Dissertation 'consists of a selection of 71 publications produced over the period 1975-2001, which were drawn from the more complete list of 198 original research papers, review articles and books published over the same period' -- declaration. / Thesis (PhD Food Sc )--Stellenbosch University, 2001. / ENGLISH ABSTRACT: One of the curious facts about the food industry is that many of the processes
in use today were being practised, in some form or other, by the Roman legions as
they marched across Europe and beyond. Certainly they were familiar with the basic
techniques of fermentation, and much current research into fermented foods is
concerned with understanding the fundamental nature of these traditional processes,
and how the individual stages in a particular fermentation can be better controlled.
Recent developments in the dairy industry have tended to reflect this pattern
and, over the years, my research group has done much to support the expanding
markets for yoghurt and similar fermented milks. Our evaluation of the
polysaccharide-producing characteristics of starter cultures, for example, encouraged
yoghurt manufacturers to match physical properties to the perceived demands of
consumers, and most culture suppliers followed this lead by labelling their products
with precise designations as to their potential for imparting viscosity to a retail item.
Similarly, my group was the first to record the unique physical properties of
the concentrated yoghurt, labneh, C 230 g 1-1 total solids) that had been made for
hundreds of years by draining whey from natural yoghurt hanging in a cloth or
animal-skin bag. This detailed analysis of the product facilitated the application of
ultra-filtration to natural yoghurt to generate a product with a quality that matched
traditionallabneh and, today, factories in the Middle East, Greece and elsewhere are
using modern membrane-filtration plants to satisfy a growing market demand.
Our success in publicising the attractive properties of concentrated yoghurt encouraged me to devote time to yet another 'historical' concept, namely the apparent
'health benefits' derived by small communities in Eastern Europe from consuming
kefir and koumiss. In the West, the flavour and texture of these latter products have
never been accepted, but employing similar cultures to produce 'health-promoting'
bio-yoghurts opened an entirely new avenue for research. As clinical evidence in
support of the prophylactic and therapeutic properties of Lactobacillus acidophilus and
a species of Bifidobacterium became available, so it became apparent that the
therapeutic advantage that accompanies the regular ingestion of 'bio-yoghurts'
depended on the survival of these microfloras over the stipulated shelf-lives of the
retail vehicles. However, no laboratory medium was immediately available for the
simultaneous enumeration of Lb. acidophilus and Bifidobacterium along with the
yoghurt cultures, i.e. Streptococcus thermophilus and Lactobacillus delbrueckii sub-sp.
bulgaricus. Designing such a medium became a priority for one of my students, and,
even today, the procedures that he derived are being used by consumer groups that
monitor the performance of the major dairy companies in England.
If the improved quality of yoghurts and 'bio-yoghurts' had a major impact on
consumer perceptions of fermented milks, the food sector in England gradually
became aware of an even more dramatic change in consumer attitudes. Thus twenty
years ago, cheese meant 'Cheddar' but, following a 'deluge' of television publicity
about the attractions of 'exotic' catering, housewives began demanding mozzarella and
mascarpone for lavish desserts, Feta to sprinkle over salads and Halloumi to grill or
fry. In turn, exporting countries like Italy, Greece and Cyprus came under intense
pressure to increase supplies of top quality products. Local manufacturers soon realised, however, that there was little information available concerning the scientific
basis to the procedures employed to make some of these traditional cheeses, and my
research group was selected by Funding Agencies in Greece and Cyprus to act as a
focus for a series of studies of Feta and Halloumi cheese.
The need to eliminate pathogens from the storage brines of Feta cheese without
killing the yeasts and bacteria associated with maturation became an important
consideration for exporters, and one of my students exploited a novel procedure
employing furocoumarins and long-wave ultra-violet light to achieve the desired
selective inactivation. At present, the economics of commercial application are
somewhat dubious but, as soon as cheap, synthetic, non-toxic furocoumarins become
more readily available, the system may well merit re-evaluation. We did confirm,
however, that the metabolic activities of the yeasts and bacteria typically isolated from
storage brines are essential for flavour development in Feta cheese, and that similar
microfloras are instrumental in the development of the important charactistics of
traditional Halloumi cheese. In particular, a new species of lactic acid bacterium,
Lactobacillus cypricasei, was isolated from samples of the traditional ovine cheese,
but whether or not the species has a unique role(s) in the maturation process remains
an open question.
Clearly there is still much to learn but, if the activities of my reseach group
have added just a little to the scientific background essential for future studies of
cheese and fermented milks, then their completion will have been worthwhile. / AFRIKAANSE OPSOMMING: Een van die merkwaardigste feite omtrent die voedselindustrie is dat baie van die
prosesse wat vandag gebruik word, in een of ander vorm deur die Romeinse magte
gebruik is toe hulle deur Europa marsjeer het. Basiese fermentasie tegnieke was aan hulle
bekend, en heelwat huidige navorsing oor gefermenteerde voedsel is gemik daarop om die
fundamentele natuur van hierdie tradisionele prosesse te verstaan en hoe die individuele
stappe in 'n spesifieke fermentasie beter beheer kan word.
Onlangse ontwikkelinge in die suiwelindustrie reflekteer hierdie patroon, en my
navorsingsgroep het oor die jare heelwat gedoen om die groeiende markte vir joghurt en
soortgelyke gefermenteerde melk te ondersteun. Ons evaluasie van die polisakkariedproduserende
eienskappe van suursels het byvoorbeeld joghurtvervaardigers gehelp om
fisieke eienskappe daar te stel wat verbruikers tevrede sal stel. Meeste verskaffers van
kulture het hierdie voorbeeld gevolg deur hul produkte so te etiketteer dat duidelik gewys
word watter potensiaal dit het om viskositeit aan die finale produk te verleen.
Verder was my groep die eerste om die unieke fisiese eienskappe van die gekonsentreerde
joghurt, labneh (230 g 1-1 totale vastestowwe) te bepaal, wat vir honderde jare gemaak is
deur die wei van natuurlike joghurt te dreineer deur dit in "n materiaal- of diervelsak te
hang. "n Gedetailleerde analise van hierdie tradisionele produk het bygedra tot die
gebruik van ultrafiltrasie op natuurlike joghurt om "n produk te gee met dieselfde
kwaliteit as tradisionele labneh. Vandag gebruik fabrieke in die Midde Ooste, Griekeland
en elders moderne membraan-filtrasie aanlegte om in die groeiende vraag na die produk te voorsien.
Ons sukses met die bekendmaking van die aantreklike eienskappe van
gekonsentreerde joghurt het my aangespoor om tyd te spandeer aan nog 'n sogenaamde
"historiese" konsep, naamlik die skynbare gesondheidsvoordele van klein gemeenskappe
in Oos-Europa wat kefir en koumiss verbruik. In die Weste is die smaak en tekstuur van
hierdie produkte nooit werklik aanvaar nie, maar om soortgelyke kulture te gebruik om
"gesondheidsbevorderende" bio-joghurt te produseer, het 'n hele nuwe navorsingsveld
daargestel. Soos kliniese bewyse van die terapeutiese en voorkomende voordele van
Lactobacillus acidophilus en 'n spesie van Bifidobacterium bekend gemaak is, het dit
duidelik geword dat die terapeutiese voordele wat saamgaan met die gereelde inname van
"bio-joghurts", afhang van die oorlewing van hierdie mikroflora oor die gestipuleerde
rakleeftyd van die kommersiële produkte. Geen laboratorium medium was egter
onmiddellik beskikbaar vir die gelyktydige telling van Lb. actdophilus en Bifldobacterium
tesame met die joghurt kulture Streptococcus thermophilus en Lb. delbrueckii sub-sp.
bulgaricus. Die ontwikkeling van so 'n medium het een van my studente se prioriteit
geword, en selfs vandag word die prosedures wat deur hom ontwikkel is, gebruik deur
verbruikersgroepe wat die optrede van groot suiwelmaatskappye in Engeland monitor.
lndien die verbeterde kwaliteit van joghurts en bio-joghurts 'n groot impak gehad het op
verbruikers se persepsie van gefermenteerde melk oor Wes-Europa heen, het die
voedselsektor in Engeland bewus geraak van selfs 'n meer dramatiese verandering in
verbruikers se houding. Twintig jaar terug het kaas "Cheddar" beteken, maar na 'n
stortvloed televisie advertensies oor die aanloklikheid van eksotiese geregte, het daar by
huisvroue 'n vraag ontstaan na Mozzarella en Mascarpone vir nageregte, Feta oor slaai en Halloumi om te bak of te braai. Italië, Griekeland en Siprus wat hierdie produkte
uitgevoer het, het onder kwaai druk gekom om groter hoeveelhede, top-kwaliteit produkte
te lewer. Plaaslike vervaardigers het gou agtergekom dat min inligting beskikbaar was
oor die wetenskaplike basis van die prosedures wat gebruik word om hierdie tradisionele
kase te maak en my navorsingsgroep is deur befondsingsagentskappe in Griekeland en
Siprus genader om studies te doen oor sekere aspekte van die vervaardiging van Feta en
Halloumi kaas.
Dit het vir beide in- en uitvoerders belangrik geword om die patogene te elimineer
uit die soutoplossing waarin Fetakaas gestoor word, sonder om die giste en bakterieë wat
rypwording aanhelp, te dood. Een van my studente het 'n innoverende prosedure
ontwikkel wat furocoumarins en lang-golf-ultra-violet lig gebruik om selektiewe
inaktivering te kry. Op die oomblik is daar effense onsekerheid oor die ekonomiese
implikasies van die kommersiële toepassing, maar sodra goedkoop, sintetiese, nie-toksiese
furocoumarins geredelik beskikbaar word, moet die sisteem weer geëvalueer word. Ons
het egter bevestig dat die metaboliese aktiwiteite van die giste en bakterieë in die
stooroplossing noodsaaklik is vir geurontwikkeling in Feta kaas en dat soortgelyke
mikrofloras instrumenteel is in die ontwikkeling van die belangrike karaktereienskappe
van tradisionele Halloumi kaas. 'n Unieke melksuurbakterium, Lactobacillus cypricasei,
is uit monsters tradisionele skaap Halloumi geïsoleer, maar of hierdie spesie 'n unieke
rol speel in die verouderingsproses is nog 'n ope vraag.
Duidelik is daar nog baie om te leer, maar indien my navorsingsgroep se
aktiwiteite slegs 'n klein bydrae gemaak het tot die wetenskaplike agtergrond wat
essensieel is vir toekomstige navorsing, was die voltooiing daarvan die moeite werd.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52465 |
| Date | 12 1900 |
| Creators | Robinson, R. K. (Richard Kenneth) |
| Contributors | Britz, T. J., 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 | 1 v. (various pagings) : ill. |
| Rights | Stellenbosch University |
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