Question
I work as a Post Production Officer at a Food Processing Plant in South Asia. I am glad to mention here that I have gone through the Postharvest Technology Center’s well maintained website on the postharvest techniques of fruits and vegetables.
However, I would like to state that the processing plant that I am working with
is still in its initial inception which requires techniques to prevent postharvest losses. A large amount of orange (Citrus sinensis) is lost yearly due to lack of postharvest technology related facilities. Our working team has recently come up with converting surplus orange into orange pulp to reduce losses due to spoilage.
Therefore, I would like to inquire if there are any innovative postharvest
techniques pertaining to orange fruit in particular. Looking forward to your
help. (S.D.)
Answer
I believe you are asking for guidance on general handling of citrus fruits as it pertains to processing. In California our major market is the fresh market and although we have processing plants they are not on the scale that they have in Florida where the vast majority of fruit are processed for juice. I have also forwarded your email to Dr. Mark Ritenour at the University of Florida for his input.
To be successful, whether one is focused on the fresh or processed market, proper handling protocols for the fruit are absolutely essential. Citrus fruit are easily damaged during the harvesting process and are prone to decay due to two wound pathogens, Penicillium digitatum (green mold) and P. italicum (blue mold). Worldwide these are the two most serious decay pathogens of citrus. It is essential therefore to make sure the fruit are processed or packed in a timely manner following harvest so that these decay pathogens do not cause serious losses. There are several other postharvest pathogens that can also be a problem but these are dependent on the fruit maturity, growing conditions etc. In California, which has a dry Mediterranean climate, we seasonally can have problems with other pathogens but in warmer, more humid climates such as Brazil, Florida, and I imagine in your region, you can have serious losses if the fruit are not processed in a timely manner due to these other pathogens.
For the fresh market we recommend that the fruit be treated with a postharvest fungicide within 24 hours of harvest (the sooner the better, however). For processed product I would use this time frame as a reference and ensure your fruit is processed quickly after harvest. Hot water dips have been found to be efficacious for controlling Penicillium and brown rot (caused by Phytophthora) and may be something you might want to consider for the processed product if you have to hold the fruit prior to processing for a day or so, but I would not recommend it.
There are several books available on citrus processing. The best source for these books that I have found is Florida Science Source, LLC. They can be found at www.ultimatecitrus.com/fssource/index.html
-- Mary Lu Arpaia
Additional input from Dr. Mark Ritenour:
Dr. Arpaia's comments are excellent, including resources for more detailed information. Additional information on citrus can also be found at our postharvest website (http://irrec.ifas.ufl.edu/postharvest/) and the UF EDIS database (a link is provided at our postharvest website).
I work primarily with the fresh citrus growers/shippers, but have several colleges that work with the processors that I can consult with as well.
In Florida, we experience much more decay pressure due to stem-end-rots (mostly Diplodia [now called Lasidiplodia]) and sometime early season Anthracnose or Phytopthora (brown rot).
While there are many factors that influence the health and holding capacity (shelf life) of the fruit, Dr. Arpaia summarized the most important ones (e.g., rapid, careful handling and the importance of timely fungicide application if delays in processing are anticipated).
Recommendations will depend on the specific conditions and problems that are experienced.
-- Mark Ritenour