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Overripeness
Overripeness in apricots.

APR6 - Overripeness

Definition

Overripeness (OR) in apricot fruit manifests as translucent breakdown of the flesh tissue below the fruit skin which spreads inwards towards the stone with increasing severity and from which cell fluids can be readily expressed.

General information

While internal disorders are a consequence of abnormal physiological events, OR is a natural and inevitable consequence of the senescence phase which follows the growth and maturation phases that occurs in all fruit. Fruit ripening commences during the later stages of maturation and continues into senescence.  Therefore, while OR is not a disorder from a scientific perspective, it remains a very important fruit quality parameter.

Typically, OR in apricots is quite easy to detect because the fruit skin has an advanced skin colour. Fruit with advanced OR may even exhibit a dull brown colour through the skin, emanating from the underlying deteriorating flesh tissue.  The fruit is very soft to the touch.  The flesh tissue has a translucent appearance and is soft and watery, unlike gel breakdown, where the affected flesh tissue tends to be dry. The wateriness of overripe flesh tissue is ascribed to cell membranes loosing integrity due to senescence. This allows cell fluids to leak from the inside of the cells into the cell wall area at a stage that pectins located in the cell walls have already been metabolised to such an extent that they are water soluble.

 

Causes and remedies

Harvest maturity:

A common of cause of OR is harvesting apricots at post-optimum maturity.  Therefore, it is important to harvest fruit within the prescribed optimum maturity window for the specific cultivar. Post optimum fruit should not be packed for long term storage or export, since even low percentages (e.g. 10%) of overripe fruit at the arrival inspection may lead to rejections.

To reduce OR it is recommended to harvest on the less mature side of the optimum window with the aim to deliver fruit to the market slightly backward in colour and relatively firm. Because apricots ripen rapidly when exposed to temperatures higher than 15,0 °C after low temperature storage, the customer can easily ripen such fruit as required.

Generally, to ensure good quality apricots, in particular for storage durations required for sea export, it will  be necessary to pick through trees several times to ensure that only optimum and uniform maturity fruit is packed.

Cold chain:

Sub-optimal temperature management resulting in increases in fruit pulp temperature, at any stage in the handling chain can result in OR.  Packing fruit as soon as possible after harvest (within 6 hours), followed by commencement of forced-air cooling as soon as possible, in times of approximately 12 to 24 hours is recommended. Subsequent cold storage should be as near to -0,5 °C as possible, without breaks in the cold chain. Since OR development tends to increase with longer storage, it is good practice to store as short as possible.  Sometimes OR becomes a problem when it is least expected, because while it may not be a problem at the end of cold storage, it can develop very rapidly as soon as fruit is subjected to higher shelf-life temperatures.  Experience has shown that the incidence and severity of OR escalates exponentially the longer the storage duration prior to shelf life, and that this effect is more pronounced the more advanced the harvest maturity. It is good practice to curtail storage of export apricots to 28 to 38 days depending on cultivar and packaging.

Injury:

Apricots are highly perishable.  Rough handling during harvest and packing sometimes damages fruit that slips by undetected on the pack-line and ends up in the carton. Even once packed, damage to the fruit skin and underlying flesh tissue can occur in the form of vibration abrasions, rub marks or bruising. Injuries to the fruit harvested in the optimum maturity window cause a rapid production of the ripening hormone ethylene.  This causes rapid ripening of affected fruit which can lead to OR and secondary development of decay at the wound site.  If this ethylene wounding response is restricted to individual fruits, it can result in mixed maturities in a box which is often a cause for rejection by the buyers.  In the worst case, ethylene production from individual fruits can also stimulate other healthy healthy fruit to ripen faster than intended.

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