 Walts
Crisp Maris Otter 3 5.69 49.5 AJdL
Muntons Maris Otter 3 5.84 51.4 AJdL
(unspecified) Maris Otter 3 5.82 47.0 KT (2010)
Weyermann Vienna 3 5.65 51.8 KT
Briess Goldpils Vienna (4) 5.65 57.6 Geurts
Briess Ashburne Mild (4) 5.50 59.2 Geurts
5.69±0.11 52.3±4.5 Ave ± SD
Munich
Weyermann Munich I 6 5.57 45.6 Walts
5.44 52.3 KT
Franco Belges Munich Light 7 5.62 60.7 KT
Weyermann Munich II 8 5.54 56.7 KT
Briess Munich 10L 10 5.72 52.1 Bies
(12) 5.51 54.9 Geurts
5.57±0.10 53.7±5.1 Ave ± SD
Aromatic
Briess Aromatic (16) 5.39 49.5 Geurts
20 5.39 45.5 TS
Dingemans Aromatic 19 5.38 64.7 TS
5.39±0.01 55.1±13.5 Ave ± SD
Biscuit / Amber / Brown
(unspecified) Biscuit 25 5.08 52.8 KT
Briess Victory 28 5.19 36.8 TS
Crisp Amber 29 5.10 35.5 TS
Briess Carabrown 55 5.19 31.4 TS
5.14±0.06 39.1±9.4 Ave ± SD
Crisp Brown 65 4.97 TS
Melanoidin / Honey / Brumalt
Weyermann Melanoidin 27 4.96 56.3 Walts
4.93 68.9 TS
4.94±0.02 62.6±8.9 Ave ± SD
Gambrinus Honey 25 4.82 95.4 TS
Briess Special Roast 40 4.91 99.1 TS
Other
Briess Extra Special 130 4.55 58.8 TS

16
D. M. Riffe and M. Spencer Grist pH and Buffering Capacity

TABLE VI: Values of pHi and Bi for crystal, caramel, and dextrine malts from this study (TS) and previous studies.
Malt-color values are generally the midpoint of published values. For each group of malts the average value (Ave) ± 1 standard
deviation (SD) is indicated.
Grain Color pHi −Bi Study
(◦ L) (mEq/kg)
C2
Crisp Dextrin 2 5.54 33.2 Walts
Weyermann Carafoam 2 5.88 36.5 AJdL
5.71±0.24 34.8±2.4 Ave ± SD
C 10
Briess Caramel L10 10 5.13 54.0 Geurts
5.38 48.6 KT
5.34 47.7 TS
Simpsons Caramalt 14 5.18 46.7 Walts
5.26±0.12 49.3±3.25 Ave ± SD
C 20
Briess Caramel L20 20 5.12 58.4 AJdL
5.01 53.4 Bies
5.05 59.1 Geurts
5.22 47.9 KT
5.07 59.7 TS
Cargill Caramel 20 20 5.43 48.6 Walts
5.15±0.016 54.5±5.3 Ave ± SD
C 40
Briess Caramel 40L 40 4.71 66.1 Bies
4.85 62.1 Geurts
5.02 61.0 KT
4.90 72.2 TS
Simpsons Crystal Light 40 4.92 53.3 Walts
Weyermann CaraMunich I 34 5.10 60.5 KT
Weyermann CaraMunich II 45 4.71 80.182 KT
4.89±0.15 65.0±8.8 Ave ± SD
C 60
Briess Caramel 60L 60 4.87 65.7 Bies
4.75 70.8 Geurts
4.66 78.5 KT
Cargill Caramel 60 60 4.97 68.6 Walts
Weyermann CaraMunich III 57 4.7 61.5 Walts
4.92 64.8 KT
4.81±0.13 68.3±5.9 Ave ± SD
C 80
Briess Caramel 80L 80 4.71 72.4 Geurts
4.77 73.0 AJdL
4.70 72.3 TS
Briess Caramel 90L 90 4.77 78.4 KT
4.74±0.04 74.0±2.9 Ave ± SD
C 120
Briess Caramel 120L 120 4.87 84.2 Bies
4.58 73.1 Geurts
4.75 78.4 KT
4.70 77.2 Walts
4.63 75.0 TS
Simpson’s DRC 113 4.58 74.2 Walts
4.68±0.11 77.0±4.0 Ave ± SD
C 140
Briess Caramel 150L 150 4.48 79.4 KT
Weyermann Caraaroma 133 4.48 98.8 KT
4.48±0.00 89.1±13.7 Ave ± SD

17