Pg. 46-48 The effect of modified atmosphere packaging and post-harvest treatments on the microbial population of litchi fruit

Diverse genera of bacteria, fungi and yeasts occur on fruit surfaces. These microbial communities play a vital roll in the ecological balance on the fructoplane. The application of post-harvest treatments may disturb this balance resulting in development of infections on the fruit. Therefore investigating the dynamics of these communities in relation to the application of post-harvest treatments is crucial in understanding the relationship between epiphytic micro-organisms and plant diseases. In view of this the microbial dynamics of the litchi fruit after application of different post-harvest treatments were studied on both Mauritius and McLean’s Red litchis in the 2006/07 season. Microbial counts of bacteria, fungi and yeasts were monitored at 14, 21 and 30 days after treatment. Results indicate that the populations of all three organisms have changed through the simulated export storage period.

Summary:

• The study investigated the microbial dynamics on the surface of litchi fruit after different post-harvest treatments and modified atmosphere packaging (MAP) during simulated export storage.
• Treatments included 1-Methylcyclopropene (1-MCP) at various concentrations, chitosan dips, sulphur dioxide (SO₂) fumigation, and MAP alone.
• Microbial populations of bacteria, fungi, and yeasts were monitored at 14, 21, and 30 days after treatment on two litchi cultivars: Mauritius and McLeans Red.
• Results showed that 1-MCP treatments, particularly moderate concentrations, significantly suppressed fungal populations, reducing decay caused by fungi.
• Yeast populations increased in fruit treated with chitosan, MAP, and some 1-MCP treatments due to the microaerophilic nature of yeasts and changes in oxygen and humidity in MAP.
• Chitosan treatments unexpectedly increased fungal populations, possibly due to acidification of the fruit peel from the acetic acid used to dissolve chitosan, favoring Penicillium colonization.
• SO₂ treatment significantly decreased bacterial and yeast populations but allowed fungi to increase, potentially creating conditions for opportunistic fungal decay.
• The study highlights the importance of understanding microbial interactions and the effects of post-harvest treatments for improving fruit quality and controlling disease.
• Moderate 1-MCP concentrations emerged as a promising alternative to SO₂ for controlling fungal decay on litchis.
• The findings emphasize the need to evaluate both microbial populations and fruit quality when applying post-harvest treatments and MAP for litchi export.