Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Agriculture in the Western Cape is not only one of the most important economic sectors
but also provides many job opportunities. Over the last few years the sustainability of this
successful industry has become threatened by the faecal pollution of rivers used to irrigate
produce that will be consumed raw or after minimal processing. This situation not only
poses an enormous risk to the health of the consumer but also to farmers who stand to
lose their export licenses.
The purpose of this study was to determine the microbial types and loads in river
water, irrigation water and on irrigated produce. A baseline study was done on four sites
in two Western Cape rivers. These sites were chosen to allow for the sampling of river
water, irrigation water and irrigated produce so as to determine whether a link between the
use of contaminated irrigation water and the microbial population found on irrigated
produce exists.
The physico-chemical analyses used in the study consisted of: pH, alkalinity, water
temperature, conductivity and chemical oxygen demand. The microbial monitoring
included the aerobic colony counts (ACC) and the enumeration of the total coliforms,
faecal coliforms, staphylococci, enterococci, and aerobic and anaerobic sporeformers
present in the water samples. The presence or absence of the potential pathogens like E.
coli, Listeria and Salmonella, was also determined.
During the baseline study faecal coliform counts as high as 160 000
organisms.100 mL-1 were noted in the Plankenburg River, while counts as high as 460 000
organisms.100 mL-1 were found in the Mosselbank River. Apart from this, high numbers of
staphylococci and intestinal enterococci were often found, while E. coli, Listeria and
Salmonella were present in samples from both of these rivers.
Based on the results of the baseline study on the two rivers it was decided to do a
more intensive study on the microbial load of the river and irrigation water as well as
irrigated produce from the Mosselbank site. Lettuce and cabbages from a commercial
farmer’s fields were chosen as the irrigated produce. During the warmer summer months,
ACC counts in the river samples peaked at 12 8000 000 cfu.mL-1, while faecal coliform
counts of 1 600 000 organisms.100 mL-1 were found. The three potential pathogens (E.
coli, Listeria and Salmonella) were present in all the river samples taken during this period.
While the counts of indicator bacteria in the irrigation water was often lower, faecal
coliform counts as high as 1 600 000 organisms.100 mL-1 and several other potential
pathogens were found on the irrigated lettuce and cabbage. This could indicate a possible “build-up” of contamination on the produce with the repeated application of the tainted
irrigation water.
According to guidelines published by DWAF in 2008, water to be used for irrigation
should not contain more than 4 000 organisms.100 mL-1 faecal coliforms if it is used for the
irrigation of crops that are to be consumed raw or after a minimal processing step, as this
would increase the health risk to the consumer. Guidelines published by the South African
Department of Health are even stricter and state that raw vegetables and fruit should not
contain more than 200 coliform organisms per gram, while E. coli and L. monocytogenes
should be absent in one gram, and Salmonella spp. in 25 grams of the produce,
respectively. From the data obtained during this study it was evident that the two rivers
monitored regularly contained faecal indicators at levels much higher than those proposed
in national and international guidelines for safe irrigation, making them unfit for the
irrigation of MPF’s.
It could be concluded that the rivers investigated during this study contained high
levels of faecal contamination. Since some of the pathogens isolated from the river and
irrigation water and the irrigated produce, it suggests a carry-over of microbial
contamination from the river water to the irrigated produce. This was, however, only done
using the traditional international methods and the presence of specific pathogens should
in future be confirmed by means of molecular techniques. / AFRIKAANSE OPSOMMING: Landbou is nie net die een van die belangrikste ekonomiese sektore in die Wes-Kaap nie,
maar verskaf ook vele werksgeleenthede. Oor die afgelope paar jaar word die
volhoubaarheid van hierdie suksesvolle industrie egter bedreig deur die fekale
kontaminasie van riviere wat gebruik word vir die besproeiing van voedsel wat rou of na ‘n
minimale prosesserings stap ingeneem word. Hierdie situasie hou nie net ‘n groot gevaar
vir die gesondheid van verbruikers in nie, maar ook vir boere wat hul uitvoerlisensies
hierdeur kan verloor.
Die doel van hierdie studie was om die ladings en tipes mikrobes in rivier water,
besproeiingswater en op besproeide produkte vas te stel. ‘n Basiese studie van vier
liggings in twee Wes-Kaapse riviere is gedoen. Hierdie liggings is só gekies dat dit
moontlik was om die rivier water, besproeiingswater en die besproeide produkte te monitor,
en daar sodoende vasgestel kon word of daar ‘n verhouding is tussen die gebruik van
gekontamineerde besproeiingswater en die mikrobe populasie wat op die besproeide
produkte aanwesig was.
Die fisiko-chemiese analises wat gedurende die studie gedoen is, het pH, alkaliniteit,
water temperatuur, geleidingsvermoë en die chemiese suurstof vereiste (COD) ingesluit.
Die mikrobiese analises het die aërobe kolonie tellings (ACC) en die enumerasie van die
totale kolivorme, fekale kolivorme, staphylococci, enterococci en die aërobe en anaërobe
spoorvormers ingesluit. Daar is ook vir die aanwesigheid van potensiële patogene soos E.
coli, Listeria en Salmonella getoets.
Gedurende die basiese studie is fekale kolovorme tellings van so hoog as 160 000
organismes.100mL-1 in die Plankenburg Rivier aangeteken, terwyl tellings van so hoog as
460 000 organismes.100mL-1 in die Mosselbank Rivier gevind is. Hoë tellings stafielokokki
en intestinale enterokokki is gereeld genoteer, terwyl E.coli, Listeria en Salmonella uit die
waters van beide hierdie riviere geïsoleer is.
Gebaseer op hierdie resultate is daar besluit om ‘n meer intensiewe studie van die
rivier, besproeiingswater en die besproeide produkte van die Mosselbank Rivier te doen.
Blaarslaai en kool van ‘n kommersiële boer se lande is vir hierdie doel gekies. Gedurende
die warmer somer maande het die aërobe kolonie tellings in die rivier ‘n piek van 12 800
000 kve.mL-1 bereik, terwyl fekale kolivorme tellings van 1 600 000 organismes.100mL-1
genoteer is. Die drie potensiële patogene (E. coli, Listeria en Salmonella) was aanwesig
in al die monsters wat gedurende hierdie tydperk van die rivierwater geneem is. Alhoewel
die tellings indikator bakterieë in die besproeiingswater meestal laag was, is tellings fekale
kolivorme van so hoog as 1 600 000 kve.100mL-1 en verskeie ander potensiële patogene op die besproeide blaarslaai en kool gevind. Dit kan dui op ‘n moontlike opbou van
kontaminasie op die produkte met die herhaalde besproeiing met gekontamineerde
besproeiingswater.
Volgens die riglyne wat in 2008 deur DWAF gepubliseer is, mag water wat vir die
besproeiing van minimaal geprosesseerdevoedsels gebruik word nie meer as 4 000
organismes.100mL-1 bevat nie, aangesien dit die gesondheid van die gebruiker in gevaar
mag stel. Die riglyne van die Suid-Afrikaanse Departement van Gesondheid is selfs
strenger en beveel aan dat rou vrugte en groente nie meer as 200 kolivorme en geen L.
monocytogenes per gram, en geen Salmonella spp. in 25 g van die produk mag bevat nie.
Vanuit die data wat tydens hierdie studie ingesamel is, is dit duidelik dat die twee riviere
gereeld fekale indikators bevat het teen vlakke baie hoër as wat in die nasionale en
internasionale riglyne aanbeveel word. Hierdie water is dus nie geskik vir die besproeiing
van minimaal geprosesseerde produkte nie.
Die afleiding kan gemaak word dat die riviere wat tydens hierdie studie gemonitor is,
hoë vlakke van fekale kontaminasie bevat het. Aangesien sommige van die patogene
vanuit beide die rivier- en besproeiingswater, en vanaf die besproeide produkte geïsoleer
is, kan dit dui op ‘n moontlike oordrag van mikrobiese kontaminasie vanuit die rivierwater
na die besproeide produkte. Tydens hierdie studie is daar egter net van die tradisionele
internasionale metodes gebruik gemaak. Vir toekomstige navorsing word dit aanbeveel
dat die aanwesigheid van die spesifieke patogene deur die gebruik van molekulêre
metodes bevestig word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4339 |
| Date | 03 1900 |
| Creators | Lotter, Marijke |
| Contributors | Sigge, G. O., Britz, T. J., University of Stellenbosch. Faculty of Agrisciences. Dept. of Food Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Format | 95 p. : ill. |
| Rights | University of Stellenbosch |
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