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labelling limit, and one in 161 being greater than four
times that level.
Across the 965 servings, the overall average gluten is cal-
culated to be 1.18 ppm per serving (i.e. 1.18 mg kg
1
per
serving). This is assuming 0 mg kg
1
for BLQs and
80 mg kg
1
for ALQs. However, only forty-eight of the
965 servings contain any measurable gluten. Of those, if
one conservatively assumes an AQL reading as 80 ppm,
seventeen contain about 71% of total gluten observed,
averaging about 48 ppm (so, about one in fifty-seven serv-
ings at this level).
It is important to note that the above referenced results
were all single test outcomes per serving. Our recent
research has shown that when a gluten-containing kernel
exists in a serving of oatmeal, a single test result can
underestimate overall serving gluten content (Fritz
et al.
,
2017). This is because gluten from the contaminate kernel
tends to end up lognormally distributed in the ground
sample (even with grinding performed under current best
grinding practices). In other words, much of the gluten
from the contaminant kernel remains concentrated in a
few pockets within the serving after grinding, not being
well dispersed. So consequently, a small test amount,
randomly selected from the serving, is more likely than
not to undercount overall gluten. With this insight, it was
found that for samples initially testing ‘gluten positive
yet compliant’ (i.e. 5 to
<
20 ppm), when ten additional
tests per sample were conducted, about half ended up
averaging noncompliant, that is
≥
20 ppm (Fritz
et al.
,
2017). It is fair to assume that additional tests (beyond
ten per serving for this ‘positive yet compliant’ group)
could provide higher proportions of samples averaging
>
20 ppm, due to the lognormal distribution of gluten in
these already deemed ‘gluten-positive’ ground samples.
Figure 1 provides a graphical depiction of the gluten
distribution observed in the survey. It shows both the
single test per serving outcomes and the assumed more
accurate distribution if initially found ‘positive yet
compliant outcomes’ were subjected to multiple tests
per serving (using 50% of 5 to
<
20 ppm servings end-
ing up in the 20
–
80 ppm category due to this).
The overall gluten per serving circumstance uncov-
ered, that is where most servings measure BLQ and
then are interspersed with occasional noncompliant
servings, holds at the ‘date code’ level as well. Of the
thirteen of twenty-one date codes possessing noncom-
pliant servings, the maximum noncompliant serving
rate was also 5% (like the overall data set). This maxi-
mum rate was not found statistically different from
any other date code outcomes.
So it appears a bimodal-like noncompliance pattern
(in terms of ppm) has been revealed in the GF oatmeal
marketplace in terms of gluten per serving, where
numerous BLQ servings are ‘interrupted’ by occasional
noncompliant ones, some being several times the regu-
latory limit. These results indicate the GF oatmeal
production processes of these two producers do not
have sufficient capability to effectively mitigate gluten
contamination to BLQ at the serving size level. The
pattern of defects supports the premise that kernel-
based gluten contamination is the cause, which pro-
duces high levels of gluten in oatmeal servings made
from otherwise GF, pure oats. The outcomes encoun-
tered also suggest the inspection regimens used to
assess overall process capability and lot acceptance are
incapable of detecting the level of noncompliance
observed.
This binary-like noncompliance pattern sheds light
on interpretation of what some might view errantly as
an attractive 1.18 ppm gluten average/serving found
across these 965 servings. But despite a low ppm aver-
age per serving, the gluten is obviously not well dis-
persed across them (as an average errantly implies),
but rather resides concentrated in a handful of
servings, many being noncompliant in regard to GF
labelling requirements.
The above survey insight has served as the genesis
for this work, guiding the balance of the investigation.
0
200
400
600
800
1,000
BLQ (0-5 ppm)
5-20 ppm
20-80 ppm
> 80 ppm
917
31
11
6
917
15
27
6
With a single test/serving:
100% of measurable gluten resides in ~ 5% of servings
~ 75% of measurable gluten resides in ~ 1.8% of servings
~ 50% of measurable gluten resides in ~ 0.6% of servings
Count of servings
Considered
zero gluten
Gluten containing
Distribution of Gluten in 965 U.S. Oatmeal Servings
(from two large U.S. Producers, spanning twenty-one date codes from 2014)
Figure 1
Distribution of gluten found in US
‘in-market’ survey of gluten-free oatmeal
servings. (Both as observed with single
results/serving and estimated given retests of
‘5 to
<
20 ppm’ initial outcomes). [Colour fig-
ure can be viewed at
wileyonlinelibrary.com]©
2016 PepsiCo, Inc. International Journal of Food Science & Technology published
by John Wiley & Sons, Ltd. on behalf of Institute of Food Science and Technology
International Journal of Food Science and Technology 2016
Kernel-based gluten binary-like outcomes
R. D. Fritz and Y. Chen
4