Fresh on demand, DP4: optimization of the tropical fruit supply chain : Papaya 'Tainung', experiments 2022

Summary

This report describes the results of trials done in year 2022, the last year of the four-year program Fresh on Demand, subproject ‘Optimization of the tropical fruit supply chain’. This sub-project aimed at maintaining a good quality for the consumer, while taking into account sustainability requirements. From this perspective, the transport of ‘Tainung’ papaya overseas instead of by air transport is relevant and brings both economic and environmental advantages. The challenge and goal is to maintain papaya quality as high as possible. The main points of attention for papaya quality are better control of the ripening, less water loss, and reduction of mould. To reach this, focus of the research is on two new technologies: Modified Atmosphere (MA) Packaging with liners based on a high precision laser perforation system (PerfoTec) and the use of managed- atmosphere chambers (RipeLocker). --First of all, two trials were done with these two technologies in Brazil (location Agricola Famosa) in the periods April-May 2022 and May-June 2022. As a reference, a hot-needle (HN) perforated flowpack for individual papayas was used (the current standard packaging). These two trials were guided on site by Wageningen FBR researchers. Overseas transport in reefer containers was simulated by storing papayas at 11°C for 33 and 30 days in the first and second trial, respectively. Storage was followed by a shelf-life of 3 days at 20°C.-- Quality assessments were done after 0 and 3 days of shelf-life. The observed papaya quality after these simulated transports would not have been suitable for a commercial shipment, neither for the standard HN flowpack, nor for the tested technologies. Especially the amounts of anthracnose and other moulds were high. These high percentages are related to the production time of year and the long storage duration.-- Additionally, the relative humidity in the storage room was very high (mostly 95-100 % RH) compared to reefer settings for commercial sea transport (65 % RH).-- Overall, there was no clear effect of the treatments (alternative technologies) on moulds. However, the advantage of both PerfoTec liners and RipeLocker chambers (‘RipeLockers’ in short) over HN-bags was found in reduced weight loss, decreased shrivelling and delayed colouring, leading to a fresher look, both after 0 and 3 days of shelf-life. --Papayas from RipeLockers showed a reddish translucent discolouration of the pulp (associated with softer fruit) that needed to be further investigated to better understand this phenomenon. --A third trial in November-December 2022 with RipeLockers was aimed at understanding the problem of reddish translucent tissue. Variation in papaya maturity stages and in RipeLocker settings led to valuable insights. The observed discoloration seems to be a sign of very advanced ripening, which was especially seen for fruits that were relatively ripe at harvest and were stored under conditions that enhanced ripening, e.g. temperatures above optimal and possibly ethylene accumulation as well. --For various other aspects, the trials contributed to a better understanding of both technologies to optimize practical application. -- A main problem for papaya quality is anthracnose, the infection with which originates in the field. In practice, the mould pressure was compared to previous years due to new restrictions on fungicide use. Anthracnose infections may decrease in the drier season, but will remain a major concern. For successful commercial sea transport to Europe, a solution to reduce anthracnose seems is paramount.