Postharvest handling update for lychee 

Steven A. Sargent, Extension Postharvest Specialist, Horticultural Sciences Department University of Florida, Gainesville FL 32611

A)  Buyers, consumers prefer a sweet, juicy pulp and small seed

  • Bright-red peel
  • Large, firm fruit
  • Uniform size fruit in carton

1.  Factors contributing to quality loss during harvest, handling and marketing

  • Rapid loss in pericarp (peel) quality, within 24 hours when not cooled
  • Browning
  • Water loss (peel hardening)
  • Cracking, promoting decay

This results in reduced commercial value or total loss

2.  Common postharvest peel disease organisms

  • Alternaria sp
  • Cladosporium sp.
  • Penicillium sp

4.      Other factors contributing to quality loss include

  • Short harvest season, resulting in limited availability of fruit
  • Improper handling
  • No cooling or inadequate cooling prior to shipping or during shipping
  • Handlers and retailers often unfamiliar with handling requirements
  • Lack of U.S. grade standards
  • Perceived quality vs. actual quality (i.e., lychees with brown peel can still have high-quality pulp)

 B)  Previous postharvest research results

 

1.  Hydrocooling and packing in plastic film liner and corrugated carton were recommended for ‘Hong Huay’ lychee (Ketsa and Lelawatana, 1992)

2.  Coating maintained peel color: (McGuire and Baldwin, 1996)

  • Low pH; >2% cellulose

3.  Detached fruits shriveled less than fruits attached to panicles (Vilasachandran and        Sargent, 1997)

4.   Optimal cooling and storage conditions for ‘Mauritius’ and ‘Brewster’ lychee       (Pornchaloempeng, Sargent and Fox, 1997)

  • Cool to 5°C (41F°) and maintain 90% relative humidity (RH)

5.  Modified/controlled atmosphere slowed browning and decay in ‘Mauritius’       (Pornchaloempeng, Sargent and Fox, 1998)

  • 4% oxygen, 5-7.5% carbon dioxide, balance nitrogen at 5°C (41° F) and 90% RH

6.  Other effective treatments, but not permitted in U.S.:

  •  Acid dip/SO2 gassing to control browning (Israel, S. Africa)

               *  Maximum 10 ppm (pulp) and 250 ppm (peel)

               *  Restricted or banned in several countries

  • Benomyl dip for decay control

               *  500-1000 ppm at 52°C (125°F) for 2 minutes

 

7.  Patented heat-treatment process: “5 weeks in refrigeration + 3 days at 82° F (28°C) 

      (Moranim Subtropical Fruit Company, Israel; details not specified)

8.  Preliminary Research Results from our 1999 tests:

   a.  Postharvest dip treatments with 4-hexylresorcinol:

          - 0.01% 4-HR dip for 3 minutes resulted in redder peel, less browning than other 

            treatments (‘Mauritius’)

         - 4-HR is GRAS approved (Generally Regarded As Safe) by the FDA


C)  Current  postharvest  recommendations for lychee

  1. At harvest, clip panicles from branches
  2. Carefully handle in low-height, clean field containers to minimize bruising and decay
  3. Clip fruits from panicles to minimize water loss during shipping
  4. Cooling method: Hydrocool within a couple hours of harvest to 41°F (5°C), about 15 minutes using ice-water mixture and use use chlorinated water (150 ppm free chlorine, pH 6.8 - 7.2)
  5. Pack in plastic liners and carton or in 1-pound, rigid plastic (clamshell) containers
  6. Store/ship ‘Mauritius’ at 41°F (5°C), ‘Brewster’ at 38°F (3°C) and 85-90% relative humidity for up to14 days postharvest life
  7. For extended storage from 21 to 28 days: (P. Porchaloempong, M.S. Thesis. 1999) use refrigeration + controlled or modified atmosphere storage:

a)  ’Mauritius’: 41°F (5°C)/85-90% relative humidity; 4% oxygen/7.5% carbon dioxide

b)  ’Brewster’: 38°F (3°C)/85-90% relative humidity; 2% oxygen/5% carbon dioxide

 

Note:  Our limited research on longans indicates this crop can be handled under the same storage and shipping conditions as lychees.