Thesis (MSc Food Sc )--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The rapid urbanisation of the African population has led to the establishment of large
low-income communities in and around almost every major town and city in South
Africa. Several factors prevent these people from producing or obtaining their
traditional fermented milk drink, Maas (Amasi), often resulting in the occurrence of
malnutrition in low-income urban African communities.
A product with the potential to satisfy the demand for a fermented milk product
is Kefir. Kefir, a self-carbonated fermented milk, is commonly manufactured by
fermenting unpasteurised or pasteurised milk with re-usable Kefir grains. These Kefir
grains consist of a combination of mainly lactic acid bacteria and yeasts. Neither
Kefir, nor Kefir grains are as yet marketed in South Africa, thus creating an excellent
opportunity to launch these products locally.
It is often difficult for the low-income communities to obtain high quality
unpasteurised or pasteurised milk, resulting in a serious health risk. The inhibitory
activity of Kefir towards certain spoilage and pathogenic microorganisms was,
therefore, studied. Strains of Escherichia coli, Staphylococcus aureus, Bacillus
cereus, Usteria monocytogenes and Clostridium tyrobutyricum were inoculated (10 ³ -
10 ⁴ cfu.ml⁻¹ ) into pasteurised milk together with Kefir grains (18 gram per litre) and
incubated at 25°C. Uninoculated milk samples and milk samples inoculated only with
test organisms served as controls. Growth of all the test organisms were inhibited
substantially (>-99.9%) in Kefir over the 30 h incubation period and substantial
reductions in microbial log cycles were observed for many of the organisms. This
coincided with a steep decrease in pH (6.57 - 4.06) and increase in titratabie acidity
(0.20 - 0.72%).
If Kefir is eventually marketed to low-income urban African consumers, it will
have to compete with Maas and, therefore, comparative sensory testing of Kefir and
Maas was conducted. The differences in the sensory properties of Kefir, 'laboratory'
Maas (representing traditional Maas) and commercial Maas (containing thickener,
colourants and flavourants) were determined by a trained panel. These
characteristics were identified as "yeasty" and "cowy" tastes (p < 0.05),
"effervescence" (p < 0.01), as well as "sourness," "creaminess" and "smoothness" (p
< 0.001). The effect of different incubation temperatures (25°, 30° and 35°C) on the Kefir sensory properties was studied to simulate the effect of the large temperature
variations that would be found in the dwellings of low-income African urbanites. The
"sourness" and "creaminess" of the Kefir was found to increase with increase in
incubation temperature but no strong off-flavours were found to develop. Sensory
preference testing was conducted by consumer panels consisting of panellists of
different ages and population groups to indicate whether the specific panels
significantly prefer Kefir, commercial Maas or laboratory Maas. It was found that
commercial Maas was significantly (p < 0.001) preferred to Kefir by young African
urbanites. Adult Africans, who presumably still have traditional taste preferences,
however, equally (p > 0.05) preferred Kefir and laboratory Maas, identifying this
segment of the African population as the appropriate starting target market for Kefir.
Kefir and laboratory Maas were also tested for preference by a wider panel
consisting of people (aged between 18 and 25) representing the different population
groups in South Africa. Kefir and laboratory Maas were preferred equally (p > 0.05)
by all the groups.
Several arguments supporting Kefir marketing to the low-income urban African
population of South Africa have been identified. These include: Kefir's ease of
preparation; the re-usability of Kefir grains and subsequent affordability; good
packaging, distribution and storage possibilities; Kefir's acceptability by lactoseintolerant
individuals; high nutritional value; the inhibitory activity of Kefir against
potential spoilage and pathogenic organisms and subsequent enhanced safety and
keeping ability; and Kefir's acceptable refreshing taste. / AFRIKAANSE OPSOMMING: Die toenemende verstedeliking van Swart Suid-Afrikaners het gelei tot die vestiging
van groot lae-inkomste gemeenskappe in en om die meeste groot dorpe en stede.
Verskeie faktore verhoed dat hierdie gemeenskappe hul tradisionele gefermenteerde
melk, naamlik Maas (Amasi), self kan maak of koop. Dit lei dikwels tot wanvoeding
onder lae-inkomste stedelike Swart verbruikers.
Kefir het die potensiaal om te voorsien in die vraag na 'n gefermenteerde melk
produk in lae inkomste stedelike Swart gemeenskappe. Kefir is 'n selfgekarboneerde,
gefermenteerde melk wat vervaarding word deur die fermentasie
van ongepasteuriseerde of gepasteuriseerde melk met herbruikbare Kefirkorrels.
Hierdie Kefirkorrels bestaan uit 'n kombinasie van hoofsaaklik melksuurbakterieë en
giste. Kefir en Kefirkorrels word glad nie in Suid-Afrika bemark nie, en bied 'n
fantastiese geleentheid om hierdie produkte plaaslik bekend te stel.
Dit is dikwels moeilik om hoë kwaliteit ongepasteuriseerde of
gepasteuriseerde melk in lae-inkomste gemeenskappe te verkry. Die risiko om
siektes deur die verbruik van hierdie melk op te doen, bestaan dus. Om hierdie rede
is die inhiberende effek van Kefir teenoor spesifieke bederf- en patogeniese
bakterieë bestudeer. Rasse van Escherichia coli, Staphylococcus aureus, Bacillus
cereus, Usteria monocytogenes en Clostridium tyrobutyricum is geïnokuleer (10 ³ -
10 ⁴ cfu.ml⁻¹) in gepasteuriseerde melk tesame met Kefirkorrels (18 gram per liter) en
geïnkubeer by 25°C. Melkmonsters wat slegs geïnokuleer is met die
toetsorganismes het as kontroles gedien. Die groei van al die toetsorganismes is
substansieël geïnhibeer (>-99.9%) in Kefir gedurende die 30 h inkubasieperiode.
Substansiële afnames in logsiklusgetalle is waargeneem vir baie van die organismes.
Dit het gepaard gegaan met 'n skerp afname in pH (6.57 - 4.06) en toename in
titreerbare suurheid (0.20 - 0.72%) vir die Kefirmonsters gedurende die 30 h
inkubasieperiode.
lndien Kefir bemark word aan lae-inkomste stedelike Swart verbruikers sal dit
moet kompeteer met Maas. Vergelykende sensoriese toetse is dus uitgevoer. Die
verskille in die sensoriese eienskappe van Kefir, 'laboratorium' Maas
(verteenwoordigend van tradisionele Maas) en kommersiële Maas (wat verdikker,
kleur- en geurmiddels bevat) is bepaal deur 'n opgeleide paneel en geïdentifiseer as die" "gis-" en "koeismake" (p < 0.05), die "gasserigheid" (p < 0.01) asook die
"suurheid", "romerigheid" en "gladheid" (p < 0.001) van die monsters. Die effek van
verskillende inkubasietemperature (25°, 30° en 35°C) op die sensoriese eienskappe
van Kefir is bestudeer om die effek van die groot temperatuurvariasies wat in laeinkomste
behuising mag voorkom, te simuleer. Daar is bevind dat die "suurheid" en
"romerigheid" van Kefir toeneem met verhoging in inkubasietemperatuur terwyl geen
afsmake ontwikkel nie.
Sensoriese voorkeurtoetse is deur verbruikerspanele van verskillende
ouderdomme en bevolkingsgroepe uitgevoer om te bepaal of die spesifieke panele 'n
beduidende voorkeur toon vir Kefir, laboratorium Maas of kommersiële Maas. Daar
is bevind dat stedelike Swart jongmense kommersiële Maas beduidend (p < 0.001)
bo Kefir verkies. Swart volwassenes met verwagte tradisionele smaakvoorkeure het
egter Kefir en laboratorium Maas ewe veel verkies (p > 0.05). Hierdie segment van
die Swart bevolking is dus die geskikte teikenmark vir die bekendstelling van Kefir.
Voorkeur vir Kefir en laboratorium Maas is ook getoets deur 'n paneel (ouderdom 18
- 25 jaar) wat bestaan uit mense van verskillende bevolkingsgroepe. AI die groepe
het Kefir en Maas ewe veel verkies (p > 0.05).
Verskeie argumente ten gunste van die bemarking van Kefir aan lae-inkomste
stedelike Swart gemeenskappe in Suid-Afrika is geïdentifiseer. Dit behels die
volgende: die gerief van Kefirvervaardiging; die herbruikbaarheid van Kefirkorrels en
gevolglike bekostigbaarheid; goeie verpakkings-, verspreidings- en
opbergingsmoontlikhede; Kefir se aanvaarbaarheid vir laktose-intolerante individue;
Kefir se hoë voedingswaarde; die inhiberende aktiwiteit wat Kefir teenoor potensiële
bederf- en patogeniese organismes het en die gevolglike verhoging in veiligheid en
rakleeftyd van melk; en Kefir se aanvaarbare verfrissende smaak.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51989 |
| Date | 12 1900 |
| Creators | Van Wyk, Juliette |
| Contributors | Britz, T. J., Myburgh, A. 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 | 131 p. : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0033 seconds