PRO*ACT Crop Update: Citrus re-greening and de-greening

Fruit grown in warmer climates doesn’t always develop a deep orange color and sometimes keeps some green on the skin. As the weather warms in the summer months the skin of Valencia oranges starts to reabsorb chlorophyll, which causes the fruit to turn partially green usually near the stem end — re-greening. The green is due to chlorophyll produced on the peel of the orange to protect itself from sunburn. Chlorophyll is vital for photosynthesis which allows the fruit to absorb energy from sunlight. Cold temperatures in the winter inhibit chlorophyll pigments, which give oranges their deep orange color.

Re-greening can also be caused by the position of the fruit on the individual tree. Fruit tucked in among the leaves tends to have more green as it is trying to maximize its reach for the sun’s rays.

Re-greening is a common occurrence this time of year and is purely cosmetic. It is a temporary change to the fruit’s appearance and can still be safely consumed and enjoyed. Most importantly, this does not affect the flavor, sweetness or quality of the fruit. Some growers believe that citrus with re-greening can have more sugar and a sweeter taste than fruit with a deep orange color. The debate continues.

De-greening is the process of removing the green coloring (chlorophyll) from the skin of citrus fruit. This is achieved by introducing measured amounts of ethylene gas into a temperature and humidity-controlled environment. Ethylene gas helps change the rind color from yellow or green to orange. Ethylene is a naturally produced plant growth hormone that is effective as a de-greening agent. It does not change any other characteristic of the orange.

Only mature fruit is suitable for de-greening, which is primarily a cosmetic treatment that improves the fruit’s appearance; it does not affect the quality or flavor of the fruit.

With over 30 years in the produce industry, Tim Lynch started as an inspector and advanced into quality control and food safety. Beyond work, he's an avid sports fan, relishing in activities like boating, fishing, and diving. Originally from Hollywood, California, Tim attended Cal Poly SLO before making Marina his home since 1994.