Made available in DSpace on 2014-07-29T15:22:58Z (GMT). No. of bitstreams: 1 dissertacao flavio pereira.pdf: 1203680 bytes, checksum: bcaf62e9eb5545119172fb4728bdaaee (MD5) Previous issue date: 2010-02-26 / Raw milk is a natural culture medium for the microbial growth and easy deterioration, because of that, thermal processing is needed as soon as possible. A new technology has been used to improve the food quality, active packaging, such as antimicrobial films, wich the intention to control the microbial growth in the products. The aim of this study was to evaluate the UHT milk quality produced in Goiás State, isolation and identification of Bacillus sporothermodurans, beside create a antimicrobial film for inhibition of this microrganism high heat resistance spore former. The isolation of psychrotrophic in raw milk was used PCA with incubation at 21 °C for 72h. To evaluate the UHT milk has been doing research on aerobic mesophilic in PCA with incubation at 30 °C for 72h and to thermoresistents microrganisms was in ABHI with incubation at 35 °C for 48h. The identification of isolates was performed according to convetional methods of biochemistry identification. From raw milk, the psychrotrophic microrganisms most isolates were Staphylococcus sp. and Corynebacterium sp., both with 21,5% from 70 isolates, verifying a higher contauge of Gram-positive microrganisms (82,85%). Considering the 157 UHT isolates, just 31 were identified as Gram-positive microrganisms through biochemical tests, only 2 correponded to B. sporothermodurans, although there are differences from the tests and their results between various authors, requiring more accurate identification using molecular biology. The antimicrobial film maded of cellulose acetate with addition of nisin to inhibit the development of B. sporothermodurans, the results indicated action of nisin in inhibition this microrganism, however, when incorporated into the film, did not show the expected results in both tests, solid and liquid medium, although the specific rate (μ) growth of the microrganism was changing iin the lowest concentration tested. There is a need to conduct testing in foods, mainly in dairy products which have been reported contamination by B. sporothermodurans. / O leite por ser um alimento rico, constituí-se em um meio natural para o desenvolvimento de vários microrganismos, principalmente bactérias; desta forma, muito perecível. É necessário tratamento térmico o mais rápido possível, a fim de manter a qualidade. Uma nova tecnologia vem sendo utilizada na melhoria dos alimentos, denominada de embalagem ativa, como os filmes antimicrobianos, na intenção de controlar o desenvolvimento microbiano no produto. O objetivo deste trabalho foi de avaliar a qualidade de leite UAT produzido no Estado de Goiás, assim como isolar e identificar microrganismos psicrotróficos de leite cru e microrganismos de leite UAT, sendo que para este direcionado para identificação de Bacillus sporothermodurans, bem como criação de filme antimicrobiano para inibição deste microrganismo produtor de esporos altamente resistentes. Para o isolamento de psicrotróficos em leite cru, foi utilizado PCA e incubação à 21°C por 72h. Para avaliação de qualidade do leite UAT, foi feito a pesquisa de aeróbios mesófilos em PCA com incubação à 30°C por 72h e o isolamento de microrganismos termorresistentes foi realizado em ABHI com incubação a 35°C por 48h. A identificação dos isolados foi realizada conforme metodologias clássicas de identificação bioquímica. Segundo esta identificação, os microrganismos psicrotróficos mais isolado foram Staphylococcus sp. e Corynebacterium sp. com 21,5% cada, dos 70 isolados, verificando uma percentagem maior de microrganismos Gram-positivos (82,85%). Considerando os isolados de leite UHT, dos 157, apenas 31 foram identificados como sendo bastonetes Gram-positivos que submetidos a testes bioquímicos, apenas 2 corresponderam ao B. sporothermodurans seguindo-se os resultados conforme registrado, apesar de haver divergências quanto a alguns testes e seus resultados, necessitando de identificação mais apurada utilizando-se de biologia molecular. Quanto ao filme antimicrobiano a base polimérica utilizada foi o acetato de celulose com incorporação de nisina, a fim de inibir o desenvolvimento do B. sporothermodurans com o intuito de verificar a ação deste peptídeo antimicrobiano frente a este microrganismo. Os resultados obtidos indicaram ação da nisina na inibição do microrganismo estudado, no entanto, quando incorporado ao filme, não apresentou o resultado esperado, tanto em testes em meio sólido como em meio líquido, apesar de ter alterando a velocidade específica (μ) de crescimento do microrganismo na concentração mais baixa testada. Há a necessidade de realização de teste em alimentos, especialmente em leite e derivados em que foram relatados a contaminação pelo B. sporothermodurans

L’objectif de ce travail est de développer une démarche permettant de prédire l’évolution de la charge microbienne à la surface de carcasses de porc lors d’un transport frigorifique selon les conditions opératoires (température et humidité de l’air de soufflage) et des conditions initiales (profil de température en sortie de chambre froide d’abattoir). La croissance microbienne dépendant notamment de la température et de l’activité de l’eau, il est nécessaire d’étudier les transferts de chaleur et de matière de type diffusif au sein des carcasses et de type convectif autour des carcasses. Ces derniers dépendent de la circulation d’air dans le véhicule frigorifique lorsqu’il est chargé de centaines de demi-carcasses ce qui rend la géométrie particulièrement complexe.De ce fait, ce travail fait appel à diverses disciplines : mécanique des fluides, transferts thermiques et microbiologie prévisionnelle. Le couplage de ces trois disciplines permet d’apporter des réponses scientifiques quant à la qualité sanitaire des carcasses de porc.En travaillant sur un dispositif expérimental reproduisant une semi-remorque chargée de carcasses de porc à l’échelle réduite, les écoulements d’air ont pu être caractérisés par vélocimétrie laser Doppler 2D dans deux configurations de distribution d’air (avec et sans conduits). De plus, les coefficients de transfert convectifs locaux ont pu être estimés à la surface de différentes parties des carcasses de porc et à différentes positions dans la semi-remorque à l’échelle réduite. Un schéma simplifié des écoulements d’air a été établi, il permet de localiser les « zones à risque » dans la semi-remorque chargée (faible circulation d’air et faible coefficients de transfert convectif).En se basant sur les résultats de l’étude expérimentale à l’échelle laboratoire et sur ceux récoltés au cours de vrais transports frigorifiques, la variabilité des paramètres caractérisant l’air circulant autour des carcasses a pu être estimée. Ces informations ont servi de conditions aux limites d’un modèle de transfert de chaleur et de matière (eau) au sein de la partie la plus sensible au niveau microbiologique: le jambon. Ce modèle 3D, résolu par la méthode des éléments finis, permet de prédire l’évolution de la température, de la teneur en eau et de la charge microbienne (Pseudomonas) à la surface de la partie maigre du jambon pour différents scénarios de transport frigorifique. Les résultats ont montré que si le transport commence alors que le cœur des carcasses est encore tiède (15°C au lieu de 7°C selon la réglementation actuelle) la croissance des microorganismes à la surface des carcasses de porc n’est globalement pas plus importante entre l’abattage et l’arrivée sur le site de découpe.Enfin, une étude de terrain a permis de valider les données obtenues à l’échelle du laboratoire et de réaliser une étude énergétique. Il apparait que quelle que soit le pourcentage de carcasses tièdes dans la semi-remorque, la capacité frigorifique du système de production de froid est généralement suffisante pour évacuer la chaleur des carcasses.Cette étude a permis de développer des méthodes de caractérisation des écoulements et des transferts dans une géométrie particulièrement complexe. Elle a montré l’intérêt de coupler des modèles de transfert et de microbiologie prévisionnelle. Les expérimentions à l’échelle laboratoire ont été construites en reproduisant au plus près les conditions réelles grâce à l’appui de spécialistes de la filière viande. Ainsi les carcasses modèles ont été réalisées dans des moules obtenus par impression 3D d’après des scanners X de vraies carcasses. Les résultats de cette étude sont directement utilisables par la profession et les pouvoirs publics pour l’adaptation de la réglementation des transports réfrigérés. La démarche développée pourra être adaptée pour des problèmes similaires dans des enceintes ventilées très encombrées. / The objective of this work is to develop an approach allowing to predict the evolution of the microbial load on the surface of pork carcasses during a refrigerated transport according to the operating conditions (temperature and humidity of the blowing air) and initial conditions (temperature profile at the outlet of the slaughterhouse cold room). Since microbial growth depends mainly on temperature and water activity, it is necessary to study heat and mass transfer the transfer within and around the carcasses. These phenomena depend on the circulation of air in the refrigerated vehicle loaded with hundreds of half-carcasses which makes the geometry particularly complex.Thus, this work involves various disciplines: fluid mechanics, heat transfer and predictive microbiology. The coupling of these three disciplines makes it possible to provide scientific answers as to the sanitary quality of the pork carcasses.By conducting experiments on a semitrailer loaded with pork carcasses on a reduced scale, the air flows could be characterized by 2D Doppler laser velocimetry in two air distribution configurations (with and without air ducts). In addition, local convective heat transfer coefficients could be estimated at the surface of different parts of pork carcasses and at different positions in the reduced-scale trailer. A simplified model of the airflow has been established, that makes it possible to identify the "risk zones" in the loaded semi-trailer (low air circulation and low convective transfer coefficients).Based on the results of the experimental laboratory scale study and those collected during actual refrigerated transport, the variability of the parameters characterizing the air circulating around the carcasses could be estimated. This information served as boundary conditions for a model of heat and mass (water) transfer within the most sensitive part at the microbiological level: the ham. This 3D model, solved by the finite element method, makes it possible to predict the evolution of the temperature, the water content and the microbial load (Pseudomonas) on the surface of the lean part of the ham for different scenarios. The results showed that if the transport begins while the heart of the carcasses is still warm (15°C instead of 7°C according to current regulation) the growth of microorganisms on the surface of pork carcasses is generally not more between slaughter and arrival at the cutting site.Finally, a field study validated the data obtained at the laboratory scale and carried out an energy study. It appears that whatever the percentage of warm carcasses in the semi-trailer, the cooling capacity of the cooling system is generally sufficient to evacuate the heat of the carcasses.This study has made it possible to develop a method that characterizes airflow and heat transfer methods in a particularly complex geometry. It showed the interest of coupling transfer models and predictive microbiology models. Experiments at the laboratory scale were built by reproducing the real conditions as closely as possible thanks to the support of specialists in the meat sector. Thus the model carcasses were made in molds obtained by 3D printing from X-Ray scanners of real carcasses. The results of this study are directly usable by the profession and the public authorities for the adaptation of the refrigerated transport regulations. The approach developed may be adapted for similar problems in very congested ventilated enclosures.

Este trabalho avaliou os efeitos de diferentes períodos de armazenamento do leite de cabra in natura sobre a qualidade do produto em pó. Foram avaliadas as alterações microbiológicas, físico-químicas e bioquímicas do leite cru e a influência nas características microbiológicas, físicas, bioquímicas e sensoriais do leite em pó durante o armazenamento por 0, 60, 120 e 180 dias. Foram realizados 3 ensaios idênticos nos quais cerca de 105 L de leite de cabra recém-ordenhado foram igualmente divididos em 3 partes e armazenados a temperatura controlada de 4 ºC por até 5 dias. Nos dias 1, 3 e 5 após a coleta do leite in natura, uma alíquota de 500 mL foi coletada para a realização das análises. O restante da fração (aproximadamente 35L) foi submetido à pasteurização (65 ºC por 30 min), concentração sob vácuo (40% de sólidos totais) e secagem por atomização. Os lotes de leite de cabra em pó obtidos foram avaliados através de análises de composição (umidade, teores de proteína, gordura, lactose e cinzas), dispersibilidade, cor, atividade de água, índice de peróxidos, atividades proteolítica e lipolítica e análise sensorial por uma equipe de provadores treinados. Foram observados efeitos (P < 0,05) do período de armazenamento do leite in natura e/ou do leite em pó, ou mesmo interação destes efeitos sobre determinadas características durante o armazenamento do leite em pó, como: aumento linear das populações de micro-organismos mesófilos, psicrotróficos lipolíticos e psicrotróficos proteolíticos do leite in natura, aumento da intensidade da cor branca (L*) do leite em pó, da atividade lipolítica e da oxidação do leite em pó. Também foram observados efeitos (P < 0,05) em características sensoriais como: redução da coloração amarela do pó de do leite reconstituído, aumento do odor cáprico e dos sabores rançoso e amargo do leite reconstituído. Considerando-se a avaliação global das variáveis estudadas, recomenda-se que o período de armazenamento a 4 oC do leite de cabra in natura não ultrapasse 3 dias, para que ocorra a preservação da qualidade do leite de cabra em pó por até 180 dias. / This study evaluated the effects of different storage periods of raw goat milk on the quality of the powder product. Alterations in microbiological and physical-chemical properties of raw milk and their influence on the microbiological, physical, biochemical and sensory characteristics of milk powder during storage for 0, 60, 120 and 180 days were evaluated. There were 3 identical tests in which about 105 L of recently milked goat milk were divided into 3 parts and stored at controlled temperature of 4 ºC for up 5 days. On days 1, 3 and 5 after storage, an aliquot (500 mL) of raw milk was collected to perform microbiological, physico-chemical and biochemical analysis. The remaining fraction (about 35 L) was subjected to pasteurization (65 ºC for 30 min), vacuum concentration (40% of total solids) and spray drying. The powders produced were evaluated through analysis of composition (moisture, protein, fat, lactose and ash), dispersibility, color, water activity, granulometry, peroxide value, proteolytic and lipolytic activities and sensory analysis by a selected team of panelists. Effects of storage of raw milk or/and powdered milk or their interaction were observed (P <0.05) on certain characteristics during storage of milk powder, as the increasing of mesophilic, lipolytic psychrotrophic and proteolytic psychrotrophic microorganisms populations in raw milk, increasing of the white color (L*), the lipolytic activity and the peroxide value of milk powder. There were also observed effects (P < 0.05) on sensory characteristics such as decreasing of yellow color of milk powder and reconstituted milk, increasing of capric smell, rancid and bitter flavour of reconstituted milk. Considering the overall evaluation of studied variables, it\'s recommended that the raw goat milk storage at 4 oC does not exceed 3 days to preserve the quality of goat milk powder until 180 days.

Submitted by Deyse Queiroz (deysequeirozz@hotmail.com) on 2018-05-29T17:56:21Z No. of bitstreams: 1 INÁCIA DOS SANTOS MOREIRA - DISSERTAÇÃO PPGSA PROFISSIONAL 2014..pdf: 1960619 bytes, checksum: 0eec38ed3470ea1ff2f29f63cf555e2b (MD5) / Made available in DSpace on 2018-05-29T17:56:21Z (GMT). No. of bitstreams: 1 INÁCIA DOS SANTOS MOREIRA - DISSERTAÇÃO PPGSA PROFISSIONAL 2014..pdf: 1960619 bytes, checksum: 0eec38ed3470ea1ff2f29f63cf555e2b (MD5) Previous issue date: 2014-02-26 / O presente trabalho teve como objetivo caracterizar a qualidade da romã „Molar‟ durante o armazenamento dos frutos in natura, sob diferentes temperaturas de refrigeração, e avaliar o uso de biofilmes à base de fécula de mandioca e Spirulina platensis nos frutos armazenados sob as condições ambiente à 25ºC e sob condições de armazenamento refrigerado a 10ºC. O estudo foi subdividido em duas etapas no Laboratório de Análise de Alimentos da UFCG, no Campus de Pombal - PB. Na primeira etapa, os frutos foram armazenados nas temperaturas 6°C, 10°C e 12°C e analisados ao 0, 12, 18, 24, 30, 36 dias de refrigeração, sendo cada intervalo acrescidos de dois dias de permanência em sala sob condição ambiente (24 ± 2ºC e 43 ± 5% UR), para simular as condições de comercialização (Shelf life). Na segunda etapa, foram selecionados doze frutos para sua caracterização inicial, os outros frutos receberam os seguintes tratamentos: T1 - Testemunha, sem recobrimento; T2 - 1% de fécula de mandioca; T3 - 3% de fécula de mandioca; T4 - 1% de Spirulina platensis; T5 - 3% de Spirulina platensis; T6 - 1% de fécula de mandioca e 1% de Spirulina platensis e T7 - 3% de fécula de mandioca e 3% de Spirulina platensis. Ao receber os tratamentos, os frutos foram separados em dois experimentos para o estabelecimento das condições de armazenamento, onde: Experimento I – Frutos tratados e armazenados em sala climatizada, com controle de temperatura e umidade, simulando condições de comercialização em temperatura ambiente (25,1ºC e 43,3% UR) durante 6 dias e Experimento II - Frutos tratados e refrigerados em B.O.D. (10ºC e 56,7% UR) por um período de 12 dias acrescidos de dois dias de permanência sob condições ambiente (Shelf life). Avaliou-se características biométricas, visuais e físico-químicas. Romãs „Molar‟ armazenadas a 10ºC por 36 dias seguidos de „shelf life‟ de dois dias a 24°C, se mantêm satisfatórias para comercialização in natura, sem prejuízos nos atributos de qualidade biométricos, visuais e físico-químicos. O armazenamento dos frutos a 6ºC proporciona prejuízos na qualidade visual dos frutos devido ao aparecimento de manchas, prejudicando a aparência externa. A temperatura de armazenamento a 12ºC proporciona sintomas de murcha apenas ao final do armazenamento. As temperaturas de armazenamento a 6ºC, 10ºC ou 12ºC podem ser temperaturas apropriadas para o armazenamento de romãs destinadas à indústria, por não prejudicarem os atributos internos de qualidade da romã „Molar‟, especialmente relacionados à integridade das sementes, arilos, rendimento de suco, sólidos solúveis, acidez tituláveis, flavonoides e antocianinas. O revestimento com 1% de fécula de mandioca no armazenamento a 25ºC reuniu boas caracterisiticas biométricas, visuais e físico-químicas para a conservação pós-colhetia da romã; A elevada perda dos diâmetros em frutos armazenados em condição ambiente foi fator limitante na qualidade e vida útil pós-colheita de romã „Molar‟. O revestimento com 3% de fécula de mandioca e com 3% de fécula de mandioca mais 3% de Spirulina plantensis associados à refrigeração apresentaram melhor qualidade biométrica, visual e fisico-química durante os quatorze dias de armazenamento. / The present study aimed to characterize the quality of Pomegranate ' Molar ' during storage of raw fruits under different cooling temperatures and evaluate the use of biofilms based on cassava starch and Spirulina platensis in fruits stored under ambient conditions at 25°C and under conditions of cold storage at 10ºC. The study was divided into two stages at the Laboratory of Food Analysis UFCG, Campus de Pombal - PB. In the first stage , the fruits were stored at temperatures 6°C , 10°C and 12°C and analyzed at 0, 12, 18, 24, 30, 36 days of refrigeration and each range , plus two days of stay in room under ambient conditions (24 ± 2ºC and 43 ± 5% RH) to simulate marketing conditions (Shelf Life). In the second stage, twelve fruits were selected for initial characterization , the other fruits received the following treatments : T1 - control , Uncoated; T2 - 1% of cassava starch ; T3 - 3% of cassava starch ; T4 - 1% of Spirulina platensis; T5 - 3% of Spirulina platensis; T6 - 1 % of cassava starch and 1% Spirulina platensis and T7 - 3 % of cassava starch and 3% Spirulina platensis . Upon receiving the treatments, fruits were separated into two experiments to establish the conditions of storage, where: Experiment I - Fruits processed and stored in a climatic chamber with controlled temperature and humidity conditions simulating marketing at room temperature (25,1ºC and 43,3 % RH) for 6 days and Experiment II - Fruits treated and chilled in BOD (10ºC and 56,7 % RH) for a period of 12 days plus two days under ambient conditions (Shelf Life). It was evaluated biometric, visual and physical- chemical characteristics. Pomegranates 'Molar' stored at 10ºC for 36 days followed by 'shelf life' two days at 24°C, remains satisfactory for fresh fruit market without losses in quality attributes biometric, visual and physical chemistry. The storage of fruits at 6ºC provides visual loss in fruit quality due to the appearance of blemishes, impairing external appearance. The storage temperature to 12ºC provides wilt symptoms only at the end of storage. Storage temperatures to 6°C, 10°C or 12°C may be appropriate temperatures for storage of pomegranates for industry not to harm the internal quality attributes of pomegranate ' Molar ', especially related to integrity seeds, arils, juice yield , solids soluble, titratable acidity, flavonoids and anthocyanins. The coating with 1% of cassava starch in storage at 25ºC has gathered good biometric, visual and physic chemical's characteristic for postharvest conservation pomegranate; The high loss of diameter in fruits stored at ambient condition was a limiting factor in the quality and postharvest pomegranate 'Molar' life. The coating with 3% of cassava starch and 3% of cassava starch 3% Spirulina plantensis associated with refrigeration showed better biometric, visual and physico-chemical quality during storage fourteen days.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-03-21T15:26:57Z No. of bitstreams: 2 Dissertação - Anicézio José Da Silveira Guimarães - 2017.pdf: 1539465 bytes, checksum: b9439c568716432c687b903a7777b394 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-03-21T15:27:15Z (GMT) No. of bitstreams: 2 Dissertação - Anicézio José Da Silveira Guimarães - 2017.pdf: 1539465 bytes, checksum: b9439c568716432c687b903a7777b394 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-03-21T15:27:15Z (GMT). No. of bitstreams: 2 Dissertação - Anicézio José Da Silveira Guimarães - 2017.pdf: 1539465 bytes, checksum: b9439c568716432c687b903a7777b394 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-02-21 / Milk is a highly nutritious agricultural product and the basis of a productive chain that generates employment and income, but its quality is historically deficient and seasonal in several regions of Brazil, affected mainly by climatic variations and production conditions. In order to improve the quality of this raw material, control measures and incentives have been implemented by the dairy sector, such as normative instructions and payment for quality. Regulatory criteria are very strict, but if milk quality is not legally satisfactory, it may not only affect industrial yield but also food security and producer remuneration. Thus, this study aims to evaluate the quality of raw milk refrigerated in relation to the legal framework and the effect of its seasonality on the price paid to producers. Results of monthly analyzes of fat, lactose, protein, total dry stratum (TDS), dry defatted stratum (DDS), somatic cell count (SCC) and total bacterial count (TBC) of 35,245 samples of milk from expansion tanks of the Catalan/GO Microregion. The averages were analyzed for variance and Tukey's test (p≤0.05) for comparison of means, considering the effects of the months, seasons and periods (dry and rainy) of the year, besides the legal parameters and model of Parameters for Milk Quality Payment (PMQP). According to legal parameters, the quality of refrigerated raw milk from expansion tanks was not adequate, as approximately 25% of the samples presented legal disagreement. The total bacterial count (TBC) was the only requirement whose geometric means were above the maximum limits allowed, and the somatic cell count (SCC) was reduced in the percentage of samples in legal compliance in the temporal period. The quality of the milk was better in the months of April to June (autumn) and in the dry period of the year, when it presented high physicochemical composition and reduced microbiological composition in relation to the other periods. Considering the 'Parameters for Milk Quality Payment' (PMQP) proposed in this study, the seasonality of milk quality influenced the price paid to producers, providing a subsidy of 3.8% to 6.9% in their remuneration. The biggest bonuses occurred in April and May, in the fall and dry period of the year, being the major contributions of fat and protein, while TBC caused a penalty. The results show that the main problems of the quality of refrigerated raw milk are those related to hygiene in the production and maintenance of the product and express the relevance of programs that penalize the goals not reached, but which also subsidize the quality of milk as an incentive for producers to produce Of good quality milk. Future studies are expected to be closer to the dairy farms and producers in order to guide and justify appropriate quality improvement programs for this raw material. / O leite é um produto agropecuário altamente nutritivo e base de uma cadeia produtiva geradora de emprego e renda, porém, sua qualidade é historicamente deficiente e sazonal em várias regiões do Brasil, afetada principalmente pelas variações climáticas e condições da produção. Visando melhoria da qualidade desta matéria-prima, medidas de controle e incentivos têm sido implementadas por órgãos do setor lácteo, tais como, instruções normativas e pagamento por qualidade. Os critérios normativos são bastante rígidos, mas caso a qualidade do leite não seja legalmente satisfatória, pode prejudicar não só o rendimento industrial, como também a segurança alimentar e a remuneração do produtor. Assim, este estudo tem por objetivo avaliar a qualidade do leite cru refrigerado em relação ao enquadramento legal e o efeito da sua sazonalidade sobre o preço pago aos produtores. Utilizou-se resultados de análises mensais de gordura, lactose, proteína, estrato seco total (EST), estrato seco desengordurado (ESD), contagem de células somáticas (CCS) e contagem bacteriana total (CBT) de 35.245 amostras de leite de tanques de expansão da Microrregião de Catalão/GO, coletadas entre 2006 a 2015. Submeteu-se as médias à análise de variância e teste de Tukey (p≤0,05) para comparação de médias, considerando-se efeitos dos meses, das estações e dos períodos (seco e chuvoso) do ano, além dos parâmetros legais e modelo de Parâmetros para Pagamento por Qualidade do Leite (PPQL). De acordo com os parâmetros legais, a qualidade do leite cru refrigerado de tanques de expansão não se apresentou adequada, pois cerca de 25% das amostras apresentaram desconformidade legal. A contagem bacteriana total (CBT) foi o único requisito cujas médias geométricas ficaram acima dos limites máximos permitidos, já a contagem de células somáticas (CCS) sofreu redução do percentual de amostras em conformidade legal, no período temporal. A qualidade do leite foi melhor nos meses de abril a junho (outono) e no período seco do ano, quando apresentou elevada composição físico-química e reduzida composição microbiológica em relação aos demais períodos. Considerando-se os 'Parâmetros para Pagamento por Qualidade do Leite' (PPQL) proposto neste estudo, a sazonalidade da qualidade do leite influenciou o preço pago aos produtores, proporcionando bonificação de 3,8% a 6,9% em sua remuneração. As maiores bonificações ocorreram em abril e maio, no outono e período seco do ano, sendo as maiores contribuições da gordura e proteína, enquanto a CBT causou penalização. Os resultados apontam como principais problemas da qualidade do leite cru refrigerado os relacionados à higiene na obtenção e manutenção do produto e expressam a relevância de programas que penalizam pelas metas não alcançadas, mas que também bonificam pela qualidade do leite como incentivo aos produtores para a produção do leite de boa qualidade. Estudos futuros devem se aproximar das unidades exploradoras do leite e dos produtores, a fim de nortear e fundamentar programas adequados de valorização da qualidade desta matéria-prima.

Este trabalho avaliou os efeitos de diferentes períodos de armazenamento do leite de cabra in natura sobre a qualidade do produto em pó. Foram avaliadas as alterações microbiológicas, físico-químicas e bioquímicas do leite cru e a influência nas características microbiológicas, físicas, bioquímicas e sensoriais do leite em pó durante o armazenamento por 0, 60, 120 e 180 dias. Foram realizados 3 ensaios idênticos nos quais cerca de 105 L de leite de cabra recém-ordenhado foram igualmente divididos em 3 partes e armazenados a temperatura controlada de 4 ºC por até 5 dias. Nos dias 1, 3 e 5 após a coleta do leite in natura, uma alíquota de 500 mL foi coletada para a realização das análises. O restante da fração (aproximadamente 35L) foi submetido à pasteurização (65 ºC por 30 min), concentração sob vácuo (40% de sólidos totais) e secagem por atomização. Os lotes de leite de cabra em pó obtidos foram avaliados através de análises de composição (umidade, teores de proteína, gordura, lactose e cinzas), dispersibilidade, cor, atividade de água, índice de peróxidos, atividades proteolítica e lipolítica e análise sensorial por uma equipe de provadores treinados. Foram observados efeitos (P < 0,05) do período de armazenamento do leite in natura e/ou do leite em pó, ou mesmo interação destes efeitos sobre determinadas características durante o armazenamento do leite em pó, como: aumento linear das populações de micro-organismos mesófilos, psicrotróficos lipolíticos e psicrotróficos proteolíticos do leite in natura, aumento da intensidade da cor branca (L*) do leite em pó, da atividade lipolítica e da oxidação do leite em pó. Também foram observados efeitos (P < 0,05) em características sensoriais como: redução da coloração amarela do pó de do leite reconstituído, aumento do odor cáprico e dos sabores rançoso e amargo do leite reconstituído. Considerando-se a avaliação global das variáveis estudadas, recomenda-se que o período de armazenamento a 4 oC do leite de cabra in natura não ultrapasse 3 dias, para que ocorra a preservação da qualidade do leite de cabra em pó por até 180 dias. / This study evaluated the effects of different storage periods of raw goat milk on the quality of the powder product. Alterations in microbiological and physical-chemical properties of raw milk and their influence on the microbiological, physical, biochemical and sensory characteristics of milk powder during storage for 0, 60, 120 and 180 days were evaluated. There were 3 identical tests in which about 105 L of recently milked goat milk were divided into 3 parts and stored at controlled temperature of 4 ºC for up 5 days. On days 1, 3 and 5 after storage, an aliquot (500 mL) of raw milk was collected to perform microbiological, physico-chemical and biochemical analysis. The remaining fraction (about 35 L) was subjected to pasteurization (65 ºC for 30 min), vacuum concentration (40% of total solids) and spray drying. The powders produced were evaluated through analysis of composition (moisture, protein, fat, lactose and ash), dispersibility, color, water activity, granulometry, peroxide value, proteolytic and lipolytic activities and sensory analysis by a selected team of panelists. Effects of storage of raw milk or/and powdered milk or their interaction were observed (P <0.05) on certain characteristics during storage of milk powder, as the increasing of mesophilic, lipolytic psychrotrophic and proteolytic psychrotrophic microorganisms populations in raw milk, increasing of the white color (L*), the lipolytic activity and the peroxide value of milk powder. There were also observed effects (P < 0.05) on sensory characteristics such as decreasing of yellow color of milk powder and reconstituted milk, increasing of capric smell, rancid and bitter flavour of reconstituted milk. Considering the overall evaluation of studied variables, it\'s recommended that the raw goat milk storage at 4 oC does not exceed 3 days to preserve the quality of goat milk powder until 180 days.

Dans cette étude, le comportement aérodynamique du jet pariétal (Re = 8000) cisaillé latéralement par un courant de perturbation externe (ELS) de profil de vitesse uniforme (Ulf) a été étudié et analysé. Les expérimentations ont été réalisées par PIV et LDV sur une maquette aéraulique isotherme à échelle réduite d’un meuble frigorifique de vente. L’étude est centrée sur la région du jet située à proximité de la section de soufflage (x/e < 10) qui correspond à la zone dans laquelle se développent les instabilités et le processus de transition vers la turbulence. L’analyse des résultats obtenus avec et sans perturbation a mis en évidence que la perturbation entraîne une diminution significative du pouvoir d’entraînement du jet, une forte décroissance de la vitesse moyenne maximale, un faible épanouissement du jet et une augmentation globale des valeurs des moments d’ordre deux de toutes les composantes des contraintes de Reynolds. L’analyse par PIV résolue en temps (10 kHz) montre une topologie déformée et allongée des structures de Kelvin-Helmholtz (K-H) pour (Ulf = 0,5 ms-1) et détachée pour (Ulf = 1 ms-1). Les résultats de l’interaction mutuelle ente les couches interne et externe indiquent que le courant ELS brise partiellement le mécanisme de formation des dipôles de vortex qui deviennent irréguliers et moins prédictifs, ce qui conduit à l’allongement de la zone de transition et retarde donc l’apparition de la zone auto-similaire du jet. D’après la technique POD, l’ELS engendre une redistribution énergétique entre les modes. Le courant ELS affecte également les instabilités K-H en perturbant leur organisation bidimensionnelle, leur topologie, leur alignement et leur fréquence de passage mettant en évidence l’effet inhibiteur exercé sur le développement des structures primaires. Les corrélations spatiales Rvv reflètent la diminution des échelles de longueur dans le cas d’un jet perturbé. / In this study, the aerodynamic behavior of the plane wall jet (Re = 8000) sheared laterally by an external lateral stream (ELS) of a uniform velocity profile (Ulf) was studied and analyzed. The experiments were carried out by PIV and LDV on a reduced-scale isothermal aeraulic model of a refrigerated display cabinet. The study focuses on the near-field region of the jet (x / e <10) which corresponds to the zone of transition to turbulence and onset and development of instabilities. The results obtained with and without perturbation showed a significant decrease in the entrainment rate, a strong decrease in the maximum velocity decay rate, a lower jet expansion and an overall increase in the values of second order moments of the Reynolds stress components. The time-resolved PIV analysis (10 kHz) shows a distorted and elongated topology of the Kelvin-Helmholtz (K-H) structures for (Ulf = 0,5 ms-1) and a detached topology for (Ulf = 1 ms-1). The results of the mutual interaction between the inner and outer layers indicate that the ELS partially breaks the vortex dipole formation mechanism which becomes irregular and less predictive, leading to the elongation of the transitional region and a lag effect in the beginning of the self-similarity region. POD technique reveals the role of the ELS in redistributing energy between the modes. The ELS also affects the K-H instabilities by disrupting their two-dimensional organization, topology, alignment and shedding frequency, highlighting the inhibitory effect exerted on the development of primary structures. The spatial correlations Rvv reflect the decrease of the length scales in the case of a perturbed jet.

La préservation de la chaîne du froid est un paramètre particulièrement important dans le cadre de la distribution urbaine, où les fréquentes ouvertures de portes induisent une charge thermique d’infiltration. Afin de réduire les transferts de masse et de chaleur et de protéger l’ouverture, des rideaux d’air ont récemment été installés au niveau de l’ouverture des camions frigorifiques. L’objet de la présente étude est d’étudier ce type confinement. Deux modèles CFD ont été développés pour simuler les champs de températures et de vitesses dans un camion réfrigéré clos. Ils ont permis de montrer que la variation de la vitesse de soufflage ne modifie pas de manière significative la structure des écoulements. Différents conduits d’air sont modélisés. Les résultats numériques montrent que la configuration avec un conduit ouvert améliore fortement le renouvellement d’air. Puis, une étude numérique est réalisée dans le but d’étudier les infiltrations de chaleur et de masse au cours de l’ouverture des portes. Ces écoulements sont bien prédits par le modèle CFD, excepté à la transition entre les deux régimes d’infiltration. Une caisse expérimentale a été équipée d’un dispositif de rideau d’air composé d’un jet ambiant, d’un jet froid ou d’un jet double. En parallèle, un modèle numérique CFD a été développé pour étudier l’influence de différents paramètres. Une bonne concordance entre les résultats numériques et expérimentaux a été observée. L’efficacité du rideau d’air ambiant est maximale lorsque le point d’impact du rideau se situe dans le plan de l’ouverture. Le rideau double maintient efficacement l’homogénéité de la température pour de courtes ouvertures. Le rideau d’air froid est la meilleur configuration, il limite fortement l’augmentation de température de l’enceinte et permet des gains énergétiques importants. / Cold chain safety is a key parameter for urban distribution where the frequent door-opening induces a heat infiltration. In order to reduce heat and mass transfer, air curtain have recently been installed to protect the doorway of refrigerated truck. The aim of this work is to study this type of door insulation. Two CFD numerical models were developed to simulate the temperature and velocity fields in a closed refrigerated truck. These models showed that modifying the blowing velocity does not modify the air flow structure inside the cavity. Different air chutes were modelled. Numerical results demonstrate that the configuration with a convergent and an open duct strongly improves the air renewal. A numerical investigation was performed in order to study heat and mass infiltration rates during the opening. The infiltration flow rate is well predicted by the CFD model, except at the transition between both flow regimes. An experimental truck was equipped with an air curtain setup, composed by an ambient air jet, a cold air jet or a double jet. In parallel, a numerical CFD model was developed to study the influence of various parameters. Experimental and numerical results were found to be in good agreement. The maximum efficiency of the ambient air curtain is reached when the impact point of the jet occurs in the door plane at the ground level. This configuration is only relevant for short opening times. The double air curtain efficiently maintains the temperature homogeneity for short openings. The cold air curtain is the best configuration which strongly limits the temperature increase during the opening and allows important energy savings.

L'utilisation des meubles frigorifiques de vente fermés a augmenté régulièrement dans les supermarchés en raison des économies d'énergie réalisées par rapport aux meubles ouverts. D’où la nécessité d'élargir les connaissances scientifiques à ce type de meuble. Pour l’instant la plupart des études de la littérature ont porté sur l'amélioration de l'efficacité énergétique après l'installation de portes, tandis que les études sur les mécanismes de transfert de chaleur dans les meubles frigorifiques fermés sont rares. De plus, il convient d’étudier également les circulations d’air car ils influencent les échanges de chaleur entre l’air et les produits, donc leur température. Cette thèse a pour objectif de mieux comprendre les phénomènes d’écoulement d’air et de transfert de chaleur dans les meubles frigorifiques fermés par la mise en œuvre d'approches expérimentales et numériques.Des investigations expérimentales ont été menées sur un meuble frigorifique fermé placé dans une cellule d’essai à température contrôlée. Quatre-vingts thermocouples calibrés répartis dans le meuble ont permis d’observer les évolutions spatio-temporelles des températures de l’air et du produit dans différentes conditions de fonctionnement. Nous avons fait varier la température de l'air ambiant (15, 19, 24 et 29 ° C), le volume occupé par le produit (meuble vide ou plus ou moins chargé de blocs de méthylcellulose) et la fréquence d'ouverture des portes (0 : fermé en permanence, 10, 20, 40, 60 Ouvertures Par Heure - OPH). Des expériences ont également été réalisées dans une configuration ouverte du meuble frigorifique (portes complètement retirées) afin de déterminer les avantages des portes sur les performances thermiques.Les résultats ont montré que lorsque les portes étaient fermées en permanence, les champs de température étaient similaires quels que soient la température ambiante et le pourcentage de volume occupé : la température la plus élevée se situe à l’avant de l'étagère supérieure alors que la température la plus basse est observée à l’arrière de l'étagère inférieure. Cette répartition change lorsque les portes sont périodiquement ou définitivement ouvertes : la position où la température est la plus élevée migre vers l’avant de l'étagère du milieu. Même pour une fréquence très élevée d’ouverture des portes (60 OPH), les températures de l’air et des produits dans le meuble fermé sont restées plus basses d’au moins 1,0 ° C par rapport au meuble sans portes.Des mesures de vitesse d'air par anémométrie à fil chaud au niveau du rideau d’air ont permis d'observer son allure générale tandis que les mesures effectuées dans le conduit arrière ont permis de quantifier la répartition du flux d'air à travers le plaque arrière perforée. L’utilisation d’une technique de vélocimétrie par image de particules (PIV) a permis de caractériser le rideau d’air avec une résolution et une précision spatiale supérieures. Les résultats ont notamment montré l’existence d’une zone de recirculation de l'air dans la partie supérieure du meuble où l’on observe également une infiltration d'air ambiant chaud par les fentes présentes autour des portes. Ceci induit une augmentation de la température du rideau d'air. Des simulations numériques bidimensionnelles d’écoulement (CFD) avec le modèle de turbulence k-ε ont permis de reproduire les principaux phénomènes d'écoulement observés par PIV et de voir leur influence sur la distribution de température dans le meuble.Enfin, un modèle simplifié des transferts de chaleur a été développé par une approche zonale en régime permanent et en régime transitoire ce qui permet respectivement de prévoir les températures moyennes de l’air et du produit et les fluctuations de température en fonction des cycles marche / arrêt du compresseur. Le modèle transitoire a été résolu avec une approche spectrale. L'influence de différents paramètres sur les niveaux de température et l'amortissement des fluctuations peut ainsi être identifiée. / The use of closed refrigerated display cabinets in supermarkets has been increased steadily because of the potential energy savings compared to open ones. This growing trend has contributed to the necessity to expand research in the field of retail refrigeration. Most studies in literature, however, focused on the improvements of energy efficiency after door installation while studies on the mechanism of heat transfer and airflow within closed display cabinets are still limited. In fact, the airflow pattern influences the heat exchange between air and products, thus, product temperature. This PhD thesis aims to gain an insight into the mechanism of airflow and heat transfer in closed refrigerated display cabinets by the implementation of experimental and numerical approaches.Experimental investigations were conducted in a closed refrigerated display cabinet (an integral type with a single band air curtain and two double-glazing doors) located in a controlled-temperature test room. Air/product temperatures and air velocity are the main parameters taken into investigations. Eighty calibrated thermocouples distributed throughout the cabinet made it possible to observe the spatial and temporal evolutions of the air and product temperatures under different operating conditions. These conditions were ambient air temperature (15, 19, 24 and 29 °C), product-occupied volume (unloaded, half-loaded and full-loaded with test packages made of methylcellulose), door-opening frequency (0 - permanently closed, 10, 20, 40, 60 Openings Per Hour - OPH) and opening duration (15s and 30s). An automatic door opening system was developed and allowed to apply the opening regime as prescribed in the standard test (EN ISO 23953-2, 2015). The experiment was also conducted in an open configuration of the cabinet (doors were completely removed) to determine the benefits of the doors on the temperature performance. The results showed that when the doors were permanently closed, the temperature distribution in the cabinet was similar whatever the ambient temperatures and occupied-volume percentages – the highest temperature position at the front-top shelf and the lowest temperature position at the rear-bottom shelf. The temperature distribution changed when the doors were periodically or permanently open – the front of the middle shelf became the highest temperature position while the lowest temperature position remained at the rear-bottom shelf. However, the air and product temperatures in the cabinet with doors remained lower despite a very high door-opening frequency (i.e. 60 OPH, product temperatures at least 1.0 °C lower), compared to the case without doors.Air velocity measurement using a hot-wire anemometer at the front of the cabinet from the discharge to the return air grilles allowed to observe the shape of the air curtain, while the measurement in the rear duct allowed to quantify the air flow distribution over the perforated back panel of different shelves. The use of a Particle Image Velocimetry (PIV) technique allowed the characterization of the air curtain with higher spatial resolution and accuracy. The result showed a zone of air recirculation at the upper part of the cabinet where warm ambient air infiltration through the door gaps was also observed, leading to an increase in the air curtain temperature. A 2D-CFD k-ε turbulence model was developed to reproduce the main flow phenomena observed by PIV so that its influence on the internal temperature distribution can be examined.Finally, a simplified heat transfer model was developed based on a zonal approach in both static and dynamic regimes which permits, respectively, the predictions of time-averaged air and product temperatures and temperature fluctuations according to the on/off cycle of the compressor regulation. The dynamic model was solved with a spectral approach, thus the influence of different parameters on the damping of the temperature fluctuations can be identified.