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Thursday, November 23, 2017

WSU-TFREC/Postharvest Information Network/Reducing Handling Injuries During Fruit Harvest



Reducing Handling Injuries During Fruit Harvest


Manuscript

There is considerable concern with the level of surface handling injury that is currently encountered in moving fresh fruit from the tree to the packinghouse. The injury is sufficiently severe that some fruit industries are funding studies to evaluate the problem and to quantify the benefits of practices that may reduce the problem. In the interim several steps can be taken to reduce the problem.

Surface marking is associated with abrasion and vibration. Abrasion may occur when fruit rubs against some surface--the picking bag or bucket, the field lug or bin, or even another fruit. Abrasion in the field can be reduced or eliminated by good supervision of harvest crews. During transport within the field and to the packinghouse the fruit may be injured by a combination of abrasion (especially against bin sides when jolts occur) and vibration as the fruit gets into motion within the bin.


To Reduce Injury

Several steps may be useful in reducing these problems, all of which must be coupled with good harvest supervision.

  1. Keep all container surfaces clean and nonabrasive. This may require frequent washing of picking bags and buckets and of field lugs and bins. It may also require some type of coating or liner within the container to reduce the problem of rough surfaces.

  2. Avoid excessive movement by forklift or forklift attachments in the field. Bins can bounce severely while being moved over rough field surfaces on such equipment.

  3. Consider whether bin trailers that have no spring suspension system are aggravating the injury problem. Try to minimize the distance and speed of travel of such equipment.

  4. Grade farm roads to eliminate ruts, potholes and bumps.

  5. Try to select public roads that are in reasonable condition, even if it means hauling a somewhat longer distance to the packinghouse.

  6. Restrict transport speed limits to a level that will avoid free movement of the product. This may require varying the speed limits on different roads.

  7. Reduce tire air pressure on transport trucks and field trailers. Softer tires will absorb more motion and reduce motion transmitted to bins and product.

  8. To evaluate injury, draw samples from bins on arrival at the packinghouse and hold them at least 24 hours before scoring. The visual surface marking results from browning oxidation of injuries, and some time is required for oxidation to be completed. You may get a false sense of security by too early an evaluation.


Studies by UC Davis

During the 1984 season we studied problems of transit injury prior to packing. These studies were supported by the nectarine, peach, pear and plum committees of the California Tree Fruit Agreement. We evaluated the role of several factors involved in surface marking susceptibility of the fruits and explored possible handling modifications to reduce injury. The tests produced some interesting results.


Transport Vehicles

The amount of surface marking injury was proportional to the vibration level of bins while in transit. Semi-trailers and double trailers generally showed the highest injury levels. There were large differences between vehicles of essentially identical construction traveling over identical routes. The front bin position on the trailers showed the highest vibration level, the second position was next (and about equal to the rear position), and the lowest vibration readings were in the middle of the trailer.

Air suspension systems greatly reduced vibration levels, with the greatest response when air suspension was installed on all axles of truck and trailer. One test of the same vehicle with the same load, route, speed and driver showed a 50% reduction in vibration level after air suspension was installed.


Bin Liners

Some corrugated bin liners have been used, especially with pears. Injury level was about equal for fruit in contact with corrugated liners or unlined bins. Plastic liners, however, provided an excellent barrier between fruit and bin, and reduced injury intensity of pears by 80% and stone fruit by 50%. That injury reduction was constant whether a single layer plastic film liner or a bubble liner was used. All of these liners were used on the bin sides only.

On stone fruits injury developed across the top of the bin as well as against the bin sides. The use of thick bubble liners resulted in lower injury scores in all locations, suggesting some damping of horizontal motion. Pears showed no measurable injury of top fruit not in contact with the bins (following the under 25 mile transit distances tested).


Top Padding

For several years pear handlers have used bin top pads to reduce injury to pears transported long distances between districts. The same system was tested with stone fruit that were transported more than 40 miles to packinghouses. With these stone fruits, some modification was needed to avoid fruit injury from the pad. The pad consisted of 5/8-inch plywood cut to fit inside the bins, and faced with either 2 layers of ½ inch thick bubble liner material or 2-inch thick foam plastic. Short rubber straps were fitted through side ventilation slots near the 4 corners, pulled up inside the bin, and hooked into eyes on top of the 4 corners of the pad. This avoided bin modification and maintained constant top pad pressure on the fruit.

The top pads substantially reduced stone fruit injury in all tests. When combined with bubble bin liners, the overall injury reduction was about 60%.


Temperature Effects

Past studies have shown that temperature influences stone fruit injury susceptibility, with least injury at intermediate temperatures (about 45 to 60°F). Fruit harvested throughout the day showed similar effects. Injury susceptibility rose sharply when fruit temperatures exceeded 80°F. Hydrocooling following transport did not reduce injury level. In laboratory tests, Hydrocooling before transport reduced injury somewhat, but fruit wetting without cooling resulted in increased injury.


Conclusions

These projects allowed quantifying of potential treatment benefits. Substantial transport injury was often encountered in unmodified shipments. The injury level was influenced by the vehicle used, distance traveled, truck speed, road condition, fruit temperature, variety, and other unknown factors. With truck-trailer vehicles, air suspension installed on all axles substantially reduced the injury level. Plastic liners also greatly reduced injury of fruit in contact with bin sides, and thick bubble liners reduced injury of stone fruit across the top of the bin. Using top bin pads reduced injury to top fruit in the bin, a problem for stone fruit and pears in long distance transport. Managers can substantially reduce transit damage by combining these procedures, reducing transport speed, and selecting smoother roads.

F. Gordon Mitchell, Postharvest Extension Specialist

University of California, Davis

Post Harvest Pomology Newsletter, Vol. 3, No. 2.
May-June 1985

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