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Tart Cherry Processing
Cherries are ready to harvest when the fruit is red and the stem detaches easily from the pit. Mechanical harvesting (shaking) has replaced hand picking. Harvesters shake the fruit from the tree onto a fabric apron.
Mechanically harvested cherries contain immature fruit mixed with fully-ripened fruit. The sugar content of immature cherries is low. Since sugar retards oxidation, the poor color and character of immature cherries is noticeable in the finished product.
After cherries are removed from the tree they are placed in cold water to prevent scalding (discoloration). Cherries are delivered to the processing plant in water. For this reason, cherries are bought by volume.
Cherries going through
an intitial wash |
Cherries being unloaded
from a grower's tank |
Mechanically harvested cherries contain many attached stems. A stemming operation is necessary. Stems are classified as harmless extraneous material if they are included in the frozen cherries. Incoming cherries receive some type of inspection prior to processing. The processor rejects cherries with defects. Cherries are held in large soak tanks of cold water to firm the fruit prior to pitting and processing. Improperly firmed fruit is easily "pitter torn." Cherries are flumed from the soaking tank to a sorting belt.
Sorting personnel remove the most obvious defects, such as damaged fruit, loose pits, stems,and foliage. Electric-eye sorting equipment is used to reject defective cherries. However, the same machine cannot reject both dark and light colored individual cherries at a given setting.
Overview of the
processing line |
Sizing cherries
to detect defects |
Cherries usually go directly to the final container after pitting and sorting. Bulk containers comprise the volumeof the frozen cherry pack with 30-pound cans and polyethylene-lined steel drums used for thispurpose.Cherries are normally covered with sugar and/or sirup to provide a barrier to inhibit oxidation. Cans and drums are covered and moved into cold storage.
Quick freezing is desirable to prevent deterioration. In some processing plants, the cold storage facility is too small to hold all of the filledcontainers at the peak of the season. Excess containers are often trucked considerable distance toreach commercial cold storage facilities. Cherries are also packed IQF (Individually Quick Frozen).This process freezes the fruit quickly and it is packed "free-flowing" without a packing medium. IQFcherries are bright in color but discolor quickly after thawing.
Freezing Cherries |
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Cherry Products