Effect of irrigation water quality on the microbiological safety of fresh vegetables

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dc.contributor.advisor Buys, E.M. (Elna Maria) en
dc.contributor.postgraduate Ijabadeniyi, Oluwatosin Ademola en
dc.date.accessioned 2013-09-06T22:25:54Z
dc.date.available 2011-06-23 en
dc.date.available 2013-09-06T22:25:54Z
dc.date.created 2011-04-14 en
dc.date.issued 2011-06-23 en
dc.date.submitted 2011-06-15 en
dc.description Thesis (PhD)--University of Pretoria, 2011. en
dc.description.abstract Irrigation water is perhaps the leading pre-harvest source of contamination of fresh vegetables in the world. In this thesis, the effect of source water from the Olifants River and the Wilge River on the bacterial quality of water in the Loskop Canal that they feed and also the subsequent contribution to the bacterial contamination of fresh vegetables was determined for a period of twelve months. Also effect of attachment time on the survival of Listeria monocytogenes and the effect of chlorine on L. monocytogenes attached to vegetables were determined. Finally, a step-wise logistic regression analysis was made to determine whether various predictor variables could be used to predict the occurrence of L. monocytogenes, Salmonella spp and intestinal Enterococcus in irrigation water and vegetables (i.e., cauliflower and broccoli). COD and turbidity were higher in the Olifants River and the Wilge River than in the Loskop Canal that they feed, according to the water guidelines set by the World Health Organisation (WHO) and the Republic of South Africa (RSA). The level of the COD and turbidity were significantly different in terms of the two rivers in comparison with the canal. Levels of faecal coliforms and Escherichia coli were also higher than the WHO standard. Staphyloccocus aureus, intestinal Enterococcus, Salmonella, L. monocytogenes were recovered from the two rivers and the canal. Apart from L. monocytogenes that was not recovered from cauliflower, all bacterial pathogens recovered from the surface water were recovered from the vegetables. This study also indicated that L. monocytogenes could attach to both surface and subsurface structures of both tomatoes and spinach within 30 min, and that even after 72 h, it still remained viable. It also indicated that chlorine treatment is more effective against surface L. monocytogenes compared with subsurface inoculated L. monocytogenes. Finally, the logistic regression analysis of the sampled data showed that COD was statistically reliable to indicate a high probability of L. monocytogenes, turbidity reliable to indicate a high probability of intestinal Enterococcus and faecal coliforms and coliforms reliable to indicate a high probability of Salmonella in irrigation water. Low aerobic colony count (ACC) was statistically significant for the prediction of the three pathogens on vegetables. en
dc.description.availability unrestricted en
dc.description.department Food Science en
dc.identifier.citation Ijabadeniyi, OA 2010, Effect of irrigation water quality on the microbiological safety of fresh vegetables, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/25555 > en
dc.identifier.other D11/397/ag en
dc.identifier.upetdurl http://upetd.up.ac.za/thesis/available/etd-06152011-115126/ en
dc.identifier.uri http://hdl.handle.net/2263/25555
dc.language.iso en
dc.publisher University of Pretoria en_ZA
dc.rights © 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. en
dc.subject Fresh vegetables en
dc.subject Contamination en
dc.subject Irrigation water quality en
dc.subject Bacterial quality of water en
dc.subject Microbiological safety en
dc.subject UCTD en_US
dc.title Effect of irrigation water quality on the microbiological safety of fresh vegetables en
dc.type Thesis en


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