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ESTIMATION OF OPTIMUM HARVEST DATE FOR APPLES
BY MORE PRACTICAL METHOD
Ibrahim Tahir
SLU, Section of Top Fruit Production-Kivik
Box 97, 277 21 Kivik-Sweden
ibrahim.tahir@hvf.slu.se
Picking fruits in optimum date, is the best way to carry out high quality and minimum losses
during storage. However the determination of this date is cultivar and production-area depend,
and this situation causes many difficulties at the choosing of the accurate ripening index.
Various maturity indexes have been used to estimate the last save harvest date for long- term
storage. Many investigations showed that ethylene production and / or respiration rate were
most useful. According to these results, the long of safety period can not be shorter than one
week and no longer than four weeks. ( Faragher & Brochier 1981, Liu 1978). Whereas
measurement of ethylene production is not practical for the growers, many other indexes were
used such as : days from full bloom, flesh firmness, soluble solids concentration, starch test,
acidity, color, skin wax and ease of separation from spurs. The purpose of this work is to
examine the accuracy of three practical ripening indices ( firmness, solid soluble
concentration and starch content ) by correlation with storage results and ethylene production.
Material and methods
Fifteen trees / cultivar ( Aroma, Cox´s Orange Pippin and Ingrid Marie) were mentioned
randomly in Kiviks orchard during the seasons 1993 – 1997. Fruits were picked ( 12
fruits/tree) early in the morning twice a week, during the period between end of August and
end of October. At all of picking times, a lot of 30 fruits were analyzed and 150 fruits hold on
2-3C , 90% RH. After 15 weeks of storage, fruits were removed, quality parameters, fungal
decay, and disorders controlled.
Analyses:
Flesh firmness by Penetrometer.
Solid soluble concentration by refrectometer.
Ethylene production by gas chromatography.
Ground and superficial color by Minolta Chromameter CR 200.
Starch content by Iodine –test.
Acidity by titration.
All data were subjected to analysis of variance, using the Microsoft Excel 5 spreadsheet.
Results & Discussion
During the five seasons, the flesh firmness and starch content of the three cultivars fruits
decreased with maturation as well as solid soluble concentration increased. Our results
showed that there was a period of fruit development, distinguished by very slow changes in
these ripening parameters. This period that was 2- 4 weeks long, intervened two
other development’s phases when the changes in the same parameters took place in higher
rates.
To control our conclusion in correlation with storage results, we found that fruits which
picked during these weeks had better storability than other fruits. ( Table 1 – 3 ) However,
slow change in the three parameters was not always a good index to predict storability, since
we found fruits with slow change that had bad storability and also fruits with faster changes
which had good storability. Due to this problem we shortened the period and found that