Three types of dried milk (whole, nonfat, and buttermilk) were packaged in a modified atmosphere with a novel palladium-based oxygen removing catalyst and stored for eight weeks at 50°C. Powders stored in air with no catalyst and powders stored with the catalyst in an atmosphere modified to contain 5.7% hydrogen in nitrogen were evaluated by instrumental, chemical, and sensory methods. Hexanal concentrations were measured weekly using solid phase microextraction (SPME) and gas chromatography (GC) to compare the degrees of oxidation in the powders stored with the catalyst to those stored without it. Color changes were also monitored weekly using Hunter's L-, a-, and b-values. At the end of the eight-week period, a paired comparison sensory test was used to ascertain if the catalyst had an effect on odor. Anisidine values were also measured at this point to determine levels of oxidation in the powders. No significant difference was found in levels of oxidation between samples packaged with and without the catalyst in the modified atmosphere. At the end of eight weeks, the average hexanal concentration in the whole milk powder stored with the oxygen scavenger was 1.19 ± 0.20 ppm, while the average hexanal concentration in the air-packed whole milk powder was 1.06 ± 0.08 ppm. The average hexanal concentrations for the buttermilk stored with the catalyst and without were 0.84 ± 0.18 and 0.79 ± 0.15 ppm, respectively. In the nonfat milk powder, the sample stored with the catalyst had an average hexanal concentration of 0.91 ± 0.14 ppm and the sample stored in air without the catalyst had an average hexanal concentration of 0.83 ±0.20 ppm. Difference testing by volunteer sensory panelists also revealed no significant differences. It was expected that the milk powders stored with the catalyst in the modified atmosphere would have lower levels of oxidation and off-odors at the end of the eight weeks. However, the treatment ultimately resulted in no chemical or sensory differences. Thus, the catalyst proved ineffective in the given conditions. This could be due to a loss of the hydrogen required for the catalyst to function as time progressed or a lack of significant oxidation under the conditions employed. / Master of Science in Life Sciences

Aflatoxina M1 (AFM1) foi pesquisada em 300 amostras de leite em pó distribuído pelo Programa de Alimentação Escolar do Município de São Paulo, SP-Brasil. As análises foram efetuadas através do ensaio por enzimas imuno-adsorvidas (ELISA), mediante o emprego de conjuntos de reativos produzidos em escala comercial. As amostras foram reconstituídas em água a 1:8 e submetidas diretamente ao ensaio, sem etapas de purificação. Os resultados revelaram 72 amostras (24,0 por cento ) positivas para AFM1, em concentrações de O,01 - 1,00 ng/ml, com média de O,15 ng/ml. Concentrações acima de 0,10 ng/ml foram observadas em 33 amostras (11,0por cento ). O método de ELISA foi avaliado no laboratório, através da execuçao de análises repetidas em amostras de leite experimentalmente contaminado com a toxina. Para os níveis de 0,10; 0,20; 0,50 e 1,00 ng/ml, os percentuais de recuperação foram, respectivamente, 83,0por cento ; 87,5por cento ; 103,0por cento e 111,8por cento . O desvio padrão relativo, para as referidas concentrações foi, respectivamente, 65,5por cento ; 31,8por cento ; 10,9por cento e 13,6por cento (n = 10, para cada nível de contaminação). Utilizando-se os dados de consumo de leite, adotados pelo Programa, para crianças de 4 meses de idade (máxima ingestão), estimou-se a ingestão diária média de 3,7 ng de AFM1/kg de peso corpóreo/dia. Discute-se a importância destes dados para a saúde humana, bem como os principais aspectos relativos ao estabelecimento de limites de tolerância para a AFM1 em leite e derivados. / Aflatoxin M1 (AFM1) was surveyed in 300 samples of milk powder distributed by the School Food Supply Program of São Paulo, SP-Brazil. The analysis were performed by commercially available test sistems of competitive enzyme-linked immunosorbent assay (ELISA). Samples were reconstituted in water (1:8) and submitted directly to the assay, without clean-up procedures. Results showed 72 (24.0per cent ) positive samples for AFM1 at levels of 0.01 - 1.00 ng/ml (mean: 0.15 ng/ml). Concentrations above 0.10 ng/ml were observed in-33 samples (11.0per cent ). The method performance was evaluated experimentally in the laboratory, through repeated analysis of milk samples spiked with the toxin. Recoveries of AFM1 added to milk at levels of 0.10, 0.20, 0.50 and 1.00 ng/ml were 83.0per cent , 87.5per cent , 103.0per cent and 111.8per cent , respectively. Relative standard deviations for the concentrations refered were 65.5per cent , 31.8per cent , 10.9per cent and 13.6per cent , respectively (n = 10, per spiking level). By using data on milk consumption patterns, adopted by the Program for children aging 4 months (highest intake), a mean daily intake of 3.7 ng of AFM1/kg body weight/day was estimated. The implications of these data on human health, as well as the approaches for the establishment of regulations for AFM1 in milk and milk products, are discussed.

Aflatoxina M1 (AFM1) foi pesquisada em 300 amostras de leite em pó distribuído pelo Programa de Alimentação Escolar do Município de São Paulo, SP-Brasil. As análises foram efetuadas através do ensaio por enzimas imuno-adsorvidas (ELISA), mediante o emprego de conjuntos de reativos produzidos em escala comercial. As amostras foram reconstituídas em água a 1:8 e submetidas diretamente ao ensaio, sem etapas de purificação. Os resultados revelaram 72 amostras (24,0 por cento ) positivas para AFM1, em concentrações de O,01 - 1,00 ng/ml, com média de O,15 ng/ml. Concentrações acima de 0,10 ng/ml foram observadas em 33 amostras (11,0por cento ). O método de ELISA foi avaliado no laboratório, através da execuçao de análises repetidas em amostras de leite experimentalmente contaminado com a toxina. Para os níveis de 0,10; 0,20; 0,50 e 1,00 ng/ml, os percentuais de recuperação foram, respectivamente, 83,0por cento ; 87,5por cento ; 103,0por cento e 111,8por cento . O desvio padrão relativo, para as referidas concentrações foi, respectivamente, 65,5por cento ; 31,8por cento ; 10,9por cento e 13,6por cento (n = 10, para cada nível de contaminação). Utilizando-se os dados de consumo de leite, adotados pelo Programa, para crianças de 4 meses de idade (máxima ingestão), estimou-se a ingestão diária média de 3,7 ng de AFM1/kg de peso corpóreo/dia. Discute-se a importância destes dados para a saúde humana, bem como os principais aspectos relativos ao estabelecimento de limites de tolerância para a AFM1 em leite e derivados. / Aflatoxin M1 (AFM1) was surveyed in 300 samples of milk powder distributed by the School Food Supply Program of São Paulo, SP-Brazil. The analysis were performed by commercially available test sistems of competitive enzyme-linked immunosorbent assay (ELISA). Samples were reconstituted in water (1:8) and submitted directly to the assay, without clean-up procedures. Results showed 72 (24.0per cent ) positive samples for AFM1 at levels of 0.01 - 1.00 ng/ml (mean: 0.15 ng/ml). Concentrations above 0.10 ng/ml were observed in-33 samples (11.0per cent ). The method performance was evaluated experimentally in the laboratory, through repeated analysis of milk samples spiked with the toxin. Recoveries of AFM1 added to milk at levels of 0.10, 0.20, 0.50 and 1.00 ng/ml were 83.0per cent , 87.5per cent , 103.0per cent and 111.8per cent , respectively. Relative standard deviations for the concentrations refered were 65.5per cent , 31.8per cent , 10.9per cent and 13.6per cent , respectively (n = 10, per spiking level). By using data on milk consumption patterns, adopted by the Program for children aging 4 months (highest intake), a mean daily intake of 3.7 ng of AFM1/kg body weight/day was estimated. The implications of these data on human health, as well as the approaches for the establishment of regulations for AFM1 in milk and milk products, are discussed.

Dans une perspective de sociologie économique attentive à l’influence de la matérialité du produit sur les modalités de sa mise en marché, cette thèse analyse l’évolution des liens marchands qui organisent le commerce de poudre de lait entre un lieu de production (la France) et un lieu de consommation (le Mali). La première partie étudie la genèse du marché mondial de la poudre de lait et son évolution marquée par la libéralisation des politiques agricoles qui renforce la prégnance des mécanismes marchands. La sujétion des producteurs laitiers, français et maliens, au marché mondial est toutefois limitée par le caractère imparfait de la substitution entre les deux matières premières laitières utilisées dans les procès de transformation : la poudre de lait (produit du commerce international) et le lait cru à la circulation marchande restreinte. La seconde partie s’appuie sur deux enquêtes ethnographiques. La première examine la mise en valeur internationale de la poudre de lait par des traders dont le travail spéculatif est d’autant plus valorisé que le produit est rare et ses prix futurs, incertains. La saisonnalité de la production et la périssabilité du produit limitent toutefois leur pouvoir spéculatif. La seconde, effectuée au marché de Bamako, s’intéresse à la traduction de la norme marchande internationale (rapport entre une qualité et un prix) le long de deux circuits de distribution, distingués selon que la poudre est conditionnée industriellement ou artisanalement. L’efficacité du circuit artisanal tient, en partie, au fait que, en permettant une adaptation rapide par la qualité ou les quantités, il s’ajuste au plus près au contexte international marqué par la volatilité des prix et l’irrégularité des qualités disponibles. / This research is based on economic sociology approaches focusing on the influence of materiality of products on their marketization. It analyses the evolution of market relationships that organize trading of powdered milk between a production area (France) and a consumption area (Mali). The first part studies the genesis of powdered milk's world market and its evolution, characterised by a phase of liberalization of agricultural policies that strenghten market mecanisms. The dependence of French and Malian milk producers on the world market is nevertheless limited, due to an imperfect substituability of the two dairy products used for processing: powdered milk (produced for international trade) and raw milk which has a limited circulation capacity. The second part of the research is based on two ethnographic studies. The first one considers the international valuation of powdered milk by traders whose speculative activity becomes more valuable when products are rare and future prices uncertain. Production seasonality and product perishability limit however their speculation capacity. The second study was carried out in Bamako's market. It deals with the translation of international market norms (relationship between a quality and a price) along two distribution channels, differentiated by the type of powdered milk conditioning (industrial or artisanal). The efficiency of the artisanal value chain relies partly on its fast adaptation through quality or quantities. Thus it adjustes to the international context of price volatility and irregularity of available qualities.

Made available in DSpace on 2014-12-17T15:41:56Z (GMT). No. of bitstreams: 1 AlessandraMC_DISSERT.pdf: 3533058 bytes, checksum: de92ff683335d9aa6c119013acb5b5d0 (MD5) Previous issue date: 2011-08-15 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work calibration models were constructed to determine the content of total lipids and moisture in powdered milk samples. For this, used the near-infrared spectroscopy by diffuse reflectance, combined with multivariate calibration. Initially, the spectral data were submitted to correction of multiplicative light scattering (MSC) and Savitzsky-Golay smoothing. Then, the samples were divided into subgroups by application of hierarchical clustering analysis of the classes (HCA) and Ward Linkage criterion. Thus, it became possible to build regression models by partial least squares (PLS) that allowed the calibration and prediction of the content total lipid and moisture, based on the values obtained by the reference methods of Soxhlet and 105 ? C, respectively . Therefore, conclude that the NIR had a good performance for the quantification of samples of powdered milk, mainly by minimizing the analysis time, not destruction of the samples and not waste. Prediction models for determination of total lipids correlated (R) of 0.9955, RMSEP of 0.8952, therefore the average error between the Soxhlet and NIR was ? 0.70%, while the model prediction to content moisture correlated (R) of 0.9184, RMSEP, 0.3778 and error of ? 0.76% / Neste trabalho foram constru?dos modelos de calibra??o para determinar os teores de lip?dios totais e umidade em amostras de leite em p?. Para isso, utilizou-se a espectroscopia no infravermelho pr?ximo por reflect?ncia difusa, aliado ? calibra??o multivariada. Inicialmente, os dados espectrais foram submetidos ? corre??o multiplicativa do espalhamento da luz (MSC) e alisamento de Savitzsky-Golay. Em seguida, as amostras foram divididas em subgrupos por aplica??o da an?lise por agrupamento hier?rquico das classes (HCA) e crit?rio de Ward Linkage. Desta forma, tornou-se poss?vel construir modelos de regress?o por m?nimos quadrados parciais (PLS) que permitiu a calibra??o e previs?o dos teores de lip?dios e umidade, com base nos valores obtidos por m?todos de refer?ncia de Soxhlet e secagem a 105 ? C, respectivamente. Portanto, conclui-se que o NIR apresentou um bom desempenho para quantifica??o de amostras de leite em p?, principalmente pela minimiza??o do tempo das an?lises, n?o destrui??o das amostras e n?o gera??o de res?duos. Os modelos de previs?o para determina??o de lip?dios totais apresentaram correla??o (R) de 0,9955, RMSEP de 0,8952, por conseguinte, o erro m?dio entre o Soxhlet e o NIR foi ? 0,70%, enquanto o modelo de previs?o para teor de umidade apresentou correla??o (R) de 0,9184, RMSEP, 0,3778 e erro de ? 0,76%