The period after fruit ripening is the most important phase in the annual work cycle during apple production, as any failure at this stage would cause the greatest possible economic losses.
To reduce losses during this period, it is necessary to understand the factors that cause these losses.
Biological factors include breathing, through which the temperature rises, causing losses in quality, nutritional value, reserves, and consuming weight; ethylene – a hormone produced in plant tissues that affects the ripening and aging of fruits; transpiration – the loss of water through evaporation.
Physiological factors - appearance of spots, loss of color, rot, development of pathogens, halt of ripening processes as a result of long storage, then exposure to low (-1.5°C) and high (>30°C) temperatures.
Mechanical damages - Occur during fruit handling in the form of scratches, bruises accompanied by brown coloring, and decay of the fetal tissue.
Damage from pathogens - Caused by the presence of microorganisms under certain conditions such as temperature, humidity, mechanical injuries, improper fruit ripening, unbalanced nutrition, etc.
Limiting losses
To limit losses, measures must be taken at different times: before harvest, during harvesting, after harvest, and during storage
Pre-harvest measures
As a preventive measure, it is recommended to select cultivars resistant to diseases and pests, along with appropriate agrotechnical measures (irrigation, fertilizing, pruning, treatments, maintenance, and phytohygiene of the orchard)
Measures during harvesting
These measures include determining the harvest time and the harvesting process.
The determination of the harvest time can be made based on several predictions, such as the number of days from flowering to ripening, and observations over several years. But the main and measurable criteria in determining fruit ripeness are:
Harvesting process – It can be done manually or mechanically. Hand picking is done so that the fruit is grasped with the palm of the hand while the index finger is placed on the swollen part of the stem where it is tied by a branch, then it is gently moved toward the swollen part of the stem, which detaches easily. To carry out the harvest, it is necessary to provide the necessary tools such as chests, a kangaroo pouch, appropriate ladders, and when there are large areas, the appropriate harvesting platform.
Post-harvest measures – After harvesting, fruits are placed in boxes, transported, and sent to the site for cleaning, sorting, and packaging. During this time, care must be taken to ensure that transport is done with appropriate means without mechanically damaging the fruits; cleaning should be done with clean water (chlorinated at 0.01% or 100 liters of water with 10 g chlorine), and the packages must also be clean and disinfected with hyperchlorite of K, N, or Cl at a concentration of 0.01%. The storage area or storage area for fruits must also be cleaned and disinfected beforehand. One of the methods is sulfur disinfection, where 2-3 grams of sulfur are burned per 1 m² of storage area in special containers. The storage remains closed in this way for 2-3 days and then ventilated.
Fruit preservation – Through preservation, the aim is to extend the period of fruit use with minimal losses and achieving high commercial values. There are several preservation methods:
- Storage in natural conditions,
- Storage with mechanical cooling (refrigerators),
- Storage with cooling (refrigerator) and controlled atmosphere.
Preservation in natural conditions
To store apples for a certain period of 3-4 months or even longer in the simplest and most affordable way, it is necessary to have: newspaper paper (or some other type), crates, apples, and a cool storage space. Cleaning the fruit would be welcome but not necessary. The spoilage of the fruit is influenced by the storage time, mechanical injuries, and direct contact between the fruits.
Time – cultivars with a sour taste such as Jonathan, Idared, Greni, and Smith last longer compared to those containing more sugars, such as Golden and Red Delishe.
Selection – Care must always be taken during fruit handling, from harvesting to packaging for storage, to prevent damage. Only healthy fruits are chosen for storage, while damaged ones are consumed fresh or processed. To preserve fruits longer, a solution can also be prepared in which the fruits should be soaked for a few minutes before placing them in the crates:
Prepared solution: 10 l of water; 0.4 kg of calcium chloride; 20 g of wine preservatives (vinobran); 10 ml of Chromov or Radov.
Contact – to avoid contact between fruits during storage, we individually wrap them in newspaper, except for colored paper, due to heavy metal poisoning, or wrap them in other clean paper. Wrapping does not mean it has to be airtight but just enough to stay normally in the storage box without being unwrapped.
Storage – it is important for the storage to have optimal humidity of 80-90%, good ventilation, temperature not lower than 2°C, the storage must be dark, other products should not be stored in the same place, especially potatoes, crates should be 15–20 cm above floor level, and there should be moisture - water on the floor.
Mechanical refrigeration storage (refrigerators) – Fruit storage using this method is done at controlled temperatures of 0.5 - 4 °C as well as at controlled relative air humidity of 90–95%
Refrigerated storage and controlled atmosphere
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