Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-01-09T13:58:43Z No. of bitstreams: 1 alancamposdasilva.pdf: 1251147 bytes, checksum: aa102a0e377862594d75e5865529db3d (MD5) / Approved for entry into archive by Diamantino Mayra (mayra.diamantino@ufjf.edu.br) on 2017-01-31T11:22:38Z (GMT) No. of bitstreams: 1 alancamposdasilva.pdf: 1251147 bytes, checksum: aa102a0e377862594d75e5865529db3d (MD5) / Made available in DSpace on 2017-01-31T11:22:38Z (GMT). No. of bitstreams: 1 alancamposdasilva.pdf: 1251147 bytes, checksum: aa102a0e377862594d75e5865529db3d (MD5) Previous issue date: 2016-08-12 / Doce de leite (DL) é um dos produtos lácteos concentrados mais populares no Brasil. Entretanto, o elevado valor calórico, teor de açúcar e/ou a presença de lactose limitam sua difusão entre os consumidores. Portanto, o desenvolvimento de produtos lácteos para dietas restritivas, principalmente, intolerância à lactose e valor calórico reduzido, é um desafio para a indústria laticinista e uma oportunidade de mercado. O objetivo deste trabalho foi desenvolver e caracterizar DL sem adição de sacarose e sem lactose (SL) e sem adição de sacarose (SA), bem como avaliar sua aceitação sensorial e intenção de compra pelos consumidores. Produziram-se os três tipos de DL, tradicional (TR), SL e SA. O leite destinado à produção do DL SL foi hidrolisado pela enzima β-galactosidase e o grau de hidrólise acompanhado pelo índice crioscópico. A fabricação ocorreu em tacho aberto com concentração para um teor de sólidos solúveis de 61 – 68 °Brix. Os DL foram analisados, quanto à hidrólise da lactose, por meio de Eletroforese de Carboidratos Assistida por Fluoróforo (FACE) e caracterizados através da composição centesimal, cor, cristais e requisitos microbiológicos. Foi realizada análise sensorial utilizando teste de aceitação em escala hedônica (1 a 9) e análise da intenção de compra (1 a 5). Os resultados foram avaliados pela ANOVA e comparação a posteriori de médias pelo teste t de Student com intervalo de confiança de 95%. Os leites utilizados nas produções demonstraram composição centesimal, crioscopia e acidez dentro dos padrões legais vigentes. A hidrólise da lactose no leite, pela enzima β-galactosidase, foi atingida com 80 minutos a 40 °C, na concentração de 0,7 g/L e confirmada no DL SL pela FACE por meio das bandas eletroforéticas de glicose e galactose. Os DL produzidos apresentaram características composicionais em conformidade com o Regulamento Técnico de Identidade e Qualidade (RTIQ), embora diferentes entre si. Em relação à cor, o DL SA exibiu coloração mais clara (L = 44,09 ± 0,73). O número de cristais por grama de doce de leite nos DL TR e SA foram 2,63 x 104 ± 19,00 e 4,63 x 106 ± 298,22, e tamanho de cristais 29,78 μm ± 27,84 e 24,83 μm ± 1,04, respectivamente. Quanto à aceitação sensorial, o DL TR obteve as maiores notas na maioria dos atributos julgados e na análise de intenção de compra. Cristais de lactose não foram percebidos no DL SL, possivelmente em função da hidrólise da lactose e sua aceitação foi igual (p>0,05) ou superior (p<0,05) ao DL TR em relação aos atributos cor, consistência e textura. O DL SA foi o menos aceito pelos consumidores. / Doce de leite (DL) is the one most popular concentrated dairy product in Brazil. However, the high-calorie, sugar content and/or the presence of lactose limit its spread among consumers. Therefore, the development of dairy products to restrictive diets, especially lactose intolerance and the reduced-calorie is a great challenge for the dairy industry and a market opportunity. Thus, the aim of this work was the development and characterization of DL with no added sucrose and lactose (SL) and without the addition of sucrose (SA) as well as, to evaluate the sensory acceptability and the purchase intent by consumers. Three sort of DL were produced, the traditional one (TR), SL and SA samples. For the preparation of the DL SL, the milk was hydrolyzed by β-galactosidase enzyme and the hydrolysis degree was accompanied by the cryoscopic index. The production took place in open pan with soluble solids concentration of 61-68 °Brix. DL were analyzed regarding lactose hydrolysis by Fluorophore-Assisted Carbohydrate Electrophoresis (FACE), and characterized as regards chemical composition, color, crystals presence and microbiological requirements. Sensory analysis was performed using acceptance test in hedonic scale (1 to 9) and the purchase intent analysis (1 to 5). The results were evaluated by ANOVA and a posteriori comparison of average by the Student's t test with confidence interval of 95%. The milk samples used in the DL production showed centesimal composition, freezing point and acidity values within the current legal standards. Lactose hydrolysis was achieved with 80 minutes at 40 ° C, with concentration of 0.7 g/L, confirmed in the DL SL sample by FACE analysis through glucose and galactose electrophoretic bands. The prepared DL showed compositional features in accordance with the Technical Regulation of Identity and Quality (RTIQ), even though different from each other.. Regarding color, the DL SA sample exhibited lighter color (L = 44.09 ± 0.73). The number of crystals per gram of doce de leite in the DL TR and SA sample was 2.63 x 104 ± 19.00 and 4.63 x 106 ± 298.22, with crystal size of 29.78 ± 27.84 µm and 24.83 ± 1.04 µm, respectively. As for sensory acceptance, DL TR obtained the highest scores in the most judge attributes and in the purchase intent analysis. Lactose crystals were not perceived in the DL SL sample, most likely as a result of the lactose hydrolysis and their acceptance was equal (p>0.05) or greater (p<0.05) when compared to color, texture and consistency of the DL TR sample. The DL SA sample was the least accepted by consumers.

Doctor of Philosophy / Food Science Institute / Jayendra K. Amamcharla / Lactose is commercially produced from whey, whey permeate, or milk permeate as α-lactose monohydrate in crystalline form. Focused Beam Reflectance Measurement (FBRM) as a potential tool for in situ monitoring of lactose crystallization at concentrations relevant to the dairy industry was evaluated. Applicability of FBRM at supersaturated lactose concentrations 50%, 55%, and 60% (w/w) was reported in comparison with Brix values obtained from a Refractometer during isothermal crystallization at temperatures 20ºC and 30ºC. FBRM technique was shown to be a valuable tool for monitoring chord length distributions during lactose crystallization. In a different study, the influence of cooling rate during crystallization of lactose in concentrated permeates was studied. Three cooling rates accounting for approximately 17, 11, and 9 h were applied during lactose crystallization to evaluate the lactose crystal yield and quality of lactose crystals. There was no significant difference (P>0.05) found in lactose crystal yield, mean particle size obtained at the end of crystallization. This study suggested that increasing the cooling rate during lactose crystallization within the range explained in this study can save approximately 8 h of crystallization time. These studies evaluated FBRM as a potential tool to monitor lactose crystal chord lengths and counts. Also, process improvements were suggested to increase the productivity of lactose crystallization process by reducing the crystallization time. In chapters 5 and 6, calcium-reduced milk protein concentrates (MPCs) were used as an ingredient to improve the stability of high-protein dairy beverages. Heat stability increased significantly (P>0.05) in 8% protein solutions made from 20% calcium-reduced MPC. A significant increase in heat stability was observed in beverages formulated with 20% calcium-reduced MPC in the absence of chelating agent. In another study, it was evident that the dairy beverage formulation with 20% calcium-reduced MPC showed no sedimentation and age gelation indicating an improved storage stability. These studies confirmed that 20% calcium reduced MPC contributed towards improved heat stability and storage stability of the high-protein beverages.

Lactase persistence (LP) is a genetically determined trate caused by the expression of lactase in adulthood. Lactase is the intestinal enzyme responsible for digestion of milk sugar, lactose. Its production in the small intestine decreases during the childhood, this physiological condition is called lactose intolerance. However, in some individuals production of this enzyme is not stopped. The persistence of lactase activity is a recent phenomenon, which arose independently in several parts of the world over the past roughly 10,000 years, in connection with the emergence of agriculture, specifically milk production and is (likely) still under strong selection pressure. LP was first observed in Europe, where it is associated with a mutation -13 910*T. Frequency of this mutation correlates with latitude. In Africa, the presence of LP is conversely associated with herding and falls under the hypothesis of genetic and cultural co-evolution associated with cattle and the use of secondary food sources. Pastoral populations living in different areas of Africa have different LP mutations that are linked to their origin. Although many investigation on LP have already been carried out, neither analysed the Tuareg populations. This study is focused on the analysis LP mutations in 93 samples of Tuaregs from...

Comparative studies of taste perception have found that primates may differ markedly in their sensitivity for substances perceived as sweet by humans. These findings raise questions about the reason that may underlie these differences in sweet-taste sensitivity between species. The aim of the present study was to assess the taste responsiveness of chimpanzees (Pan troglodytes verus) to seven substances tasting sweet to humans and to compare the results with those of other primate species. Using a two-bottle preference test (1 min) I found that the taste preference thresholds of the chimpanzees for five food-associated carbohydrates ranged between 20-30 mM for sucrose, 20-50 mM for fructose, 60-80 mM for glucose, 50-80 mM for maltose, and 30-80 mM for lactose. Taste preference thresholds for two steviol glycosides ranged from 0.04-0.05 mM for stevioside, and 0.03-0.05 mM for rebaudioside A. The chimpanzees displayed clear preferences for all sweet-tasting substances presented. In line with data obtained in other primates, the taste preference threshold of the chimpanzees for sucrose was lower compared to the other carbohydrates presented and the taste preference thresholds for stevioside and rebaudioside A were lower compared to sucrose. In general, the taste sensitivity of the chimpanzees fell into the range of data reported in other nonhuman primate species. Interestingly, the taste preference thresholds of the chimpanzees reported here are similar to the taste detection thresholds obtained in humans, despite the fact that the former are only a conservative approximation of an animal’s taste sensitivity. This suggests that chimpanzees may be as sweet-taste sensitive as humans.

The aim of this study was to develop and examine the validity of using a phenotype scoring system (PTS), a new concept, in evaluating milk yield and constituents in different goat genotypes (Indigenous, British Alpines, Saanen and Toggenburg) raised in small scale production systems. Strategic decisions of small scale African farmers are mostly based on visual appraisal or body condition scoring (BCS) of their animals. BCS has been highly recommended as a means to evaluate both the energy and the health status of animals, especially in beef farming, but this method has been criticized for being too simple and too subjective because its evaluation is often done too late after the damage has already happened. Phenotype scoring (an approach which includes breed, udder size and BCS of the animal) is presented in this study as a better tool to evaluate milk yield in different goat genotypes raised under free range conditions. This has also been a good opportunity firstly to indicate which, among the three dairy breeds of goat under discussion, can adapt best to the African small scale farming system; secondly to review the relevance of some blood metabolites in characterizing milk production in different goat breeds and thirdly to study the milking capacity of the indigenous compared to the dairy goats raised under small scale production systems in South Africa. Thirty-two goats (8 Indigenous, 8 British Alpines, 8 Saanen and 8 Toggenburg) were raised in a free range system at the ARC-Irene experimental farm close to Pretoria. The experiment was a completely randomized experimental design with eight replicates per treatment group. Blood samples were collected by jugular venipuncture into 10 ml heparinised tubes in the morning before feeding on a weekly basis over a period of two months. Blood plasma was immediately aspirated after centrifugation (3000G), kept on ice and brought to the laboratory for the analysis of glucose, cholesterol, urea nitrogen (BUN) and free fatty acid (FFA) concentrations. Immediately after, all does were entirely milked (followed by 1ml oxytocin IM injection and the kids taken away for a period of four hours) before a second milking session took place to measure the daily milk yield of the does. Milk samples were analyzed for lactose, milk proteins, milk fat, milk urea-nitrogen (MUN) and milk somatic cell count (SCC). In addition body condition score (BCS), age and data related to the goat genotype (breed, udder characteristics) were recorded. Results confirmed that milk yield from dairy goats was higher (p<0.001) than the milk yield of indigenous goats during the entire period of study. Milk lactose values recorded in this study (between 3.9 and 4.9%) were the most stable constituent in goat’s milk. Milk protein concentration (between 3.1 and 4.5%) was significantly higher in the indigenous than in dairy breeds, especially in week one and from week four onwards. Milk fat values (between 3.3 and 7.7%) displayed a decline in all breeds; but as from week three, the fat in milk of indigenous does increased and from week five onwards, it remained significantly higher (p<0.001) compared to that of dairy breeds. In conclusion, the superiority of dairy breeds in milk yield was proven while the quality of indigenous goat milk was recognized. Studies on the characterization of milk production in different breeds revealed that the Toggenburg was superior to the other breeds, followed by the British Alpines and the Saanen; but the British Alpines showed a better adaptability to the environment followed by the Toggenburg and the Saanen. The latter could not produce milk without feed supplementation and lost most body condition as compared to the other breeds. Statistical analyses indicated that breed influenced milk yield, milk fat and the protein content of milk (especially in the Saanen and Toggenburg goats). BCS influenced fat content, lactose, milk proteins, MUN and SCC and also milk yield. Udder size influenced milk proteins and milk yield while udder attachment was associated with milk yield only. These results show that PTS, because it takes into account BCS, breed and udder size, is a better tool for predicting milk yield of goats herded in small scale farming systems. Africans interested in dairy goat farming should adopt PTS as a means to evaluate milk yield especially since milk is sold per volume and not by quality in Africa. Finally, milk from the indigenous goats is superior in terms of lactose, fat and protein content. The latter quality attributes can be used as selection criteria since the milk industry pays premiums for the fat and protein content of milk. / Thesis (PhD)--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted

In this research, beta-lactoglobulin was chemically modified by attaching different levels of stearic acid to the protein. The effect of this modification on hydrophobic!ty, emulsifying and foam properties, digestibility and allergenicity of the protein was investigated. It was found that the effect of fatty acid attachment or lipophilization depended on the amount of fatty acids attached to the protein. Incorporation of the hydrophobic ligands led to increased hydrophobic interactions, resulting in a decreasing solubility with extent of incorporation. Furthermore, the surface hydrophobicity measurements showed that the two fluorescence probes 8-anilinonaphthalene-l-sulfonate (ANS) and cis-parinaric acid (CPA) used for the surface hydrophobicity measurements were not equivalent This may support the. observation by earlier workers that ANS measures aromatic hydrophobicity and CPA aliphatic hydrophobicity. The studies on surface functional properties i.e. emulsifying and foaming properties, indicated that there was some improvement in these functional properties at low and medium levels of incorporation which decreased as the extent of fatty acid attachment further increased. The improvement, of these functional properties could be attributed to improved amphiphilicity of the proteins at these levels of incorporation. This research also showed that both high solubility and high ANS surface hydrophobicity is needed for the best emulsifying properties. In vitro digestibility studies showed a decrease in digestibility of the modified proteins with increased lipophilization. From the passive cutaneous anaphylaxis experiments, it was found that the level of fatty acid attachment to the protein had a significant effect on its ability to elicit IgE antibodies. Increased ability to elicit IgE antibodies was observed at a low level of fatty acid. When a medium level of fatty acid was attached the ability to elicit antibodies was reduced and almost completely destroyed when a higher level of fatty acid was incorporated. The above observations could be explained by the fact that the low level incorporation of fatty acid led to changes in the protein structure which exposed more allergenic sites. The almost complete destruction of the allergenicity could be attributed to denaturation of the protein which reduced or destroyed available allergenic sites. The antigenicity or binding of the modified proteins to the IgG antibodies raised against the native protein was studied by both direct and competitive enzyme linked immunosorbent assay. It was found that at low and medium levels of incorporation, the proteins demonstrated increased binding ability compared to the native protein. This was attributed to the increased exposure of antigenic sites on the protein with fatty acid incorporation. However, the protein with high level of incorporated fatty acid showed decreased binding ability. / Land and Food Systems, Faculty of / Graduate

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2015-11-09T13:45:39Z No. of bitstreams: 1 texto completo.pdf: 600665 bytes, checksum: ee26156d6dc7124f99efde31caf1f198 (MD5) / Made available in DSpace on 2015-11-09T13:45:39Z (GMT). No. of bitstreams: 1 texto completo.pdf: 600665 bytes, checksum: ee26156d6dc7124f99efde31caf1f198 (MD5) Previous issue date: 2010-04-12 / Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A permease de lactose de Kluyveromyces lactis, Lac12, media o transporte de lactose e o de galactose de baixa afinidade. Aqui é apresentado o estudo do efeito de fontes de carbono na internalização de Lac12 através do uso de linhagens contendo o gene quimérico LAC12-GFP. Quando células de K. lactis pré-cultivadas em galactose ou lactose foram transferidas para um novo meio, Lac12-GFP foi removida da membrana plasmática e localizada intracelularmente. Surpreendentemente, mesmo a presença de galactose ou lactose no novo meio de transferência causou essa internalização, e a resposta celular foi diferente para esse dois açúcares. Os resultados obtidos revelam que o processo de internalização é dependente do tipo de açúcar presente e de sua concentração. A internalização de Lac12-GFP causou redução nas taxas de captação de lactose[C14] e também foi observada em uma linhagem mutante Klsnf1; portanto, esse evento independe da atividade de KlSnf1. Evidências indicam que glicose-6-fosfato é o sinal intracelular, uma vez que a internalização foi induzida por 2-deoxiglicose, e a inibição da atividade da enzima fosfoglimutase por lítio impediu a internalização por galactose, mas não por lactose ou glicose. A internalização não ocorreu em 6-deoxiglicose, e, em ausência de síntese protéica, o evento foi irreversível. / Kluyveromyces lactis Lac12 permease mediates lactose and low-affinity galactose transports. In this study we have investigated the effects of carbon sources on internalization of Lac12 by using a LAC12-GFP fusion construct. When galactose- or lactose-grown cells are shifted to a fresh sugar medium, Lac12-GFP is removed from the plasma membrane and localized intracellularly. Surprisingly, even galactose or lactose in the new media caused the internalization, and cells responded differently to theses two sugars. Our results reveal that this process is dependent of sugar species and also sugar concentration. Lac12-GFP internalization causes reduction on [C14]lactose uptake rates and also occurs in a Klsnf1 mutant strain; thereby, it is independent of KlSnf1 activity. We suggest that glucose-6-phosphate is the intracellular signal, since internalization was induced by 2-deoxyglucose and inhibition of phosphoglucomutase by lithium prevented galactose- but not lactose- or glucose-induced internalization. Lac12-GFP internalization was not triggered by 6-deoxyglucose, and was irreversible in absence of protein synthesis.

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2015-11-20T13:46:53Z No. of bitstreams: 1 texto completo.pdf: 946177 bytes, checksum: 530b92322ea1b6035983e2dbd5f2c361 (MD5) / Made available in DSpace on 2015-11-20T13:46:53Z (GMT). No. of bitstreams: 1 texto completo.pdf: 946177 bytes, checksum: 530b92322ea1b6035983e2dbd5f2c361 (MD5) Previous issue date: 2015-04-29 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / No presente trabalho, a espectroscopia FT-Raman foi explorada como um método rápido para avaliar a presença de lactose e identificar fraude por adição de maltodextrina (2.5 – 50.0%) em leite em pó. Através dos espectros Raman foi possível diferenciar as amostras de leite em pó sem a necessidade de preparação das amostras, enquanto os métodos de controle de qualidade tradicionais, incluindo cromatografia líquida de alta eficiência (HPLC) são relativamente lentos e trabalhosos. Espectros Raman foram obtidos de amostras de leite em pó com alto e baixo teor de lactose, ambos com e sem adição de maltodextrina, totalizando 45 amostras em 4 tipos de tratamentos. Foram observadas diferenças entre os espectros das amostras quanto ao teor de lactose, assim como quanto a presença do adulterante. Como complemento, foram empregadas análise de componentes principais (PCA) e análise discriminante por mínimos quadrados parciais (PLS-DA) a fim de classificar as amostras. Os modelos PLS-DA desenvolvidos permitiram classificar todas as amostras, tanto em relação ao teor de lactose quanto à presença de maltodextrina. Os resultados demonstraram a utilidade da técnica de espectroscopia Raman em combinação com a quimiometria para determinar a presença de lactose e de maltodextrina nas amostras de leite em pó. / In this work, FT-Raman spectroscopy has been explored as a quick screening method to evaluate the presence of lactose and identify milk powder samples adulterated with maltodextrin (2.5 – 50.0%). Raman measurements can differentiate samples of milk powder, without the need for sample preparation, while traditional quality control methods, including high performance liquid chromatography, are cumbersome and slow. FT-Raman spectra were obtained from samples of high lactose and low lactose milk powder, both without and with addition of maltodextrin. Differences were observed between the spectra involved in identifying samples with low lactose content, as well as adulterated samples. In addition, exploratory data analysis using Raman spectroscopy and principal components analysis (PCA) and multivariate analysis was also developed to classify samples of milk powder with PCA and partial least squares discriminant analysis (PLS-DA). The PLS-DA models obtained allowed to classify all samples, both in relation to the content of lactose and the presence of maltodextrin. These results demonstrate the utility of FT-Raman spectroscopy in combination with chemometrics to infer about the quality of milk powder.

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.

The study was focused on molecular characterization of 42 clostridial strains. DNA was isolated by fenol-chloroform extraction procedure and precipitated with ethanol. After DNA isolation, PCR amplifications with specific primer sets were used for genus and species identification. Finally 19 strains were clasified as Clostridium tyrobutyricum and 3 strains were clasified as Clostridium butyricum. Presence of hydrogenase gene hydA was tested by PCR amplification using specific primer set HGf and HGr. Presence of hydrogenase gene was detected within 21 strains. (GTG)5 primer (rep-PCR) and Pr1 and Pr6 primers (RAPD) were used for differentiation of clostridial strains. Next, the cultivation of Clostridium tyrobutyricum S5 was studied under different conditions. The cultivation was carried out in liquid Reinforced Clostridial Medium (RCM) with lactose and cheese whey instead of glucose under anaerobe conditions. Growth was observed at laboratory temperature (20 to 23 °C) and at 37 °C, pH values ranging from 4.0 to 8.0 with 0.5 unit.