Cherries are highly perishable because of their high respiration rate. When cherries are picked from the tree they are removed from their life support system and senescence begins.
Maintaining cherry quality after harvest (part 4)
Cherries in the orchard (Continued from last issue)
When to harvest
At normal field temperatures, fruit respiration rate is so high that it will begin to destroy the cherry soon after it is harvested.
Cherry colour, bruising, respiration, stem browning and loss of water are increased by temperatures above 0C.
Determining when to harvest cherries is a balancing act between weather, fruit quality and market demands.
Skin colour an indicator
Skin colour is a good reliable indicator of ripeness. Skin colour darkened with advanced harvest dates, but the rate of darkening is variety dependent.
While cherries stay on the tree, skin colour, sugars and size all increase, while firmness and stem retention decrease.
Skin colour is directly related to firmness. All the quality attributes relate to skin colour.
Flesh colour also works as an indicator, but lags behind in timing to skin colour.
Researchers and growers in the USA make use the French Ctifl cherry colour guide to standardize fruit skin colour evaluations. In this chart, colours 2 and 3 are avoided, but 4, 5 and 6 are acceptable.
Dark cherries change from green to straw yellow, to pink, to red, to light mahogany, to mahogany, to dark mahogany, to dark.
White cherries (e.g. Royal Anne/Napoleon and Rainier) develop yellow flesh and skin as one of the first signs of maturity. Rainier is at its peak for commercial harvest when it develops a red blush on the cheek.
Be aware that browning tinge on the fruit is related to the high brix level, known as sugar browning.
Harvesting should be done in the morning during dry weather.
It should begin at daybreak and stop when the ambient temperature approaches 38C.
By harvesting in the morning the cherries will be at its largest and firmest.
The flesh temperature of cherries on the tree remains close to ambient air temperature while fruit in direct sun can be hotter than the ambient temperature.
For the best flavour, cherries should be harvested as fully ripe as possible. The skin colour of cherries may change very quickly. You will have only two to three days at the most to pick from a given tree in the orchard within the optimum maturity range.
Fortunately, cherry trees in an orchard do not turn colour at once.
After picking, cherries start to deteriorate quickly. (cont next issue)
See this article in Tree Fruit Dec 2019