GRAPE HARVESTER RECOVERY A N D
LOSSES
B. A. S N O B A R , B. F. C A R G I L L , J. H. LEVIN and D. E. M A R S H A L L
Based on cooperative research by Michigan State University, the U. S. Department of Agriculture, and the Michigan Concord Grape Production Research Fund. Michigan Agricultural Experiment Station Journal Article Number
5964.
Respectively Graduate Assistant and Professor, Department of Agricultural Engineering, Michigan State University,
East Lansing, Michigan 48823, and Agricultural Engineers, Fruit and Vegetable Harvesting Investigations, Agricultural
Engineering Research Division, United States Department of Agriculture at Michigan State University, East Lansing,
Michigan 48823.
The cooperation and assistance of James Warner, Richard Schuessler, and Dwight Brown of Michigan Wineries,
Inc.; the vineyard owners and the harvester operators; and the financial assistance from the Michigan Concord
Grape Production Research Fund are gratefully acknowledged.
Accepted for publication January 9, 1973.
ABSTRACT
The 'Concord' grape is the main variety produced
in Michigan for juice and wine. In 1971 over 85%
of the crop was mechanically harvested.
This paper reports on recovery and product losses
f r o m one make of grape harvester. The variables
studied were harvested yield and h a r v e s t e r ground
speed.
The grape losses were divided into three groups:
1) ground losses
grapes mechanically harvested
but dropped to the ground, 2) vine losses ~ grapes
left unharvested on the vine, and 3) juice losses
loss of juice on the vine leaves and from the harvester conveying system.
H a r v e s t e r recovery efficiency varied with har-
vested yield and ground speed ~ optimum recovery
occurred at 1.7 mph with the Mecca at 4 tons per
acre yields. Recovery was reduced at higher and
lower t h a n optimum ground speed. (Trade names
are used in this paper solely to provide specific information. Mention of a trade name does not constitute a w a r r a n t y of the product by Michigan State
University or the U. S. D e p a r t m e n t of Agriculture
or an endorsement of the product to the exclusion
of other products not mentioned.)
At constant ground speed grape recovery was influenced by y i e l d - increased yield resulted in
increased losses.
Michigan is one of five leading states in the production of an American hybrid, the 'Concord' grape
(Vitis labrusca) and practically all of the crop is
crushed for juice or wine.
Scarcity of hand labor at h a r v e s t i n g time and t h e
high cost of hand harvesting make h a r v e s t mechanization an essential activity if the industry is to
survive and remain economically sound.
Grape h a r v e s t i n g includes detaching f r u i t from
the vine, s e p a r a t i n g leaves and other debris, collecting fruit, and t r a n s p o r t i n g the harvested product
to the processing plant. Mechanical h a r v e s t i n g in
Michigan is relatively new. In 1969, 1970, and 1971
approximately 25, 65, and 85~/~, respectively, of
Michigan's grapes were mechanically harvested.
With the rapid increase in mechanical grape harvester usage, it was essential to look at vineyard
losses and recovery. Locating, observing, and evaluating the mechanical h a r v e s t e r losses were the first
essential steps necessary to reduce or eliminate
losses (increase vineyard recovery). This project
was p a r t of an overall research project on mechanical h a r v e s t i n g and post h a r v e s t handling (1, 2, and
3) which included: 1) the development of a complete bulk handling system (self-dumping hydraulic
vineyard trailer and bulk t a n k t r u c k ) , 2) an economic analysis of the conventional and bulk systems,
3) a comparison of juice quality of conventional and
bulk handled grapes, and 4) recovery and losses by
the grape harvester.
Grape losses during mechanical h a r v e s t i n g were
observed in 1970 while obtaining research data on
h a r v e s t e r economics and grape quality.
These
losses were observed as: 1) ground losses ~ grapes
mechanically harvested, but dropped to the ground,
2) vine losses ~ grapes left unharvested on the vine,
and 3) juice losses ~ on the vine, leaves, and the
harvester.
Various factors appeared to influence the mechanical h a r v e s t i n g losses: 1) vine yield, 2) h a r v e s t e r
ground speed, 3) shaker impact rate, and 4) stage of
grape maturity.
The objective of this project was to observe and
evaluate mechanical grape h a r v e s t i n g losses on 'Concord' grapes during the 1971 season as influenced
by yield and h a r v e s t e r operations.
Amer. J. Enol. Viticult., Vol. 24, No. 1, 1973
10
11--GRAPE HARVESTER
MATERIALS AND METHODS
g r a p e s f r o m the same row before and a f t e r the
designated 25 ft row length.
F i f t e e n sets of recovery tests were made over a
10 day period in five d i f f e r e n t vineyards. Test locations in level rows and u n i f o r m stands were selected
to minimize the effect of v i n e y a r d t e r r a i n .
A linear and non-linear regression using a least
squares method and a second degree polynomial
(4) respectively, gave the best fit curve for the data
involved. The linear equation w a s :
A series of plastic sheets 5 f t x 25 f t were placed
one on each side of an u n h a r v e s t e d g r a p e row at
various intervals down the row to m e a s u r e the
ground losses. At c o n s t a n t s h a k e r frequency (375
r p m ) , the h a r v e s t e r o p e r a t i o n was i n s t r u c t e d to
move down the row and over the plastic sheets at a
c o n s t a n t g r o u n d speed ( g r o u n d speed was varied for
the Mecca mechanical h a r v e s t e r f r o m n o r m a l 1.25 to
slow 1.1, to f a s t 2.0 m p h ) . P r o d u c t recovery per
acre was d e t e r m i n e d f r o m processing plant w e i g h t
slips. Grape losses on plastic sheets were recovered
and weighed to evaluate g r o u n d losses.
All u n h a r v e s t e d g r a p e s in the 25 ft designated row
length were removed by hand and weighed to determine the on-the-vine losses (unharvested).
Juice losses were evaluated by c o m p a r i n g the
w e i g h t of individual hand h a r v e s t e d g r a p e s to the
w e i g h t of individual mechanically h a r v e s t e d g r a p e s
obtained at the end of the h a r v e s t e r discharge conveyor while m o v i n g t h r o u g h the 25 ft designated row
length. Three cans w i t h 500 g r a m s capacity each
were held under the discharge conveyor while the
machine was m o v i n g over the designated row length.
The cans were filled and w e i g h e d ; the w e i g h t of the
t r a s h and any other f o r e i g n m a t e r i a l in the cans
and the w e i g h t of the e m p t y cans were s u b t r a c t e d
f r o m the gross w e i g h t to obtain the net h a r v e s t e d
g r a p e weight. The g r a p e s in the cans were counted
and the a v e r a g e w e i g h t of the individual mechanically h a r v e s t e d g r a p e s were obtained and comp a r e d to the w e i g h t of the individual h a n d h a r v e s t e d
Y = bo + b l X
and the non-linear equation was"
y = bo + b~x + b2x ~
where y and x were the variables: 1) h a r v e s t e r
g r o u n d speed in mph, 2) h a r v e s t i n g losses in percent, and 3) h a r v e s t e d yield in tons per acre; and
bo, b~, and b., were the constant coefficients.
Two c o m p u t e r p r o g r a m s were used (5, 6, and 7),
one to estimate the constant coefficients ( b ' s ) and
the second to d r a w the best fit curve. L i n e a r and
non-linear relationships were plotted c o m p a r i n g harvester g r o u n d speed, h a r v e s t i n g losses, ree(wery, and
yield (harvested yield). One m a k e of commercial
h a r v e s t e r was involved in the g r a p e recovery analysis; a h a r v e s t e r m a n u f a c t u r e d by Mecca Brothers,
Inc., 10838 Main Street, N o r t h Collins, N.Y. 14111.
The t e r m s used in the h a r v e s t e r recovery and
losses w e r e :
H a r v e s t e d yield = the net w e i g h t of g r a p e s t r a n s p o r t e d to the processing plant.
Total h a r v e s t i n g recovery - h a r v e s t e d yield.
G r o u n d losses (9~) =
Vine losses ( % )
Juice losses ( % )
=
g r o u n d losses
x 100.
h a r v e s t e d yield
vine losses
x 100.
h a r v e s t e d yield
Avg. w e i g h t of an
Avg. w e i g h t of an individual
individual machine
hand harvested grape
harvested grape
=
x 100.
Avg. w e i g h t of an individual machine h a r v e s t e d g r a p e
Juice losses = juice losses ( % ) x h a r v e s t e d yield.
Total h a r v e s t i n g losses = juice losses + g r o u n d losses + vine losses.
Total h a r v e s t i n g losses
x 100,
h a r v e s t e d yield
Total h a r v e s t i n g losses ( % )
=
or
= juice losses
(%)
+
g r o u n d losses ( % ) vine losses ( % ) .
P o t e n t i a l yield = h a r v e s t e d yield + total h a r v e s t i n g losses.
Total h a r v e s t i n g recovery ( % )
=
h a r v e s t e d yield
x 100.
potential yield
Amer. J. Enol. Viticult., Vol. 24, No. 1, 1973
GRAPE HARVESTER--12
RESULTS AND DISCUSSION
Figures 1 and 2 represent the relationship between
total harvesting losses and ground speed with the
Mecca harvester at constant shaker frequency (375
rpm) and four tons per acre harvested yield. The
figures indicate that there was a significant relationship between the two variables. The relationships
were as follows:
Lr = 1 0 1 . 2 4 -
108.58 S + 32.33 S °-
Lj = 4 2 . 6 3 - - 4 4 . 6 4
Lv -
S + 13.00 S 2
0.12 + 1.24 S
Lc, = 7 0 . 6 1 -
80.61 S + 24.12 S 2
Where"
LT, L~, Lv, and LG were the total, juice, vine, and
ground losses, respectively, in percent of harvested
yield. S was the ground speed in mph.
Figure 1 shows that as the ground speed increased up to 1.7 mph the total losses decreased,
increasing the ground speed beyond 1.7 mph increased the total losses. The reason is shown in
figure 2; at low ground speed the wire and vines
were being shaken more frequently ahead of the harvester and this caused excessive ground losses. Also
low ground speed resulted in increased juice losses
since the grapes were "slapped" more. Increasing
the ground speed beyond 1.7 mph caused the harvester to miss falling grapes (increasing the ground
losses). Increasing the ground speed also tended to
overload the harvester conveying system (increasing
the juice losses because of excessive grapes on the
conveyors). The vine losses remained fairly constant with only a slight increase in losses as ground
speed increased.
Figures 3 and 4 represent the relationship between yield and harvesting losses with the Mecca
harvester at a shaker frequency of 375 rpm and a
ground speed of 1.25 mph. The figures indicate that
24
24
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HARVESTED
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Figure 1. Total harvesting losses from a Mecca harvester operating at a constant shaker speed in a vineyard with 4 ton
harvested yield.
i
I
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I
~
I
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I
6
YIELD,
I
t
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TONS/
l
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8
ACRE
Figure 3. Total harvesting losses from a Mecca harvester operating at a constant ground speed of 1.25 mph compared to
harvested yield.
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Figure 2. Juice, vine, and ground losses from a Mecca harvester operating at a constant shaker speed and various ground
speeds in a vineyard with a 4 ton harvested yield.
Figure 4. Juice, vine, and ground losses from a Mecca harvester operating at a constant ground speed of 1.25 mph compared to harvested yield.
Amer. J. Enol. Viticult., Vol. 24, No. 1, 1973
13--GRAPE HARVESTER
there is a significant relationship between the two
variables. The relationships were as follows"
LT
Lj
Lv
La
5.92 + 1.83 Y
=
=
=
=
m
4.22 + 2.26 Y
2 . 0 8 m 0.22 Y
7.69
0.13 Y
Where:
LT, Lj, Lv, and La were the total, juice, vine, and
ground losses in percent of harvested yield respectively. Y was the yield in tons per acre.
Figure 3 shows that as the yield increased harvesting losses increased. The reason is shown in
figure 4 (as yield increased the juice loss increased).
Grape m a t u r i t y was a critical factor. The data collected and reported at 8 tons/acre yield was from
over m a t u r e grapes. Under these circumstances the
juice losses dominated because the tendency was to
lose juice from the ripe grapes. Because of the stage
of maturity, separation of grapes from the vine
was easy and resulted in decreased vine losses at
the 8 tons/acre yield. Ground losses remained fairly
constant as the yield increased.
SUMMARY
Grape recovery was influenced by various factors.
An optimal ground speed maximized grape recovery
(minimized grape losses). The optimal grape recovery was influenced by : 1) ground speed, 2) vineyard
yield, 3) grape maturity, and 4) harvester shaker
impact rate on the vine.
The optimal harvester ground speed for the Mecca
harvester observed was 1.7 mph. Lower or higher
ground speeds reduced the grape harvesting recovery (increased losses). The juice losses were
highest when the grapes were harvested at an over
m a t u r e stage; also in general, the total losses were
highest when over mature. The minimum total harvesting losses were a p p r o x i m a t e l y 10% of the harvested yield (at 4 t o n s / a c r e and 1.7 mph) with the
Mecca h a r v e s t e r ; the juice losses were 4.5%, the
ground losses 3.5%, and vine losses 2%. The total
harvesting losses were approximately 13.5 % (at 4
t o n s / a c r e and constant ground speed of 1.25 mph)
with the Mecca harvester.
In general, juice and ground losses were equivalent in value and more critical than the vine losses.
The research study indicated that the harvesting
losses varied with the yield, m a t u r i t y of grapes, and
harvester ground speed.
F u r t h e r research is needed to investigate the harvesting losses at higher yields (10-12 tons/acre)
and different growing practices; for example, the
Geneva Double Curtain (GDC) technique which
makes possible higher yields by using two vines on
one row or trellis. Also cultural practices (trimming
and vine height) and terrain are important factors
influencing harvesting losses.
LITERATURE CITED
1. Marshall, D. E., J. H. Levin and B. F. Cargill. Properties of
Concord grapes related to mechanical harvesting and handling. Trans. ASAE 14(2): 373-6 (1971).
2. Williams, Paul, B. F. Cargill, D. E. Marshall and J. H. Levin.
Bulk handling of Concord grapes for processing-efficiency
evaluation of various systems. ASAE paper no. 71-373A
(1971).
3. Whittenberger, R. T., D. E. Marshall, J. H. Levin and B. F.
Cargill. Bulk handling of Concord grapes for processing m
quality evaluation. ASAE paper no. 71-373B (1971).
4. Mendenhall, W. The Design and Analysis of Experiments.
Wadsworth Publishing Company, Inc., California (1968).
5. Michigan State University, Agricultural Experiment Station.
Calculation of least squares (regression) problems on the
LS routine. Stat Series Description Number 7, November,
1969.
6. Michigan State University, Agricultural Experiment Station.
Stepwise addition of variables to form a least squares equation. Stat Series Description Number 9, November, 1969.
7. Michigan State University, Agricultural Experiment Station.
Data plotting and curve drawing on the Calcomp Plotter.
Stat Series Description Number 16, December, 1969.
OTHER REFERENCES
Cargill, B. F. and Rossmiller, G. E. Fruit and vegetable harvest
mechanization, technological implications, RMC Report No. 16,
published by Rural Manpower Center, Michigan State University,
East Lansing, Michigan (1969).
Des Raj. Sampling Theory, McGraw-Hill Book Company, Inc.
(1968).
Kelsey, M., S. Carpenter, and R. Earl. Economics of grape production in Southwest Michigan. Agricultural Economics, Michigan State University Report No. 196, July, 1971.
Suggestions for stopping grape production losses. California
Farmer, September 4, 1971.
Amer. J. Enol. Viticult., Vol. 24, No. 1, 1973