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Degreening Citrus

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As we know every commodity comes to market at different times of the year every year. California Valencia season historically runs through October.  Multiple extreme heat waves over the summer months, wind fall and a lower crop yield this year ended the Valencia crop earlier than usual, creating a gap in the citrus category.  

By late October California Navels begin to enter the market.  The navels being picked at this time do not have the beautiful orange color we normally associate with a navel orange. When warmer nights occur, citrus will mature with a green cast over the skin. What brings up color on citrus is the cold nights of the fall and winter that naturally transforms the preserved chlorophyll in the fruit from green to orange.  Summer fruit lacks the chill hours needed to bring on the orange color and we normally see the best color on navels starting in December.

To determine when to harvest, growers will test the brix, or sugar levels, of the fruit in order to decide if it is ready to eat.  If the sugar levels are too low the fruit will be left on the tree longer.  When the sugar levels are sufficiently “high”, but the outside of the fruit is green, this is caused by the lack of chill hours not yet achieved when harvesting at this time of year.

Growers can choose to leave the fruit on the tree longer to color up or some citrus growers will make the decision to harvest and degreen the citrus or color them up by gassing them with ethylene. This is the same process used to color up bananas in our banana rooms. Ethylene is an odorless, colorless, natural gas released by mature fruit such as apple and bananas. You can experiment at home by putting a piece of light colored citrus in a paper bag with an apple or banana and this will naturally color up the citrus. Need a ripe avocado?  Speed up the ripening process by placing an avocado and an apple or banana in a paper bag.

Degreening citrus has been practiced at least since the early 1960’s, especially on fruit coming out of Mexico or the southern hemisphere where the nights are warm, preventing fruit from coloring up to their full potential. Fruit with a green cast is picked into bins and pre-washed in the field. The following day the fruit bins are loaded into ethylene rooms with temperatures set at 70-80 degrees and a humidity level of 80%. The degreening process can take 1-4 days to achieve the desired color. After the fruit is removed from the degreening rooms it is aired out, run through the packing line and finally washed, graded, and packed.

This process also helps to identify any problematic fruit. Fruit with quality issues, especially from the recent rain, will be accelerated in the degreening process.  All visible problematic fruit is removed on the packing line, helping to make sure that the completed box has high quality fruit. The process of degreening or coloring up with ethylene is meant to produce the customary orange color of citrus.  


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