Title page for ETD etd-11112010-212338


Document Type Master's Dissertation
Author De Reuck, Karen
Email karen.dereuck@up.ac.za
URN etd-11112010-212338
Document Title Postharvest quality retention and decay control of South African litchi in modified atmosphere packaging
Degree MSc
Department Microbiology and Plant Pathology
Supervisor
Advisor Name Title
Dr D Sivakumar Co-Supervisor
Prof L Korsten Supervisor
Keywords
  • South African litchi
  • retension and decay control
  • pericarp browning
  • desiccation
  • postharvest decay
Date 2010-09-02
Availability unrestricted
Abstract
Litchi (Litchi chinensis Sonn.) is a commercially valued fruit mainly for its attractively red pericarp and exotic taste. However, the market value of the fruit is affected by pericarp browning, desiccation and postharvest decay. Current control measures include sulphur dioxide (SO2) fumigation, low temperature storage and high relative humidity (RH). Sulphur residues on fruit, moisture loss, altered taste and decay caused by Penicillium spp., limit the use of SO2 fumigation. Technology that can provide a potential alternative method to retain the quality of fruit is modified atmosphere packaging (MAP). In this study (Chapter 3), the effect of active and passive modified atmospheres on quality retention of litchi cultivars ‘Mauritius’ and ‘McLean’s Red’ was investigated. Results indicated that ‘McLean’s Red’ is more suitable for MAP technology than ‘Mauritius’. Lidding film–4 holes significantly reduced activity of oxidation enzymes, polyphenol oxidase (PPO) and peroxidase (POD), and retained higher pericarp colour. Lidding film–10 holes retained soluble solids concentration to titratable acidity ratio (SSC/TA) (~65), thereby preventing the loss of taste and litchi fruit flavour. In order to enhance the MAP technology further (Chapter 4), chitosan coating of fruit was also assessed. Chitosan (1.0 g L-1) combined with MAP effectively prevented decay, browning and pericarp colour loss in ‘McLean’s Red’. Chitosan (1.0 g L-1) integrated with MAP reduced PPO and POD activity, retained membrane integrity, anthocyanin content and pericarp colour. ‘McLean’s Red’ was found to be more suitable for the chitosan (1.0 g L-1) and MAP integrated treatment than ‘Mauritius’ in retaining overall quality. In addition, the effect of 1-methylcyclopropene (1-MCP) in combination with MAP was determined for both cultivars (Chapter 5). In this case 1-MCP (300 nL L-1) was most effective in preventing browning and retaining colour in both cultivars after 14 and 21 days of cold storage. The effect of 1-MCP (300 nL L-1) showed more potential on ‘McLean’s Red’ than ‘Mauritius’. At higher concentrations (500 and 1000 nL L-1), 1-MCP showed negative effects on membrane integrity, pericarp browning, PPO and POD activity in both cultivars. The effect of integrated postharvest treatments i.e. modified atmosphere packaging combined with chitosan and integrated MAP and 1-MCP as well as MAP and chitosan coating on foodborne bacterial pathogens (Escherichia coli O157:H7 and Staphylococcus aureus) spike-inoculated on litchi fruit surfaces, and Penicillium spp. decay were also investigated (Chapter 6). Results showed integrated MAP and chitosan (0.1 g L-1 and 1.0 g L-1) treatments significantly reduced high and low inoculums load of E. coli O157:H7 and S. aureus on litchi fruit after 21 days of cold storage. Integrated MAP and 1000 nL L-1 1-MCP resulted in higher disease severity. Integrated MAP and chitosan (0.1 g L-1 and 1.0 g L-1) treatments showed very good decay control. The total microbial population of the litchi fruit surface was also determined. Integrated MAP and 1.0 g L-1 significantly reduced the total microbial flora after 21 days of cold storage.

© 2010 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

De Reuck, K 2010, Postharvest quality retention and decay control of South African litchi in modified atmosphere packaging, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-11112010-212338/ >

E10/763/ag

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