Progressive Crop Consultant May/June 2021

Figure 4. Sliced examples of mechanically harvested blueberries. From left to right:
Fruit with no internal bruise as indicated by no large discolored tissue; Fruit with
impact damage at the stem end as indicated by discoloration inside the seed core;
Fruit exhibiting damaged area from impact force to that triangular shaped, discolored
section; and Discolored area has been highlighted in purple with SketchAndCalc
program to calculate bruised area as 17% of the total cut surface area.
surfaces to harvest fruit with minimum damage. With the V45
harvester design, the detached blueberries dropped less than 15
inches onto a soft neoprene sheet glued to a hard catch plate and
soft sheet over the conveyor belt.
These soft surfaces reduced impact force on the fruit detached
by the V45 harvester. However, gluing a soft surface onto a hard
surface has proven to show little reduction in bruise damage
when harvesting is performed with conventional harvesters
with two vertical drum shakers and berries falling more than 30
inches. Only five V45 harvesters were sold by the now defunct
B.E.I Inc. (South Haven, Mich.), although it was thought to have
good fruit selectivity (low green fruit removal) compared to
slapper models, little ground loss (fruiting cane pushed away
from the crown) and superior quality over existing commercial
harvesters at the time with two vertical drum shakers and either
a metal or hard plastic catch surface.
Sometimes, the fruit harvested by the V45 harvester had quality
as good as commercially HH fruit. Its limitations were: 1) It
needed to be driven much slower to avoid damaging bushes; 2) It
could not harvest trellised rows or those with overhead sprinklers;
and 3) It could not harvest all varieties, especially those
with stiff, upright canes like ‘Jersey’ and many rabbiteye cultivars.
The Fulcrum harvester made by A&B Packing Equipment
(Lawrence, Mich.) has features like those of the V45 harvester.
In the last ten years or so, U.S. blueberry farmers targeting the
fresh market have been facing challenging economic situations
(e.g., rising cost of hand picking, shrinking labor force, global
competition, etc.) They and other specialty crop farmers have
a greater interest in using automation and OTR machines to
harvest their crop. The authors of this article have participated
in different aspects of machine harvesting and sorting of
blueberries to reduce the amount of internal bruise damage
and in packing line sorting technology and damage detection
systems to improve the quality of packed fruit. Several blueberry
MH manufacturers (e.g., Oxbo International, Lynden, Wash.;
A&B Packing Equipment, Lawrence, Mich.; BSK, Serbia; and
FineFields, the Netherlands) have put more efforts devoted to
developing MH systems that would impart low or no bruise
damage so that fruits can be packed for fresh market. Following
is a summary of recent developments in MH.
Bruised Berries from Mechanical Harvesting
Most OTR harvesters currently available are better suited for
harvesting processed blueberries because they can cause
excessive fruit damage. However, OTR machines have
been used to pick blueberries for fresh market. In these
instances, the fruit should be packed and transported to
consumers as quickly as possible. When blueberries are
HH, typically the picker gently picks ripe fruit selectively.
In Chile and China, for example, ripe berries are picked
individually to obtain high fresh quality.
In the Pacific Northwest and elsewhere in North America,
ripe fruit is often harvested by rubbing fruit cluster
or sometimes by “tickling” them between the thumb
and index finger and catching the detached berries in the palm
and then placing them in a small harvesting bucket. In contrast,
MH involves the shaking of the entire bush with rapid action of
shaking rods to move canes back and forth. The cane movement
causes ripe berries that need less fruit removal force than green/
red berries to be displaced from the fruit stem (pedicel) and
fall onto catching surfaces. Experienced MH operators make
slight adjustments on machine settings to obtain good selectivity
(minimize green/red berry removal and maximize ripe fruit
removal).
The blueberry bush can range from 3 to about 6 feet tall with
fruit located from the tip of the canes to branches near the
ground, which causes the berries located on the top part of bush
to fall as much as 50 inches. When an OTR harvester picks blueberries
and fruit falls from that height onto plastic catch plates
and conveyor belts, one can hear berries hitting the hard catch
surfaces.
Based on this simplified description of the blueberry MH process,
it was apparent that the interaction between the machine
and fruit should be better understood. To do this, we used a
custom-made miniature electronic sphere called the BIRD
(blueberry impact recording device developed at the University
of Georgia) to measure the fruit impacts during MH process in
2010 and 2011. The BIRD sensor for this study weighed 14 g. The
later version, BIRD II, was built to closely approximate the size
and weight of a large blueberry (9/16-in diameter and weighed 6
g) (Figure 5, see page 6).
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