Chocolate is one of the most important products for the food industry, being of economic interest all over the world. The cocoa quality depends directly on the post-harvest processing, being the cocoa-pulp fermentation a crucial step for chocolate quality development. The aim of this work was to study the diversity of aroma-producing yeasts associated with cocoa beans fermentation and to select suitable yeast starter culture to cocoa flavor modulation. A total of 39 cocoa-derived yeast isolates were screened for their capacity to produce volatile aroma compounds in a cocoa pulp simulation medium. The seven highest aroma-producing yeasts were identified by ITS-rRNA gene sequencing as belonging to Pichia kudriavzevii, in spite of exhibiting different metabolic profiles. A computer-assisted analysis of rep-PCR genomic fingerprints of Pichia kudriavzevii strains clearly differentiated the upper aroma-forming yeast strains (G1 group; P. kudriavzevii LPB06 and P. kudriavzevii LPB07) from the other strains (G2 group). This demonstrates the potential of rep-PCR technique as a promising genotypic tool for rapid and reliable speciation of aromatic yeast strains. In the second stage of this study, two strains with superior aroma production, namely P. kudriavzevii LPB06 and P. kudriavzevii LPB07, were used in cocoa beans fermentation at laboratory scale. They were able to establish an accelerated fermentation process with efficient yeast growth, sugars consumption and ethanol formation compared to the spontaneous process. The resulting cocoa beans were analyzed by diverse chemical analysis methods, including SPME-GC/MS, FTIR spectroscopy and metal and colorimetric analysis. All together, the results indicated that inoculated fermentations generated cocoa beans with better color development and richer aroma composition, suggesting that cocoa-associated yeast diversity at strain level can be exploited for flavor modulation of cocoa beans. / Atualmente, o chocolate é um dos produtos mais importantes para a indústria de alimentos, sendo de interesse econômico em todo o mundo. A qualidade do cacau depende diretamente do processamento pós-colheita, sendo a fermentação da polpa um passo crucial para o desenvolvimento da qualidade do chocolate. O objetivo deste trabalho foi estudar a diversidade de leveduras aromáticas associadas à fermentação de cacau e selecionar uma cultura iniciadora com potencial para modular o flavor de chocolate. Um total de 39 leveduras foram isoladas e caracterizadas quanto à formação de compostos aromáticos. As sete melhores produtoras foram identificadas através do sequenciamento do gene ITS-rRNA como Pichia kudriavzevii, apesar de apresentarem diferentes perfis metabólicos. Análise de impressões digitais (fingerprints) dos isolados pela técnica de rep-PCR claramente distinguiu as cepas com maior produção de compostos aromáticos, demonstrando o potencial desta técnica como uma ferramenta para rápida e confiável seleção de leveduras. Na segunda etapa deste estudo, duas cepas com superior formação de aroma (P. kudriavzevii LPB06 e P. kudriavzevii LPB07) foram testadas como culturas iniciadoras para fermentações de cacau em escala laboratorial. Estas duas cepas foram capazes de estabelecer um acelerado processo fermentativo, com eficiente consumo de açúcares e formação de etanol, em comparação ao método natural. As amêndoas de cacau resultantes destes processos foram analisadas por diferentes métodos químicos, incluindo SPME-GC/MS, espectroscopia FTIR e análises de metal e calorimetria. Os resultados indicaram que as fermentações inoculadas desenvolveram amêndoas de cacau com melhor cor e composição de aroma, sugerindo que a diversidade de levedura em fermentações de cacau pode ser explorada para a modulação do flavor de chocolate.

The objective of this study was to evaluate the survival of non-O157:H7 STEC, Salmonella spp., and S. aureus in dry fermented sausages. Chorizo and Landjager sausages were inoculated with individual bacterial cocktails and stuffed into natural casings. Temperature, relative humidity, pH, and water activity were monitored through fermentation, drying, and storage. Bacterial counts were determined by serial dilution and plated in triplicates on selective media. Plates were incubated at 37°C for 24 hours and colony forming units per gram (CFU/g) were observed. Results of the first study validate that contaminated raw materials contribute to pathogen survival and background bacteria outcompeted the starter culture. The pH critical limit of < 5.3 was met but there was no pathogen inhibition. Results from the second study confirm that pH and water activity are not enough to eliminate pathogens when post processing interventions are not used. Critical pH (< 5.3) and water activity (< 0.85) limits were met, but pathogens still survived. In chorizo, non-O157:H7 was recovered through enrichments until the end of the study. In landjager, non-O157:H7 STEC and Salmonella were recovered through enrichments until the end of the study.The studies suggest that sausages produced without post processing interventions are a health risk to consumers.

Le manioc (Manihot esculenta Crantz) est une plante, dont les tubercules servent de nourriture de base pour près de 800 millions de personnes sous les tropiques. Malgré sont importance, ce tubercule présente deux inconvénients majeurs qui limitent leur utilisation en alimentation humaine : Une toxicité liée à la présence de composés cyanés, et une faible teneur en protéines. Dans l'optique de lever ces contraintes, plusieurs procédés de transformation ont étés mis au point par l'expérience des populations et des améliorations ont été apportées par la recherche. La plupart de ces procédés incluent une étape critique de fermentation spontanée. Cette étape présente quelques problèmes dus à sa dépendance vis à vis des microorganismes épiphytes. Ces problèmes sont notamment la présence de quantités résiduelles de composés cyanés non négligeables (100 à 170ppm) un temps de ramollissement très long (4 à 5 jours) et des produits dérivés de qualités nutritionnelles et hygiéniques douteuses. Dans l'optique d'améliorer ces procédés traditionnels de rouissage du manioc cyanogène, une centaine de microorganismes ont été isolés des cossettes de manioc séché, sur la base de leurs potentialités à produire la β-glucosidase, l'α-amylase, la pectine hydrolase et la polygalacturonase. Ces enzymes sont les plus impliqués dans les phénomènes biochimiques et physico-chimiques ayant lieu au cours du rouissage du manioc. Ils sont responsables de la dégradation des composés cyanés et du ramollissement des tubercules par dégradation des pectines qui constituent le squelette du tubercule. 60% des microorganismes isolés et identifiés ont été productrices d'α-amylases, 46% de β-glucosidase, et 36%de pectinases. Les capacités des différentes souches sélectionnées à produire ces principaux enzymes, ont ensuite été évaluées. Parmi ces microorganismes, deux se sont avérés particulièrement intéressantes : Une souche de bactérie lactique identifiée comme étant Lactobacillus plantarum avec une activité α-amylase de l'ordre de 17000±100UE/ml, et une activité ß-glucosidase de 2000±300µmol CN-/mn; Une moisissure identifiée comme étant Rhizopus oryzae à activité α-amylase de 20000±500UE/ml et activité pectine hydrolase de 2,3±0,2 µmol COO-/mn/mg. Ces deux souches ont été sélectionnées et utilisées comme ferments en culture mixte avec une biomasse initiale de 106ufc/g manioc frais de Lactobacillus plantarum et 103spores/g manioc frais de Rhizopus oryzae pour la fermentation des tubercules de manioc. Les résultats obtenus ont indiqué une acidification rapide avec un pH avoisinant 3,5±1 après 24 heures de rouissage, un ramollissement plus rapide (12±3mm/5s après 48 heures de rouissage). Mais le rouissage naturel s'est avéré meilleur du point de vue dégradation des composés cyanés. En effet la très forte acidification obtenue avec le ferment dès la 24eme heure, a provoqué un blocage du processus de dégradation des glucosides cyanogénétiques au niveau de la cyanohydrine, composé par ailleurs aussi toxique que l'acide cyanhydrique. Une étude de l'influence de quelques paramètres externes nous ont permis de noter que la température optimale de croissance de Lactobacillus plantarum était de 40±5°C pour un pH optimal de 6 alors que Rhizopus oryzae avait une température optimale de croissance à 30±7°C et un pH optimal de 5. Les essais de production de biomasses, indiquent que le meilleur milieu de multiplication des germes s'est avéré être le milieu CTM de Law et al., avec pour substrat de la farine de son de manioc mélangée au milieu nutritif de Meyer.<br />Dans l'optique de mettre à la disposition des populations ce ferment, des essais de conservation des souches par séchage ont indiqué que le fluide de protection indiqué pour avoir des taux de survies acceptables au terme du séchage était le glycérol, alors que le support le plus adapté a été l'amidon de manioc. On a ainsi obtenu plus de 75±5% de survivants après séchage sur lit convectif à une température de 35°C sous un débit d'air de 10 m3/h pour tous les deux germes. Ce ferment composé de Lactobacillus plantarum (106ufc/g) et Rhizopus oryzae (103spores/g), sur support amidon a induit contrairement aux microorganismes frais, une diminution effective du taux de glucosides totaux résiduels (5% en fin de rouissage) diminution corollaire à l'ajout du NaOH réalisé après la 24ème heure, afin de contourner l'effet néfaste du pH acide sur la dégradation de la cyanohydrine.

Induction motors are widely used in industrial processes. The malfunction of a motor may not only lead to high repair costs, but also cause immense financial losses due to unexpected process downtime. Since thermal overload is one of the major root causes of stator winding insulation failure, an accurate and reliable monitoring of the stator winding temperature is crucial to increase the mean time to catastrophic motor breakdown, and to reduce the extraordinary financial losses due to unexpected process downtime. To provide a reliable thermal protection for induction motors fed by motor control devices, a dc signal-injection method is proposed for in-service induction motors fed by soft-starter and variable-frequency drives. The stator winding temperature can be monitored based on the estimated stator winding resistance using the dc model of induction motors. In addition, a cooling capability monitoring technique is proposed to monitor the cooling capability of induction motors and to warn the user for proactive inspection and maintenance in the case of cooling capability deterioration. The proposed cooling capability monitoring technique, combined with the proposed stator winding temperature monitoring technique, can provide a complete thermal protection for in-service induction motors fed by motor control devices. Aside from online thermal protection during a motor's normal operation, the thermal protection of de-energized motors is also essential to prolong a motor's lifetime. Moisture condensation is one of the major causes to motor degradation especially in high-humidity environments. To prevent moisture condensation, a non-intrusive motor heating technique is proposed by injecting currents into the motor stator winding using soft-starters. A motor's temperature can be kept above the ambient temperature due to the heat dissipation, so that the moisture condensation can be avoided. To sum up, active stator winding temperature estimation techniques for induction motors under both operating and de-energization conditions are proposed in this dissertation for both thermal protection and optimizing the operation of a motor system. The importance of these proposed techniques lies in their non-intrusive nature: only the existing hardware in a motor control device is required for implementation; a motor's normal operation is not interrupted.

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.

O objetivo deste estudo foi avaliar a ocorrência de diarreia e suas consequências no metabolismo animal em bezerros consumindo concentrado inicial contendo coprodutos como polpa cítrica, melaço e xarope de glicose; ou bezerros suplementados com probiótico. Dois experimentos foram conduzidos para avaliar o efeito da substituição de milho por coprodutos. No primeiro experimento, 24 bezerros com idade média de 2 semanas, foram distribuídos em 3 tratamentos e receberam concentrado inicial contendo doses crescentes de polpa cítrica em substituição ao milho. No segundo experimento, 32 bezerros foram divididos em 4 tratamentos, recebendo concentrado inicial contendo xarope de glicose e doses crescentes de melaço em substituição ao milho. Em ambos os experimentos, os animais foram alojados em abrigos individuais, receberam 4 L de sucedâneo lácteo por dia, dividido em duas refeições e tiveram livre acesso à água e concentrado. Após o diagnóstico da ocorrência de diarreia, foram realizadas avaliações de escore fecal, escore clínico, além de medição dos parâmetros fisiológicos, nas seguintes 24, 48 e 72 horas. Foram colhidas amostras de sangue para realização de hemograma, análises bioquímicas, análises gasométricas e eletrolíticas. A adição de coprodutos no concentrado inicial não afetou (P>0,05) o escore fecal, as características das fezes e os sinais clínicos dos animais diarreicos. As análises plasmáticas bioquímicas (glicose, proteínas totais, albumina, ?-hidroxibutirato, nitrogênio ureico plasmático, lactato total, D- e L-lactato) apresentaram valores normais e não sofreram efeito negativo (P>0,05) em resposta da substituição de milho por coprodutos no concentrado. Não houve diferença entre os tratamentos (P>0,05) nas análises gasométricas e no eritrograma, com resultados indicando ausência ou baixo nível de acidose metabólica e desidratação nos animais. De acordo com o leucograma realizado, foi constatada leucocitose e neutrofilia na maioria dos casos, significando que a diarreia foi de origem infecciosa, descartando a possibilidade que o consumo de coprodutos no concentrado fosse a etiologia da diarreia. Um terceiro experimento foi realizado para avaliar o desempenho geral de bezerros suplementados com probíóticos contendo bactérias ruminais. Foram utilizados 20 bezerros divididos em 2 tratamentos (controle e fornecimento oral de 2 gramas de probiótico/dia), sendo os animais avaliados até a 10ª semana de vida. Os animais alojados em abrigos individuais, receberam 6 L de sucedâneo lácteo por dia, e tiveram livre acesso à água e concentrado. O desaleitamento foi realizado na 6ª semana de vida, de forma a causar uma situação de estresse nos animais. O consumo diário de concentrado, ganho de peso, desenvolvimento corporal e escore fecal foram avaliados. Nas semanas 2, 4, 6, 8 e 10 foram colhidas amostras de sangue para determinação de parâmetros bioquímicos e realização do hemograma. O fornecimento de probióticos via oral não afetou (P>0,05) o escore fecal, o desempenho dos animais (ganho de peso e consumo de concentrado). Como conclusão, a substituição de milho por polpa cítrica, melaço ou xarope de glicose no concentrado inicial não apresentou efeitos negativos relacionados à diarreia e não agravou os quadros de desidratação e acidose metabólica. O fornecimento de 2 gramas diários de probióticos de bactérias ruminais não resultou em melhorias no desempenho de bezerros desaleitados precocemente. / The objective of this study was to evaluate the occurrence of diarrhea and the consequences on animal metabolism of calves consuming starter feed containing coproducts such as citrus pulp, molasses and glucose syrup; or calves supplemented with direct-fed microbial (DFM). Two trials were performed to evaluate the effect of replacing corn by coproducts. In the first trial, 24 calves were divided into three treatments, and received starter feed containing increasing doses of citrus pulp replacing corn. In the second trial, 32 calves were divided into four treatments, and received starter feed containing glucose syrup and increasing doses of molasses replacing corn. In both experiments, animals were housed in individual hutches, received 4 L/d of milk replacer, divided into two meals and had free access to water and starter feed. After the diagnosis of the occurrence of diarrhea fecal score, clinical score, and the measurement of physiological parameters were evaluated during the following 24, 48 and 72 hours.Blood samples were taken for complete blood count (CBC), biochemical, electrolytes and gases analysis. The addition of coproducts in the starter feed had no effect (P>0.05) on fecal score, characteristics of the faeces and clinical signs of diarrheic animals. The plasma biochemical analysis (glucose, total protein, albumin, ?-hydroxybutyrate, urea nitrogen, lactate total D-and L-lactate) showed normal values and were negativelly affected (P>0.05) in response to the substitution of corn by coproducts in the stater feed for calves. No alterations (P>0.05) were noted in the erythrocyte and blood gases results, suggesting absence or low level of dehydration, and metabolic acidosis in animals. According to the white blood cell count (WBC), leukocytosis and neutrophilia were observed in most cases, suggesting infectious diarrhea and rejecting the possibility that the consumption of coproducts in the starter feed were the etiology of diarrhea cases. A third trial was performed to evaluate the overall performance of dairy calves supplemented with a probiotic containg ruminal bacterias. Twenty calves divided into two treatments (control and oral and daily supply of 2 grams of probiotic), animals were evaluated up to 10 weeks of age. Animals were housed in individual hutches, received 6 L/d of milk replacer, and had free access to water and starter feed. Weaning was done at the 6th week of age, as a meaning of causing stress in animals. Daily starter feed intake, weight gain, body development, and fecal score were evaluated. At 2nd, 4th, 6th, 8th and 10th weeks, blood samples were collected for biochemical analysis and WBC. The oral supply of probiotic had no effect (P>0.05) on fecal score or animal performance (weight gain and starter feed intake). In conclusion, the substitution of corn by citrus pulp, molasses or glucose syrup in the starter feed for dairy calves had no negative effects related to diarrhea or the agravation of dehydration and metabolic acidosis. The oral and daily supply of 2 grams of probiotics containg ruminal bacteria resulted in no improvements in performance of early-weaned dairy calves.

Made available in DSpace on 2014-06-11T19:27:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-07Bitstream added on 2014-06-13T18:56:23Z : No. of bitstreams: 1 saleh_mad_me_botfmvz.pdf: 563372 bytes, checksum: 36172400b9834291774f21af16f0a28a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / No presente trabalho é proposto um método para determinação de cálcio, magnésio, sódio e potássio em amostras de rações de leitões utilizando ultra-som no processo de extração dos analitos e posterior quantificação, respectivamente, por espectrometria de absorção atômica por chama (FAAS) e espectrometria de emissão atômica (AES). As condições de extração otimizadas foram: massa de amostra de 100 mg; granulometria da amostra < 60 mm; solução extratora HCl 0,10 mol L-1; tempo de sonificação de cinco ciclos de 10 s e potência de sonificação de 102 W. O método proposto foi aplicado em estudos de digestibilidade desses nutrientes em amostras de rações utilizadas na criação comercial de leitões e os resultados obtidos mostraram-se concordantes com os resultados provenientes da mineralização ácida / The aim of the present work brings a developed and an optimized method for determination of calcium, magnesium, sodium and potassium in piglets feed and feces by using ultrasound in the extraction process of nutrients and subsequent quantification by flame atomic absorption spectrometry (FAAS) and atomic emission spectrometry (AES). The optimum established conditions of extraction were: mass of sample: 100 mg, sample particle size: < 60 mm, extractor solution: HCl 0.10 mol L-1, sonication time: five cycles of 10 s and ultrasound power: 102 W. The proposed method was applied in studies of digestibility of those nutrients in different feed used in piglets diets and their results proved to be compatible with those obtained from mineralized samples by acid digestion

This study aimed to isolate and characterize probiotic strains from fermented milk and multiplies in the swine plasma medium for inoculation in Italian salamis, with the starter culture Staphylococcus xylosus isolated from artisanal salamis. Colonies count of the fermented milks was in the MRS (De Man Rogosa Sharpe Agar, Oxoid) medium by the technique of 'pour-plate'. The strains were isolated through the technical spread plate in selective medium, MRS. Individual strains were confirmed by Gram staining, catalase test and identified by kits Api 20 A and 50 CHL (Bio Merieux SA, Marcy L'Etoile, France). After, passed the tests of resistance to sodium chloride added to the MRS agar, in concentrations of 1%, 1.5%, 2%, 2.5% and 3% and resistance to nitrite and nitrate, which were conducted by the same procedure at concentrations of 80, 100, 120, 150 and 200 ppm. They also passed through of 0.3% bile and acid resistance tests, pH: 3.0, 2.5 and 2.0 of 3M HCl for 3 and 6 hours. In the second experiment, the isolate strain of Lactococcus lactis ssp lactis 2 passed through multiplication in fermented machine for use as a starter in probiotics dry fermented sausages. The probiotic strains were multiplied in plates with swine plasma medium plus agar and isolate starter Staphylococcus xylosus in BAIRD-PARKER plate. In the treatments were used as starters the S. xylosus and Lactococcus lactis, and as probiotic strains: Lactobacillus paracasei ssp paracasei 1 and Bifidobacterium spp 2. Control treatment was added with commercial starters, the Treatment 1: with isolate starters; Treatment 2: with isolate starters adding more probiotic strain a Lactobacillus paracasei ssp paracasei 1 and Treatment 3: starters more probiotic isolate strain Bifidobacterium spp 2. Were evaluated microbiological, physic-chemical and sensory aspects. Samples of fermented milks examined showed higher counts to 107CFU.g-1 and the strains were: Actinomyces israelli, 7 Actinomyces naeslundii, Lactobacillus acidophylus/jensenii, Bifidobacterium spp 2, Lactococcus lactis ssp lactis 2 e Lactobacillus paracasei ssp paracasei 1. The strains Bifidobacterium spp 2 and Lactobacillus paracasei ssp paracasei 1 were resistant to all concentrations of sodium chloride, nitrite and nitrate, and the pH of 3.0 for 3 hours and 6 hours. The L. paracasei ssp paracasei 1 showed lower counts to 106 UFC.mL-1 at pH 2.0, with 5.63 Log UFC.mL-1 in 3 hours of incubation and 3.79 Log UFC.mL-1 in 6 hours. The strain of Bifidobacterium spp 2 lost its probiotic viability after exposure of 6 hours in the pH of 2.0 and 2.5, showing reduction of 9.4 Log UFC.mL-1 to 3.67 and 4.18 Log UFC.mL-1, respectively. The strains analyzed showed resistance to bile salts and remained in a viable state after 4 hours of exposure to 0.3% of bile salts. The propagation in a culture medium made with swine plasma achieved levels of 5.52 Log CFU.mL-1 to 8.58 Log CFU.mL-1 and optical density of 0.14 to 0.882, in 27 hours of fermentation. All final physical and chemical parameters were up to standards with pHs and activities of water in accordance with the safety standards of the product. Sensory characteristics showed that the isolated strains notes were statistically equal and/or above the commercial strains and probiotics salamis had cells in a viable state for 30 days of storage. / Este trabalho teve como objetivo isolar e caracterizar cepas probióticas de leites fermentados comerciais e multiplica-lás em meio de cultura à base de plasma suíno para inoculação em salames tipo Italiano, juntamente com a cultura starter Staphylococcus xylosus isolada de salames artesanais. A contagem das colônias dos leites fermentados foi em meio MRS (De Man Rogosa Sharpe Agar, Oxoid) pela técnica de semeadura em profundidade. As cepas foram isoladas através da técnica spread-plate em meio seletivo, MRS. Cepas individuais foram confirmadas por coloração de Gram e prova da catalase, e identificadas pelos kits Api 20 A e 50 CHL (Bio Merieux SA, Marcy L Etoile, France). Após, foram realizados os testes de resistência ao cloreto de sódio adicionado ao ágar MRS, nas concentrações de 1%, 1,5%, 2 %, 2,5% e 3% e resistência ao nitrito e nitrato, que foram realizados pelo mesmo procedimento, nas concentrações de 80, 100, 120, 150 e 200 ppm. Realizou-se também os testes de resistência a bile 0,3% e a acidez, em pH: 3,0, 2,5 e 2,0 de HCl 3M durante 3 e 6 horas. No segundo experimento, a cepa de Lactococcus lactis ssp lactis 2 isolada foi multiplicada em fermentador para uso como starter nos salames. As cepas probióticas foram multiplicadas em placas com meio de plasma suíno acrescido de ágar e o starter isolado de Staphylococcus xylosus em placas de BAIRD-PARKER. Nos tratamentos foram usados como starters o S. xylosus e Lactococcus lactis, e como cepas probióticas: Lactobacillus paracasei ssp paracasei 1 e Bifidobacterium spp 2. O tratamento Controle foi adicionado de starters comerciais; o Tratamento 1: com starters isolados; Tratamento 2: com starters isolados mais adição da cepa probiótica Lactobacillus paracasei ssp paracasei 1 e Tratamento 3: starters isolados mais cepa probiótica Bifidobacterium spp 2. Foram avaliados os aspectos microbiológicos, físico-químicos e sensoriais. As amostras de leites fermentados analisadas apresentaram contagens superiores a 107 UFC.g-1 e as cepas encontradas foram: Actinomyces israelli, Actinomyces naeslundii, Lactobacillus acidophylus/jensenii, Bifidobacterium spp 2, Lactococcus lactis ssp lactis 2 e Lactobacillus paracasei ssp paracasei 1. As cepas Bifidobacterium spp 2 e Lactobacillus paracasei ssp paracasei 1 foram resistentes a todas as concentrações de cloreto de sódio, nitrito e nitrato, e ao pH de 3,0 durante 3 horas e 6 horas. O L. paracasei ssp paracasei 1 apresentou contagens inferiores a 106 UFC.mL-1 em pH 2,0, com 5,63 Log UFC.mL-1 em 3 horas de incubação e 3,79 Log UFC.mL-1 em 6 horas. A cepa de Bifidobacterium spp 2 perdeu sua viabilidade probiótica após a exposição de 6 horas nos pH de 2,0 e 2,5, apresentando redução de 9,4 Log UFC.mL-1 para 3,67 e 4,18 Log UFC.mL-1, respectivamente. As cepas analisadas apresentaram resistência aos sais biliares, permanecendo em estado viável após 4 horas de exposição à 0,3% de sais biliares. A multiplicação em meio de cultura com plasma suíno alcançou níveis de 5,52 Log UFC.mL-1 a 8,58 Log UFC.mL-1 e densidade óptica de 0,14 a 0,882, em 27 horas de fermentação. Os parâmetros físico-químicos finais estavam todos de acordo com os padrões de pH e atividade de água, conforme as normas de segurança do produto. Com relação às características sensoriais, as cepas isoladas apresentaram notas estatisticamente iguais e/ou superiores às comerciais e os salames probióticos apresentaram células em estado viável durante 30 dias de armazenamento.

Made available in DSpace on 2015-03-26T13:51:43Z (GMT). No. of bitstreams: 1 texto completo.pdf: 310696 bytes, checksum: e605f10bbbe4b744866d2e079c4a4535 (MD5) Previous issue date: 2003-08-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Alcohol dehydrogenase, ADH, activity was investigated in Streptococcus thermophilus NCDO 1968, Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, Lactobacillus acidophilus ATCC 4356, and the probiotic strain Lactobacillus delbrueckii UFV H2b20, after growth at 37°C for 12 hours, and storage at 4°C for 21 days. L. delbrueckii subsp. bulgaricus and L. acidophilus presented positive results for ADH activity in Alcohol Indicator Medium, while L. delbrueckii UFV H2b20 presented negative results after 21 days. This method was not discriminatory for S. thermophilus. ADH activity was also measured by the oxidation of NAD(P)H and expressed as &#956;mol of NAD(P)H oxydized per min per mg protein. The average activity in L. acidophilus was 1,06x10-7 µmol.min-1.mg-1. The activity increased to 9,17x10-7µmol.min-1.mg-1 after cells were kept in MRS medium at 4°C, for 5 days. Increases in ADH activity were also detected in cell free extracts of L. delbrueckii subsp. bulgaricus and S. thermophilus. The three strains displayed low ADH activity in MRS broth after 21 days at 4°C. The headspace analysis by Gas Chromatography/ Mass Spectroscopy revealed acetaldehyde production by L. delbrueckii subsp. bulgaricus, L. acidophilus and S. thermophilus. The latter produced acetaldehyde only after storage at 4°C. Ethanol production was not detected. Despite some ADH activity was detected in liquid medium, the combined results do not support completely the hypothesis that ADH activity would be induced itself after storage at low temperatures. Other studies are still needed. / A atividade de etanol desidrogenase, ADH, foi investigada em espécies de bactérias usadas na fabricação do iogurte, Streptococcus thermophilus NCDO 1968, Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, Lactobacillus acidophilus ATCC 4356, e da linhagem probiótica Lactobacillus delbrueckii UFV H2b20, após crescimento a 37°C por 12 horas e estocagem a 4°C por 21 dias. Em meio indicador de álcool, L. delbrueckii subsp. bulgaricus e L. acidophilus apresentaram resultado positivo para atividade de ADH, enquanto L. delbrueckii UFV H2b20, resultado negativo. A detecção da atividade, nesse meio, não foi discriminatória para S. thermophilus. A atividade de ADH, em meio líquido, foi determinada pela medida da oxidação de NAD(P)H e expressa em µmoles de NAD(P)H oxidado por minuto por mg de proteína. A atividade em L. acidophilus foi, em média de 1,06x10-7 µmol.min-1.mg-1, aumentando para 9,17x10- 7µmol.min-1.mg-1, após a estocagem das células em meio MRS, por 5 dias, a 4°C. Também houve aumento de atividade de ADH nos extratos livres de células de L. delbrueckii subsp. bulgaricus e S. thermophilus. Os resultados em meio líquido mostraram que as três culturas apresentaram baixa atividade de ADH durante a estocagem por 21 dias, a 4°C. A metodologia baseada em GC/MS, por headspace, permitiu detectar acetaldeído produzido por L. delbrueckii subsp. bulgaricus, L. acidophilus e S. thermophilus, o qual produziu acetaldeído somente após a estocagem a 4°C. Entretanto, a atividade de ADH não foi observada após a incubação para crescimento a 37°C, por 12 h, nem após a estocagem a 4°C por 21 dias, não sendo observada a produção de etanol, nas condições estudadas. Estes resultados não confirmam a hipótese de uma ADH que se manifestaria após longos períodos em baixas temperaturas, embora baixa atividade da enzima tenha sido detectada em meio líquido. Outros estudos são necessários.

Lactococcus lactis est une bactérie lactique couramment utilisée dans l’industrie laitière. Elle assure en tant que ferment des fonctions technologiques multiples qui impactent la flaveur et la texture finale des produits. Cependant, la diversité fonctionnelle constatée au sein des levains de cette espèce impose de mettre en place un processus de sélections des souches. Ces travaux ont pour objectif d’identifier les déterminants de la spécificité organoleptique dite « crème » de la souche industrielle L. lactis ssp. lactis. Dans un premier temps, un diagnostic macro-cinétique de l’activité de ce ferment a été réalisé en lait pour évaluer l’impact sur la physiologie cellulaire (l’acidification, le stress oxydatif, et la thermisation différentielle du lait). Définir la singularité de notre souche d’intérêt nécessite d’évaluer la diversité fonctionnelle de levains laitiers de L. lactis ssp. lactis. Cette démarche s’est appuyée sur une approche de biologie intégrative du génotype au phénotype. Pour réduire le temps d’expérimentation, une sélection des variables discriminantes à été conduite. L’un de ses composés clef de cette typicité a fait l’objet d’une étude approfondie afin de tester les différents paramètres pouvant influencer sa synthèse. La dernière partie, plus applicative, s’est articulée sur la modélisation de la signature en fonction de quatre facteurs industriels (matière grasse, sèche, oxygénation et température) par utilisation de la méthodologie des surfaces de réponse. / The lactic acid bacterium Lactococcus lactis is widely used in dairy industry. Used as a starter, L. lactis subsp. lactis is in charge of many functional characteristics which determine the final texture and flavour of fermented products. However, the phenotypic diversity observed within the species requires strain selection development. This PhD aims at identifying the determinants of the creamy sensory specificity of the industrial strain L. lactis subsp. lactis. Firstly, a diagnosis of macro-kinetic activity of ND5F was carried out to assess the impact on cellular physiology of three environmental parameters (acidification, oxidative stress, and milk heat treatments). In order to assess the uniqueness of our strain of interest, a system biology approach from genotype to phenotype was implemented to study the functional diversity of L. lactis subsp. lactis starters. A group of nine strains representative of the genetic diversity of this subpopulation was made up. 82 variables selected as important dairy features; including physiological descriptors, production of metabolites and volatile organic compounds (VOCs); were monitored. This study demonstrated the phenotypic uniqueness of each of these genetically closely related strains, allowing strain discrimination in dairy products. To reduce the time-consuming experimentation, we developed a method of variable selection. Twenty VOCs were therefore identified as major phenotypic determinants of this diversity. They define four robust stain clusters depending on their metabolic orientations: lipolysis, proteolysis, glycolysis and unexpressed. Inclusion of genotypic diversity in addition to phenotypic characters led to adjust the functional classification by integrating strain unexpressed genotypic potentialities. Comparative proteomics analysis in milk identified protein markers of this specificity. After selecting a subset of forty-six proteins the three levels (genotype, phenotype and proteomics) involved in this diversity expression were integrated to provide a predictive classification of starter diversity.The Integration of our strain to this model enabled the identification of fourteen phenotypic determinants and seven proteins to explain ND5F specificity. The pentane-2,3-dione, a key aromatic compounds of this typicity was subjected to a comprehensive analysis to point out the different factors that may influence its synthesis. On a more applied aspect, the last part was focused on the signature modelling based on four industrial factors (milk fat and total solid level, oxygen and temperature) using the response surface methodology. It enabled to enhance the “creamy” organoleptic characteristics of the fermented products.