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Quantitation and application of bacteriocins in foodHaveroen, Melissa E 06 1900 (has links)
Several obstacles to widespread use of bacteriocins in food have been identified, including lack of specific, rapid quantitation methods, and little data on their efficacy in food systems. The first objective of this study was to develop a specific, rapid quantitation method for bacteriocins that did not rely on bioassays and their associated limitations. Phage display was chosen to reduce reliance on continued use of animals and produce antibodies to the bacteriocins leucocin A, piscicolin 126, and brochocin-A. Although the antibody libraries generated by phage display were not successful for antibody production, a strong immune response to leucocin A and piscicolin 126 was observed in mice. The second objective of the study was to determine the efficacy of brochocin-C against Clostridium botulinum in a model system and in a vacuum-packaged, chopped and formed pork product stored at refrigeration temperature. Group I Cl. botulinum was not controlled by brochocin-C, and was found to inactivate brochocin-C and several class IIa bacteriocins by proteolysis. Cell counts revealed that Group II Cl. botulinum was controlled by brochocin-C in a model meat system, but was not controlled in the chopped and formed pork product. Powdered smoke and NaCl in the pork product had a synergistic interaction against Group II Cl. botulinum, as shown by minimum inhibitory concentration testing. The choice of media for isolation of Cl. botulinum from the chopped and formed pork product was important, as the presence of background microflora isolated from the meat was found to impact growth of Group II Cl. botulinum on plating media. In the presence of the background microflora, which were identified by 16S rDNA sequencing as carnobacteria and staphylococci, inclusion of phosphate in the plating medium was found to allow growth of Cl. botulinum. Other nutrients such as magnesium, sulphur, or increased protein sources added to the medium had no effect on growth of Cl. botulinum. Two of the background microflora strains, Carnobacterium maltaromaticum MH3 and Staphylococcus pasteuri EIV-21, inhibited Cl. botulinum, while one strain, C. maltaromaticum MH2, stimulated growth of Cl. botulinum. / Food Science and Technology
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Antifungal activity of lactic acid bacteria /Magnusson, Jesper, January 2003 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.
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Fungal inhibitory lactic acid bacteria : characterization and application of Lactobacillus plantarum MiLAB 393 /Ström, Katrin, January 2005 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.
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Factors important for persistence of Lactobacillus reuteri in the gastrointestinal tract : a study of extracellular proteins, stress response and survival of mutants in a model system /Båth, Klara, January 2007 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2007. / Härtill 4 uppsatser.
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Control of bacterial pathogens associated with mastitis in dairy cows with natural antimicrobial peptides produced by lactic acid bacteria /Pieterse, Reneé. January 2008 (has links)
Thesis (MSc)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.
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Production of SO₂ and SO₂ binding compounds by Saccharomyces cerevisiae during the alcoholic fermentation and the impact on wine lactic acid bacteria /O'Neil, Allison L. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 101-116). Also available on the World Wide Web.
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Preservation of red meat with natural antimicrobial peptides produced by lactic acid bacteriaKohrs, Gertruida Ansia 12 1900 (has links)
Thesis (MScVoedselwet)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Red meat has a limited shelf-life at refrigerated temperatures, where spoilage is mainly
due to the proliferation of bacteria, yeast and moulds, acquired during the dressing
process. In addition, almost a fifth of food-borne disease outbreaks, caused by microorganisms
such as Escherichia coli 0157:H7, Listeria monocytogenes and
Staphylococcus aureus are associated with red meat. To improve the microbiological
quality of red meat, systems such as HACCP, GHP and GMP are currently practiced;
however, these practices are not able to extend the shelf-life of these products. At
present suitable food-grade preservatives are recommended, but the use of some of
these preservatives is increasingly being questioned with regard to their impact on
human health. Additionally, food service customers demand high quality products that
have a relatively long shelf-life, but still prefer the appearance of minimally processed
food. All these factors challenge the food manufacturing industry to consider more
natural means of preservation.
Antimicrobial metabolites of food grade bacteria, especially lactic acid bacteria,
are attracting increasing attention as food preservatives. Bacteriocins are antimicrobial
peptides (3 to 10 kDa) with variable activity spectra, mode of action, molecular weight,
genetic origin and biochemical properties that are bacteriostatic or bactericidal to
bacteria closely related and bacteria confined within the same ecological niche.
Micro-organisms were isolated from beef, lamb and pork, obtained from four
commercial retailers. The number of viable cells three days after the sell-by date at 4ºC
ranged from 80 cfu.g-1 to 1.4 × 108 cfu.g-1. Fifty-three percent were Gram-negative
bacteria, 35% Gram-positive and 12% yeast. The microbial population of the meat was
greatly influenced by the origin, i.e. the retailer. Bacteriocins produced by Enterococcus
faecalis BFE 1071, Lactobacillus curvatus DF 38, Lb. plantarum 423, Lb. casei LHS, Lb.
salivarius 241 and Pediococcus pentosaceus ATCC 43201 were screened for activity
against bacteria isolated from the different meat samples. Sixteen to 21% of the
isolates, identified as members of Klebsiella, Shigella, Staphylococcus, Lactobacillus,
Lactococcus, Leuconostoc, Enterococcus, Pediococcus, Streptococcus and Bacillus
were sensitive to the bacteriocins.
Curvacin DF 38, plantaricin 423 and caseicin LHS (2.35 to 3.4 kDa) had the
broadest activity range and inhibited species of Lactobacillus, Pediococcus,
Enterococcus, Listeria, Bacillus, Clostridium and Propionibacterium. The bacteriocins
remained stable at 121ºC for 20 min, in buffers with a pH ranging from 2 to 10 and in
NaCl concentrations of between 0.1 and 10% (m/v). Like most peptides, they were sensitive to proteolytic enzymes. Curvacin DF 38 is sensitive to amylase, suggesting
that the bacteriocin might be glycosylated.
To assess the efficiency of curvacin DF 38, plantaricin 423 and caseicin LHS as
meat preservatives, they were partially purified by ammonium sulphate precipitation and
separation in a Sep Pak C18 cartridge. The shelf-life of pork may be extended by up to
two days. Meat samples treated with bacteriocins were darker than the control
(untreated) sample. Descriptive sensory evaluation by a seven-member panel indicated
that there were significant differences (P ≤ 0.05) regarding the aroma, sustained
juiciness, first bite and metallic taste attributes of the control and the 4 day-treated
samples. The control and 2 day-treated samples and the 2 day- and 4 day treated
samples did not differ significantly regarding these attributes. There were no significant
differences regarding the initial juiciness, residue and pork flavour attributes.
Concluded from the results obtained in this study, bacteriocins produced by Lb.
curvatus DF 38, Lb. plantarum 423 and Lb. casei LHS effectively extended the shelf-life
of pork loins by up to 2 d at refrigerated temperatures with no drastic changes on
sensory characteristics. In edition, the stability of these bacteriocins broadens their
application as preservatives in many foods. / AFRIKAANSE OPSOMMING: Die rakleeftyd van rooivleis by yskastemperature is beperk, waar bederf hoofsaaklik
deur die vermenigvuldiging van bakterieë, giste en swamme veroorsaak word. Die
meeste van hierdie kontaminante is afkomstig van die slagtingsproses. Byna ’n vyfde
van alle uitbrake van voedselvergiftigings wat deur organismes soos Escherichia coli
0157:H7, Listeria monocytogenes en Staphylococcus aureus veroorsaak word, word
met rooivleis geassosieër. Die praktyke HACCP, GMP en GHP word tans toegepas om
die mikrobiologies kwaliteit van vleis te handhaaf, maar is egter nie voldoende om die
rakleeftyd van rooivleis the verleng nie. Die preserveermiddels wat huidiglik aanbeveel
word vir dié doel, word toenemend bevraagteken aangaande die invloed daarvan op die
menslike gesondheid. Hierby is daar ’n aanvraag na hoë kwaliteit, ongeprosesseerde
produkte met ’n verlengde rakleeftyd. Gevolglik word die voedsel vervaardigings
industries aangemoedig om meer natuurlike vorms van preservering the oorweeg.
Die aandag word tans op die anti-mikrobiese metaboliete van voedselgraad
microbes, veral melksuurbakterieë, gevestig. Bakteriosiene is anti-mikrobiese peptiede
(3 tot 10 kDa) met verskeie aktiwiteitsspektra, werkswyse, molekulêre massa, genetiese
oorsprong en biochemiese eienskappe. Bakteriosiene is meestal bakterie-dodend of -
staties teen taksonomies naby geleë organismes en organismes vanuit dieselfde
ekologiese nis.
Mikroörganismes is geïsoleer vanuit bees-, skaap- en varkvleis, verkry vanaf vier
supermarkte. Die aantal lewensvatbare selle per gram (cfu.g-1) het drie dae na die
“verkoop”-datum by 4ºC vanaf 80 cfu.g-1 tot 1.4 × 108 cfu.g-1 gevarieër. Drie en vyftig
persent van die isolate is as Gram-negatief, 35% as Gram-positief en 12% as giste
geïdentifiseer. Die sensitiwiteit van hierdie isolate teen bakteriosiene wat deur
Enterococcus faecalis BFE 1071, Lactobacillus curvatus DF 38, Lb. plantarum 423, Lb.
casei LHS, Lb. salivarius 241 en Pediococcus pentosaceus ATCC 43201 geproduseer
is, is vervolgens getoets. Tussen 16% en 21% van die isolate was sensitief teen die
bacteriosiene en is onder andere as Klebsiella, Shigella, Staphylococcus, Lactobacillus,
Lactococcus, Leuconostoc, Enterococcus, Pediococcus, Streptococcus en Bacillus
geïdentifiseer.
Die bakteriosiene met die wydste aktiwiteitsspektrum, naamlik, curvacin DF 38,
plantaricin 423 en caseicin LHS is verder ondersoek. Hierdie antimikrobiese peptiede
(2.35 tot 3.4 kDa) toon aktiwiteit teen spesies van Lactobacillus, Pediococcus,
Enterococcus, Listeria, Bacillus, Clostridium and Propionibacterium. Die bakteriosiene
is stabiel by 121ºC vir 20 min, in buffers met ‘n pH-reeks van tussen 2 en 10 en soutkonsentrasies vanaf 0.1% tot 10%. Soos die geval by meeste peptiede is hierdie
bakteriosiene sensitief vir proteolitiese ensieme. Curvacin DF 38 is ook sensitief vir
amylase, wat daarop dui dat hierdie bakteriosien moontlik geglikosileer is.
Die effektiwiteit van curvacin DF 38, plantaricin 423 en caseicin LHS as
preserveermiddel in voedselsisteme is getoets deur dit te suiwer (ammonium sulfaat
presipitasie en Sep Pak C18 kolom) en op vark lendestukke aan te wend. Mikrobiese
analise het bewys dat die rakleeftyd van vark met sowat 2 dae verleng kan word.
Volgens die vleiskleurevaluering was die bakteriosien behandelde vark donkerder as die
kontrole. Die aroma-, sappigheid-, tekstuur- en metaalgeur-eienskappe van die kontrole
en die 4-dag behandelde monster het volgens ‘n opgeleide sensoriese paneel
betekenisvol verskil (P ≤ 0.05). Die kontrole en die 2-dag behandelde en die 2-dag
behandelde en die 4-dag behandelde monsters het nie betekenisvol verskil nie. Daar
was geen betekenisvolle verskil aangaande die aanvanklike sappigheid-, residu- en
varkgeur-eienskappe nie. Hierdie sensoriese eienskappe is belangrik ten opsigte van
die verbruiker se aanvaarding van die produk.
Vervolgens kan uit hierdie resultate afgelei word dat die bakteriosiene wat deur
Lb. curvatus DF 38, Lb. plantarum 423 en Lb. casei LHS geproduseer word voldoende
is om die rakleeftyd van vark lendestuk by 4ºC met 2 dae te verleng met min of geen
effek op die sensoriese persepsie van die vleis. Hierdie bakteriosiene is ook stabiel
onder verskeie kondisies wat die toepassing as preserveermiddel aansienlik verbreed.
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Selection and metabolic characterization of mesophylic starter cultures for optimizing the sensory attributes of fruit flavoured MaasArendse, Garron Mark 03 1900 (has links)
Thesis (MSc Food Sc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Maas is a traditional fermented milk drink of the indigenous people of Southern
Africa and can thus be used to uplift the nutritional status of the South African
population, especially for the lower income groups. Furthermore, the problem of
lactose intolerance among the Black population can also be addressed by the
consumption of Maas. The objective of this study was to screen mesophylic lactic
acid bacterial strains (25 in total) from the University of Stellenbosch Food Science
Culture Collection for suitable metabolite production and then to produce traditional
Maas with a starter culture combination that produces a distinctive acid and
traditional flavour.
The representative 25 single lactic acid starter strains were identified as
Lactococcus lactis subsp. leetis biovar diacetylactis (12 strains), L. leetis subsp.
leetis (four strains) and L. leetis subsp. cremoris (nine strains). These strains were
inoculated into pasteurised full cream milk and activated for 8 h at 22°C.
Pasteurised full cream milk was then inoculated with each of the activated starter
strains, incubated at 22°C for 16 h and assessed for acid production abilities (pH =
4.6) under controlled time-temperature conditions. The results of this study showed
that nine of the single strains, L. lactis subsp. leetis biovar diacetylactis (S1, S2, S3
and S5), L. teetis subsp. lactis (S13, S15 and S16) and two L. leetis subsp. cremoris
strains (S17 and S22), produced sufficient acid, rendering them suitable for the use
as starters in the production of traditional Maas. A pH range of 4.3 - 5.1 was
reached by the nine single strains after 16 h at 22°C.
Two-strain starter combinations were then formed by combining the most
suitable single L. leetis subsp. leetis biovar diacetylactis, L. lactis subsp. lactis and L.
lactis subsp. cremoris strains, respectively. From the data, it was concluded that
acceptable Maas could be produced with four two-strain combinations (S3S 17,
S3S22, S5S17 and S5S22). This selection was again based on suitable acid and
metabolite production, as well as on sensory evaluation of the final product. These
four two-strain combinations produced sufficient acid to reach a pH in the 4.6 - 4.8
range, and showed a high metabolite concentration for the most suitable compounds
and formed a thick, smooth and creamy body texture after 16 h at 22°C.
Three-strain combinations formed between the two-strain starter combinations
and L. leetis subsp. teetis strains (813, 815 and 816), were also evaluated. With
these combinations a lack of a pronounced Maas flavour was found. Thus, it was
decided to add aroma producing strains of the species Leuconostoc mesenteroides
subsp. dextranicum (strain L1) and L. mesenteroides subsp. citrovorum (strain L2) to
the three-strain combinations. Four culture combinations (A, B, C and D) were then
formed by combining the selected Leuconostoc strains (L1 and L2) with the most
suitable Lactococcus strains (83,817,813 and 822). These combinations produced
sufficient acid to reach the pH 4.5 - 4.6 range after 14 h at 22°C. Acetaldehyde was
the major flavour metabolite formed in the Maas made with these four combinations,
with concentrations ranging between 26.6 - 89.3 mg.l ̄ ¹, while other flavour
metabolites (ethanol, acetone, diacetyl and 2-butanone) were present at lower
concentrations. It was found that three of the four culture combinations (A, C and D)
were characterised by a superior, but delicate flavour and a typical characteristic
Maas body texture.
Fruit flavoured Maas was subsequently prepared with the three most suitable
culture combinations (A, C and D) using 11 flavours and a sensory evaluation
performed. The statistically evaluated data showed that the appearance,
smoothness, flavour intensity, sweetness and overall acceptability were influenced
by the type of fruit flavour and the culture combination. Fruit flavour 4 (banana) was
the most preferred flavour. The sensory panellists also indicated that the culture
combination C gave the best overall acceptability over a three week study period.
Data on the shelf-life study of natural unflavoured Maas, prepared with the
three culture combinations (A, C and D), showed that the Maas still had an
acceptable appearance, taste and good microbiological quality after 15 d at
refrigerated temperatures. / AFRIKAANSE OPSOMMING: Maas is 'n tradisionele gefermenteerde melkdrankie onder die inheemse bevolking
van Suid-Afrika en kan gebruik word om die voedingstatus van die Suid-Afrikaanse
bevolking te verhoog, veral vir die laer inkomste groepe. Bowendien, kan die
probleem van laktose intoleransie onder die Swart gemeenskap ook aangespreek
word deur die verbruik van Maas.
Die doel van hierdie studie was om enkelstam mesofiliese melksuur bakterieë
(25 in totaal) van die Universiteit van Stellenbosch Voedselwetenskap Kultuur
Versameling te ondersoek vir geskikte metaboliet produksie en tradisionele Maas
met 'n kenmerkende suurheid en tradisionele geur met 'n geskikte kultuur
kombinasie te produseer.
Die toonaangewende 25 enkelstamme is Lactococcus lactis subsp. leetis
biovar diacetylactis (12 stamme), L. lactis subsp. lactis (vier stamme) en L. lactis
subsp. cremoris (nege stamme). Hierdie stamme was in gepasteuriseerde volroom
melk geïnokuleer en geaktiveer vir 8 h teen 22°C. 'n Inokulum van die onderskeie
geaktiveerde stamme is hierna in gepasteuriseerde volroom melk geplaas, vir 16 h
teen 22°C geïnkubeer en hul vermoë om suur te produseer (pH = 4.6) onder
beheerde tyd-temperatuur kondisies is bepaal. Die resultaat van die studie het
aangedui dat nege enkelstamme, naamlik L. leetis subsp. lactis biovar diacetylactis
(S1, S2, S3 en S5), L. lactis subsp. leetis (S13, S15 en S16) en twee L. leetis subsp.
cremoris (S 17 en S22), geskikte suurheidsvlakke vir die produksie van Maas bereik
het. 'n pH vlak van 4.3 - 5.1 is na 16 h teen 22°C deur hierdie nege enkelstamme
bereik.
Twee-stam kombinasies is onderskeidelik gevorm tussen die geskikte enkel
L. lactis subsp lactis biovar diacetylactis, L. lactis subsp. lactis en L. lactis subsp.
cremoris stamme. Die gevolgtrekking gemaak uit die data, is dat aanvaarbare Maas
voorberei kan word met vier van die twee-stam kombinasies (S3S17, S3S22, S5S17
en S5S22) op grond van suurvorming, metaboliet produksie en sensoriese
evaluasie. Hierdie vier kombinasies het genoegsame suur geproduseer om 'n pH
vlak van 4.6 - 4.8 bereik, hoë metaboliet konsentrasies geproduseer en 'n dik,
gladde en romerige tekstuur aangeneem na 16 h teen 22°C.
Drie-stam kombinasies is gevorm tussen die onderskeie twee-stam
kombinasies en L. lactis subsp. lactis stamme (813,815 en 816) en ook geëvalueer.
Die tekort aan 'n skerp Maas geur in die drie-stam kombinasies het daartoe gelei dat
Leuconostoc mesenteroides subsp. dextranicum (stam L1) en L. mesenteroides
subsp. citrovorum (stam L2) bygevoeg is. Vier kultuur kombinasies (A, B, C en D) is
gevorm deur die geselekteerde Leuconostoc stamme (L1 en L2) te kombineer met
die mees gepaste Lactococcus stamme (83, 817, 813 en 822). Hierdie
kombinasies het genoegsame suur geproduseer wat 'n pH vlak van 4.5 - 4.6 na 14 h
teen 22°C bereik het. In die Maas wat met bovermelde kombinasies gemaak is, was
die asetaldehied die mees geproduseerde geur metaboliet teen konsentrasies van
26.6 - 89.3 mg.l ̄ ¹. Ander geur metaboliete (etanol, asetoon, diasetiel, 2-butanoon)
is in laer konsentrasies geproduseer. Daar is gevind dat drie uit die vier kultuur
kombinasies (A, C en D) 'n superieur, delikate geur wat 'n tipies karakteristiek van
die Maas gehad het.
Vrugte gegeurde Maas geproduseer met die drie kultuur kombinasies (A, C
en D) deur 11 geursels te gebruik, is sensories geëvalueer. Die statistiese
geëvalueerde data het getoon dat die voorkoms, gladheid, geur intensiteit, soetheid
en die algehele aanvaarbaarheid beïnvloed is deur die tipe vrugte geursels en die
kultuur kombinasies. Die vrugte geursel 4 (piesang) het voorkeur geniet. Die
sensoriese paneellede het ook aangedui dat kultuur kombinasie C die algehele
mees aanvaarbare Maas geproduseer het oor die studie periode van drie weke.
Data van die rakleeftyd van die natuurlike ongegeurde Maas wat geproduseer
is met die drie kultuur kombinasies (A, C en D) het aangedui dat die Maas na 15 d
by yskas temperatuur steeds 'n aanvaarbare voorkoms, smaak en goeie
mikrobiologiese kwaliteit gehad het.
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Identification of bacteria isolated from malt, with the emphasis on lactic acid bacteria and their influence on brewer's yeastBooysen, Clifford 12 1900 (has links)
Thesis (MScAgric.)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Changes in the bacterial population throughout the malting process of two barley cultivars, i.e.
Clipper (local cultivar) and Prisma (imported cultivar), malted at Southern Associated Maltsters
(SAM), Caledon, South Africa, were studied. Samples were taken from four individual runs of each
cultivar at ten different stages, i.e. dry barley before steep, water from the first steep water-stand,
barley after draining the first steep, water from the second steep water-stand, barley from the second
steep water-stand, barley after draining of the second steep, barley from the first, second and third
days of germination in the germination vessels (GV), and malt after kilning. Emphasis was placed
on the taxonomy and composition of the lactic acid bacteria (LAB) isolated from the ten different
phases.
The LAB were identified to species level by using numerical analysis of total soluble cell protein
patterns, RAPD-PCR banding patterns and 16S rRNA sequencing. The Gram-negative bacteria were
identified to genus level by using the API 20E system and included Citrobacter spp., Enterobacter
spp., Pantoea spp., Proteus spp., Seratia spp., Kluyvera spp., Klebsiella spp., Vibrio spp. and
Escherichia coli. The number of viable bacteria throughout the malting process of the two cultivars
did not differ significantly, although the LAB counts in the barley before steep and on the kilned
malt were higher in Prisma than in Clipper. Leuconostoc argentinum, Leuconostoc laetis and
Weissella confusa were the most predominant in both cultivars. A few strains of Weissella
paramesenteroides, Lactobacillus casei, Lactococcus laetis and Lactobacillus rhamnosus were also
isolated. Lb. casei and Lb. rhamnosus were not isolated from the Prisma cultivar, whilst W
paramesenteroides and Le. laetis were absent in the Clipper cultivar. Kilned malt of the Clipper
cultivar contained predominantly Le. argentinum, whereas the Prisma cultivar contained mainly Le.
lactis.
The effect of these bacteria on the fermenting ability of the brewer's yeast Saccharomyces
cerevisiae SAB 05, was also studied. Fermentations were conducted in wort prepared from Clipper
and Prisma malt. Yeast in combination with the different bacteria were used in the fermentation
studies. Wort with only yeast was used as control. Emphasis was placed on the effect the bacteria
has on the gravity, pH, yeast- and bacterial- counts and the different volatile aroma compounds produced throughout the fermentations.
The presence of LAB and Gram-negative bacteria had no effect on the yeast to reduce the gravity of
the fermenting wort, whilst the LAB caused a decrease in the pH of the fermentations in both
Clipper and Prisma wort. The cell numbers of the Gram-negative bacteria decreased throughout the
fermentations, whilst the LAB cell numbers remained constant. Comparisons could be drawn
between the volatile aroma compounds produced in the control fermentation and fermentations with
yeast and Gram-negative bacteria, yeast and Lactobacillus spp. and yeast and Weissella spp.
Leuconostoc spp. had a much greater influence on the aromatic composition of fermented malt, with
much more clear variations between Prisma and Clipper. No major differences were recorded in the
aroma profiles of Prisma and Clipper malt fermented in the presence and absence of Lactococcus
spp. The Gram-negative bacteria had no significant effect on the volatile aroma compounds
produced by the yeast, whilst the LAB had a definite effect on aroma composition in both cultivars.
The levels of four of the five principle aroma compounds, present in beer, were in the acceptable
concentration range on the fmal day of fermentation. The compounds with the highest
concentrations were iso-amyl alcohol, acetic acid and acetoin, with acetic acid being present in the
highest concentration in all the fermentations. / AFRIKAANSE OPSOMMING: Veranderinge in die bakteriese populasie van die gars kultivars, Clipper (plaaslik) en Prisma
(ingevoer), vermout by Southern Associated Maltsters (SAM), Caledon, Suid Afrika, is ondersoek.
Monsters is van vier individuele lopies van elke kultivar en tydens tien verskillende fases van die
vermoutingsproses geneem. Die tien verskillende stadia het die volgende ingesluit: Droë gars voor
benatting, water van die eerste benattingsfase, gars nadat water van die eerste benattingsfase
gedreineer is, water van die tweede benattingsfase, gars van die tweede benattingsfase, gars na die
dreinering van water in die tweede benattings fase, gars na die eerste, tweede en derde dag van
ontkieming binne die ontkiemingstenke, en mout na droging. Klem is geplaas op die taksonomie en
samestelling van melksuurbakterieë (MSB) wat tydens die tien verskillende fases geïsoleer is.
Die MSB is tot spesievlak geïdentifiseer deur gebruik te maak van numeriese analise van totale
oplosbare selproteïen bandpatrone, RAPD-PKR bandpatrone en 16S rRNA volgorde-bepaling.
Gram-negatiewe bakterieë is tot op genusvlak geïdentifiseer deur gebruik te maak van die API 20E
toetssisteem. Spesies van die genera Citrobacter, Enterobacter, Pantoea, Proteus, Seratia,
Kluyvera, Klebsiella, Vibrio asook Escherichia coli is geïdentifiseer. Tydens die vermoutingsproses
van die twee kultivars is geen beduidende verskille in die lewensvatbare bakterietellings gevind nie,
alhoewel die MSB-tellings in die gars voor benatting en mout na droging in Prisma hoër was as in
Clipper. Leuconostoc argentinum, Leuconostoc laetis en Weissella confusa het die meeste
voorgekom in beide kultivars. Kleiner hoeveelhede van Weissella paramesenteroides, Lactobacillus
casei, Lactococcus laetis en Lactobacillus rhamnosus is ook geïsoleer. Lb. casei en Lb. rhamnosus
het nie in die Prisma-kultivar voorgekom nie, terwyl W paramesenteroides en Le. laetis nie in die
Clipper-kultivar teenwoordig was nie. Le. argentinum het meestal in die gedroogde mout van die
Clipper-kultivar voorgekom, terwyl Le. laetis meestal in die Prisma-kultivar waargeneem is.
Die effek van hierdie bakterieë op die fermentasievermoë van die brouersgis Saccharomyces
cerevisiae SAB 05 is ook bestudeer. Die fermentasies is in Clipper- en Prisma- wort gedoen. Vir die
fermentasiestudies is gis in kombinasie met verskillende bakterieë gebruik. Wort met slegs gis het as
kontrole gedien. Klem is geplaas op die effek van die bakterieë op die digtheid, pH, gis- en bakterietellings
en die verskillende vlugtige komponente wat tydens die fermentasies geproduseer is. Die
teenwoordigheid van MSB en Gram-negatiewe bakterieë het geen effek gehad op die vermoë van die gis om die digtheid van die gefermenteerde wort te verlaag nie. Die MSB het wel 'n verlaging
van die pH in beide Clipper- en Prisma- wort teweeggebring. Tydens die fermentasie het die Gramnegatiewe
bakterietellings verminder, terwyl die MSB-tellings konstant gebly het. 'n Verband is
gevind tussen vlugtige komponente geproduseer in die kontrole-fermentasie en fermentasies met gis
en Gram-negatiewe bakterieë, gis en Lactobacillus spp. en gis en Weissella spp. Leuconostoc spp.
het groter veskille in die samestelling van die gefermenteerde wort teweeg gebring met duidelike
verskille tussen Clipper en Prisma. Die teenwoordigheid van Lactococcus spp. het nie groot
verskille in die samestelling van die gefermenteerde wort getoon nie. Op die laaste dag van die
fermentasies was die vlakke van vier uit die vyfbelangrikste vlugtige aroma komponente wat in bier
voorkom in die kontrole fermentasies in aanvaarbare konsentrasies teenwoordig. Die Gramnegatiewe
bakterieë het geen beduidende invloed gehad op die vlugtige aroma komponente wat deur
die gis geproduseer is nie, terwyl die MSB 'n besliste effek in die aroma-samestelling van beide die
kultivars gehad het. Die komponente met die hoogste konsentrasies was, isoamiel-alkohol, asynsuur
en asetoin. Asynsuur was in al die fermentasies in die hoogste konsentrasie teenwoordig.
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The role of lactic acid bacteria in brandy productionDu Plessis, Heinrich Wilbur,1975- 12 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The presence and growth of lactic acid bacteria (LAB) in wine and their influence on wine
quality has received much attention in recent years. Lactic acid bacteria are responsible
for conducting malolactic fermentation (MLF) in wine. The benefits associated with
malolactic fermentation in terms of deacidification of wine and the contribution to wine
flavour and complexity have also recently been the topic of research. It is impossible to
describe malolactic fermentation as distinctly desirable or undesirable in terms of its
influence on the final quality of wine. The benefits and disadvantages are dependent upon
viticultural region, grape variety, wine composition, winemaking techniques and the style
and objectives of the winemaker.
Brandy production is a multi-stage process in which base wine production, distillation
technique and wood maturation all have a large influence on the final chemical profile and
organoleptic quality of the brandy. The volatile composition of the base wine, which
basically undergoes a concentration process during the subsequent double distillation
phase, is critical in determining the aroma and flavour quality of the final brandy product.
Thus, the brandy is only as good as the base wine it is distilled from.
The aims of this study were to determine the effect of lactic acid bacteria and
spontaneous malolactic fermentation on the quality of brandy base wine and the resulting
distillate, and to determine which LAB species had been responsible for the occurrence of
spontaneous MLF.
This study showed that LAB are present at high numbers and are able to conduct
spontaneous MLF of brandy base wines. It was shown that the incidence of spontaneous
MLF varied from year to year. In 1998, 50% of the commercially produced base wines had
undergone partial MLF prior to distillation. In 1999 and 2000 respectively, 34% and 45% of
the commercial base wines had undergone partial MLF prior to distillation. The occurrence
of spontaneous MLF had an influence on the chemical composition and the sensory
quality of the base wine and distillate. There was an increase in the concentrations of ethyl
lactate, acetic acid and diethyl succinate in samples that had undergone MLF. There was
also a decrease in the concentrations of esters, such as iso-amyl acetate, ethyl acetate,
ethyl caproate, hexyl acetate and 2-phenethyl acetate in these same samples. Sensory
evaluation of the base wines and distillates demonstrated that samples that had
undergone MLF differed significantly from samples that had not undergone MLF. It was
also shown that distillates that had not undergone MLF had a slightly better aroma profile
than those that had. Sweet aromas, like chocolate and caramel, as well as negative
aromas, like chemical or solvent, were more prominent in brandy distillates that had
undergone MLF. Herbaceous and fruity aromas were more intense in distillates not having
undergone MLF.
Fifty-four strains, all Gram-positive and catalase negative, were isolated at different
stages of brandy production. Seven strains were isolated from the grape juice, 15 strains were isolated from the base wine, 20 strains were isolated during MLF and 12 strains were
isolated from the base wine after MLF had been completed. Based on C02 production
from glucose and gluconate, 17 strains were classified as facultatively heterofermentative
and 37 strains as obligately heterofermentative. Fifteen of the 37 obligately
heterofermentative strains were rod-shaped and were regarded as lactobacilli. The
remaining 22 strains were oval or cocci-bacilli shaped. The isolates were identified to
species level by using numerical analysis of the total soluble cell protein patterns, 16S
rRNAsequencing and polymerase chain reaction (PCR) with species-specific primers.
The facultative heterofermentative lactobacilli were identified as Lactobacillus
paracasei and Lactobacillus p/antarum. The fifteen obligately heterofermentative
lactobacilli were identified as members of the species Lactobacillus brevis, Lactobacillus
verrniforme, Lactobacillus buchneri and Lactobacillus hi/gardii. The 22 obligate
heterofermentative isolates, with a coccoid morphology, could be grouped into two clusters
and were identified as Oenococcus oeni. O. oeni was the species responsible for the
occurrence of spontaneous MLF in most of the commercial base wines. Lb. brevis,
Lb. hi/gardii and Lb. paracasei were also isolated from commercial base wines that had
undergone spontaneous MLF. In nine out of 14 experimental base wine samples that had
undergone spontaneous MLF, O. oeni was again the predominant species. Lb. brevis,
Lb. hi/gardii and Lb. paracasei were identified in the remaining experimental base wine
samples. This is the first report of the presence of Lb. perecese! and Lb. vermiforme in
brandy base wine. It was shown that the occurrence of spontaneous MLF had a negative
effect on the quality of brandy base wine, but that was shown to be due to the different
species and strains performing MLF. In the non-preferred distillate samples, Lactobacillus
spp. had performed MLF or had developed after or during MLF. / AFRIKAANSE OPSOMMING: Die teenwoordigheid en die vermoë van melksuurbakterieë (MSB) om in wyn te groei, is 'n
onderwerp wat al heelwat nagevors is. Melksuurbakterieë is verantwoordelik vir die
uitvoering van appelmelksuurgisting (AMG) in wyn. Die voordele verbonde aan
appelmelksuurgisting, ten opsigte van die verlaging van die totale suurinhoud en die
bydrae tot die verbeterde geur en kompleksiteit van die wyn, is ook al goed bestudeer.
Wat die invloed op die finale wynkwaliteit betref, is dit byna onmoontlik om AMG as
uitsluitlik gewens óf ongewens te beskou. Die voordele en nadele van AMG is afhanklik
van verskeie faktore, nl. wingerdkundige streek, druifkultivar, wynsamestelling,
wynmaakpraktyke, asook die styl en doelwitte van die wynmaker.
Die produksie van brandewyn is 'n multistapproses waarin die bereidingsmetode van
die basiswyn, die distillasietegniek en houtveroudering 'n groot invloed op die finale
kwaliteit en chemiese samestelling van die brandewyn het. Die vlugtige verbindings van
die basiswyn, wat tydens die dubbele distillasieproses gekonsentreer word, is van
wesenlike belang in die bepaling van die aroma en geur van die finale brandewynproduk.
Brandewyn is dus inderdaad net so goed soos die basiswyn waarvan dit gestook is.
Die doelwitte van hierdie studie was om te bepaal wat die invloed van MSB en die
voorkoms van spontane AMG op die kwaliteit van die basiswyn en die distillaat is, asook
om die MSB wat vir die voorkoms van spontane AMG verantwoordelik was, te identifiseer.
Hierdie studie het bewys dat MSB in hoë getalle teenwoordig was en dat dit in staat is
om die spontane AMG van basiswyne uit te voer. Daar is bewys dat die voorkoms van
spontaneAMG moontlik van jaar tot jaar kan verskil. In 1998 het 50%, in 1999 het 34% en
in 2000 45% van die kommersieel-geproduseerde basiswyn gedeeltelike AMG spontaan
voor distillasie ondergaan. Daar is ook gevind dat spontane AMG 'n invloed op die
chemiese samestelling en sensoriese kwaliteit van die basiswyn en die distillaat gehad
het. Daar was 'n toename in die konsentrasies van etiellaktaat, asynsuur en
diëtielsuksinaat in monsters wat spontane AMG ondergaan het. In dieselfde monsters was
daar ook 'n afname in die konsentrasies van iso-amielasetaat, etielasetaat, etielkaproaat,
heksielasetaat en 2-fenielasetaat. Sensoriese evaluering van die basiswyne en distillate
het getoon dat daar betekenisvolle verskille was tussen die monsters wat AMG ondergaan
het en dié wat nie AMG ondergaan het nie. Daar is bewys dat die distillate wat nie AMG
ondergaan het nie, 'n beter aromaprofiel gehad het as dié wat AMG ondergaan het. Soet
geure, soos sjokolade en karamel, en negatiewe geure, soos "chemies" en "oplosmiddel",
was prominent in distillate wat AMG ondergaan het. Kruidagtige en vrugtige geure was
meer intensief in distillate wat nie AMG ondergaan het nie.
Vier-en-vyftig bakteriese rasse, almal Gram-positief en katalase-negatief, is gedurende
die verskillende stadia van brandewynproduksie geïsoleer. Sewe rasse is uit druiwesap,
15 rasse gedurende die alkoholiese fermentasie, 20 rasse gedurende AMG en 12 rasse
na voltooiing van AMG geïsoleer. Op die basis van koolstofdioksied (C02)-produksie vanaf glukose en glukonaat is 17 rasse as fakultatief heterofermentatief en 37 rasse as obligaat
heterofermentatief geklassifiseer. Vyftien van die 37 obligaat-heterofermentatiewe rasse
was staafvormig en is as lactobacilli geïdentifiseer. Die oorblywende 22 het ovaal of
kokkus-bacillusvormige selmorfologie getoon. Identifikasie tot op spesievlak is gedoen
deur van numeriese analise van die totale oplosbare selproteïenprofiele, 16S-rRNAvolgordebepalings
en spesie-spesifieke inleiers vir die polimerasekettingreaksie (PKR)
gebruik te maak.
Die fakultatief-heterofermentatiewe rasse is as Lactobacillus paracasei en
Lactobacillus p/antarum geklassifiseer. Die 15 obligaat heterofermentatiewe stafies is as
Lactobacillus brevis, Lactobacillus buchneri, Lactobacillus hi/gardii en Lactobacillus
vermiforme geïdentifiseer. Die 22 ovaal, obligaat heterofermentatiewe isolate kon in twee
groepe ingedeel word en is as Oenococcus oeni geïdentifiseer.
Daar is bevind dat O. oeni-isolate vir die voorkoms van spontane AMG in die meeste
van die kommersiêle basiswyne verantwoordelik was. Lb. brevis, Lb. hi/gardii en
Lb. paracasei is ook uit kommersiêle basiswyne wat spontane AMG ondergaan het,
geïsoleer. In nege uit 14 van die eksperimentele basiswyne wat spontane AMG ondergaan
het, was O. oeni die dominante spesie. In die oorblywende eksperimentele wyne is
Lb. brevis, Lb. hi/gardii en Lb. paracasei aangetref. Hierdie is die eerste vermelding van
die teenwoordigheid van Lb. paracasei and Lb. vermiforrne in brandewynbasiswyn. Daar is
gevind dat die voorkoms van spontane AMG "n negatiewe invloed op brandewynkwaliteit
het, maar dit is as gevolg van die verskeidenheid van MSB-spesies en rasse wat voorkom.
In die distillate wat deur die proepaneel afgekeur is, het Lactobacillus spesies die AMG
deurgevoer, of het dit tydens of na AMG ontwikkel.
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