Analytical Session
Mark R Schmitt, USDA Agricultural Research Service, Madison WI USA
Co-author(s): Allen Budde, USDA Agricultural Research Service (retired), USA
ABSTRACT: Many malting quality analysis methods have
several versions available, often an original manual method and a newer
automated version. For determination of wort free amino nitrogen (FAN)
concentration, a long-established manual method (ASBC Wort-12) is
available but infrequently used, and an automated segmented flow
analysis (SFA) version has recently been recommended for acceptance as
an approved method (MacLeod et al, JASBC 69(4):295, 2011). A third
format, a 96-well microtiter plate-based assay, is attractive in certain
situations. In this study, we compared the manual Wort-12 method for
FAN analysis, a standard SFA method (plus several variations), and two
microplate versions, using chemistry derived from either the manual or
the SFA version. We examined a number of variables, including reagent
(ninhydrin) source and grade, incubation time and temperature, and
reductant concentration, for the two microplate versions. In general,
the adaptation of the SFA reagent yielded a more robust assay with
results that matched manual and SFA assays. In contrast, direct
adaptation of the chemistry from Wort-12 to a microplate format
generated results that did not consistently match those from the other
methods. In addition, the Wort-12 process in a microplate format
required longer incubations (up to 15 min) at higher temperatures (up to
99°C) for full color development, indicating the assay could be more
susceptible to variations in color development. The assay derived from
the SFA reagents worked well, generated results that matched those from
existing manual and automated methods, and is recommended for FAN
analysis in a microplate format.
Mark Schmitt received a Ph.D.
degree in plant physiology/plant biochemistry from the University of
Wisconsin, Madison. He joined USDA’s Agricultural Research Service in
Madison in 2003. His research emphasis is on malting quality.
VIEW PRESENTATION 92
