Ashby, B. Hunt

Craig, William L.

Fischer, Dieter F.

Woolsey, Michael D.

English

Research Papers in Economics

Simulated In-Transit Vibration Damage
To Fresh Market Raspberries
by
W. L. Craig
Agricultural Marketing Specialist
Agricultural Marketing Service, U.S,D.A
Washington, DC
M. D. Woolsey
Agricultural Marketing Service, U.S,D.A
Washington, DC
B. H. Ashby
Agricultural Marketing Service, U.S.D.A
Washington, DC
D. F. Fischer
Agricultural Marketing Service, U.S.D.A
Washington, DC
Introduction
In-transit vibration damage causes millions
of dollars damage to fresh produce annually. A
possible way to reduce damage is to alter transport
vehicle suspensions. The initial step in imple-
menting this solution is to determine which vibra-
tion frequencies are causing the damage. To
accomplish this we exposed fruits to several vibra-
tion frequencies in our laboratory.
One commodity we worked with was rasp-
berries, which are one of the most delicate,
costly, and perishable fruits. In-transit vibration
causes abrasions and bruises, which affect color of
berries and encourage mold and decay. Reduction
of this damage would result in extended shelf life
and enhanced marketability.
Journal of Fcxxl Distribution Research
Objective
The objective of this study was to determine
the influence of position in a stack of boxes and
the most damaging vibration frequency. Previous
research has shown that, as stack height increases,
damage increases; and most product damage
occurs within a very narrow critical frequency
band.
Methodology
Raspberries were purchased in standard
berry flats. Each of these flats contained 12]A
pint baskets of berries. Three vibration frequency
ranges were used for this study. They were 6.5-
9, 9-11.5, and 11.5-14 hertz, respectively. These
June 921page 69ranges were chosen because previous research
showed critical frequencies of other types of fruit
to be in the 6.5-9 and 9-11.5 hertz ranges and
preliminary testing showed maximum movement
of stacked flats of raspberries in the 6.5-9 and 9-
11.5 ranges. The 11.5-14 hertz range was used to
see if damage would decrease at a higher fle-
quency.
Flats of raspberries were stacked 20 high on
a pallet. Sample baskets were placed in the top,
middle, and bottom flats. They were vibrated for
% hour at % g. Accelerometers mounted on the
pallet and the top of the stack monitored force
levels. This process was repeated 3 times at each
frequency range, using fresh berries each time.
After each vibration treatment the baskets of
sample berries were removed from the stack and
rated for bruise and abrasion damage. The ratings
were: “No Damage,” berries with less than 10
percent of surface affected; “Moderate Damage, ”
berries with up to 50 percent of surface affected;
and “Severe Damage, ” unsalable berries with
more than 50 percent of surface affected.
Next, the berries were evaluated with a
calorimeter. This device evaluates color through
three measurements, “L” which represents light-
ness or darkness, “a“ which represents redness or
greenness, and “b”which represents yellowness or
blueness.
Results and Dkcussion
The analysis of variance was used, first to
determine if there were significant differences in
damage between treated and non-treated product.
Next, data from treated product were analyzed to
assess effect of stack position and treatment fre-
quency.
The percentage of sample berries considered
unsalable, or showing severe bruises and abra-
sions, after treatment was significantly greater
(a < 0.05) in t.b 6.5-9 and 9-11.5 hertz fre-
quency ranges and at the top stack position.
Within the 9-11.5 hertz range, the top stack posi-
tion received more than twice as much damage as
the bottom, and more than three and one half
times as much as the middle.
Color analysis for treated product by stack
position showed that mean “L” values declined as
stack height increased, indicating darker berries
toward the top stack position. The “L” value at
the top stack position was significantly lower
(a < 0.05) than at the bottom stack position.
Mean “a” values increased, indicating redder
berries, as stack height increased. The “a” value
at the top stack position was significantly greater
(~ < 0.05) than the “a” values at both the middle
and bottom positions. Mean “b” values were
roughly constant across the three stack positions.
Color analysis by frequency showed lower
mean “L” values and higher mean “a” and “b”
values for the 6.5-9 and 9-11.5 hertz ranges.
However, only “a” values showed a statistically
significant difference (u < Q.05) between the 9-
11.5 and 11.5-14 hertz ranges. Mean “a” values
for the 9-11.5 range were higher indicating redder
berries than the 11.5-14 hertz range.
Conclusions
Most damage occurred in top boxes. Mid-
dle boxes appeared to show somewhat less damage
than bottom boxes, however these differences
were not statistically significant. The 6.5-9 and
9,5-11 hertz ranges were the most damaging.
These results indicate significant reduction
of in-transit damage to fresh raspberries may be
accomplished by altering transport vehicle suspen-
sions to damp out frequencies below 11.5 hertz.
June 921page 70 Journal of Food Distribution Research

SIMULATED IN-TRANSIT VIBRATION DAMAGE TO FRESH MARKET RASPBERRIES

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