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AOAC RESEARCH INSTITUTE
AOAC
OFFICIAL METHODS OF ANALYSIS
(OMA)
OMAMAN-13: Determination Of Dietary Starch In Animal Feeds And Pet Food By An Enzymatic-
Colorimetric Method Collaborative Study*
Study Director: Mary Beth Hall, U. S. Department of Agriculture – Agricultural Research Service, U.S.
Dairy Forage Research Center, 1925 Linden Drive, Madison, WI 53706, USA
ER 5
Same temperature for both enzymatic procedures, allowing better efficiency. Changed to quadratic
curve due to the slight non-linearity of the standards.
ER 6
It would be interesting to understand why leaving the sample (taking a break) after dilution of fully
digested samples has an impact on recovery (line 699, p31)
ER 7
good
ER 8
n/a
Analytical Range
ER 1 1-100%
ER 2
0-100 mg starch in the assay
ER 3
Range studied was 1.00% - 69.6%. Corn starch was used as a spiking agent which suggests this material
can be tested directly on this material (89% dietary starch) as long as enzymes are keep in sufficient
excess/
ER 4
See method collaborative study report.
ER 5
~1% to 100%
ER 6
about 1 (lowest amount in samples tested in MLT) - 100% starch (considering corn starch used as
control)
ER 7
good
ER 8
Acceptable
LOQ
ER 1 Approx. 0.3% (probably a little larger)- definitely less than 1%
ER 2
0.9% of starch sample weight basis
ER 3
0.3%. Acceptable limit.
ER 4
See method collaborative study report.
ER 5
0.3%
ER 6
This has been estimated as 0.2% dietary starch by using reagent blanks. The approach seems
reasonable, although one may expect the practical LoQ to be higher when applied to samples (and is
probably not independent of the free glucose content of a sample)
ER 7
good
ER 8
Acceptable
Accuracy/Recovery
ER 1 99.3 pure corn starch, 90@ control corn starch.
ER 2
89.9% +/- 3.7%
ER 3
993.8% wi+/- 0.8% is excellent
ER 4
See method collaborative study report.
ER 5
Pure corn starch: 99.3% ± 0.8% (Theoretical = 100%) Corn Starch: 89.9% ± 3.7% (Estimated = 89.4)
ER 6
This does not appear to have been extensively tested. Pure starch products have been assayed and the
recoveries are greater than 95%, Dextrins appear to be more problematic, but this does not seem to
have been discussed.
ER 7
good