Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The importance of indigenous fruit wines is not well researched and documented. There
is a need to develop and exploit these valuable food resources through improved
production practices, storage, preservation and utilization technologies. The maruia fruit
is beneficial in many ways, it can be used for making juice, jam, beer or can be eaten as
a whole fruit. The highly nutritive nature of the fruit, its distinctive tropical flavor, its wild
occurrence and demand by the local and international communities for the by-products
of the fruit necessitated efforts to optimize the technological processes for the
production of the possible by-products. This study focuses on the fermentation
technology of the maruia fruit.
The effect of enzymes prior to the fermentation process and post-fermentation
was evaluated. For pre-fermentation processes we focused on the ability of commercial
enzymes to increase juice yield, improve the clarification and filterability. For pre- and
post-fermentation applications, aroma release was considered. The results indicated a
significant increase in the yield depending on the enzyme used. An increase of at least
2% was recorded and a maximum of 12% yield increase was observed. The enzymes
also had a phenomenal effect on the release of bound monoterpenes and hence
enhancing the flavor of the juice. The panel of judges confirmed the results from the gas
chromatography analyses by noting an increase in flavor intensity in the enzyme treated
juice.
The possibility of selecting a yeast strain that performs best during the
fermentation of maruia pulp was also looked at. This study aimed at selecting a strain
that produces wine and distillate with the typical maruia flavor complex. We showed the
effect of the different yeast strains, in the wines and distillates, on the principal volatile
compounds. We then correlated the performance of the different strains as perceived by
the panel to the various volatile compounds. The effect of fermentation temperature on
the performance of the different yeast strains was also considered. Fermenting the
maruia pulp at different temperatures resulted in the production of wines and distillates
with different volatile profiles for the different yeast strains. The wines and distillates
fermented at a low temperature of 15°C were preferred to the wines and distillates
fermented at 30°C. However, not all strains performed well at 15°C, strains like NT116
performed better at 30°C. The different commercial strains produced wines and
distillates with significantly different flavor profiles. These differences in the flavor profiles
were reflected in the sensory evaluation where, depending on the interaction of the
volatile compounds some wines and distillates were preferred to others. The effect of the
different commercial enzymes and yeast strains should thereof be further evaluated and
optimized on a larger scale. This would greatly help prevent variation in quality of the
fermented by-products of the maruia fruit. / AFRIKAANSE OPSOMMING: Die belang van inheemse vrugtewyne is nie goed nagevors en gedokumenteer
nie. Daar is 'n behoefte om hierdie waardevolle voedselbronne te ontwikkel en te benut,
deur verbeterde produksiepraktyke, storing, preservering en benuttingstegnologieë. Die
maroelavrug is veelsydig op baie wyses, deurdat dit gebruik word vir die maak van sap,
konfyt, bier, of as heel vrug geëet kan word. Die vrug is hoog in voedingswaarde, het In
kenmerkende tropiese geur, kom wild voor, en is in aanvraag by plaaslike en
internasionale gemeenskappe vir die by-produkte van die vrug. Dit maak dit essensieel
om die tegnologiese prosesse vir die produksie van hierdie moontlike by-produkte te
optimiseer. Hierdie studie fokus op die fermentasie-tegnologie van die maroelavrug.
Die effek van ensieme voor en na die fermentasie-proses is geëvalueer. Vir
prosesse wat voor fermentasie plaasvind, het ons gefokus op die vermoë van
kommersiële ensieme om sapopbrengs te verhoog, asook om verheldering en filtrering
te verbeter. Vir beide voor- en na-fermentasie toepassings is die vrystelling van aroma
gemonitor. Die resultate dui op 'n betekenisvolle verhoging in die sapopbrengs,
afhangende van die ensiem wat gebruik is. 'n Verhoging van ten minste 2% is
opgeteken, en 'n maksimum van 12% opbrengsverhoging is waargeneem. Die ensieme
het ook 'n geweldige effek op die vrystelling van gebonde monoterpene gehad, en dus
die verhoging in die geur van die sap. Die proepaneel het die resultate bevestig van die
gaschromatografie-analises, deur 'n verhoging in die geurintensiteit in die ensiembehandelde
sap te bemerk.
Daar is ook gekyk na die moontlikheid om 'n gisras te selekteer wat die beste
presteer tydens die fermentasie van maroela-pulp. Hierdie studie het die doelstelling
gehad om In gisras te selekteer wat wyn en distillaat produseer met In tipiese maroelageurkompleks.
Ons het die effek van verskillende gisrasse aangedui in die wyne en
distillate, op grond van van vlugtige komponente. Ons het dan die prestasie van die
verskillende rasse, soos waargeneem deur die paneel, gekorrelleer met die verskeie
vlugtige komponente. Die effek van fermentasie-temperatuur op die werkverrigting van
die verskillende gisrasse is ook in ag geneem. Fermentasie van die maroela-pulp by
verskillende temperature het gelei tot die produksie van wyne en distillate met
verskillende vlugtige profiele vir die verskillende gisrasse. Die wyne en distillate wat by
In laer temperatuur van 15°C gefermenteer is, is verkies bo die wyne en distillate wat by
30°C gefermenteer is. Alle rasse het egter nie baie goed presteer by 15°C nie, soos
byvoorbeeld NT116 wat beter presteer het by 30°C. Die verskillende kommersiële rasse
het wyne en distillate geproduseer met betekenisvol verskillende geurprofiele. Hierdie
verskille in geurprofiele is gereflekteer in die sensoriese evaluering waar, afhangende
van die interaksie van die vlugtige komponente, sommige wyne en distillate bo ander
verkies is. Die effek van die verskillende kommersiële ensieme en gisrasse moet verkieslik verder op groter skaal geëvalueer en geoptimiseer word. Dit sal veral help om
variasie in kwaliteit van die gefermenteerde by-produkte van die maroelavrug te
voorkom.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52390 |
| Date | 03 1900 |
| Creators | Fundira, Margaret |
| Contributors | Van Rensburg, P., Pretorius, I. S., Blom, M., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 90 p. : ill. |
| Rights | Stellenbosch University |
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