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Optimization of the rheological properties of probiotic yoghurts supplemented with milk proteins

MARAFON, Ana Paula; SUMI, Adriana; ALCANTARA, Maria Regina; TAMIME, Adnan Y.; OLIVEIRA, Marice Nogueira de
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.41%
This study aimed to optimize the rheological properties of probiotic yoghurts supplemented with skimmed milk powder (SMP) whey protein concentrate (WPC) and sodium caseinate (Na-Cn) by using an experimental design type simplex-centroid for mixture modeling It Included seven batches/trials three were supplemented with each type of the dairy protein used three corresponding to the binary mixtures and one to the ternary one in order to increase protein concentration in 1 g 100 g(-1) of final product A control experiment was prepared without supplementing the milk base Processed milk bases were fermented at 42 C until pH 4 5 by using a starter culture blend that consisted of Streptococcus thermophilus Lactobacillus delbrueckii subsp bulgaricus and Bifidobacterium (Humans subsp lactis The kinetics of acidification was followed during the fermentation period as well the physico-chemical analyses enumeration of viable bacteria and theological characteristics of the yoghurts Models were adjusted to the results (kinetic responses counts of viable bacteria and theological parameters) through three regression models (linear quadratic and cubic special) applied to mixtures The results showed that the addition of milk proteins affected slightly acidification profile and counts of S thermophilus and B animal`s subsp lactis but it was significant for L delbrueckii subsp bulgaricus Partially-replacing SMP (45 g/100 g) with WPC or Na-Cn simultaneously enhanced the theological properties of probiotic yoghurts taking into account the kinetics of acidification and enumeration of viable bacteria (C) 2010 Elsevier Ltd All rights reserved; FAPESP[2007/03588-8]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq

Modelagem e otimização de propriedades nutricionais e sensoriais de misturas protéicas através da metodologia estatística de superfície de resposta; Protein mixtures and their nutritional properties optimized by response surface methodology

Castro, Inar Alves de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 16/12/1999 PT
Relevância na Pesquisa
36.18%
Gelatina Hidrolisada (GH), Glúten de Trigo (GT) e Isolado Protéico de Soja (IPS) foram misturados em diferentes proporções com o objetivo de substituir proteínas lácteas em uma formulação alimentícia utilizada em programas institucionais de alimentação escolar, buscando-se uma redução de custos sem alterações significativas das propriedades nutricionais e sensoriais do produto final. A qualidade nutricional das misturas foi avaliada de acordo com os métodos "Escore Químico corrigido pela Digestibilidade PDCAAS" e "Razão de Eficiência Protéica - NPR". As misturas, aplicadas àformulação de uma bebida láctea, foram avaliadas sensorialmente através do método de "Diferença Escalar do Controle". Os resultados obtidos experimentalmente pelo delineamento simplex-centróide foram utilizados para modelar equações canônicas de Scheffé que pudessem descrever o efeito da proporção de cada componente na qualidade final. Todos os resultados foram correlacionados através de análise multivariada e representados na forma de Análise de Componente Principal (ACP). Uma "solução de compromisso" contendo 25% de GH, 15% GT e 60% de IPS foi selecionada na otimização conjunta das respostas nutricional, sensorial e econômica...

Avaliação de co-produtos na alimentação de vacas leiteiras mantidas em pastagens tropicais durante a estação chuvosa e alimentadas no cocho durante a estação seca do ano; Evaluation of byproducts inclusion on concentrate supplements for dairy cows grazing tropical pastures during rainy season and confined during dry season

Martinez, Junio Cesar
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/08/2008 PT
Relevância na Pesquisa
26.55%
O presente estudo teve por objetivo avaliar o uso de co-produtos na composição de concentrados fornecidos para vacas em lactação em pastagens de capim elefantes durante a estação chuvosa e alimentadas no cocho com cana-de-açúcar durante a estação seca. Todos os trabalhos foram conduzidos no Departamento de Zootecnia da ESALQ/USP, Piracicaba - SP. O primeiro experimento estudou a inclusão de 0, 14 e 34% de caroço de algodão na dieta de 16 vacas Holandesas alimentadas no cocho durante a estação seca e tendo cana-de-açúcar como base (62,7% da MS), em delineamento de QL 4x4 com quatro repetições. As análises estatísticas foram realizadas utilizando-se o procedimento GLM do SAS. Os tratamentos afetaram a produção e composição do leite, consumo de matéria seca e consumo de lipídios, mas não afetaram o peso vivo, condição corporal e parâmetros sanguíneos. Portanto, o caroço de algodão pode ser utilizado em dietas com cana-de-açúcar quando incluído em até 17% da MS total. O segundo experimento substituiu o milho moído fino em até 75% por farelo de glúten de milho no concentrado oferecido para vacas mantidas em pastagens tropicais durante a estação chuvosa. A pastagem foi adubada com 80 kg de N/ha para cada ciclo de pastejo que teve intervalo de desfolha de 23 dias. O delineamento estatístico adotado foi em Quadrado Latino 4 x 4 com quatro repetições das os dados de desempenho e comportamento ingestivo. O estudo avaliando metabolismo ruminal foi realizado com somente um Quadrado Latino. As análises estatísticas foram realizadas através dos procedimentos GLM e MANOVA do SAS (2002). Utilizou-se 16 animais da raça Holandesa com 485 kg de PV e 141 dias de lactação. Os tratamentos não afetaram a produção e a composição do leite...

Otimização das propriedades reológicas e sensoriais de iogurtes probióticos enriquecidos com proteínas lácteas; Optimization of the rheological properties of probiotic yoghurts supplemented with milk proteins

Marafon, Ana Paula
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 21/05/2010 PT
Relevância na Pesquisa
26.39%
Este estudo teve como objetivo otimizar as propriedades reológicas dos iogurtes probióticos suplementados com leite em pó desnatado (SMP), concentrado proteico de soro (WPC) e caseinato de sódio (Na-Cn), usando desenho experimental tipo simplex centroide, para modelagem de misturas. O estudo das interações entre os ingredientes (proteína concentrada de soro, caseinato de sódio e leite em pó) incluiu sete experimentos sendo três com os ingredientes puros, dois correspondentes a misturas binárias e um para a uma mistura ternária. Em paralelo aos sete experimentos delineados, foi realizado ensaio controle com leite não suplementado. Os leites foram fermentados a 42 °C até pH 4,5 empregando-se as culturas Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus e Bifidus lactis. A cinética de acidificação foi determinada bem como as análises físico-químicas, contagem de bactérias viáveis e características reológicas dos iogurtes. Modelos foram ajustados para os resultados (respostas cinética, contagem de bactérias viáveis e parâmetros reológicos) através de três métodos de regressão (linear, quadrático e cúbico especial) e aplicados às misturas. Os resultados deste estudo mostraram que a fortificação da base de leite com proteína concentrada de soro...

Mozzarella de búfala: avaliação da reação em cadeia pela polimerase (PCR) para detectar fraude devido à adição de leite de vaca ao de búfala; Buffalo mozzarella: assessment by polymerase chain reaction (PCR) to detect fraud due to the addition of cow milk to buffalo

Souza, Gisele Oliveira de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 06/12/2010 PT
Relevância na Pesquisa
36.29%
Mozzarella de búfala é um queijo de fácil fabricação e que tem grande aceitabilidade no mercado. Esses fatos, associados ao melhor rendimento de fabricação e maior valor agregado, quando comparado ao similar feito com leite de vaca, têm estimulado a fraudação. Embora a PCR já seja uma técnica reconhecida para garantir a autenticidade da mozzarella de búfala em outros países, é necessária sua validação para as condições do rebanho nacional. O presente trabalho teve como objetivo avaliar a PCR para a detecção de adulteração de queijo tipo mussarela de búfala no Brasil, em condições experimentais. Utilizou-se dois primer, já descritos na literatura, para detecção do gene citocromo b (cytb) de bovino e de bubalino. Esses primers foram testados em sangue das raças Nelore e Holandês (representantes, respectivamente, das espécies Bos indicus e Bos taurus), e em sangue da raça Mediterrânea (Bubalus bubalis). Também foram testados em leite e na mozzarella, tanto nos produtos puros como em misturas. Os primers reconheceram especificamente o DNA bovino e bubalino tanto no sangue quanto no leite e mozzarella. A técnica foi mais sensível para detectar a fraude na mozzarella que no leite. Na mozzarella foi possível detectar a presença de 0...

Avaliação do perfil de acidificação e viabilidade de bactérias probióticas em misturas leite-soro para elaboração de bebidas lácteas utilizando soro de queijo Minas frescal; Profile evaluation acidification and viability of probiotic bacteria in milk-whey mixtures for beverage production using whey Minas frescal cheese

Almeida, Keila Emilio de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 20/12/2007 PT
Relevância na Pesquisa
26.52%
A tecnologia de fabricação de bebidas lácteas envolve a mistura de leite e soro, podendo ser fermentada por bactérias do iogurte ou probióticas e adicionada de polpa de fruta e outros aditivos permitidos. O produto final deve conter bactérias lácticas viáveis em número adequado. Os objetivos deste trabalho foram desenvolver bebidas lácteas probióticas a partir das misturas leite-soro e estudar sua vida-de-prateleira. O efeito da composição da cultura probiótica (Lactobacillus delbrueckii subsp. bulgaricus, L. acidophilus, L. rhamnosus e Bifidobacterium animalis subsp. lactis em co-cultura com Streptococcus salivarius subsp. thermophilus) e o efeito do pH final da fermentação na cinética de acidificação, pós-acidificação e contagem de bactérias probióticas foram estudados em soro de queijo Minas frescal e em diferentes misturas leite-soro. Bebidas lácteas probióticas foram desenvolvidas a partir das diferentes misturas leite-soro e a vida-de-prateleira foi determinada ao longo de 28 dias de armazenamento do produto a 4°C. As características dos produtos foram seguidas pelas determinações físico-químicas, microbiológicas e sensoriais. O soro apresentou efeito positivo sobre a velocidade máxima das co-culturas estudadas...

Propriedades macro- e microscopicas de geis de proteinas do leite e k-carragena; Macro- and microscopic properties of milk proteins and k-carrageenan gels

Katiuchia Pereira Takeuchi
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 27/02/2008 PT
Relevância na Pesquisa
36.13%
A avaliação do processo de gelificação ácida de caseinato de sódio (CS) induzida por glucona-d-lactona (GDL) foi realizada em diferentes taxas e com ampla faixa de concentração de proteína (2-6% p/p). A cinética de acidificação e gelificação foi avaliada desde o pH 6,7 até o ponto isoelétrico das caseínas através da medida de pH e de propriedades mecânicas obtidas em compressão uniaxial (tensão e deformação na ruptura). A formação da rede do gel foi mais influenciada pelas interações eletrostáticas do que pelas diferentes taxas de acidificação, principalmente em pH próximo ao pI das caseínas. Além disso, interações hidrofóbicas e ligações de hidrogênio também estiveram envolvidas na estabilização da estrutura da rede, promovendo géis mais fortes. Também foi avaliado o processo de gelificação de proteínas do leite em pH 6,7 em sistemas contendo carragena. Neste caso, a ?-carragena foi adicionada em concentração de 0,3 a 0,8% (p/p) em misturas contendo caseinato de sódio (2 a 8% p/p), isolado protéico de soro (0,5 a 7% p/p) ou sacarose (5 a 30% p/p). Estes sistemas foram estudados a partir de ensaios reológicos em cisalhamento oscilatório, propriedades mecânicas e microestrutura. A temperatura de início da gelificação ou do desenvolvimento de estrutura (Ts) aumentou com a concentração de carragena em sistemas puros...

Effects of grass silage and soybean meal supplementation on milk production and milk fatty acid profiles of grazing dairy cows

Rego, Oldemiro Aguiar do; Regalo, S. M. M.; Rosa, Henrique José Duarte; Alves, Susana Paula A.; Borba, Alfredo Emílio Silveira de; Bessa, Rui José B.; Cabrita, Ana R. J.; Fonseca, A. J. M.
Fonte: American Dairy Science Association Publicador: American Dairy Science Association
Tipo: Artigo de Revista Científica
Publicado em /07/2008 ENG
Relevância na Pesquisa
36.33%
Copyright © American Dairy Science Association, 2008.; The effects of supplementation with grass silage and replacement of some corn in the concentrate with soybean meal (SBM) on milk production, and milk fatty acid (FA) profiles were evaluated in a replicated 4 × 4 Latin square study using 16 dairy cows grazing pasture composed of ryegrass, Kentucky bluegrass, and white clover. Each experimental period lasted for 3 wk. The 4 dietary treatments were PC, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn-based concentrate mixture (96% corn; C); PCSB, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn- and SBM-based concentrate mixture (78% corn and 18% SBM; CSB); SC, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of C concentrate; and SCSB, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of CSB concentrate. The concentrate mixtures were offered twice each day in the milking parlor and were consumed completely. Grass silage supplementation reduced dietary crude protein and concentration of total sugars, and dietary SBM inclusion increased dietary crude protein concentration and decreased dietary starch concentration. Milk yield and energy-corrected milk were increased by SBM supplementation of cows with access to grass silage. Milk protein concentration was lower in cows offered grass silage...

Effect of different concentrations of dietary safflower seed on milk yield and some rumen and blood parameters at the end stage of lactation in dairy cows

Oguz,Mustafa Numan; Oguz,Fatma Karakas; Buyukoglu,Tulay Ileri
Fonte: Sociedade Brasileira de Zootecnia Publicador: Sociedade Brasileira de Zootecnia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2014 EN
Relevância na Pesquisa
36.3%
In this study, the effects of different concentrations of dietary safflower seeds (SS) were examined for milk production, milk fat and some rumen and blood parameters at the end stage of lactation in dairy cows. Four Holstein cows were assigned to a 4 × 4 Latin Square design with four stages. All stages had 14 d of adaptation and 7 d of data collection periods. The diets were formulated as isoenergetic and isonitrogenous. Cows were fed four concentrate mixtures containing 0% (Control; C), 12.5% (S-I), 25% (S-II), or 37.5% (S-III) crushed SS during the experimental period. Safflower seed intake was distributed as 0 (C), 1 (S-I), 2 (S-II) and 3 (S-III) kg/d/cow. Cows were fed 8 kg concentrate, 2 kg wheat straw, and corn silage ad libitum (approximately 20 kg). Diet S-III caused a decrease in efficiency of milk production and diet S-II provided a much further efficiency in milk production (C = 13.39±0.23, S-I = 12.94±0.26, S-II = 13.46±0.24 and S-III = 11.83±0.52 kg). Diets had no significant effect on milk fat (C = 3.99±0.18, S-I = 4.09 ± 0.16, S-II = 3.87±0.35 and S-III = 3.75±0.30%). There was no difference in rumen fluid and blood parameters. Short-time feeding of up to 2 kg/d safflower seed had no negative effects on milk yield...

Associative Growth Studies in Three-Strain Mixtures of Lactic Streptococci1

Reddy, M. S.; Vedamuthu, E. R.; Washam, C. J.; Reinbold, G. W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1972 EN
Relevância na Pesquisa
36.38%
A recently developed differential agar medium was used to study associative growth patterns in 17 different heterologous, three-strain mixtures of Streptococcus lactis, S. cremoris, and S. diacetilactis grown in milk. Mixtures were made by combining equal volumes of 18-hr milk cultures of the three species. Relative populations of component species were followed through three successive transfers in milk after the initial mixed propagation. Direct evidence for strain dominance and compatibility was obtained. A procedure also was developed to estimate the extent of suppression of S. lactis and S. diacetilactis in a mixture containing a dominant S. cremoris strain. The technique described could be successfully applied in quality-control work in the dairy-starter manufacturing industry.

Coupling Flash LC with MS for enrichment and isolation of milk oligosaccharides for functional studies

Strum, John S.; Aldredge, Danielle; Barile, Daniela; Lebrilla, Carlito B.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.47%
Mass spectrometry has been coupled with flash liquid chromatography to yield new capabilities for isolating non-chromophoric material from complicated biological mixtures. A flash LC/MS/MS method enabled fraction collection of milk oligosaccharides from biological mixtures based on composition and structure. The method is compatible with traditional gas-pressure driven flow flash chromatography, widely employed in organic chemistry laboratories. The on-line mass detector enabled real-time optimization of chromatographic parameters to favor separation of oligosaccharides that would otherwise be indistinguishable from co-eluting components with a non-specific detector. Unlike previously described preparative LC/MS techniques, we have employed a dynamic flow connection that permits any flow rate from the flash system to be delivered from 1–200 mL/min without affecting the ionization conditions of the mass spectrometer. A new way of packing large amounts of graphitized carbon allowed the enrichment and separation of milligram quantities of structurally heterogeneous mixtures of human milk oligosaccharides (HMOs) and bovine milk oligosaccharides (BMOs). Abundant saccharide components in milk, such as lactose and lacto-N-tetraose, were separated from the rarer and less abundant oligosaccharides that have greater structural diversity and biological functionality. Neutral and acidic HMOs and BMOs were largely separated and enriched with a dual binary solvent system.

Advances in Analysis of Human Milk Oligosaccharides123

Ruhaak, L. Renee; Lebrilla, Carlito B.
Fonte: American Society for Nutrition Publicador: American Society for Nutrition
Tipo: Artigo de Revista Científica
Publicado em 04/05/2012 EN
Relevância na Pesquisa
36.22%
Oligosaccharides in human milk strongly influence the composition of the gut microflora of neonates. Because it is now clear that the microflora play important roles in the development of the infant immune system, human milk oligosaccharides (HMO) are studied frequently. Milk samples contain complex mixtures of HMO, usually comprising several isomeric structures that can be either linear or branched. Traditionally, HMO profiling was performed using HPLC with fluorescence or UV detection. By using porous graphitic carbon liquid chromatography MS, it is now possible to separate and identify most of the isomers, facilitating linkage-specific analysis. Matrix-assisted laser desorption ionization time-of-flight analysis allows fast profiling, but does not allow isomer separation. Novel MS fragmentation techniques have facilitated structural characterization of HMO that are present at lower concentrations. These techniques now facilitate more accurate studies of HMO consumption as well as Lewis blood group determinations.

Caracterização físico-química, reológica e sensorial de iogurte obtido pela mistura dos leites bubalino e caprino

Bezerra, Maria de Fátima
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Química; Pesquisa e Desenvolvimento de Tecnologias Regionais Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Química; Pesquisa e Desenvolvimento de Tecnologias Regionais
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
36.34%
Milk from different animals can be used for dairy production. Yoghurt is a popular fermented milk product and considered to be one of the greatest importance in terms of consumer acceptance and consumption. The present research deals with the production of strawberry set-type yoghurt by mixing goat and buffalo s milk and it has the objective of taking advantage of the intrinsic characteristics of each milk to produce a final product with desirable attributes. It was conducted by analyzing five experimental groups with different proportions of goat and buffalo s milk: C 100% goat s milk; 7C3B - 70% goat s milk and 30% buffalo s milk, 5C5B - 50% goat s milk and 50% buffalo s milk, 3C7B 30% goat s milk and 70% buffalo s milk; B - 100% buffalo s milk. Each group was evaluated for total solids content and the acidification profile was monitored every 30 minutes by pH analysis. The yoghurt samples were analyzed for physical-chemical (pH, acidity, protein, fat, total and reducing sugars, ash and total solids), rheological (syneresis and viscosity) and sensory characteristics (appearance, odor, consistency and flavour). Samples with higher percentual of bubaline milk reached Vm faster, but the time necessary for pH 4.6 (Te) were similar between groups. Statistical differences (p<0.05) were observed for fat and total solids content of yoghurt...

Utilização de técnicas de eletroforese em gel de poliacrilamida na identificação da adição de leite de vaca ao leite de cabra; Detection of cow´s milk and goat´s milk mixtures by polyacrylamide gel electrophoresis techniques

Fonte: UNIVERSIDADE FEDERAL DE LAVRAS; DCA - Programa de Pós-graduação; UFLA; BRASIL Publicador: UNIVERSIDADE FEDERAL DE LAVRAS; DCA - Programa de Pós-graduação; UFLA; BRASIL
Tipo: Dissertação
PT_BR
Relevância na Pesquisa
36.13%

Quantification of Milk Fat i Chocolate Fats by Triacylglycerol Analysis using Gas-Liquid Chromatography

BUCHGRABER MANUELA; ANDRONI SIMONA; ANKLAM ELKE
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Articles in Journals Formato: Printed
ENG
Relevância na Pesquisa
26.41%
The development and in-house testing of a method for the quantification of milk fat I chocolate fats is described. A database consisting of the triacylglycerol profile of 310 genuine milk fat samples from 21 European countries and 947 mixtures thereof with chocolate fats was created under a strict quality control scheme using 26 triacylglycerol reference standards for calibration purposes. Out of the individual triacylglycerol fractions obtained, a-palmitoyl-2-stearoyl-3-butyroul-glycerol (PSB) was selected as suitable marker compound for the determination of the proportion of milk fat I chocolate fats. A comparison with the widely used butyric acid method, which is currently used to determine the milk fat content in non –milk fat mixtures, showed that both methods were equivalent in terms of accuracy. The Advantage of the presented approach is that for further applications, i.e., determination of foreign fats in chocolate fats, just a single analysis is necessary, whereas for the same purpose the C4 method requires two different analytical methods.; JRC.D.8-Food safety and quality

Determination of Total Selenium and Selenomethionine in cow milk by HPLC coupled to ICP-MS

Gueifão, Sandra; Coelho, Inês; Castanheira, Isabel; Jitaru, Petru; Fisicaro, Paola
Fonte: Instituto Nacional de Saúde Doutor Ricardo Jorge, IP Publicador: Instituto Nacional de Saúde Doutor Ricardo Jorge, IP
Tipo: Conferência ou Objeto de Conferência
Publicado em /01/2011 ENG
Relevância na Pesquisa
36.25%
This study focused on the determination of total selenium and selenomethionine (SeMet) species in milk samples. Accurate determination of total selenium was carried out by Inductively Coupled Plasma Mass Spectrometry and Isotope Dilution (ID-ICP-MS). SeMet species was determined by a hyphenated technique, namely High Performance Liquid Chromatography coupled with ICP-MS equipped with a dynamic reaction cell (HPLC-DRC ICP-MS). In order to eliminate possible interferences (Ar-Ar, Ca-Ca and Ca-Ar) that occur either for determination of total selenium and SeMet, the DRC-ICP-MS operating conditions were optimized, using different flows of gases (Helium/Hydrogen) mixtures. The milk sample was digested by using a closed-vessel microwave system and various parameters, such as the ratio nitric acid/peroxide hydrogen, temperature, pressure and time were investigated. The ID was also compared with the standard addition method. Reproducibility, repeatability and trueness of the method for the determination of total selenium were evaluated using two reference materials, SRM-1549 and BCR-063R. The results obtained were in both cases in a good agreement with certified values. Both enzymatic and acid hydrolysis of the milk proteins were investigated as extraction procedures in view of SeMet determination in milk and the conditions used in this work seemed effective to achieve accurate determination of total selenium and SeMet in this difficult matrix.

Amyloid fibril formation by bovine milk αs₂- and κ-casein, and its inhibition by the molecular chaperones αs₁- and β-casein.

Thorn, David C.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010
Relevância na Pesquisa
36.18%
The caseins (αs ₁, αs₂, β, and κ) are the predominant proteins of bovine milk. While having little sequence homology, they have similar structural and behavioural characteristics, e.g. they lack well-defined tertiary structures and exhibit a strong tendency to associate with themselves and each other to form milk micelles. This thesis describes work examining the propensity of individual casein proteins, their mixtures, and their minor components, to form long, rope-like, β-sheet-rich aggregates, termed amyloid fibrils. Amyloid fibril formation is of considerable research interest because of its intimate association with a wide range of debilitating diseases, including Alzheimer's, Parkinson’s and Huntington’s diseases and type II diabetes. Amyloid fibrils were formed at physiological pH and temperature by αs₂-casein and κ-casein, but not αs₁-casein, β-casein, or whole casein, i.e. the mixture of all casein proteins. Fibril formation was assessed via dye binding assays, transmission electron microscopy and X-ray fibre diffraction. What sets αs₂₋ and κ-casein apart from the other casein proteins is that they both possess intra- and intermolecular disulfide linkages, giving rise to monomers and disulfide-linked dimers...

Bacteriostasis of Escherichia coli by milk. II. Effect of bicarbonate and transferrin on the activity of infant feeds.

Dolby, J. M.; Stephens, S.; Honour, P.
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Artigo de Revista Científica
Publicado em /04/1977 EN
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26.36%
Fresh human and bovine milk are bacteriostatic in vitro for only some (milk-sensitive) strains of E. coli. The addition of bicarbonate to the test system potentiates the bacteriostasis so that otherwise milk-resistant strains are inhibited. By titration of the bicarbonate in the milk, it is possible to determine the minimum concentration that will activate milk aganinst a milk resistant strain but be ineffective in boiled milk, i.e. it potentiates a heat-labile system in milk and does not merely exert a direct toxic effect. This concentration is lower for human milk than for cow's milk and can be reduced even further by the addition of more iron-binding protein. Lactoferrin and bicarbonate may be present in the gut of the newborn. In an attempt to imitate conditions in the infant gut, we therefore reinvestigated, in vitro and in the presence of added bicarbonate and transferrin, the bacteriostatic activity against E. coli of fresh breast-milk, commercial bottle-milk, and mixtures of these as fed to infants in the study. The results, and information about events in vivo deduced from the ratio of milk-sensitive to milk-resistant strains of E. coli isolated from babies' stool suggest that neonatal intestinal secretions may contribute to the bacteriostatic activity of their feeds so that (1) in fully breastfed babies all strains of E. coli are inhibited to the same extent; there is no selection on the basis of milk sensitivity and equal numbers of strains resistant and sensitive to milk are found in the stools; (2) in fully bottle-fed babies E. coli is not inhibited since the milk is non-bacteriostatic and again there is no selection; (3) in babies fed at the breast but bottle-milk supplemented...

THE REACTION OF COW'S MILK TO BLOOD SERUM PRECIPITIN

Jones, F. S.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 31/03/1926 EN
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It seems well established that during normal lactation there passes a slight but well defined quantity of blood protein into the udder. When a specific serum precipitin is applied to diluted milk the reaction occurs at a relatively uniform level of dilution. This line may well be considered the normal level of blood protein elimination. In the main the serum protein level is the same when mastitis streptococci are present as when they are absent, provided they are not too numerous. On the other hand it has been shown that when streptococci are present in large numbers the milk while apparently normal reacts at dilutions considerably higher than the normal. In the non-lactating udder, particularly during the latter end of gestation, serum proteins accumulate. Little and Orcutt have shown that certain antibodies tend to become greatly concentrated within the udder. Howe and others have shown that the colostrum of cows is rich in blood proteins. It is to be noted, however, that colostrum while rich in serum proteins usually reacts with serum precipitin to about one-half the titer of the blood serum itself. It may well be that certain proteins of the blood passing into the acini are reabsorbed, leaving a portion of the antigen within the udder. Thus a gradual accumulation of antigen may occur. Shortly after parturition the udder may be drained with a consequent marked fall in serum content. There...

Flow behaviour of inulin-milk beverages: Influence of inulin chain length and of milk fat content

Villegas, Beatriz; Costell, Elvira
Fonte: Conselho Superior de Investigações Científicas Publicador: Conselho Superior de Investigações Científicas
Tipo: Presentación Formato: 248588 bytes; 2459 bytes; application/pdf; text/plain
ENG
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Inulin is used either as a macronutrient substitute or as a supplement added in foods mainly for its nutritional properties. Chemically, inulin consists of a long chain made up of fructose molecules and one glucose molecule at one end. The fructose molecules are connected by β-(2-1) bonds and the last fructose is linked with a glucose by an α-(1-2) bond as in sucrose [1, 2]. The average molecular weight and degree of polymerisation of inulin depend on the source of inulin, the time of harvest and the process of production. In native chicory inulin, the number of fructose units linked together ranges from 2 to more than 60, with an average degree of polymerisation of the order of 10 and the high performance forms of inulin have an average degree of polymerisation of 25 [3]. The rheological behaviour of inulin and inulin-hydrocolloids mixtures in water were characterised by Bishay [4] who found a synergistic effect between inulin and calcium alginate. The objective of this work was to study the influence of the addition of inulin of different chain lengths on the flow behaviour of dairy beverages model systems with different milk fat content and with and without κ-carrageenan added.; MEC Proyecto AGL 2003-0052 Brenntag Química SKW Biosystems Central Lechera Asturiana