Recent years there has been a large increase in the worldwide sales of cultured products containing probiotics. The obstacle in the production of fermented products incubated with probiotic strains is its effect on sensory, chemical and physical properties. This Master´s Thesis investigates how extended storage times in fermentation tank as well as buffer tank during production of probiotic yoghurts affect final product quality. Through experimental studies, maximum storage times for probiotic yoghurts were to be recommended. The study includes analyses of pH, viscosity, stability, acetic acid concentration, microbial viability and sensory evaluations. Design of experiments (DOE) was used to construct a 32-factorial design for the experiment where different storage times were tested. The analyses showed that: pH decreases with both storage time in fermentation tank and buffer tank. Viscosity increases with long storage times in fermentation tank, while it decreases with long storage times in buffer tanks. Many samples had a sandy/grainy and slimy texture which could be related to high levels of Bifidobacteria or high fermentation temperatures. High levels of acetic acid was found in all samples. All measurements data where within the specification limits, whereas no recommendation for maximum storage times during production could be given.

Yoghurt is a fermented milk product which is produced by Streptococcus thermophilus and Lactobacillus delbrueckii spp. bulgaricus. The production of yoghurt has started in Middle East and spread all over the world. The aim of this study is to select the culture combination which is appropriate to Turkish taste and have the best yoghurt characteristics by means of post-acidification and whey separation properties, texture of gel formation, exopolysaccharide and acetaldehyde content / and to observe the effect of freeze-drying of cultures on these yoghurt properties. At the first part of this study, six L.delbrueckii spp. bulgaricus isolates and six S.thermophilus isolates were used with different combinations to produce 36 yoghurt samples. These isolates were selected among a strain collection which contains 111 L.delbrueckii spp. bulgaricus and 56 S.thermophilus isolates which were isolated from traditional Turkish yoghurt according to their acidification activity and acetaldehyde production properties. In addition, two commercial S.thermophilus isolates and one commercial L.delbrueckii spp. bulgaricus isolate were used to produce two commercial yoghurt samples. 38 yoghurt samples were examined in terms of pH and total titratable acidity changes during 21-day storage, syneresis and hardness. According to these three analyses, six yoghurt samples were chosen, which give the best results, for the determination of exopolysaccharide and acetaldehyde content. In addition, two yoghurt samples produced by commercial cultures and one sample, which gives average results in experiments, were also examined for these compounds to provide a good comparison. In the second part of the study the amount of exopolysaccharide and acetaldehyde of nine yoghurt samples were determined. In addition, sensory analysis was conducted to see consumer perception. According to the results, one culture combination was obtained as the best combination which produces the appropriate yoghurt to Turkish taste with the closest chemical analysis results to the commercial samples. In the last part, freeze drying process was examined if this has a significant effect on the selected LAB combination as well as yoghurt produced by using this.

The object of the dissertation was the monitoring of the quantity of the yogurt culture microbes Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus in selected yogurts after the end of the mature process and the consideration of the observed values with the requirements of the legislation. The literary search mentions the fermented dairy products and their classification, the characterization of individual types of lactic fermentation microbes and also the pure milk cultures used for the production of soured dairy products are not left out. The experimental part deals with the evaluation of microbiological analysis and the acidity of selected yogurts according to the influence of the producer and the storage life. The observed results showed, that the legislative requirement for the quantity of live microbes has been kept not only during the prescribed best-before period, but also during the complete experiment, it means also on the 56th day of the storage.

The thesis deals with changes in proportion of fatty acids in bovine milk. The aim of this study was to assess the profile of fatty acids in milk and subsequently in yoghurt produced from it. The thesis also evaluates the influence of breeding management, breed as well as region. The results of the thesis confirmed that processing of milk into yoghurt has little to no effect on fatty acids profile and proportion of fatty acids is stable. Processing milk into yoghurt alters nutritional value of the product only minimally and the changes in fatty acids profile are not statistically relevant. Profile of fatty acids in the end product was mostly influenced by breeding management, where nutritionally most valuable milk and therefore yoghurt comes from grazing dairy cows. Breed itself has influence more over content of main elements, such as fat or protein content, in milk rather than over fatty acids profile. Influence of region tightly relates to breeding management where in highlands pasturing is more common and in lowlands it is more common to have dairy cows in stables.

Made available in DSpace on 2014-06-11T19:32:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-11-01Bitstream added on 2014-06-13T19:22:12Z : No. of bitstreams: 1 kinouchi_fl_dr_arafcf.pdf: 729249 bytes, checksum: 40dc0249a850a1d16d680548a8140cb6 (MD5) / Universidade Estadual Paulista (UNESP) / O crescimento da demanda por alimentos saudáveis está estimulando a inovação e o desenvolvimento de novos produtos na indústria alimentícia. Os alimentos saudáveis são chamados de alimentos funcionais, que são alimentos consumidos como parte de uma dieta usual que produzem efeitos metabólicos ou fisiológicos, com capacidade de reduzirem o risco de doenças crônico - degenerativas, além de suas funções nutricionais básicas. Entre os alimentos funcionais, o presente estudo destaca os produtos derivados da soja e os probióticos. As isoflavonas da soja parecem ser os componentes principais no combate ao câncer, por apresentarem, atividade antioxidante, aumento da apoptose, inibição da angiogênese e modulação da resposta imune. O produto fermentado por bactérias láticas, induz resposta imune inata e adaptativa. Os mecanismos pelos quais o produto fermentado pode inibir o crescimento do tumor são diminuição da resposta inflamatória induzida pelo carcinógeno, aumento da IgA, aumento da apoptose celular e aumento da taxa de TNF-a . Considerando o efeito benéfico dos fitoestrogênios da soja em relação à inibição do câncer e considerando, também, o fato de que determinadas bactérias láticas apresentam atividade anti-tumoral, parece-nos plenamente justificável a realização do estudo para verificar se os alimentos: produto de soja não fermentado (PSNF); iogurte de soja (IS) e iogurte de soja suplementado com isoflavonas (ISS), e Ração (R) exercem efeito no desenvolvimento do câncer de mama e verificar os níveis das citocinas, bem como a concentração de óxido nítrico liberado por macrófagos, e IFN-g em cultura de células esplênicas, indução da apoptose/necrose em macrófagos e angiogêneses no tumor. / The growing demand for healthy foods is encouraging the development of new products by the food industry. Functional foods are normally part of a regular diet, but besides their nutritional properties, they also elicit metabolic and physiologic responses that may reduce the risk of chronic degenerative diseases. This study focuses on probiotics and soy-derived products. Soy isoflavones seem to play the most important role in the fight against cancer because, besides their anti-oxidant effects, they stimulate apoptosis, inhibit angiogenesis and modulate the immune response. Probiotics may inhibit tumor growth by diminishing the inflammatory response provoked by the carcinogen and by increasing apoptosis and TNF-_ and IgA levels. Considering the beneficial effects of soy phytoestrogens on cancer and the fact that some lactic bacteria have antitumor activity, is seems reasonable to carry out a study that analyzes whether non-fermented soy product (PSNF), soy yoghurt (IS), soy yoghurt supplemented with is flavones (ISS) and regular feed (R) have an effect on the development of breast cancer by assessing: 1. levels and nitric oxide (NO) produced by macrophages; 2. levels of IL-10 and IFN-g in spleen cell cultures; 3. induction of apoptosis/necrosis in macrophages; and 4. tumor angiogenesis.

Orientador: Elizeu Antonio Rossi / Banca: Iracilda Zeppone Carlos / Banca: Daniela Cardoso Umbelino Cavallini / Banca: Susana Marta Isay Saad / Banca: Elaine Cristina Pereira de Martinis / Resumo: O objetivo desse trabalho foi investigar a influência do consumo do "iogurte" de soja fermentado com Enterococcus faecium CRL 183 sobre o perfil e atividade metabólica da microbiota intestinal de animais e humanos, de maneira a evidenciar prováveis mecanismos de ação indireta na diminuição do risco de ocorrência de câncer de cólon. Os ratos foram divididos em 6 grupos (n=10): I - animais que receberam ração à base de caseína; II - animais que receberam ração à base de carne + 3 mL/kg peso corpóreo/dia do produto não fermentado; III - animais que receberam ração à base de carne + 3 mL/kg peso corpóreo/dia de E. faecium ; IV - animais que receberam apenas ração à base de carne; V - animais que receberam ração à base de carne + 3 mL/kg peso corpóreo/dia de "iogurte" de soja esterilizado; VI - animais que receberam ração à base de carne + 3 mL/kg peso corpóreo/dia do "iogurte" de soja. Os animais consumiram os diferentes produtos ("iogurte" de soja, "iogurte" de soja esterilizado, suspensão de E. faecium e produto não fermentado) durante 4 semanas do período experimental. Foram estudadas a capacidade de aderência de Enterococcus faecium CRL 183 ao cólon e de sobrevivência nas fezes de ratos, além das determinações de pH, concentração de amônia e composição da microbiota fecal. A sobrevivência desse microrganismo no trato gastrointestinal foi verificada por técnicas de isolamento e identificação a partir do cólon e das fezes dos animais que receberam este microrganismo na forma de produto fermentado ("iogurte" de soja) e cultivo puro. Para a confirmação da espécie E. faecium foi utilizada a técnica de PCR. A composição da microbiota fecal foi verificada realizando a enumeração dos seguintes grupos de bactérias: aeróbios e anaeróbios totais, Enterococcus sp, Lactobacillus spp, Bifidobacterium spp... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study was to investigate the effect of the consumption of soy yoghurt, fermented with Enterococcus faecium CRL 183, on composition and metabolic activity of intestinal microbiota of animals and humans, and to verify potential mechanisms involved in the anti-carcinogenic action. The rats were placed in 6 groups, distinguished by their diets: for 90 days, group I was given a standard casein-based rodent feed and groups II-VI, the beef-based feed. From the 30th day, groups II, III, V and VI also received the following products: II) unfermented soy product; III) pure suspension of E. faecium CRL 183; V) sterilized soy yoghurt; VI) soy yoghurt. The animals received the different products during 4 weeks. The capacity of E. faecium to adhere on colon and to survive gastrointestinal passage was determined by monitoring rat faecal samples and colon by microbiological and molecular analysis. Species confirmation of E. faecium was performed by PCR amplification. The composition of the faecal microbiota was determined by counting culturable bacteria in the following groups: total aerobes and anaerobes, Enterococcus spp. Enterobacteria, Clostridium spp., Bacteroides spp., Lactobacillus spp. and Bifidobacterium spp. Enzymatic activities of b-galactosidase, b-glucosidase and b-glucuronidase were verified in rat faecal samples. Nitroreductase and azoreductase activities were determined in the caecal contents of mice. The culture of E. faecium CRL 183 was tested for antimicrobial substance production by spot-on-the-lawn assay. Forty healthy adult volunteers who were between 40 and 50 years old participated of this study. The subjects consumed 100 mL/day of soy yoghurt (group F) or unfermented product (group P) during 4 weeks. In feces of volunteers enzymatic activities of bgalactosidase, b-glucosidase and b-glucuronidase were verified. The administration of soy yoghurt and pure suspension... (Complete abstract click electronic access below) / Doutor

Orientador: Elizeu Antonio Rossi / Banca: Iracilda Zeppone Carlos / Banca: Sérgio Eduardo de Andrade Perez / Resumo: A osteoporose é uma doença crônica que afeta principalmente mulheres na pós-menopausa, e caracteriza-se por perda de massa óssea e deterioração da arquitetura do tecido ósseo, sendo considerada como um sério problema de saúde pública. A Terapia de Reposição Hormonal (TRH) é talvez o tratamento mais efetivo para reduzir a perda óssea, no entanto vem acompanhada por efeitos adversos como o aumento do risco de câncer de mama e de endométrio. Terapias alternativas, como a ingestão de isoflavonas, vêm sendo propostas a fim de se prevenir a osteoporose. As isoflavonas, um tipo de fitoestrógeno, parecem desenvolver atividade biológica parecida com a dos estrógenos de mamíferos, pois apresentam habilidade para se ligarem aos receptores estrogênicos. Além disso, estudos em animais e em humanos têm mostrado que as isoflavonas vêm se constituindo numa alternativa interessante para o controle do metabolismo lipídico e da obesidade. Além das isoflavonas, uma das possíveis maneiras de se prevenir a perda óssea é por meio da ingestão de quantidades adequadas de cálcio, um dos componentes dietéticos de maior importância para a manutenção da integridade óssea. Desta forma, o objetivo deste trabalho foi estudar o efeito da ingestão do “iogurte” de soja, fermentado com Enterococcus faecium e Lactobacillus jugurti, suplementado com isoflavonas e cálcio sobre o peso corpóreo e tecido ósseo de ratas maduras ovariectomizadas. Os animais foram divididos em 5 grupos, cada qual com 9 animais: pseudo-ovariectomizado, ovariectomizado; ovariectomizado que ingeriu o produto fermentado suplementado com isoflavonas e cálcio, ovariectomizado que ingeriu o produto fermentado suplementado com cálcio e ovariectomizado que ingeriu placebo suplementado com cálcio. O tratamento durou 3 meses e foram utilizados tíbias e fêmures de cada animal para... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: Osteoporosis is a chronic disease that affects mainly postmenopausal women, and it is characterized by bone loss and deterioration of the bone tissue architecture, and it considered a serious problem of public health. The Hormonal Replacement Therapy Hormonal (HRT) is the most effective treatment to reduce the bone loss, however it may be associated with adverse effects as the increase of the risk of endometrium and breast cancer. Alternative therapies, as intake of isoflavones, have being proposed to prevent the osteoporosis. Isoflavones, a type of phytoestrogens, seem to have biological activity like the mammals estrogens, because they present ability to bind to the estrogens receptors. Moreover, studies in animals and in human have shown that isoflavones may be an interesting alternative for the control of the lipidic metabolism and the obesity. On the other hand, the intake of adequate amounts of calcium, one of the dietary components of bigger importance for the maintenance of the bone integrity, is also considerate to be able to prevent the bone loss. Then, the objective of this research was to study the effect of the intake of the soy "yoghurt", fermented with Enterococcus faecium and Lactobacillus jugurti, supplemented with isoflavones and calcium on the corporal weight and bone tissue of ovariectomized mature rats. The animals had been divided in 5 groups, each one with 9 animals: sham-ovariectomized, ovariectomized; ovariectomized treated with soy “yoghurt” supplemented with isoflavones and calcium, ovariectomized treated with soy “yoghurt” supplemented with calcium and ovariectomized treated with placebo supplemented with calcium. The treatment lasted 3 months and the tibia and femur of each animal were used for following analysis: bone length; mechanical assay of three points; weight, volume and bone density; bone mineral content; bone... (Complete abstract, click electronic address below). / Mestre

Orientador: Mirna Lúcia Gigante / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-17T19:33:08Z (GMT). No. of bitstreams: 1 Ribeiro_MariaCeciliaEnes_M.pdf: 1602434 bytes, checksum: ce0e42604e0e4016991a097694b0633f (MD5) Previous issue date: 2011 / Resumo: A microencapsulação de micro-organismos probióticos tem se mostrado como uma técnica promissora para manter sua viabilidade tanto nos produtos aos quais são adicionados, bem como durante sua passagem pelo trato gastrointestinal. O objetivo geral deste trabalho foi avaliar a fabricação e as características durante o armazenamento refrigerado de iogurte batido probiótico adicionado de Lactobacillus acidophilus nas formas livre e encapsulada. O micro-organismo probiótico foi microencapsulado por gelificação iônica e coacervação complexa, utilizando-se pectina e concentrado proteico de soro como materiais de parede. Antes de serem adicionadas ao iogurte, as microcápsulas foram avaliadas quanto à característica físico-química e viabilidade do micro-organismo probiótico. Os iogurtes foram fabricados com leite homogeneizado esterilizado e padronizado adicionado de 2,5% (v/v) da cultura láctica tradicional para fabricação de iogurte e submetidos aos seguintes tratamentos: 1) adição de 1% (v/v) de L. acidophilus livre; 2) adição de 10% (p/v) de microcápsulas úmidas contendo L. acidophilus e 3) adição de 13% (p/v) de microcápsulas liofilizadas reidratadas contendo L. acidophilus. O tempo de fermentação foi considerado o necessário para que o produto atingisse pH 4,8 ± 0,05. Os produtos foram caracterizados quanto à sua composição centesimal e população dos microorganismos. Após 1, 7, 14, 21, 28 e 35 dias de armazenamento refrigerado, os iogurtes foram avaliados quanto à pós-acidificação e viabilidade dos micro-organismos da cultura tradicional de iogurte e probiótica. A viabilidade do L. acidophilus durante a simulação da passagem do iogurte através das condições gastrointestinais foi avaliada após 35 dias. O experimento completo foi repetido três vezes e o delineamento experimental utilizado foi o Split¿plot, em um planejamento do tipo fatorial 3 x 6, em blocos completamente aleatorizados. O efeito dos tratamentos, do tempo de armazenamento bem como da interação desses fatores sobre as variáveis estudadas foi avaliado por ANOVA aplicando-se teste de Tukey para comparação entre as médias ao nível de 5% de significância. O tempo de fermentação dos produtos variou de 180 a 200 minutos. Um dia após a fabricação, o iogurte obtido com o micro-organismo livre apresentou menor pH que os iogurtes adicionados do micro-organismo encapsulado. Os iogurtes produzidos com o micro-organismo encapsulado apresentaram maior teor de proteína quando comparados ao produzido com o L. acidophilus livre. A interação entre os tratamentos e o tempo de armazenamento refrigerado afetou significativamente a pós-acidificação e o número de células viáveis de S. thermophilus, L. bulgaricus e L. acidophilus no iogurte. Os iogurtes probióticos adicionados de L. acidophilus na forma microencapsulada apresentaram menor pós-acidificação e maior sobrevivência do micro-organismo probiótico após 35 dias de armazenamento quando comparado ao iogurte com probiótico adicionado na forma livre. Na forma livre, a população de células viáveis de L. acidophilus reduziu 0,98 ciclos logarítmicos, enquanto na forma encapsulada (úmida e liofilizada) essa redução foi de 0,20 ciclos logarítmicos. Esses resultados indicam a sobrevivência de aproximadamente 10% e 62% do L. acidophilus nas formas livre e encapsulada, respectivamente. Após 35 dias de armazenamento refrigerado, a simulação da passagem dos produtos pelo trato gastrointestinal indicou maior sobrevivência do L. acidophilus encapsulado do que do micro-organismo livre. A microencapsulação do L. acidophilus por gelificação iônica e coacervação complexa utilizando-se pectina e proteína de soro como materiais de parede, conferiu proteção ao micro-organismo, tanto durante o armazenamento refrigerado do produto por 35 dias, como durante a simulação gastrointestinal / Abstract: Microencapsulation of probiotic microorganisms has been shown to be a promising technique to maintain their viability either in products to which they are added and during their passage through the gastrointestinal tract. The aim of this study was to evaluate the manufacture and characteristics during refrigerated storage of probiotic stirred yoghurt added of Lactobacillus acidophilus in both free and encapsulated forms. The probiotic microorganism was microencapsulated by ionotropic gelation and complex coacervation, using pectin and whey protein concentrate as wall materials. Before being added to yoghurt, the microcapsules were evaluated for physical chemical characteristics and viability of the probiotic microorganism. The yoghurts were manufactured with sterilized, homogenized and standardized milk added of 2.5% (v/v) yoghurt starter culture and submitted to the following treatments: 1) addition of 1% (v/v) of free L. acidophilus, 2) addition of 10% (w/v) of moist microcapsules containing L. acidophilus and 3) addition of 13% (w/v) of rehydrated freeze-dried microcapsules containing L. acidophilus. The fermentation period was considered the enough time for the product to reach pH 4.8 ± 0.05. The products were characterized to their centesimal composition and population of microorganisms. After 1, 7, 14, 21, 28 and 35 days of refrigerated storage, the yoghurts were evaluated for post-acidification and viability of yoghurt starter culture and probiotic microorganism. The viability of L. acidophilus during simulation of the passage of yoghurt through gastrointestinal conditions was also evaluated after 35 days. The complete experiment was repeated three times and the experimental design was a Split-Plot in a factorial design of the type 3 x 6, in completely randomized blocks. The effect of treatments, storage time and the interaction of these factors on these studied variables was evaluated by ANOVA according to the Tukey test for comparison between the averages, in 5% of significance level. The fermentation period of the products ranged from 180 to 200 minutes. One day after manufacturing, the yoghurt obtained with free microorganism showed lower pH than the yoghurt produced with added encapsulated microorganism. The yoghurts produced with the encapsulated microorganism showed higher protein content than that produced with free L. acidophilus. The interaction between treatments and time of refrigerated storage affected significantly the post-acidification and the number of viable cells of S. thermophilus, L. bulgaricus and L. acidophilus in yoghurt. The probiotics yoghurts added by L. acidophilus in microencapsulated form showed less post-acidification and increased survival of probiotic microorganism after 35 days of storage than yoghurt added of probiotic in free form. The counting of viable cells of L. acidophilus reduced 0.98 log cycles in free form, while in encapsulated form (moist and freeze-dried) the reduction was 0.20 log cycles. These results indicate the survival of approximately 10% and 62% of L. acidophilus in both free and encapsulated forms, respectively. After 35 days of refrigerated storage, the simulation of the passage of yoghurts through the gastrointestinal tract showed a higher survival of L. acidophilus encapsulated than the free microorganism. Microencapsulation of L. acidophilus by ionotropic gelation and complex coacervation, using pectin and whey protein concentrate as wall materials provide protection to microorganism, both during refrigerated storage for 35 days and during simulated gastrointestinal conditions / Mestrado / Engenharia de Alimentos / Mestre em Tecnologia de Alimentos

Orientador: Helena Maria Andre Bolini / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T23:53:19Z (GMT). No. of bitstreams: 1 Antunes_AdrianeElisabeteCosta_D.pdf: 4612302 bytes, checksum: 3df0997d6dfe4b4f15d6acfe1679d1a0 (MD5) Previous issue date: 2004 / Resumo: O concentrado protéico do soro de leite (CPS) vem sendo aplicado em diversos produtos devido às suas propriedades funcionais. Iogurtes desnatados apresentam consistência frágil e dessoragem, e uma das atribuições do CPS é de agir como substituinte da gordura. A presente pesquisa foi dividida em quatro estudos. No primeiro estudo objetivou-se avaliar as propriedades de textura, retenção de água e aparência dos géis ácidos de CPS. No segundo, realizou-se uma triagem de diferentes percentuais de adição de proteínas e de combinações de CPS e leite em pó desnatado (LPD) na produção de iogurte desnatado objetivando alcançar propriedades de textura e dessoragem semelhantes às do iogurte padrão (integral, adicionado de LPD). O terceiro estudo observou a cinética de fermentação, perfil de textura, sinérese, microestrutura e análise sensorial dos iogurtes contendo 5% de adição de proteína pelas seguintes proporções de CPS e LPD: 1:0, 1,5:0,5, 1:1, 0,5:1,5, 0:1. O objetivo do quarto estudo foi avaliar a adição do CPS na viabilidade das culturas probióticas, perfil de textura, pós-acidificação, e dessoragem durante o armazenamento dos iogurtes desnatados, bem como analisar características sensoriais dos produtos. Através dos resultados concluiuse que géis ácidos de CPS, formulados nas maiores faixas de concentração protéica, tempo e temperatura de desnaturação tenderam a apresentar os maiores valores de dureza, coesividade, elasticidade, gomosidade e capacidade de retenção de água. No pH 4,0 os géis apresentaram-se mais elásticos, opacos, amarelados e com maior capacidade de retenção de água, enquanto que os géis formados em pH 4,9 a 5,2 foram mais firmes, coesos, gomosos e brilhantes. Iogurtes desnatados com perfil de textura instrumental, sinérese, propriedades sensoriais (aparência, sabor, textura e impressão global) similares às do iogurte padrão foram obtidas com a formulação de iogurte desnatado adicionado de 5% de proteína, sendo a relação dos ingredientes LPD:CPS de 1,5:0,5. O CPS acelerou a fermentação dos iogurtes. A microestrutura foi muito semelhante entre os iogurtes, embora as amostras tenham variado de 13,8 até 21,8% de sólidos totais. Durante o armazenamento foram intensificadas a firmeza, gomosidade e capacidade de retenção de água dos iogurtes. O iogurte com fermento probiótico L. acidophilus apresentou maior dessoragem, no entanto, a adição de CPS compensou essa tendência. Não foi observada variação significativa na pósacidificação dos iogurtes conferida pela adição de CPS. No entanto, a pósacidificação foi influenciada pela quantidade de L. bulgaricus empregada. O CPS potencializou o crescimento e viabilidade dos microrganismos L. acidophilus e B. longum / Abstract: The whey protein concentrate (WPC) has been used in several products due to its functional properties. The fat-free yogurt shows poor consistency and syneresis and the WPC is known as a fat substitute. The present work was divided in four studies. The first one aimed at the evaluation of the texture profile, water holding capacity and appearance of acid WPC gels. In the second one we did a screening of different protein perceptual addition and combinations of WPC and skim milk powder (SMP) to produce a fat-free yogurt with similar texture properties and syneresis of the control (full fat yogurt with SMP addition). The third study looked at the fermentation kinetics, texture profile, syneresis, microstructure and sensorial analysis of yogurts with 5% protein addition in the following proportions of WPC and SMP: 1:0, 1.5:0.5, 1:1, 0,5:1.5, 0:1. The objective of the fourth study was to evaluate the effect of WPC addition on the probiotic cultures viability, texture profile, postacidification and syneresis along the shelf life of fat-free yogurts; and also, the sensory characteristics of the products. It was concluded that the WPC acid gels, made at higher protein concentration, time and temperature of denaturation had the tendency of been harder and more cohesive, springy, gummy, and with better water holding capacity. At pH 4.0 the gels were springier, yellowier and with more opacity and higher water holding capacity. On the other hand, the gels made at pH 4.9 to 5.2 were harder, shinier, more cohesive and gummy. The fat-free yogurts with similar instrumental texture profile, syneresis and sensory properties (appearance, flavor, texture and overall impression) to the control were obtained by the formulation of fat-free yogurt added by 5% protein, with SMP:WPC at 1.5:0.5. The WPC shortened the yogurt fermentation time. The microstructure was very similar among the yogurts, although the total solids of the samples varied among 13.8 to 21.8%. During the storage the firmness, gumminess and water holding capacity were intensified. The yogurt with L. acidophilus showed more syneresis, however, the WPC addition diminished this tendency. It was not observed a significant variation on the yogurt postacidification due WPC addition. However postacidification was a function of concentration of L. bulgaricus added to the culture. The WPC intensified the growth and viability of L. acidophilus and B. longum / Doutorado / Doutor em Alimentos e Nutrição

This thesis deals with the study of yogurt preparation and changes during its storage. The theoretical part contains information about parameters affecting both the preparation and properties of the final product. The experimental part describes methods and procedures used for determination of critical parameters such as lactic acid, lactose, glucose and galactose concentrations (HPLC-RI), amounts of streptococci and lactobacilli. The data was graphically evaluated and commented on. The work also included sensory analysis in which the prepared yogurt was compared with commercially available products. The results of this work can serve both consumers and smaller yogurt producers.