Thesis (MSc Food Sc )--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Fermented fish products are popular food products mainly consumed and
produced in Southeast Asia. These products are not produced in South Africa,
and those available to the public are imported. The main action during the
production and fermentation of this sort of product, is that of proteolysis, either by
the bacteria or enzymes naturally present in the fish.
The prevalent microbes present in six fermented fish samples from
Bangkok (Thailand) and seven from Khon Kaen (Thailand), were determined, and
using numerical methods, clustered into similarity groups using the calculated
dendrogram .distance (Do) technique to determine their relation to reference
strains. Forty-seven different bacterial strains were isolated, but no yeasts,
moulds or lactic acid bacteria were found. Five Gram-negative, oxidase-positive
species, five different Staphylococcus species and nine different
endospore-forming species of the genus Bacillus, were isolated and identified
using the API systems. The data indicated that members of the genus Bacillus
were the prevalent organisms in all the products examined.
The isolates were also scanned for general enzyme activity using the API
Zym technology, and the production of proteases was investigated using the
Standard Methods Caseinate and the Universal Protease Substrate methods. It
was found that most of the isolated organisms produced protease, which is of
major importance in the production of fermented fish products.
Proteolytic cultures from the fermented fish products, as well as lactic acid
starters, were used in the production of a fermented fresh water fish product.
Production parameters including: glucose, inoculum, moisture content and
incubation time, were evaluated in order to select optimum fermentation
conditions. Fermentation efficiency was determined by measuring the final pH,
titratable acid and the free amino nitrogen content. Optimum efficiency was
obtained with 5% (w/w) added glucose at a moisture level of 150 ml water per 100
g fish.
A factorial design (3 x 3 x 3) was used to indicate viable trends to facilitate
optimisation of the fermentation process. The main effects, two-factor and
three-factor interactions were calculated. Optimum trends obtained were a glucose concentration of 5% (wlw) , inoculum concentration of 1x10⁸ kve.ml ̄ ¹, an
incubation period of 15 days and temperature of 30°C. Three lactic acid starters
(226 - Lactobacillus plantarum, 140 - Lactococcus diacetylactis and 407 -
Pediococcus cerevisiae) were selected as they produced some of the best
fermentation results and are safe to use in food. It was found that a combination
of all three strains (226, 140 and 407) yielded the best results.
By using the above parameters, an acceptable product was produced in terms of
consistency, colour and aroma. Further studies need to be conducted to optimise
the safety of the product as well as the flavour, both chemically and sensorically
optimisation of the product. / AFRIKAANSE OPSOMMING: Gefermenteerde visprodukte is populere voedselprodukte in die lande van
Suidoos-Asie. Die produkte word nie in Suid-Afrika geproduseer nie, maar slegs
ingevoer. Die hoof aksie tydens die fermentasie proses is proteolise deur die
bakteriee en ensieme wat natuurlik teenwoordig is in vis.
Die oorheersende mikrobes teenwoordig in ses gefermenteerde vis
produkte van Bangkok (Thailand) en sewe van Khon Kaen (Thailand), is bepaal.
Numeriese metodes is gevolg om die isolate in groepe te sorteer en te groepeer
deur gebruik te maak van die berekende dendrogram afstand (Do) tegniek om hul
verwantskap ten opsigte van die verwysingsorganisme te bepaal.
Sewe-en-veertig verskillende bakteriee is ge·isoleer, maar geen fungi of
melksuurbakteriee is ge·identifiseer nie. Vyf Gram-negatiewe, oksidase-positiewe
spesies, vyf verskillende Staphylococcus spesies en nege verskillende
endospoorvormende spesies van die genus Bacillus, is geisoleer en
ge·identifiseer deur gebruik te maak van die API CHB sisteme. Die data het
getoon dat lede van die genus Bacillus die oorheersende organismes was.
Die isolate is daarna ondersoek vir algehele ensiemaktiwiteit deur van die
API Zym tegnologie gebruik te maak. Daar is veral klem gelê op die protease
aktiwiteit en dit is gemeet deur van die "Standard Methods Caseinate Agar"
metode asook die "Universal Protease Substrate" metodes gebruik te maak. Daar
is gevind dat die oorgrote meerderheid organismes proteolitiese ensieme
produseer wat belangrik is in die produksie van gefermenteerde visprodukte.
Kulture wat ge·isoleer is uit gefermenteerde visprodukte asook
melkssuurkulture is gebruik vir die produksie van 'n gefermenteerde varswater
visproduk. Produksieparameters insluitende: glukose-, inokulum- en voginhoud
asook inkubasie tyd is ondersoek om die optimum fermentasie kondisies te
bepaal. Optimum effektiwiteit is gevind by 'n 5% glukose konsentrasie en
vogvlakke van 150 ml water per 100 9 vis.
'n Faktoriale ontwerp (3 x 3 x 3) is gebruik om die optimum kondisies te
bepaal. Die hoof effekte asook die twee faktor en drie faktor interaksies is
bereken. Optimum neigings is gevind by 'n glukose konsentrasie van 5%, inokulum konsentrasie van 1x10⁸ kve.ml ̄ ¹, 'n inkubasie tydperk van 15 dae en
temperatuur van 30°C. Drie melksuurbakteriee (226 - Lactobacillus plantarum,
140 - Lactococcus diacetylactis en 407 - Pediococcus cerevisiae) is gekies
aangesien hulle die beste resultate gelewer het en veilig vir gebruik in
voedselprodukte is. Daar is gevind dat die drie melksuurkulture saam in
kombinasie die beste fermentasie resultate opgelewer het.
Deur gebruik te maak van die bogenoemde fermentasie kondisies, kon 'n
aanvaarbare produk, in terme van kleur en geur, gelewer word. Verdere studies
moet gedoen word om die veiligheid asook die geur, chemies asook sensories, te
optimiseer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51649 |
| Date | 12 1900 |
| Creators | Lubbe, Beatrix |
| Contributors | Britz, T. J., Basson, D. S., Stellenbosch University. Faculty of AgriSciences . Dept. of Food Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 164 p. : ill. |
| Rights | Stellenbosch University |
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