POSTHARVEST BROWNING IN SOUTH AFRICAN SUBTROPICAL EXPORT FRUITS

Autor: V. Claassens, F. J. Kruger, M. Kritzinger, L. Tait, M. Bezuidenhout
Rok vydání: 1999
Předmět:
Zdroj: Acta Horticulturae. :225-230
ISSN: 2406-6168
0567-7572
DOI: 10.17660/actahortic.1999.485.31
Popis: Browning is a major obstacle when exporting fresh subtropical produce by sea. The problem, however, has various causes and dissimilar processes are involved in the different crops. This paper offers a review on investigations conducted at the Institute for Tropical and Subtropical Crops of which the aim was to characterise and address the issue in South African avocados, mangoes, pineapples, papayas and litchis. In avocados, mangoes and pineapples the browning is primarily internal and due to enzymatic oxidation. In avocados we found that the oil content in the fruit rises dramatically during specific periods following excessive rain and that the highest incidence of internal browning (pulp spot and grey pulp) also occurs during this phase. Our recommendation is that the fruit should be exported under controlled atmosphere when these conditions prevail. Of the mango cultivars cultivated in South Africa, 'Heidi' is the most sensitive to browning. This takes place in three areas, namely, in the zone surrounding the pedicel, directly under the skin and in the ripest tissue around the seed. We have found that in order to combat browning, the fruit should be harvested mature but as green as possible and be exposed to a hot water treatment at a lower temperature but for a longer period than the currently used regime. Controlled atmosphere also proved to be useful. Due to its composite morphology, browning (blackheart) is difficult to control in 'Queen' pineapples and limited success has been attained with this fruit. We are, nevertheless, intensely investigating this fruit and are of the opinion that adaptation of certain preharvest horticultural practices in combination with selected postharvest techniques may retard blackheart and enable exportation of this fruit by sea. With papayas and litchis, browning is primarily an external problem. In 'Sunrise Solo' papaya we found browning to be a pathological problem occurring when inappropriate hydroheating takes place. This was rectified through adaptation of the hydroheating technique. In litchis the pericarp browns as a result of the breakdown of the red anthocyanins. We found postharvest dipping of the fruit in a tartaric acid solution with a pH of 0.5 to be effective in acidifying the anthocyanins and thereby retaining the red colour during exportation. The research is continued.
Databáze: OpenAIRE
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