Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 129-132).

No description available.

Thèse de doctorat : Génétique Moléculaire : Nancy 1 : 2008. / Titre provenant de l'écran-titre.

The biochemical activity of Streptococcus thermophilus and Lactobacillus bulgaricus in a 1:1 ratio (Chr. Hansen's Lab - CH-III) were studied at 43 C in goat and cow milk during the manufacture and storage of yogurt. Determination of pH, titratable acidity, lactose content, proteolytic activity, and enumeration of the starters were performed on samples taken at hourly intervals until the yogurt became set, and after 8, 16, 24 hours, 11 and 22 days of storage at 4 C. In goat milk the number of starter culture organisms showed higher values than those in cow milk. Fermentation was considered to be finished when the pH decreased to 4.7 and 0.7% of lactic acid was produced. Those values were reached after 3 and 4 hours for goat and cow milk respectively. The values for pH in both milks were stable at 4.7 during storage at 4 C. Goat milk and goat milk yogurt had higher levels of free amino acids (12.65 mg/dl and 24.39 mg/dl respectively) than cow milk (10.31 mg/dl) or cow milk yogurt (20.20 mg/dl). During storage at 4 C free amino acids in goat milk decreased by 20%, in cow milk they increased by 70% from values found in fresh yogurt. The proteinase activity in goat milk during elaboration of yogurt was from 2 to 3 hours after incubation, was then stable until 24 hours of storage at 4 C and then decreased. No change in the proteinase activity in cow milk yogurt was seen until 4 hours of incubation for experiments 1 and 2 and 3 hours in experiment 3. During the storage at 4 C, proteinase activity in cow milk yogurt was stable. Polyacrylamide gel electrophoresis of caseins failed to reveal marked changes during the manufacture of yogurt and storage after 22 days at 4 C. However, a scanning gel densitometer showed that the area corresponding to alpha-casein decreased by 22% and for beta-casein 13.32% during the elaboration of goat milk yogurt. After 22 days of storage at 4 C, the alpha-casein fraction decreased an additional 14%, but no change was observed in beta-casein. The area corresponding to alpha- and beta-caseins decreased by 7.16 and 14.48% respectively during yogurt manufacture and an additional 6.74 and 8% during storage of cow milk yogurt. The overall results found in this study suggest that the metabolic activity of S. thermophilus and L. bulgaricus is greater in goat milk than in cow milk during elaboration and storage of yogurt.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1944. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-10-16Bitstream added on 2014-06-13T19:40:53Z : No. of bitstreams: 1 lopes_gaz_dr_arafcf.pdf: 431628 bytes, checksum: 1b5a3a4e245823f5eae44d8181c8c704 (MD5) / Universidade Estadual Paulista (UNESP) / A utilização do grão de amendoim (Arachis hypogaea) vem sendo pesquisada com o objetivo de obter alimentos proteicos e com boas características sensoriais, além de baixo custo. O objetivo do trabalho foi elaborar e caracterizar extrato aquoso à base de amendoim e extrato fermentado com Streptococcus thermophilus e Lactobacillus delbrueckii ssp bulgaricus, além da elaboração de um produto tipo hambúrguer com a farinha do resíduo da extração. Os grãos foram aquecidos em solução de bicarbonato de sódio a 0,5% (1:4, p/v) até ebulição, com posterior drenagem, lavagem, desintegração com água aquecida a 97º C nas proporções de 1:5; 1:6; 1:7 e 1:8 (p/v), seguido de filtração. O produto fermentado foi elaborado com adição de 2% de lactose, 10% de sacarose, 0,3% de gelatina e 2% do fermento lático ao extrato aquoso. O produto tipo hambúrguer foi elaborado com adição de 10, 20 e 30% da farinha do resíduo (1:5) nas formulações. As diluições (p≤0,05) dos componentes dos extratos aquosos de amendoim foram de 36% para sólidos totais, 29% para proteína e 43% para lipídeos. O abaixamento do pH foi mais lento para a formulação com extrato mais concentrado (p≤0,05) e a porcentagem inicial de ácido lático (0,12%) aumentou para 0,37 a 0,39% após 6 horas de incubação. O valor de ºBrix variou de 9,83 a 7,42. A consistência foi o único atributo sensorial significativamente afetado pelas proporções grão:água. Os resultados relativos às análises do produto tipo hambúrguer indicaram que à medida que houve aumento da farinha do resíduo de amendoim (20 e 30%) obtiveram-se maiores rendimentos de cocção e menores capacidades de retenção de água para estes produtos. A maior luminosidade foi obtida para o produto com 30% de farinha de resíduo, e a intensidade de vermelho (a*) diminuiu com o aumento da... / The use of kernel peanut (Arachis hypogaea) has been researched in order to obtain protein foods with good sensory characteristics, and low cost. The objective of this study was to prepare and characterize aqueous extract made with peanut and fermented extract with Streptococcus thermophilus and Lactobacillus delbrueckii ssp bulgaricus, besides the development of a product type beef hamburger with the peanut residue flour of this extraction. The kernels were heated in a solution of sodium bicarbonate, 0.5% (1:4 w / v) until boiling with subsequent draining, washing, disintegration with water heated to 97 ° C in the ratios of 1:5, 1:6 ; 1:7 and 1:8 (w / v), followed by filtration. The fermented product was produced with addition of 2% lactose, 10% sucrose, 0.3% gelatin and 2% lactic ferment to the aqueous extract. The product type beef hamburger was prepared by adding 10, 20 and 30% of the the peanut residue flour (1:5) in the formulations. Dilutions (p ≤ 0.05) of the components of the extracts were 36% for total solids, 29% protein and 43% lipids. Lowering of pH was slower for the formulation with more concentrated extract (p <0.05) and the initial percentage of 0.12% lactic acid increased to 0.37 until 0.39% after 6 hours of incubation. The Brix value ranged from 9.83 to 7.42. The consistency was the only sensory attribute significantly affected by proportion grain: water. The results for the product type beef hamburger analyzes indicated that as there was an increase in peanut residue flour (20 to 30%) there were also higher yields of cooking and lower water retention capacity for these products. The highest brightness was obtained for the product with 30% the peanut residue flour, and redness (a *) decreased with increase of the percentage of residue. Microbiological analyzes met the minimum quality requirements. The sensory... (Complete abstract click electronic access below)

The technology of modern fermented milk production is not complicated and relies largely on the characteristics of the microorganisms used in its manufacture. Biochemical substances excreted by the starter cultures contribute to the chemical, physical and organoleptic properties of cultured milks. Chemical and organoleptic properties of yoghurt starter cultures have been widely studied over several decades. Conversely the biosynthetic processes and genetic control of the production of viscous extracellular material (slime) by selected thermophillic streptococci is still insufficiently understood. This study attempted to elucidate physiological aspects and the genetic control of slime production. An attempt to chemically induce ropiness was also preformed. Twenty strains of Gram positive, thermo-tolerant, milk dotting, catalase negative cocci were collected from a variety of sources. All strains were identified as Streptococcus thermophilus. Four of the isolates were identified as capable of producing an extracellular, ‘ropy’ capsular material. A negative staining method for highlighting capsular material under light microscopy was described. Ropy isolates displayed thick capsular zones of between 6-8 μm. The isolates graded as non-ropy produced only small capsular zones (less than 2 μm); two variants displayed no capsular material. Instability of the ropy phenotype during subculture and prolonged storage was described for all four ropy isolates at varied temperatures. Instability during transfer was reported as moderate with a loss of no more than 45% of ropy colonies after 15 subcultures at 48°C A significant increase in instability, during transfer, associated with an increase in incubation temperature (37-48°C) was also reported. Prolonged storage of ropy variants over ten days resulted in a drop in the number of ropy colonies. The loss was minimal when cultures were stored at 8°C, but excessive (approaching 100%) at 37°C This suggested the presence of capsular degradative substances. Analysis of the plasmid profiles of 20 strains identified only two strains harboured plasmid DNA. All plasmids were small, less than 23kilobases, and each strain possessed a single plasmid species. Only one ropy strain contained plasmid DNA that was shown, with the aid of curing experiments, not to be linked to production of the ropy phenotype. The amino acid analogue p-fluoro-DL-phenylalanine was unsuccessful in generating ropy colonies from non-ropy variants of Streptococcus thermophilus at low concentrations. Some technological considerations for the use of ropy variants of Streptococcus thermophilus in yoghurt starter cultures were made.

The present investigation was undertaken to characterize a number of strains of Lactobacillus bulgaricus and Streptococcus thermophilus intended for use by a commercial starter supply company. Thorough characterization of each culture was required in order to combine compatible strains so that their usefulness in Mozzarella cheese manufacture would be maximized. In this regard, cocci were assayed for formate and carbon dioxide production, rods for proteolysis, and both types for salt and phosphate tolerance as well as rate of acid production. In addition, certain combinations of cocci and rods were assayed as mixtures for these characteristics. Analyses of the various strains of lactobacilli and S. thermophilus were performed. Proteolysis, as determined by the Church method, for the rods (L. bulgaricus , L. helveticus and L. lactis ) varied from as low as 11.3 to as high as 34.7 mM when incubated for six hours. Proteolysis analyses for S. thermophilus also revealed a wide range of values from a low of 18.5 to a high of 46.4 mM. However, when strains were incubated for 16 hours, rods were shown to be nearly twice as proteolytic as cocci. When mixed cultures were tested for proteolysis, results were dependent on strain synergism. Values ranged from a low of 5.1 mM to 70.5 mM in mixed cultures. Various strains of S. thermophilus and mixed cultures were assayed for formate production. The S. thermophilus strain values were from a low of 4.2 to as high as 20.3 mg/L. Formate production in mixed cultures varied from traces of formate in one culture to quantities two and a half times that produced by the single S. thermophilus strains tested. Carbon dioxide production for the rods (L. bulgaricus , L. helveticus , and L. lactis ) varied from as low as 0 μl to as high as 376 μl when incubated for six hours at 44 °C. Carbon dioxide production for S. thermophilus ranged from 5 μl to 1259 μl. Also, S. thermophilus strains produced significantly more carbon dioxide than rod cultures, with only three exceptions. All mixtures were weak producers of carbon dioxide. Nine of 19 L. bulgaricus strains were stimulated by 0.1% phosphate ion and one strain showed stimulation at 0.3% phosphate ion. Thirteen of 19 strains were severely inhibited by 0.5% phosphate. Three of 10 L. helveticus strains were stimulated by 0.1% phosphate and another three strains were unaffected. All strains were inhibited by 0.5% phosphate. Two L. lactis strains showed stimulation at 0.1% phosphate, but inhibition at 0.3% and 0.5%. Acid production by strains of S. thermophilus was inhibited in 11 of 13 cases at 0.1% phosphate. The two strains not inhibited were slightly stimulated by 0.1% and 0.3% phosphate and unaffected by 0.5% phosphate. The mixed cultures of L. bulgaricus CR 14/ S. thermophilus 2 and L. bulgaricus Ql S. thermophilus 2 were not inhibited by 0.1% phosphate, but inhibition occurred at higher concentrations. Mixed cultures of L. bulgaricus C, E/ S. thermophilus 7, 12 and L. bulgaricus C, G/ S. thermophilus 4, 12 were stimulated by all three concentrations of phosphate salts tested. Sodium chloride produced toxic effects on the rods at concentrations ranging from 2.5% to 3.0%, and acid production was stimulated 7 of 32 strains by low salt concentrations(0.5%). In general, cocci were more sensitive to NaCl, with 6 of 13 strains showing sensitivity at 0.5%. Sensitivity to salt was a more gradual effect in the cocci as revealed by a gradual reduction in rate of acid production as NaCl concentrations increased. Mixed cultures were more tolerant to NaCl with no inhibition occurring at concentrations of 1.0%. Culture L. bulgaricus C, GIS. thermophilus 4, 7 were stimulated at concentrations through 1.5%. The synergistic properties of the mixed strains increased NaCl tolerance. / Graduation date: 1993

Thèse doctorat : Génétique moléculaire : Nancy 1 : 2005. / Titre provenant de l'écran-titre.

Thèse doctorat : Génétique moléculaire : Nancy 1 : 2005. / Titre provenant de l'écran-titre.