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Development of bacteriophage inhibitory bulk starter medium for the cultivation of thermophilic lactic acid bacteriaRajagopal, S. N. 01 August 1986 (has links)
Internally-pH-controlled, phosphate containing and non-phosphate
containing Italian bulk starter media were compared to
reconstituted nonfat dry milk and commercial bulk starter media
for their ability to support the growth and activities of
commercially frozen thermophilic lactic acid cultures. Cultures
grown in internally-pH-controlled media demonstrated superior
acid-production capability. The cheese made from cultures grown
in internally-pH-controlled media was comparable to that made
from the culture grown in commercial medium. However, the
internally-pH-controlled media were not bacteriophage inhibitory,
nor were the reconstituted nonfat dry milk or two of the three
commercial bulk starter media. Hence, cheese whey and nonfat milk
based, low solids, bacteriophage inhibitory bulk starter media
were formulated for the cultivation of mixed cultures of
Streptococcus thermophilus and Lactobacillus bulgaricus. The new
media supported the growth of lactobacilli better than the
commercial media. Even at low solids levels, the buffering
capacities of the new media were comparable to commercial media.
Late addition of magnesium hydroxide as a neutralizing agent to
commercial as well as experimental bulk starter media resulted in
increased growth and improved activities of rod-coccus cultures.
The cultures also retained their activities longer under
refrigerated storage. Late addition of magnesium hydroxide did
not encourage the proliferation of bacteriophages in the growth
media. / Graduation date: 1987
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Development of an internal pH-controlled, phage inhibitory bulk starter medium for the propagation of thermophilic lactic acid bacteria used in the production of mozzarella cheeseWhitehead, William E. 27 May 1993 (has links)
Graduation date: 1994
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Effect of starter cultures on Lactobacillus acidophilus survival and gene expression in yogurt a thesis /Ng, Elizabeth Wei-Yin. Tong, Phillip S. January 1900 (has links)
Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on June 18, 2009. Major professor: Phillip S. Tong, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Agriculture, with Specialization in Dairy Products Technology." "May 2009." Includes bibliographical references (p. 79-93). Also available on microfiche.
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Development of a starter culture for the production of Gari, a traditional African fermented foodEdward, Vinodh Aroon January 2010 (has links)
Submitted in fulfilment of the requirements for the Degree of Doctor of Technology: Biotechnology, Durban University of Technology, 2010. / Cassava, (Manihot esculenta Crantz), is used for the production of a variety of West African foods and ranks fourth in the list of major crops in developing countries after rice, wheat and maize. Gari is one of the most popular foods produced from cassava. Cassava may contain high levels of linamarin, a cyanogenic glucoside, which in its natural state is toxic to man. Therefore, some processing methods that can enhance the detoxification of cassava and lead to the improvement of the quality and hygienic safety of the food are vitally important for less toxic products to be obtained. Quality, safety and acceptability of traditional fermented foods may be improved through the use of starter cultures. There has been a trend recently to isolate wild-type strains from traditional products for use as starter cultures in food fermentation. A total of 74 bacterial strains and 21 yeast strains were isolated from a cassava mash fermentation process in a rural village in Benin, West Africa. These strains were assessed, together with 26 strains isolated at the CSIR from cassava samples sent from Benin previously, for phenotypic and technological properties. Twenty four presumptive lactic acid bacteria (LAB) were selected for further phenotypic, genotypic and technological characterization during a research visit to the BFE (now Max Rubner Institute of Nutrition and Food). After assessment, the strains VE 20, VE 36, VE 65b, VE 77 and VE 82 were chosen for further study as starter cultures. These L. plantarum strains were chosen on the basis of predominance and possession of suitable technological properties. The investigation of this study was complemented by further, similar studies on further Gari isolates in Germany by the BFE. That study was done independently from this study, but both studies served to select potential starter cultures for cassava fermentation for the production of Gari, as this was the common goal of the project. Thus, a wider final selection of potential starter cultures was decided on at the project level and this selection was further tested in fermentation experiments. A total of 17 strains were grown in optimized media in 2 L fermenters. These strains were freeze-dried and thereafter tested in lab-scale cassava mash fermentation trials. xiii
The strains performed well in the small scale bucket fermentations. There was a rapid acidification evidenced by the increase in titratable acidity, ranging from 1.1 to 1.3 % at 24 hours, and 1.3 to 1.6 % at 48 hours. The effect of the starter was obvious in that it lowered the pH much faster and to lower levels than the control. It appeared that both the processing and starter culture addition played a role in the removal of cyanide during processing of the cassava into Gari. This was evident from the lower cyanide values obtained for fermentations that included starter cultures. The study also showed that especially the L. plantarum group strains could be produced as starter cultures at lower costs than compared to L. fermentum, W. paramesenteroides or L. mesenteroides strains. Overall the results of this study were crucial for the project in showing that a starter culture which is easy and economical to produce and which has the desired attributes is a feasible possibility for application in the field.
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The evaluation of malolactic fermentation starter cultures under South African winemaking conditionsVan der Merwe, Hanneli 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2007. / ENGLISH ABSTRACT: With ever increasing pressure on wine producers to lower the financial costs involved in
winemaking to be able to compete in the market, all while maintaining a high level of wine
quality, the focus on maintaining control over all aspects of the winemaking process are
greatly emphasized.
Malolactic fermentation (MLF) is one of the important processes in red wine production.
The advantages of this process, when performed successfully, is widely known and
accepted. One way to gain control over MLF is the use of MLF starter cultures. Starter
cultures usually consist of Oenococcus oeni that has been isolated from grapes or wines
and is in most cases available in a freeze-dried form ready for direct inoculation into the
wine when MLF is desired. Starter cultures are induced into wine and usually ensure the
immediate onset as well as a fast and clean execution of the process. Starter cultures
used in South Africa are in most cases isolated from cooler viticultural regions in the
Northern hemisphere. The constitution of wines from cooler viticultural regions, differ from
those in South Africa, which has a warm climate. The most important difference is the acid
content of the wines which is lower in South African must/wines and results into a higher
pH. The three most important changes that develop in wine during MLF are a decrease in
acidity due to the conversion of malic acid to the less harsh lactic acid, enhanced flavour
and aroma of wine and an increase in the microbiological stability of wine. The decrease
in acidity is very important for wines produced for grapes grown in cool viticulture regions.
In South Africa though, the climate is warm and higher pH’s are present in the musts and
wines and the de-acidification due to MLF is not the main aim but rather the
microbiological stabilisation. One of the compounds that could be produced by lactic acid
bacteria (LAB) is biogenic amines (BA’s). These compounds can be hazardous to human
health. This thesis focussed on the performance of MLF starter cultures in high pH South
African red wines.
The first objective of the study was to stretch MLF starter cultures in high pH red wines
of South Africa. Stretching means to use less than the prescribed dosage or the re-use of
starter cultures. The difference in MLF rate, the influence of the natural occurring LAB and
the levels of biogenic amines formed during MLF were determined for the different
stretching treatments. The results showed that different rates in malic acid degradation
were experienced between the treatments, but in all cases MLF fermentation was completed. Biogenic amines were formed at various levels and the influence of the natural
occurring LAB also played a role.
The second objective of the study was the evaluation of the effect of a wine isolated
LAB (Lactobacillus) and an acetic acid bacteria (AAB), inoculated with a MLF starter
culture had on MLF at different wine pH’s. It was found that especially in the case where
the Lactobacillus was inoculated in combination with the MLF starter culture a possible
stimulatory effect was experienced with regards to malic acid degradation rate. Biogenic
amine concentration was measured at the end of MLF and it was found that no histamine
and tyramine were formed in any of the treatments, while the putrescine and cadaverine
levels were found to be at approximately similar levels for the different treatments.
The third objective was to evaluate the possible influence of commercial tannin
additions and a pectolytic enzyme on rate of MLF and phenolic composition of high pH red
wine. The commercial tannins had possible inhibitory as well as stimulatory effects on the
rate of malic acid degradation especially during the initial stages of MLF, with the highest
dosage having the significant effect. The BA results showed difference in the levels
produced due to tannin additions as well as strain differences could exist. The phenolic
content showed a decrease in colour density, total red pigments, total phenolics and
anthocyanins between AF and MLF.
The fourth objective was to evaluate inoculation time of MLF starter cultures. The
results showed that the fastest AF/MLF time was with simultaneous inoculation of the
yeast and MLF starter cultures. It was also for this treatment where no histamine or
tyramine was detected at the end of MLF compared to the other inoculation strategies
(before the end of AF and after AF).
This study generated a large amount of novel data which made a valuable contribution
with regards to MLF in high pH red wines of South Africa. / AFRIKAANSE OPSOMMING: Die druk om wyne van hoë gehalte teen lae insetkoste te lewer om deel te bly van ’n
kompeterende mark, plaas die fokus weer sterk op onder andere die beheer van alle
aspekte van die wynmaak proses.
Appelmelksuurgisting (AMG) is een van die belangrikste prosesse van rooiwyn produksie.
Die voordele van AMG, in die geval van die suksesvolle implementering daarvan is
vandag bekend en word geredelik aanvaar. Een van die metodes om beheer te verkry oor
the proses van AMG is deur die gebruik van AMG aanvangskulture. AMG
aanvangskulture bestaan uit Oenococcus oeni wat geïsoleer word vanaf druiwe of
mos/wyn en is in meeste gevalle beskikbaar in ’n gevries-droogte vorm wat direk in wyn
geïnokuleer kan word. Aanvangskulture word in wyn geïnduseer om die onverpose
aanvang van AMG te bewerkstellig asook om ’n vinnige en skoon deurvoering van die
proses te verseker. Die aanvangskulture wat in Suid-Afrika vir hierdie doeleinde gebruik
word is in meeste van die gevalle verkry uit koue wingerdbou gebiede in die Noordelike
Halfrond. Die samestelling van druiwe van koue wingerdbou gebiede en dié van
Suid-Afrikaanse warm wingerdbou gebiede verskil. Die belangrikste verskil word ervaar in
die suur inhoud, wat laer is in Suid-Afrikaanse druiwe en dus lei tot ‘n hoër pH inhoud. Die
drie mees belangrikste veranderinge wat gedurende AMG in wyn plaasvind is die
vermindering van die suur, as gevolg van die omskakeling van appelsuur na melksuur, die
verbetering van die aroma en geur van wyn en die verbeterde mikrobiologiese stabiliteit.
Die afname in suur is veral belangrik in wyne van koue wingerbou gebiede omdat die
suur-inhoud daarvan soveel hoër is. In Suid-Afrika kan hierdie verlaging in suur egter lei
tot ’n verdere verhoging in die pH wat plat wyne en uiteindelik ’n verlaging in die kwaliteit
van wyn tot gevolg kan hê. Biogene amiene (BA) is verbinding wat melksuurbakterieë
(MSB) kan vorm gedurende AMG en kan ernstige implikasies hê vir die mens se
gesondheid.
Hierdie tesis fokus op die evaluering van AMG aanvangskulture in hoë pH rooi wyne
van Suid-Afrika.
Die eerste doelwit gedurende hierdie studie was om AMG kulture te rek en die invloed
daarvan in hoë pH rooiwyn te evalueer ten opsigte van the tempo van AMG, die rol van die
natuurlike MSB te bestudeer asook om die vlak van biogene amiene te bepaal vir die
verskillende behandelings. Die resultate het aan die lig gebring dat die rek van kulture verskille in die tempo van appelsuur afbraak tot gevolg het, maar dat AMG in alle gevalle
wel suksesvol deurgevoer kon word. Die BA’e wat gevorm is, was teenwoordig in
verskillende hoeveelhede.
Die tweede doelwit was om die effekt van die gesamentlike inokulasie van ’n wyn
geisoleerde MSB (Lactobacillus) asook ’n asynsuurbakterie (ASB) met ’n kommersiële
AMG aanvangskultuur op AMG te evalueer. Hierdie eksperiment is uitgevoer by
verskillende pH’s. Daar is gevind dat veral in die kombinasie inokulasie met die
Lactobacillus, die tempo van appelsuur afbraak moontlik gestimuleer was. Geen
histamien of tiramien is tydens AMG gevorm in hierdie eksperiment gevorm nie, terwyl
putresien en kadaverien teenwoordig was teen ongeveer gelyke vlakke vir die
behandelings.
Die derde doelwit was om die moontlike invloed van kommersiële tannien toevoegings
en die toevoeging van ’n pektolitiese ensiem te evalueer ten opsigte van AMG tempo die
fenoliese samestelling van rooiwyn te bestudeer. Verskillende kommersiële tanniene het
’n moontlike sowel as inhiberende uitwerking gehad, veral gedurende die aanvanklike
stadium AMG. Die grootste verskille is waargeneem in die behandelings waar die hoogste
dosisse tannien bygevoeg is. Die BA resultate toon dat verkillende vlakke geproduseer
was en dat hierdie verskille onstaan het as gevolg van verskille in tannien dosisse sowel
as aanvangskulture. Die fenoliese inhoud het ’n afname in kleur intensiteit, totale rooi
pigmente, totale fenole en antosianiene getoon vir die periode vanaf AF tot die einde van
AMG.
Die vierde doelwit was om the tyd van inokulasie van AMG aanvangskulture te
bestudeer. Die resultate het getoon dat die vinningste tydperk van AF/AMG was
ondervind in die geval waar die gis aanvangskulture gelyktydig met die AMG
aanvangskulture geïnokuleer was. Geen histamine en tyramine het ook in hierdie
behandeling ontwikkel nie, terwyl daar wel vlakke teenwoordig was in die ander
behandelings (inokulasie net voor die einde van AF en na afloop van AF).
Tydens hierdie studie is ’n groot hoeveelheid nuwe data geskep wat ‘n groot bydrae
ten opsigte van AMG in hoë pH rooi wyne vanaf Suid-Afrika kan lewer.
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Production of kepi grains using pure cultures as startersCronje, Marise Christine 03 1900 (has links)
Thesis (MSc Food Sc )--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Kepi is a refreshing, fermented dairy beverage that differs from other fermented milk products
in that it is produced with a mixed microbial community which is confined to discrete grains.
These grains can be recovered as a solid matrix at the end of the fermentation and then be reutilised
as a starter to ferment the next batch of milk. The grain microbial community
consists of a symbiotic association of yeasts and lactic acid bacteria, but the overall
composition of the grains has not been completely elucidated. The microbes in the grains are
embedded in a protein-polysaccharide Kefiran matrix, which appears essential for grain
formation. The mechanism of grain formation is still not fully understood and it thus remains
undecided which organism is really responsible for the production of this proteinpolysaccharide
matrix. The aim of this study was to isolate, characterise and identify the
microbes present in Kefiran from mass cultured South African grains and then to evaluate
grain formation with these purified cultures isolated from Kefiran strings using a mass
cultivation process.
Sixteen strains of lactic acid bacteria and one yeast strain were isolated from Kefiran
strings produced during the mass cultivation of South African Kepi grains. API technology,
numerical clustering and DNA sequence comparisons were used to identify the purified
isolates. The isolates were grouped into seven clusters by numerical clustering and clustering
distance from selected reference and marker strains. The heterofermentative lactobacilli were
identified as Lactobacillus parakefiri and Lb. kefiri and the homofermentative strains as Lb.
delbrueckii ssp. bulgaricus, Lb. gallina rum, Lb. acidophilus and Lb. bavaricus. One isolate
was found to be a member of the genus Lactobacillus, but was not positively identified to
species level.
Cultures isolated from Kefiran were evaluated for ability to grain formation by
adding 1 x 109 cfu.ml:' bacteria and 1 x 108 cfu.ml' yeast to double pasteurised, full cream
milk during the mass cultivation process. It was found that the control and all the cultures in
double pasteurised milk showed grain accumulation indicating that other microbes were
present in pasteurised and double pasteurised milk which had an influence on the grain
forming ability. The cultures isolated from pasteurised and double pasteurised milk included
members of the species Pediococcus, Acinetobacter, Lactococcus laetis ssp. lactis, Candida
lipolytica, C. guilliermondii, Chryseobacterium meningosepticum, Pseudomonas putida and
four isolates of the Bacillus cereus group. It was found that these rod-shaped "milk isolates"
resulted in grain accumulation when inoculated into UHT milk and it was concluded that the
"milk isolates" did contribute to grain formation. These isolates were then combined with the Kefiran cultures and this resulted in grains very similar to the traditional Kepi grains. These
grains were made from Lb. gallinarum in double pasteurised milk as well with a combination
of Lb. gallinarum, Lb. acidophilus, Lb. kefiri, Lb. delbrueckii ssp. bulgaricus, Candida
lambica and Pseudomonas putida in URT milk. The grains were firm, elastic and did not
dissolve in water but kept their structure and were retained when sieved. An acceptable Kepi
beverage was produced from these grains.
From these typically traditional grain characteristics it was concluded that, even
though the microbial compositions were probably not the same, the general appearance was
similar to traditional grains and that it is thus possible to produce grains from pure single
strain Kefiran cultures and "milk isolates". Furthermore, it was possible to produce a Kepilike
beverage from these grains, which included similar characteristics as the traditional Kepi
beverage. / AFRIKAANSE OPSOMMING: Kepi is "n verfrissende, gefermenteerde suiweldrankie wat van ander gefermenteerde produkte
verskil in die opsig dat dit vervaardig word deur Kepi korrels in melk te inkubeer. Die Kepi
korrels kan aan die einde van die fermentasie herwin word en weer gebruik word om die
volgende lot melk te fermenteer. Die korrels bestaan uit "n simbiotiese samestelling van giste
en melksuurbakterieë, maar die presiese samestelling van die korrels is steeds onbekend. Die
mikro-organismes is vasgevang in "n proteïen-polisakkaried Kefiran matriks en die Kefiran
word as essensieel beskou vir korrelvorming. Die meganisme van korrelvorming bly steeds
onbekend en daar is nog nie tot "n gevolgtrekking gekom oor watter organisme die Kefiran
produseerder is nie. Die doel van die studie was om die mikro-organismes in Kefiran te
isoleer en te identifiseer deur Suid-Afrikaanse Kepi korrels te massa kweek. Hierdie mikroorganismes
was dan verder geëvalueer ten opsigte van korrel vorming.
Sestien melksuurbakterieë isolate en een gis isolaat is geïsoleer vanuit die Kefiran.
API tegnologie, numeriese groepering en DNA volgorde vergelykings was gebruik om die
isolate te identifiseer. Die isolate is in sewe groepe verdeel volgens numeriese groepering.
Die afstand van verwysings en merker organismes is ook in ag geneem. Die
heterofermentatiewe organismes is geïdentifiseer as Lactobacillus parakefiri en Lb. kefiri en
die heterofermentatiewe organismes as Lb. delbrueckii ssp. bulgaricus, Lb. gallina rum, Lb.
acidophilus en Lb. bavaricus. Een isolaat kon nie geïdentifiseer word tot op spesie vlak nie,
maar is verwant aan die genus Lactobacillus.
Hierdie geïsoleerde Kefiran kulture is geëvalueer ten op sigte van korrelvorming,
deur 1 x 109 kve.ml' van die bakterieë en 1 x 108 kve.ml' van die gis by dubbel
gepasteuriseerde volroom melk te voeg tydens die massakwekings proses. Die kontrole wat
geen bygevoegde kulture bevat nie, sowel as die wat wel bygevoegde kulture bevat, het korrel
vorming getoon. Laasgenoemde toon dat daar organismes teenwoordig is in gepasteuriseerde
en dubbel gepasteuriseerde melk wat "n rol kan speel tydens korrelvorming. Die kulture wat
geïsoleer is vanuit gepasteuriseerde en dubbel gepasteuriseerde melk, sluit in: Pediococcus,
Acinetobacter, Lactococcus laetis ssp. lactis, Candida lipolytica, C. guilliennondii,
Chryseobacterium menigosepticum, Pseudomonas putida en vier isolate van die Bacillus
cereus groep. Hierdie organismes wat uit melk geïsoleer is, het korrelvorming getoon in UHT
melk en die gevolgtrekking kan gemaak word dat die "melk organismes" wel "n rol speel
tydens korrel vorming. Hierdie "melk isolate" in kombinasie met die Kefiran kulture het
korrels tot gevolg gehad wat baie dieselfde was as tradisionele Kepi korrels. Laasgenoemde
korrels is gemaak deur Lb. gallina rum in dubbel gepasteuriseerde melk, sowel as deur "n kombinasie van Lb. gallina rum, Lb. acidophilus, Lb. kefiri, Lb. delbrueckii ssp. bulgaricus,
Candida lambica en Pseudomonas putida in UHT melk. Die korrels was stewig, elasties, het
nie opgelos in water nie en het hulle struktuur behou wanneer gesif.
Wanneer hierdie tipiese tradisionele korrels se eienskappe in ag geneem word, kan
die gevolgtrekking gemaak word dat alhoewel die mikrobiese samestelling van die korrels nie
dieselfde is as die tradisionele korrel nie, is die algemene voorkoms en eienskappe dieselfde
en dat dit wel moontlik is om korrels te produseer deur isolate geïsoleer vanuit Kefiran en
melk. Verder was dit moontlik om "n drankie te vervaardig met die korrels wat baie dieselfde
is as tradisionele Kepi.
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