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1586
H
aselberger
&
J
acobs
:
J
ournal of
AOAC I
nternational
V
ol
. 99, N
o
. 6, 2016
that could complicate CF assignment following the guidance
for Part I analysis.
Minimum Detection Limit (MDL)/LOQ
The LOQ was empirically demonstrated by analysis of a low-
level spike solution, also containing a high level of sucrose.
scFOS was spiked into laboratory water at a concentration of
0.03 g/100 g. Sucrose was added to this sample at a concentration
of 9 g/100 g. This solution was analyzed in triplicate on each
of 3 days. Average recovery, repeatability, and intermediate
precision were calculated from this data.
Results and Discussion
Linearity
A graphical summary of the relative errors for each standard
from the 43 calibration data sets is presented in Figure 2. These
results indicate that, consistent with expectations, uncertainty
(as evidenced by the dispersion) increases as concentration
decreases. However there is no significant evidence of a
concentration dependent bias and relative calibration errors are
less than 4% for every individual standard. Consequently, it can
be concluded that fit of calibration data to the quadratic model
is consistently acceptable.
Accuracy (Spike Recovery)
Results of the various recovery experiments are summarized
in Tables
2016.06B
,
2016.06C
, and Table 1. Average recoveries
ranged from 92.9 to 108%. The lowest recoveries (92.9 and
94.2%) were obtained for scFOS from the SPIFAN adult
Nutritional RTF high-fat product, while the highest (108 and
105%) were for oligofructose from the SPIFAN toddler formula
powder, milk based. All of the average recoveries were with the
acceptable range of 90–110%, as specified in SMPR 2014.002.
Precision
Precision metrics are summarized in Table
2016.06A
.
Repeatability RSDs (RSD
r
) ranged from 1.09 to 3.67%, all well
below the requirement of 6%. Intermediate precision RSDs
(RSD
IP
) ranged from 2.57 to 6.79%. Intermediate precision
requirements are not explicitly called out in SPIFAN SMPRs,
however, in all but one case, intermediate precision performance
met the stated requirement for repeatability.
Specificity
As indicated in Table 2, no detectable fructose was found
in any of the unfortified SPIFAN products when they were
subjected to quantitative testing (Part II) for total fructan
content. Because of the diversity of these matrixes, including
carbohydrate systems, this is good evidence of the ability to
selectively detect fructans (as enzymatically released fructose).
Example chromatograms relevant to the qualitative
Part I analysis for CF assignment are shown in Figures 3–5.
Maltodextrin-containing matrixes tend to be potentially the
most problematic, especially with respect to assessing the
presence or absence of GF
3
and/or GF
4
. It is important, though,
to recognize that this step is not a screening tool to confirm
whether or not fructans are present. It is intended only to
provide sufficient information to allow selection of the most
appropriate correction factor. The quantitative determination of
enzymatically released fructose not only provides the basis for
Figure 3. Example of product containing scFOS at ~0.28 g/100 g (Part I) – Upper trace: inulin (Beneo Orafti HP); middle trace: SPIFAN child
formula powder, 00866RF00; lower trace: Ingredion Nutraflora scFOS. Time interval from 36–44 min zoomed in to show detail.
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