Agriculture Reference
In-Depth Information
(a)
6
5
4
3
2
1
0
Trailer tip
Hopper to
soil extract
Inspection
To sizer
screen
To cross
conveyors
Store
conveyors
Elevator to
heap
(b)
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Manual box
tip
Hopper to
washer
Roller drier
to
inspection
Chute to
conveyor
Distribution
conveyor
Auto-pack
weighter
Handling
packs
Figure 16.7
Results obtained from instrumental spheres designed to estimate the level of impact
experienced by potato tubers at different stages of handling. Typical maximum impact readings obtained
during (a) grading into store and (b) the pre-pack line. Figures given in y-axis are for comparison of the
damage level for different operations. (Maunder
et al
. 1990, with permission.)
relation to impact sensivity based on the principle that the
majority of the intercelluar space is water. “The procedure
consists of the freezing and thawing one-mm thick slices of
tubers wrapped in a thin plastic film to retain moisture
during the test. After thawing (3 hours approximately)
slices can be photographed using a digital camera and
directly imported into a computer program, Adobe
PhotoShop™, converted into greyscale and the K value
from the CMYK system can be measured as a percentage
of grey. This procedure takes approximately six hours and
can be correlated with the chemical potential reported in
the literature.” Baritelle
et al
. (1999b).
Quantification of mechanical dynamic failure properties
is normally done by a pendulum method. Schippeers
(1971) produced a review of the bruising methods used and
divided them into methods by which the place and the size
of impact can be quantified (drop weight or pendulum
methods) and, secondly “bulk bruising methods” where
several tubers are used at once and may be no more than
running a sample of potatoes over a grader.
There has been extensive use of pendulum systems to give
tuber data (Grant & Hughes 1995; Skrobacki
et al
. 1985;
Gall
et al
. 1996). In general, the weight of the pendulum used
is 76-292 g, the height of fall 100-500 mm and the radius of
