Transport and Packaging to Optimize Pear Quality
Types of Damage
This report discusses the causes and approaches to reduce mechanical damage to pears.
Types of Damage
Roller bruising or vibration damage - This causes a dark mark on the fruit skin but does not damage the flesh. Damage occurs when fruit is subjected to vibration that has an acceleration of greater than one g. This is the threshold acceleration that just allows the fruit to move with respect to neighboring fruit or packaging. This type of damage usually occurs during highway transport.
Impact - Fruit that falls against a hard surface will have damaged flesh at the point of impact but will have little immediately noticeable damage to the skin. Drop height that causes damage is dependent of fruit firmness and shape and hardness of the landing surface. An intermediate firmness is often least susceptible to damage. Safe drop heights are lowest when fruit strikes a hard round surface (pipe), greater when fruit hits a hard flat surface, and greatest when fruit contacts a resilient surface.
Compression - A slowly applied pressure causes flesh damage with only a small effect on the skin surface. This damage is caused by weak packaging that allows the fruit to support the weight of product above it. Pears are most susceptible to compression damage when they are ripe and have a low flesh firmness.
Scuffing - This damage is caused by fruit rubbing or being pushed against a hard surface. Rough field bins and pickers leaning against filled canvas picking bags can cause this damage.
Harvest damage to pears can be reduced by:
- Teaching pickers to not lean against the picking bag.
- Using smooth-sided field bins - keeping plastic bins clean and lining wooden bins with plastic sheeting.
- Grading orchard roads.
- Keeping tractors speeds low.
- Using air ride suspended trailers to move fruit bins.
- Covering fruit in bins with a padded top that is pulled down against the fruit with rubber chords.
Highway Transport Damage
Vibration damage in highway transport is most noticeable on fruit on the top two or three box layers on the two rear-most pallet positions on a truck. Fruit is usually not damaged in the front of the trailer because it is supported by the tractor, which often has an air ride suspension. The rear of many trucks is on a steel-spring suspension that transmits a great deal of damaging vibration and the vibration. Top boxes are more subject to vibration damage because vibration is amplified as it is transmitted through a load of boxes.
Damage can be reduced by immobilizing the fruit in its package or by reducing the level of vibration transmitted to the product.
- Pack pears in 3- to 5-lb plastic bags.
- Ship fruit on an air-ride suspended trailer.
- Do not load pears in the two rear-most pallet positions of a truck.
University of California, Davis
3022 Banier Hall
Davis, CA 95616
16th Annual Postharvest Conference, Yakima, WA
March 14-15, 2000