Mechanical Injury of Fresh Produce 87
vary with cultivars. Storage of carrots for 180 days, even in a cold environment,
resulted in 55% absolute wastage for mechanical harvesting, with 8% additional
wastage after finishing off. Wastage was 7% for manual harvesting. Mechanical
damage during harvest and preparation affects the internal as well as external quality
of carrots. Damage of mechanically harvested carrots may be reduced by reducing
the fall distance of carrots between parts of the preparation equipment and reducing
the number of right angles through which carrots must pass.^65 Carrots harvested by
hand or machine and given additional mechanical stress by shaking in a transport
simulator, however, showed no significant difference from machine-harvested carrots
with regard to chemical or sensory variables. Principal component analysis showed
only slightly different placing of these samples in the score plot.^66 Experiments
examining causes of damage also showed that the number of damaged carrots was
increased by the frequency of impacts; harvested carrots packed in 3-kg plastic bags
broke more easily than those packed in 1-kg bags. The damage caused by falling
depended on the surface; the effects of a 30-cm drop onto steel were greater than
those of a 90-cm drop onto a conveyor belt. The degree of damage also varied with
orientation of the carrot; falls onto the point caused considerably more damage than
those onto the side or head.^65 Hand-lifted boxes containing carrot samples also stored
better than machine-lifted ones, although storage life did not correlate with obvious
mechanical damage.^67
The need to harvest potato tubers at maturity to decrease mechanical damage,
and for favorable storage conditions, was indicated by Muresan et al.^68 They reported
that mechanical damage resulted in wet and dry infections that decreased the total
value of potato tubers harvested for bulk sale. Temporary storage in sacks in the
field raised temperature, increased necrotic diseases, and gave time for the appear-
ance of disease symptoms and injury suberization. Kundzicz,^69 however, found that
the influence of harvest date on the storage loss was considerable. In a study that
used three cultivars, Sokol, Sowa, and Pola, the highest losses during storage of
Sokol and Sowa occurred for potatoes harvested at later dates. For the Pola variety,
the largest losses occurred for harvesting at the earliest date. Based on the observation
that early-maturing varieties (harvested late August to mid-September) suffer less
damage than varieties harvested a month later, Schuhmann and Oertel^70 concluded
that the resistance of tubers to mechanical damage is genetically controlled with
strong environmental effects. Haulm destruction seems to be effective in reducing
peeler-type damage. A comparison of the effect of a number of reciprocating riddle
diggers with elevator diggers indicated that the elevator digger with a main web
(elevator chain) and without an agitator had the lowest mechanical damage index.
The differences among the elevator diggers tested were not significant.^71 Harvesters
with rotary working elements tested in clay soil to determine whether mechanical
damage of potatoes could be reduced showed that they improved soil separation by
1.5 to 2 times compared to a conventional harvester, and mechanical damage to
tubers did not exceed 3%.^72 High soil NPK levels could also result in an increased
mechanical damage index and proportion of damaged tubers.^73
A comparison of fruit quality of sour cherry (Prunus) cv. Nefris after mechanical
and manual harvesting indicated that mechanical damage of fruits was below 2% under
both harvesting methods. Fruit elasticity and fruit firmness assessment indicated that