Agriculture Reference
In-Depth Information
the SDS-insoluble fraction decreased to a
minimum value of 15% of SDS-insoluble pro-
teins extracted from fl our after 4, 8, and 20 min
in mixograph, farinograph, and alveograph
(Chopin Technologies, Villeneuve-la-Garenne,
France) mixers, respectively, indicating higher
intensity in the mixograph pin-mixer. Availabil-
ity of instruments such as the Brabender Docorder
(Brabender Instruments, Inc., South Hacken-
sack, New Jersey), the newer Brabender farino-
graphs, and the Newport Scientifi c Doughlab
(Newport Scientifi c Pty. Ltd., Warriewood,
NSW, Australia), which can all be run at variable
speeds, allows investigators to observe dough
behaviors at variable mixing intensities within
the same mixing geometry.
In the descending portion of mixing curves,
rapid reduction in resistance to mixing (consis-
tency), steeper angles of decline, and faster
decreases in the bandwidth of the mixing curve
are all indicative of lower tolerances to overmix-
ing and generally weaker dough characteristics.
The outputs from the RDMs are well able to rank
material in breeding programs for mix times and
indicators of mixing tolerances. The RDMs
are also amenable in commercial applications to
investigate the suitability of incoming grain or
fl our lots for a specifi c manufacturing facility
through empirical relationships observed between
RDM outputs and performance characteristics of
specifi c mixers.
All of the RDMs have limitations and advan-
tages. Notably the limitations of the mixograph
are its inability to measure optimum water absorp-
tion, which needs to be calculated from fl our
protein content beforehand and adjusted by trial
and error for the effects of other fl our compo-
nents. The z-arm mixers are able to measure
water absorption of fl our based on the amount of
water needed to achieve a predetermined but
arbitrary level of dough consistency. The com-
mercially available z-arm mixers also have the
advantage of jacketed bowls that allow tempera-
ture control, which is becoming more sophisti-
cated as newer RDMs and newer models of
existing RDMs are released. The mixograph has
an advantage of somewhat shorter analysis times
as a result of its higher mixing intensity. The
RDMs are produced in various size ranges based
on the amount of fl our used: mixograph, 10 and
35 g of fl our (a 2-g direct-drive prototype was also
produced); farinograph, 10, 50, and 300 g; Dough-
Lab, 50 and 300 g; Micro-DoughLab (prototype
Z-arm mixer) (Newport Scientifi c Pty. Ltd.,
Warriewood, NSW, Australia) 4 g; Alveo-
consistograph (Chopin Technologies, Villeneuve-
la-Garenne, France), 250 g. Smaller mixer
capacity and higher mixing intensity (shorter
overall analysis times) are particularly applicable
in breeding programs.
Recently attempts have been made to apply
more rigorous mathematical analyses of RDM
outputs, particularly to mixograms. Gras et al.
(2000) analyzed mixograph outputs as a series
of microextensions (also described as elongate-
rupture-relax oscillations) and suggested that
variation in curve bandwidth was a potentially
useful parameter in assessing the extensional
dough strength. Verbyla et al. (2007) used a
Fourier transform analysis to determine the main
cyclic patterns in high-resolution mixograph data.
Patterns correlated with the movement of the
mixing pins relative to fi xed pins and three main
frequencies were detected. Using only the major
frequency the technique provided estimates of
peak height and time-to-peak that correlated with
standard computer-assisted estimates of mixing
curve parameters. The Fourier analysis for the
major frequency provided a repeatable estimate of
bandwidth that was considered to give greater
resolution among samples than computer-assisted
bandwidth estimates.
Technology has further evolved to monitor
dough development in commercial-scale mixers.
Examples include NIRS, the use of mechanical
probes to directly measure the physical state of
the dough, and methods to measure mixer torque
(Wilson et al., 1997; Wesley et al., 1998; Demp-
ster et al., 2007). The output from a typical spiral
mixer observed using the BRI-Australia Easymix
system (BRI Research, North Ryde, NSW, Aus-
tralia) to measure torque conformed to the basic
template for mixing curves from the smaller
RDMs (Rasper and Walker 2000). The use of
NIRS to estimate dough mixing properties is dis-
cussed further below.
