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Sensors and Portable Instruments for Postharvest AgricultureLerud, Ryan M. 10 June 2019 (has links)
The sensing needs for the fresh produce industry can be split into two primary stages: during maturation in the field, also referred to as Precision Farming, and during storage and transport of the produce, or Postharvest Storage. This work seeks to improve the accuracy and reliability of commercially available electrochemical and spectroscopic sensors tailored to the sensing needs of the fresh produce industry. For electrochemical sensing, this study proposes the use of an inline filter to remove polar organic compounds, which can interfere with the readings of a platinum-based electrochemical sensor. A 50% improvement in measurement accuracy was achieved when monitoring the storage headspace of a container of apples. For portable spectroscopy instruments, this study suggests improvements for the alignment of the optical bench and the spectral collect protocol. Methods to reduce the influence of environmental noise, such as variability of background light (sunlight in the field) and thermal effects on hardware performance, are presented. This study also presents the first report of the calibration transfer of spectral regressions developed with Karl Norris's Derivative Quotient Method. The motivation for this aspect of research was to develop methods to collect stable and accurate data in the field, which can be used to improve the quality of fresh produce reaching the customer and reduce premature food spoilage.
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Focal plane array-Fourier transform-infrared (FPA-FTIR) spectroscopy as a tool in the simple and rapid classification of common environmental and food spoilage fungiPinchuk, Orley R. (Orley Rachel), 1980- January 2008 (has links)
Environmental and food spoilage fungi cause billions of dollars in damage in North America alone each year, in the form of rotted wood and crops, spoiled food, and human and animal illness. Each of these threats could be drastically reduced if early and more rapid detection processes are developed to replace the serological methods that are currently in practice. The current North American protocol for establishing identification of contaminating fungi both in environment and food have a time frame of approximately one week to twenty-two days. The use of a Fourier transform infrared (FTIR) spectrometer, coupled with a focal-plan-array (FPA) detector, can theoretically shorten the time (analysis within minutes after obtaining a pure culture) it takes to identify and classify a fungal cell. FPA-FTIR spectroscopy is advantageous as little to no sample preparation is required and results are obtained in less than one minute per sample. The fungal subset chosen for this study includes representatives from five phyla, including Zygomycota (Mucor heimalis), Ascomycota (Neurospora crassa, Ophiostoma minor, Chaetomium globosporum, Alternaria brassicicola), Basidiomycota (Schizophyllum commune, Chaetomium globosporum), Deutromycota (Aspergillus niger, Penicillium notatum, Aureobasidium pullulans) and the Mycetozoa (dictyostelium discoideum, physarum polycephalum). Different variables were tested and evaluated, including variability in growth parameters, wet deposition of fungi versus dry smearing of fungi, optimal absorbance range, and spectral processing parameters as well as discrepancies from one instrument to another, as well as spectral reproducibility from one instrument to another. By following the experimental protocol developed, reproducible spectra were attained, and differentiation of the fungi within the set selected for this study was achieved. The results of this work demonstrate that FPA-FTIR spectroscopy can potentially be employed for the accurate identification of environmental and food spoilage fungi.
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Combination of ultra-high pressure and xanthene-derivatives to inactivate food-borne spoilage and pathogenic bacteriaWaite, Joy Gail. January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007.
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Focal plane array-Fourier transform-infrared (FPA-FTIR) spectroscopy as a tool in the simple and rapid classification of common environmental and food spoilage fungiPinchuk, Orley R. (Orley Rachel), 1980- January 2008 (has links)
No description available.
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Feasibility study of surface applications for Flashblast[TM] radiation in the food industryHidalgo B., Julio Gonzalo January 1985 (has links)
This investigation was undertaken to determine if ultra-high intensity radiant energy, can be utilized in the food industry to eliminate or significantly reduce surface contamination.
FLASHBLAST™ is the trademark of a pulsed power electromagnetic radiation apparatus developed by Maxwell Laboratories, Inc., San Diego, CA. A FLASHBLAST™ transforms electrical energy into high intensity, short duration pulses of ultraviolet, visible and infrared radiation.
FLASHBLAST™ radiation was found to be highly effective in inactivating vegetative cells, fungi and spores. It was also found to be a viable alternative for total or partial inactivation of microbial contamination on food packaging materials.
It was found that FLASHBLAST™ radiation is composed of approximately 31.4% of IR, 19.3% of UV and 49.3% of visible radiation. Only the UV spectral bands were responsible for the damage to the microorganisms.
Although it was concluded that UV absorption by protein was responsible for most of the organoleptic changes, the data indicated that by filtering the visible and IR regions of the spectrum, the undesirable organoleptic changes in food products were greatly diminished. / M.S.
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Growth and guaiacol production of species of Alicyclobacillus isolated from the South African fruit processing environmentSmit, Yvette 12 1900 (has links)
Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Bacteria belonging to the genus Alicyclobacillus are thermo-acidophilic spore-formers
that are able to spoil acidic food and beverage products through the production of
guaiacol and other taint compounds, which causes a medicinal off-flavour and/or
odour in the products. This thesis reports on the comparison of methods used for the
isolation of species of Alicyclobacillus, as well as the growth behaviour and guaiacol
production of different strains isolated from the South African fruit processing
environment. Two methods for guaiacol detection were also evaluated and
compared.
Three isolation methods frequently used by South African fruit processors
were compared with regards to their ability to isolate a strain of A. acidoterrestris
from diluted peach juice concentrate. Method 1, the International Federation of Fruit
Juice Producers (IFU) Method No. 12, makes use of spread plating onto Bacillus
acidoterrestris (BAT) agar plates; Method 2 involves pour plating using acidified
potato dextrose agar (PDA); and Method 3 makes use of membrane filtration and
incubation of the membrane on K agar. The IFU Method No. 12 was the most
effective method for the isolation of A. acidoterrestris, with a recovery of 75.97%.
These results support the use of the IFU Method No. 12 as a standard international
method for the isolation and detection of species of Alicyclobacillus.
Seven strains of Alicyclobacillus, including the type strains A. acidoterrestris
DSM 3922T and A. acidocaldarius DSM 446T and five strains isolated from a South
African fruit processing plant, A. acidoterrestris FB2, FB14, FB32, FB38 and A.
acidocaldarius FB19, were analysed based on their growth characteristics and
guaiacol production under optimum conditions. Strains were inoculated into BAT
medium at pH 4.00, supplemented with 100 mg.L-1 vanillin, and incubated at 45°C for
7 d. All the strains had similar growth patterns, with cell concentrations increasing
rapidly from 0-24 h, followed by a stabilisation around maximum cell concentrations
of 105-107 cfu.mL-1. Cell concentrations after heat shock, measured as an indication
of spore formation, increased to maximum values of 105-107 cfu.mL-1, indicating an
increase in spores as the cell density and competition for resources increased. All
the strains were able to produce guaiacol in detectable concentrations [as measured
by the peroxidase enzyme colourimetric assay (PECA)], and, therefore, possess the
potential to cause product spoilage. Bacteria belonging to the genus Alicyclobacillus are thermo-acidophilic spore-formers
that are able to spoil acidic food and beverage products through the production of
guaiacol and other taint compounds, which causes a medicinal off-flavour and/or
odour in the products. This thesis reports on the comparison of methods used for the
isolation of species of Alicyclobacillus, as well as the growth behaviour and guaiacol
production of different strains isolated from the South African fruit processing
environment. Two methods for guaiacol detection were also evaluated and
compared.
Three isolation methods frequently used by South African fruit processors
were compared with regards to their ability to isolate a strain of A. acidoterrestris
from diluted peach juice concentrate. Method 1, the International Federation of Fruit
Juice Producers (IFU) Method No. 12, makes use of spread plating onto Bacillus
acidoterrestris (BAT) agar plates; Method 2 involves pour plating using acidified
potato dextrose agar (PDA); and Method 3 makes use of membrane filtration and
incubation of the membrane on K agar. The IFU Method No. 12 was the most
effective method for the isolation of A. acidoterrestris, with a recovery of 75.97%.
These results support the use of the IFU Method No. 12 as a standard international
method for the isolation and detection of species of Alicyclobacillus.
Seven strains of Alicyclobacillus, including the type strains A. acidoterrestris
DSM 3922T and A. acidocaldarius DSM 446T and five strains isolated from a South
African fruit processing plant, A. acidoterrestris FB2, FB14, FB32, FB38 and A.
acidocaldarius FB19, were analysed based on their growth characteristics and
guaiacol production under optimum conditions. Strains were inoculated into BAT
medium at pH 4.00, supplemented with 100 mg.L-1 vanillin, and incubated at 45°C for
7 d. All the strains had similar growth patterns, with cell concentrations increasing
rapidly from 0-24 h, followed by a stabilisation around maximum cell concentrations
of 105-107 cfu.mL-1. Cell concentrations after heat shock, measured as an indication
of spore formation, increased to maximum values of 105-107 cfu.mL-1, indicating an
increase in spores as the cell density and competition for resources increased. All
the strains were able to produce guaiacol in detectable concentrations [as measured
by the peroxidase enzyme colourimetric assay (PECA)], and, therefore, possess the
potential to cause product spoilage.
iv
The influence of temperature on the growth and guaiacol production of the
Alicyclobacillus strains was also investigated and two guaiacol detection methods,
the PECA and headspace gas-chromatography mass-spectrometry (HS GC-MS),
were compared with regards to their ability to detect guaiacol. The strains were
incubated at 25°C and 45°C for 6 d and samples analysed every 24 h. Growth of the
A. acidoterrestris strains was slower at 25°C, and maximum cell concentrations were
lower than at 45°C. A decrease in cell concentrations was observed in the A.
acidocaldarius strains at 25°C, as this temperature is below their growth temperature
range. All the strains were able to produce guaiacol at 45°C, with guaiacol only
being detected once a cell concentration of 104-105 cfu.mL-1 had been reached. The
maximum guaiacol concentrations detected at 45°C in the samples containing A.
acidoterrestris were significantly higher than those detected in the A. acidocaldarius
samples. At 25°C there was a longer lag phase before guaiacol was detected in the
A. acidoterrestris samples, while no guaiacol was detected in the samples containing
A. acidocaldarius. Because guaiacol is produced at ambient temperatures, cooling of
products is recommended to control spoilage by A. acidoterrestris. The sensitivity of
the two guaiacol detection methods also differed significantly and, therefore, the
PECA is recommended for presence/absence detection of guaiacol, while HS GCMS
is recommended where accurate quantification of guaiacol is required.
Alicyclobacillus acidoterrestris FB2 was investigated for its ability to grow and
produce guaiacol in white grape juice supplemented with vanillin at different
concentrations. Alicyclobacillus acidoterrestris FB2 was inoculated into white grape
juice concentrate diluted 1:10 with distilled water containing 0-500 mg.L-1 vanillin and
incubated at 45°C for 6 d. Similar growth patterns were observed in all the samples,
except in the sample containing 500 mg.L-1 vanillin, which had a longer lag phase of
growth. Guaiacol concentrations, detected using the PECA, increased as the vanillin
concentration increased, with the exception of the sample containing 500 mg.L-1
vanillin, where less guaiacol was detected than in the sample containing 250 mg.L-1
vanillin, due to growth inhibition caused by the higher vanillin concentration. A
number of conditions need to be favourable for detectable guaiacol production to
occur and it could, therefore, be possible to minimise or prevent guaiacol production
by controlling or eliminating some of these factors. Good manufacturing practices
should be employed in order to minimise contamination and, therefore, spoilage, by
Alicyclobacillus species. / AFRIKAANSE OPSOMMING: Bakterieë wat aan die genus Alicyclobacillus behoort, is termo-asidofiliese
spoorvormers wat suur voedsel en drank produkte kan bederf deur die produksie van
guaiakol en ander bederf verbindings, wat ‘n medisinale geur en/of reuk in die
produkte veroorsaak. Hierdie tesis doen verslag oor die vergelyking van metodes
wat vir die isolasie van spesies van Alicyclobacillus gebruik word, sowel as die groei
kenmerke en guaiakol produksie van verskillende stamme wat uit die Suid-
Afrikaanse vrugte prosesseringsomgewing geïsoleer is. Twee metodes vir die
deteksie van guaiakol is ook geëvalueer en vergelyk.
Drie isolasie metodes wat algemeen deur Suid-Afrikaanse
vrugteprosesseerders gebruik word, is vergelyk ten opsigte van hul vermoë om H A.
acidoterrestris stam uit verdunde perskesap konsentraat te isoleer. Metode 1, die
Internasionale Federasie van Vrugtesap Produseerders (IFU) Metode No. 12, maak
gebruik van spreiplating op Bacillus acidoterrestris (BAT) agar plate; Metode 2
behels gietplating met aartappel dekstrose agar (PDA) and Metode 3 maak gebruik
van membraan filtrasie en inkubasie van die membraan op K agar. Die IFU Metode
No. 12 was die mees effektiewe metode vir die isolasie van A. acidoterrestris, met H
sel herwinning van 75.97%. Hierdie resultate ondersteun die gebruik van die IFU
Metode No. 12 as H standaard internasionale metode vir die isolasie en deteksie van
spesies van Alicyclobacillus.
Sewe Alicyclobacillus stamme, insluitende die tipe stamme A. acidoterrestris
DSM 3922T en A. acidocaldarius DSM 446T en vyf stamme geïsoleer uit ‘n Suid-
Afrikaanse vrugte prosesseringsaanleg, A. acidoterrestris FB2, FB14, FB32, FB38 en
A. acidocaldarius FB19, is geanaliseer met betrekking tot hul groei kenmerke en
guaiakol produksie onder optimum toestande. Stamme is in BAT medium by pH
4.00, aangevul met 100 mg.L-1 vanillin, geïnokuleer en geïnkubeer teen 45°C vir 7 d.
Al die stamme het soortgelyke groeipatrone getoon, met selgetalle wat vinnig
toegeneem het van 0-24 h, gevolg deur ‘n stabilisering rondom maksimum selgetalle
van 105-107 kve.mL-1. Selgetalle na hitte behandeling, gemeet as H aanduiding van
spoorvorming, het toegeneem tot maksimum waardes van 105-107 kve.mL-1, wat
aandui dat spore toegeneem het soos die seldigtheid en kompetisie vir
voedingsbronne toegeneem het. Al die stamme kon guaiakol in bespeurbare konsentrasies produseer [soos gemeet deur die peroksidase ensiem kolorimetriese
bepaling (PEKB)] en besit dus die potensiaal om produkte te bederf.
Die invloed van temperatuur op groei en guaiakol produksie van die
Alicyclobacillus stamme is ook ondersoek en twee guaiakol deteksie metodes, die
PEKB en topspasie gas-kromatografie massa-spektrometrie (TS GK-MS) is vergelyk
ten opsigte van hul vermoë om guaiakol op te spoor. Die stamme is geïnkubeer teen
25°C en 45°C vir 6 d en monsters is elke 24 h geanaliseer. Groei van die A.
acidoterrestris stamme was stadiger by 25°C en maksimum selgetalle was laer as by
45°C. H Vermindering in selgetalle is waargeneem in die A. acidocaldarius stamme
by 25°C, aangesien hierdie temperatuur buite hul groei temperatuur grense val. Al
die stamme kon guaiakol produseer by 45°C, met guaiakol deteksie wat eers H
aanvang geneem het nadat H sel konsentrasie van 104-105 kve.mL-1 bereik is. Die
maksimum guaiakol konsentrasies wat by 45°C in die monsters met A. acidoterrestris
opgespoor is, was beduidend hoër as die konsentrasies wat in die A. acidocaldarius
monsters opgespoor is. By 25°C was daar H langer sloerfase voor guaiakol
opgespoor is in die A. acidoterrestris monsters, terwyl geen guaiakol opgespoor is in
die monsters wat A. acidocaldarius bevat het nie. Aangesien guaiakol by
kamertemperatuur geproduseer word, word verkoeling van produkte aanbeveel ten
einde bederf deur A. acidoterrestris te beheer. Die sensitiwiteit van die twee guaiakol
deteksie metodes het ook beduidend verskil en dus word die gebruik van die PEKB
aanbeveel vir teenwoordigheid/afwesigheid deteksie van guaiakol, terwyl TS GK-MS
aanbeveel word waar akkurate kwantifisering van guaiakol vereis word.
Ondersoek is ingestel na die vermoë van A. acidoterrestris FB2 om te groei en
guaiakol te produseer in witdruiwesap aangevul met verskillende vanillin
konsentrasies. Alicyclobacillus acidoterrestris FB2 is geïnokuleer in witdruiwesap
konsentraat 1:10 verdun met gedistilleerde water wat 0-500 mg.L-1 vanillin bevat het
en is geïnkubeer teen 45°C vir 6 d. Soortgelyke groeipatrone is waargeneem in al
die monsters, behalwe die monster wat 500 mg.L-1 vanillin bevat het, wat H langer
sloerfase van groei gehad het. Guaiakol konsentrasies, soos gemeet deur die
PEKB, het toegeneem soos die vanillin konsentrasie toegeneem het, met die
uitsondering van die monster wat 500 mg.L-1 vanillin bevat het, waar minder guaiakol
opgespoor is as in die monster wat 250 mg.L-1 bevat het as gevolg van groei inhibisie
veroorsaak deur die hoër vanillin konsentrasie. H Aantal toestande moet gunstig
wees vir guaiakol produksie om plaas te vind en dit kan dus moontlik wees om guaiakol produksie te minimaliseer of te voorkom deur die beheer of uitskakeling van
sommige van hierdie faktore. Goeie vervaardigingspraktyke moet in plek gestel word
ten einde kontaminasie en bederf deur Alicyclobacillus spesies tot H minimum te
beperk.
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Développement de la spectrométrie de masse MALDI -TOF pour l'identification des champignons filamenteux d'intérêt alimentaire et étude de leur résistance aux molécules biocides / Development of MALDI-TOF MS to identify filamentous fungi and study of their resistance towards biocidal moleculesQuero, Laura 21 December 2018 (has links)
Les moisissures d’altération sont à l’origine de pertes alimentaires et économiques importantes et certaines espèces peuvent présenter un danger pour la santé humaine et animale avec la production de mycotoxines. Dans ce contexte, la maîtrise de la qualité et de la sécurité des aliments passe par une bonne connaissance des espèces impliquées. Cette connaissance repose sur une identification fiable et rapide et l’obtention d’informations sur les facteurs abiotiques impactant leur développement, tels que les conservateurs, largement utilisés dans l’industrie. Dans ce cadre, les objectifs de thèse étaient de développer l’utilisation de la spectrométrie de masse MALDI-TOF pour l’identification des moisissures et d’évaluer son application à la résolution de complexe d’espèces et au typage, et enfin d’évaluer la néphélométrie laser pour mesurer en haut-débit leur croissance en présence de conservateurs. Dans un premier temps, une base de données robuste a été construite avec près de 6500 spectres correspondant à 136 espèces fongiques. Dans un deuxième temps, la technique MALDI-TOF a été appliquée avec succès à la différenciation de 23 espèces du complexe Aspergillus section Flavi et a permis de différencier des isolats de Penicillium roqueforti appartenant à 3 populations génétiquement différenciées. Enfin, la néphélométrie laser a permis un suivi haut-débit de la croissance de 14 espèces fongiques d’altération en présence de 3 conservateurs et ainsi d’obtenir des informations sur les concentrations minimales inhibitrices de ces derniers. Ces travaux ont démontré l’applicabilité de techniques alternatives permettant d’identifier et de caractériser les moisissures d’altération. / Spoilage fungi represent a major cause of food and economic losses and certain species, which may produce mycotoxins, may also pose a threat to human and animal health. Thus, food safety and quality management relies notably on a good knowledge of the involved species. This knowledge is notably based on their fast and reliable identification and on the study of abiotic factors affecting their growth such as food preservatives, which are commonly used in the food industry. In this context, the objectives of this PhD. thesis were to develop MALDI-TOF mass spectrometry for mold identification and to evaluate its potential for species complex differentiation and strain typing, and finally, to evaluate the use of laser nephelometry to monitor fungal growth in the presence of food preservatives.First, a robust database was developed with 6500 spectra corresponding to 136 spoilage fungi. Then, MALDI-TOF MS was successfully applied to differentiate 23 species of Aspergillus section Flavi and Penicillium roqueforti isolates belonging to 3 genetically distinct populations.Finally, in 14 fungal species, laser nephelometry allowed a high-throughput monitoring of their growth after exposition to 3 different food preservatives and the determination of their associated minimal inhibitory concentrations.Overall, the obtained results demonstrate the usefulness of alternative techniques for identification and characterization of food spoilage fungi.
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Anti-microbial activity of rooibos tea (Aspalathus linearis) on food spoilage organisms and potenial pathogensSchepers, Sonette 12 1900 (has links)
Thesis (MSc Food Sc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT:Aspalafhus linearis is an indigenous fynbos plant cultivated in the Clanwilliam area
of the Western Cape, South Africa. The rooibos tea that is prepared from this
plant, has become popular worldwide mainly due to the alleged health properties.
Studies on the anti-microbial properties of green, black and oolong teas have
shown that these teas have strong anti-microbial activity against a wide range of
microbes. No studies have been done on the anti-microbial activity of rooibos tea
and the aim of this study was to determine what impact rooibos tea extracts would
have on the growth of different food spoilage and potential pathogenic microbes.
Water and ethyl acetate extracts of fermented and unfermented rooibos tea
were used to determine the inhibitory effect on the growth of an Escherichia coli
strain. The E. coli culture was grown in tea-MRS with either added fermented or
unfermented rooibos tea extracts. Both the water and ethyl acetate extracts
showed a strong inhibitory effect against the E. coli strain in that there was a
decrease in the final bacterial cell density (Nmax)(from 0.59 00 to 0.25 00) and
the maximum specific growth rate (~max)(from 1.12 h-1 to 0.20 h-1) and an increase
in the doubling time (~) (from 0.59 h to 1.80 h) and lag time (tlag)(from 4.81 h to
6.60 h) as the concentration of the soluble solids of the tea extracts was increased
from 0.5 to 5.0 g.r1
. Furthermore, it was found that the fermented rooibos tea had
a much stronger inhibitory effect (69% decrease in growth at 5.0 g.r1 soluble
solids) compared to the unfermented rooibos tea extracts (35.1% decrease in
growth at 5.0 g.r1 soluble solids). The resulting data indicated that rooibos tea had
a very strong inhibitory effect on the growth of the E. coli strain. It was also found
that the water extracts of rooibos tea showed a stronger inhibitory effect on the
growth of the E. coli than the ethyl acetate extracts, indicating that the antimicrobial
activity of rooibos tea is not exclusively due to the polyphenolic content -
individual compounds. It was also determined that the rooibos tea water extracts
showed a bacteriostatic action against the E. coli strain in that as soon as the tea
is no longer part of the growth medium, the E. coli resumed a normal growth
pattern. The data obtained showed that the inhibitory effect of rooibos tea water
extracts (69% decrease in growth) against the growth of E. coli was more
pronounced than that found when black tea water extracts (25.7% decrease in
growth) at the same concentrations were used.Rooibos tea water extracts (0.5 - 5.0 g.r1) of fermented and unfermented
tea were also used to determine the inhibitory effect on other food spoilage
microbes and potential pathogens. Strains of Staphylococcus aureus, Bacillus
cereus, Listeria monocytogenes, Streptococcus mutans, Saccharomyces
cerevisiae and Zygosaccharomyces rouxii were grown in the presence of
fermented and unfermented rooibos tea water extracts. The effect that fermented
rooibos tea had on the growth of all the microbes tested was in the following order:
Staph. aureus (90.8% decrease in growth) > L. monocytogenes (89.2% decrease
in growth) > Strep. mutans (84.1% decrease in growth) > B. cereus (80.3%
decrease in growth) > Sacch. cerevisiae (77.7% decrease in growth) > E. coli
(69.0% decrease in growth). The rooibos tea clearly had an inhibitory effect on the
growth of all the microbes, with the exception of the Z. rouxii strain where the
presence of the tea water extracts was found to enhance the growth.
The inhibitory effect of rooibos tea on the growth of these microbes was
shown by changes in the growth parameters with Nmax and IJmaxshowing
decreases, while the ld and tlagincreased as the concentration of the tea soluble
solids was increased. As with E. coli, the fermented rooibos tea water extracts
showed the stronger inhibitory effect on the growth of the various microbes.
The data obtained in this study suggests that rooibos tea is not effective as
an anti-microbial agent against all yeast species, but will strongly retard the growth
of specific Gram-positive and Gram-negative bacteria. As long as rooibos tea is
present, strong anti-microbial activity will be observed at a cup of tea concentration
of 2.5 g.r1 soluble solids. These results may be of value to support the health
claims associated with rooibos tea and may in the future lead to the use of rooibos
tea as a "natural" food preservative. / AFRIKAANSE OPSOMMING:Aspalathus linearis is 'n inheemse fynbosplant wat gekultiveer word in die
Clanwilliam area van die Wes Kaap, Suid-Afrika. Rooibostee, wat gemaak word
van hierdie plante, het baie gewild geword wereldwyd a.g.v. die
gesondheidsaspekte van hierdie tee. Studies toon dat groen, swart en oolong tee
sterk anti-mikrobiese aktiwiteit het teen 'n wye reeks mikrobes. Aangesien daar
voorheen geen studies gedoen is op die anti-mikrobiese aktiwiteit van rooibostee
nie, was die doel van hierdie studie om die effek van rooibostee te bepaal op die
groei van verskillende voedselbederwers en potensiele patogeniese mikrobes.
Water- en etielasetaat-ekstrakte van gefermenteerde en ongefermenteerde
rooibos tee is gebruik om die inhiberende effek op die groei van Escherichia coli te
bepaal. Escherichia coli is gegroei in tee-MRS met bygevoegde gefermenteerde
of ongefermenteerde rooibostee-ekstrakte. Seide die water- en etielasetaatekstrakte
van rooibostee het 'n sterk inhiberende effek gewys teen E. coli en dit
word gestaaf deur 'n afname in die finale bakteriese seldigtheid (Nmax)(vanaf 0.59
00 tot 0.25 00) en die maksimum spesifieke groeitempo (lJmax) (vanaf 1.12 h-1 tot
0.20 h-1) en 'n toename in die verdubbelingstyd (~) (vanaf 0.59 h tot 1.80 h) en die
sloerfase (tlag)(vanaf 4.81 h tot 6.60 h) 5005 wat die konsentrasie van oplosbare
vastestowwe van die tee toeneem van 0.5 tot 5.0 g.r1
. Verder is daar gevind dat
die gefermenteerde rooibostee 'n baie sterker inhiberende effek het (69% afname
in groei by 5.0 g.r1 oplosbare vastestowwe) in vergelyking met die
ongefermenteerde rooibostee-ekstrakte (35.1% afname in groei by 5.0 g.r1
oplosbare vastestowwe). Die resultate van die data dui aan dat rooibos tee 'n
baie sterk inhiberende effek het op die groei van die E. coli spesie. Die waterekstrakte
van rooibostee het 'n sterker inhibisie getoon teen die groei van E. coli
as die etielasetaat-ekstrakte, wat aandui dat die anti-mikrobiese aktiwiteit van
rooibostee nie eksklusief toegeskryf kan word aan die polifenoliese samestelling
nie. Daar is ook gevind dat rooibostee water-ekstrakte 'n bakteriostatiese effek
het teen E. coli, want sodra die tee ekstrakte nie meer teenwoordig is in die
groeimedium nie, hervat E. coli normale groei. Die data wys ook dat die
inhiberende effek van rooibostee water-ekstrakte (69.0% afname in goei) teen E.
coli baie sterker is as die van swart tee water-ekstrakte (25.7% afname in groei) by
dieselfde konsentrasies.Rooibostee water-ekstrakte (0.5 - 5.0 g.r1) van gefermenteerde en
ongefermenteerde rooibostee is ook gebruik om die inhiberende effek te bepaal
teen ander voedselbederwers en potensiele patogene. Spesies van
Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Streptococcus
mutans, Saccharomyces cerevisiae en Zygosaccharomyces rouxii is gegroei in die
teenwoordigheid van gefermenteerde en ongefermenteerde rooibostee waterekstrakte.
Die effek wat gefermenteerde rooibostee het op die groei van die
getoetste mikrobes is 5005 volg: Staph. aureus (90.8% afname in groei) > L.
monocytogenes (89.2% afname in groei) > Strep. mutans (84.1% afname in groei)
> B. cereus (80.3% afname in groei) > Sacch. cerevisiae (77.7% afname in groei)
> E. coli (69.0% afname in groei). Rooibostee het 'n duidelike inhiberende effek
gehad teen al die organismes, behalwe teen Z. rouxii spes ie, waar die
teenwoordigheid van rooibostee die groei van die organisme bevorder het.
Die inhiberende effek van rooibostee teen die groei van hierdie mikrobes
word ondersteun deur die groei parameters waar die Nmaxen IJmaxafgeneem het
terwyl die ~ en tlagtoegeneem het 5005 wat die konsentrasie van die oplosbare
vastestowwe toeneem. Die gefermenteerde rooibostee water-ekstrakte het ook 'n
sterker inhiberende effek op die groei van die verskillende mikrobes net 5005 met
E. coli.
Die data wat verkry is van hierdie studie dui aan dat rooibostee nie effektief
sal wees as 'n anti-mikrobiese middel teen aile gis spesies nie, maar dit sal die
groei van spesifieke Gram-positiewe en Gram-negatiewe bakterie sterk vertraag.
So lank as wat rooibostee teenwoordig is, sal sterk anti-mikrobiese aktiwiteit
waargeneem word by 'n koppie-tee konsentrasie van 2.5 g.r1 oplosbare
vastestowwe. Hierdie resultate kan help om die gesondheidseienskappe
geassosieer met rooibostee te ondersteun en help om die gebruik van rooibostee
as 'n "natuurlike" preserveermiddel te bevorder.
dedicated to my parents
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Fuel Cell for Food Preservation / Bränslecell för bevaring av livsmedelSpencer, Maximilian January 2016 (has links)
As foodstuffs are being produced, transported and stored in greater quantities than ever before in human history and with an alarming amount of food products being lost to spoilage every year, new, environmentally friendly ways of preserving food products are being actively researched and developed in today’s world. Oxygen is a key pathway towards food decay and destruction, due to its dual roles as a source of respiration for the multitude of microorganisms that can cause food spoilage and through direct destruction through oxidation reactions within food products that cause oxidative deterioration. Fuel cells have the theoretical potential to be an energy efficient and environmentally friendly way of preserving food, such as fish, fruit and vegetables. Because of their nature to consume oxygen through the electrochemical reactions that produces their electrical power, they have the potential to be used to reduce localised oxygen content for the storage and transportation of foods, minimising their spoilage, as well as potentially providing electrical energy for other components in potential control systems for the fuel cell. The purpose of this project is to design and build a PEM fuel cell and examine its potential for lowering of oxygen concentrations at the gas output at the cathode. The outcome of these experiments are designed to validate the theoretical capacity of fuel cells to reduce output oxygen concentrations to levels that are able to aid in the preservation of foodstuffs. It is hoped that this study, in conjunction with the researched literature, can be used as a guide for future food shipping and storage methods. The experimental stage of this diploma work was unsatisfactory. The fuel cell was unable to produce a voltage and the reactant gases were unable to flow through the fuel cell due to a design flaw. Therefore the effectiveness of a fuel cell for depletion of oxygen to levels able to preserve food is based on the theoretical basis of the internal PEM fuel cell reactions, as well as studying past literature and patents. If the theoretical ability of the fuel cell is proven, it can be asserted that PEM fuel cells have the potential to be a real contender in the field of food preservation in shipping and storage, as well as offering greater levels of control for supplies for how and when they can ship their product. However this will require more independent research development work on the effects of low oxygen concentrations on a fuel cell operation as well as the preservation effects on a greater variety of foodstuffs. Furthermore, more research is required for more efficient and cheaper fuel cell catalysts or innovative designs are required to avoid concentration losses that arise from oxygen reduction at low oxygen levels.
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Studies on the microbiology of fish and shellfish with emphasis on bacteriocin-like substances to control Listeria monocytogenesIzuchukwu, Ngozi O. January 2015 (has links)
Seafood permits the transmission of many bacterial pathogens. In order to reconcile consumer demands with important safety standards, traditional means of regulating microbial spoilage and safety hazards in foods are combined with novel technologies. These include biological antimicrobial systems, such as the use of lactic acid bacteria (LAB) and/or their bacteriocins, such as Carnobacterium maltaromaticum CS526 and its bacteriocin piscicocin CS526. The aims of this study were to investigate the presence of Listeria monocytogenes in temperate seafood, namely fresh and smoked salmon, fresh and smoked haddock, and fresh mussels and oysters. Additionally, there was an aim to recover, characterise and use bacteriocin-like-substance to control Listeria monocytogenes in cold smoked haddock. Vibrio spp., Enterobacteriaceae representatives, total aerobic heterotrophic counts and Listeria monocytogenes were isolated from commercially prepared smoked and fresh Atlantic salmon, smoked and fresh haddock, live mussels and oysters using selective media and tryptone soya agar (TSA). Vibrio spp. occurred in high densities (>106 CFU gˉ1) in mussels and Enterobacteriaceae representatives were recorded at >106 CFU gˉ1 in fresh salmon. Total aerobic heterotrophic counts in fresh salmon, live mussels and oysters reached 107, > 107, and > 106 CFU gˉ1, respectively. Listeria monocytogenes was recorded at 5.0 x 104 CFU gˉ1 in mussels. In total sixty one bacterial isolates were recovered from the seafood examined. The results revealed 19 genera of bacteria, i.e. Acinetobacter, Aerococcus, Aeromonas, Bacillus, Brochothrix, Carnobacterium, Citrobacter, Corynebacterium, Enterobacter, Escherichia coli, Moraxella, Micrococcus, Pseudomonas, Psychrobacter, Serratia, Shewanella, Staphylococcus, Vibrio and Listeria. The prominent characteristics of fish spoilage isolates were demonstrated by the ability of the isolates to reduce trimethylamine oxide (TMAO) to trimethylamine, and to produce H₂S. Sh. baltica OS185, Aeromonas spp. HB-6, Sh. baltica, Sh. putrefaciens, A. hydrophila HX201006-3, A. salmonicida subsp. achromogenes, A. hydrophila, C. freundii, Enterobacter cloacae were strong producers of TMA and H₂S. The spoilage microorganisms were tested for potential pathogenicity. The result revealed that 6/15 of the spoilage microorganisms produced proteolytic, lecithinase, blood (β and α haemolysin) and elastinase activity, respectively, whereas 7/15 of the spoilage microorganisms showed lipolytic activity. Cell free supernatants, ammonium sulphate precipitated supernatants and semi-purified bacteriocin-like substances of Carnobacterium maltaromaticum MMF-32 and KOPRI 25789 producing strains isolated from commercially prepared smoked salmon were investigated for their potential antimicrobial activity against potentially pathogenic and food spoilage microorganisms. Generally, a broad spectrum of activity was revealed against potentially pathogenic and food spoilage microorganisms in vitro. Cold-smoked haddock treated with bacteriocin producing C. maltaromaticum MMF-32, C. piscicola A9b bacˉ phenotype nonbacteriocin producing strain a mutant of C. piscicola A9b bac+, cell free supernatants, ammonium sulphate precipitated supernatants and semi-purified bacteriocin-like substances was challenged with L. monocytogenes ATCC 19114 up to 103 CFU gˉ1, respectively. Samples were stored at 4 °C for 10 days. L. monocytogenes and total bacterial counts were determined along with changes in total volatile base nitrogen (TVBN) and biogenic amines production as well as texture, colour and odour. Although the study on anti-listerial effects of C. maltaromaticum MMF-32 was not successful, this organism did have a positive effect on retention of firmness and sensory perception in cold smoked haddock.
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