Pg. 29-33 Determination of harvest maturation stages appropriate for export of Madras litchi as identified by measurable fruit attributes

Fruit deterioration during sea-transit storage is a major problem confronting Madras litchi growers in South Africa. The extent of deterioration has been observed to relate to harvest date. The aim of the current study was to show the relationship between harvest maturation stage and fruit deterioration extent after extended cold-storage, and to relate measurable fruit attributes associated with a particular stage of harvest maturation with the extent of fruit deterioration. Madras litchis were repeatedly harvested from the same trees in a commercial, irrigated orchard. Harvesting took place on January 17, 20, 24, 27, and 31, 2005. Fruit sub-samples were used to determine fruit weight, fruit circumference, pulp weight, fruit moisture content, juice total soluble solids content, juice pH, juice total dissolved solids, extent of pulp discoloration, extent of pulp discolouration in the vicinity of the pedicel, and propensity for weight loss on each harvest date. The moisture content of the soil under the trees at each harvest was additionally quantified to ascertain whether a relationship with fruit deterioration was evident. Fruit deterioration was unacceptable in the fruits harvested on and after January 24. This was due to pericarp discolouration (darkening). Excessive moisture loss and the presence of exudates and growth of Penicillium on the fruits, was associated with the darkened pericarp regions. Pulp discolouration percentage was identified as being a possible candidate for the assessment of suitability for export. Determination based on the other harvest attributes quantified was indicated to be unsuitable. In view of the limited scope of the study, it was concluded that further data are required before commercialization can be considered.

Summary:

• Fruit deterioration during sea-transit storage is a major problem for South African Madras litchi growers, linked to harvest date.
• The study aimed to correlate harvest maturation stages with fruit deterioration after extended cold storage and identify measurable fruit traits indicating suitable harvest timing.
• Madras litchis were harvested from the same commercial irrigated orchard on January 17, 20, 24, 27, and 31, 2005.
• Assessments included fruit weight, circumference, pulp weight, moisture content, juice total soluble solids (TSS), juice pH, total dissolved solids, pulp and pedicel discoloration, and weight loss propensity.
• Soil moisture under trees was also measured to check its relationship with fruit deterioration.
• Fruits harvested on January 17 or 20 showed no pericarp discoloration and remained visually appealing after cold storage.
• Fruits harvested on and after January 24 displayed unacceptable pericarp discoloration (darkening), moisture loss, exudate presence, and Penicillium mold growth.
• Pulp discoloration percentage emerged as a potential indicator for export suitability, while other attributes were less useful.
• The study highlighted that pericarp discoloration results from moisture loss and is mitigated by sulphuring after harvest.
• Fruits that reach maximum size and weight by harvest were more prone to deterioration during storage.
• No clear relationship between soil moisture content during harvest and fruit deterioration was found since there was no rainfall in that period.
• The study recommends harvesting Madras litchi at earlier maturation stages to minimize postharvest deterioration for export.
• Further studies are needed to confirm findings and consider additional factors such as farm location, soil type, rainfall, and humidity effects.