• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 40
  • 36
  • 6
  • 5
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 109
  • 109
  • 40
  • 32
  • 28
  • 24
  • 23
  • 21
  • 20
  • 18
  • 18
  • 15
  • 15
  • 15
  • 13
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

High Pressure Homogenization of Selected Liquid Beverages

Yan, Bing 30 December 2016 (has links)
No description available.
102

THE EFFECTS OF DIETARY PROTEIN ON POSTPRANDIAL ESSENTIAL AMINO ACIDS BIOAVAILABILITY AS A SUBSTRATE FOR PROTEIN ANABOLISM IN YOUNG AND OLDER ADULTS AND ON CARDIOMETABOLIC HEALTH-RELATED OUTCOMES

Gavin Connolly (15331777) 29 April 2023 (has links)
<p>Diet is the number one leading modifiable cause of poor health globally, with poor diets accounting for 10.9 million (22%) of all deaths among adults in 2017. In addition, one of our generation’s forthcoming challenges is the rapid expansion of the population aged 60 years and older. Although people are living longer, there is an associated increase in the prevalence of aged-related chronic diseases and functional impairment, such as cardiometabolic diseases and sarcopenia. As such, dietary components can play a role in positively or negatively influencing the prevention and treatment of chronic cardiometabolic diseases and sarcopenia. One such dietary component is dietary protein, which is essential throughout the life course, from gestation through old age. Evidence supports dietary protein playing an important role in reducing the risk of developing age-related chronic diseases such as sarcopenia and cardiometabolic diseases. </p> <p><em><strong>     Study 1, Chapter 2:</strong></em> The Dietary Guidelines for Americans (DGA) recommends consuming a variety of “Protein Foods” based on “ounce equivalent” (oz-eq) portions. In addition, the 2020-2030 Strategic Plan for NIH Nutrition Research includes to “define the role of nutrition across the lifespan” with an objective to “assess the role of nutrition in older adults to promote healthy aging.” However, there is a paucity of primary research that directly compares EAAs bioavailability between young and older adults consuming the same oz-eq portions of varied Protein Foods. No study has assessed the same oz-eq portions of animal- versus plant-based Protein Foods on essential amino acids (EAAs) bioavailability for protein anabolism in young and older adults. Therefore, we conducted two sequential randomized, investigator-blinded, crossover, acute feeding trials with the same study design; first in a cohort of young adults and second in a cohort of older adults. The primary objective of this project was to assess the effect of consuming two oz-eq portions of animal-based (unprocessed lean pork or whole eggs) vs. plant-based (black beans or sliced almonds) Protein Foods as part of a mixed whole foods meal on plasma EAAs bioavailability for protein anabolism. Consistent with our hypotheses, participant age did not affect postprandial EAAs bioavailability, and consuming a meal with two oz-eq of unprocessed lean pork or whole eggs resulted in greater postprandial EAAs bioavailability compared to a meal with two oz-eq of black beans or raw sliced almonds in 1) young adults; 2) older adults; and 3) young and older adults combined. These findings show on the same oz-eq basis, consuming these animal- vs. plant-based Protein Foods more effectively provide bioavailable EAAs for protein anabolism. </p> <p><em><strong>     Study 2, Chapter 3:</strong></em> Poultry meat is the most consumed type of meat worldwide and in the US. Poultry is generally considered to be a “healthy” meat as it is a high-quality protein source and provides other essential nutrients. However, research assessing poultry and its effects on and relations with chronic diseases in humans is sparse, and the forms of poultry typically consumed in the US, are not necessarily in line with recommendations provided by the DGA. Therefore, we conducted a scoping review to systematically search and chronicle scientific literature pertinent to poultry intake and human health. Main findings from this project were 1) historically, little research, especially randomized diet-controlled feeding trials, has been conducted to understand associations between and effects of consuming poultry products on human health; 2) the majority of research is from observational studies assessing relationships between poultry intake and risks of morbidity and mortality from various types of cancer; 3) a paucity of research exists to support chicken as a health-promoting food in children; and 4) research taking into account poultry product processing and cooking methods is needed. Science and health professionals, the poultry industry, and the public will benefit from new observational and experimental research to address cutting-edge scientific, public policy, and consumer topics pertinent to poultry intake and human health. </p> <p><em><strong>     Study 3, Chapter 4:</strong></em> Emerging research on whey protein supplementation suggests it may be a potential modifier of type 2 diabetes mellitus (T2DM) risk factors, including glucose control. As systematic reviews and/or meta-analyses of randomized controlled trials are gaining importance in nutrition literature, we conducted an umbrella systematic review to search for and chronicle published systematic reviews and/or meta-analyses of randomized controlled trials pertinent to whey protein supplementation and T2DM modifiable risk factors (study 3, Chapter 4). Among the 13 systematic reviews, including 12 meta-analyses critically assessed for this umbrella review, no reviews reported any adverse effects of whey protein on any reported T2DM-related risk factor. Collectively, a preponderance of evidence indicates whey protein supplementation improves multiple clinical indicators of glucose control in apparently healthy adults and those at increased risk for type 2 diabetes mellitus. </p>
103

Effects of Rosemary Extract and Propyl Gallate as Antioxidative Oil Additives and Whey Protein Isolate as an Oil Barrier on Degradation of Oil and Production of Fried Chicken

Jin, Qi 22 June 2018 (has links)
No description available.
104

Elaboration et caractérisation de nanoparticules de protéines. / Development and characterization of protein nanoparticles

Inthavong, Walailuk 18 July 2018 (has links)
Des solutions d'isolat de protéine de lactosérum (WPI) et d'isolat de protéine de soja (SPI) ont été chauffées à différentes concentrations en protéines conduisant à la formation d'agrégats fractals polydisperses de taille moyenne variable. Lastructure des solutions a été analysée par diffusion de la lumière en fonction de la concentration en protéine. La compressibilité osmotique et la longueur de corrélation dynamique diminuent quand la concentration augmente deviennent indépendantes de la taille initiale des agrégats pour les suspensions denses. Pour une taille d'agrégat donnée, la viscosité augmente initialement exponentiellement avec la concentration croissante puis diverge. Plus lesagrégats sont grands, plus l’augmentation de la viscosité apparaît à des concentrations faibles. La dépendance avec la concentration de la viscosité des solutions d'agrégats fractals est beaucoup plus forte que celle de microgels. Le comportement de mélanges de différents types d’agrégats (fractals/fractals ; fractals/microgels et WPI/SPI) a étéétudié principalement par rhéologie.Le recouvrement de fluorescence après photoblanchiment (FRAP) a été utilisé pour étudier la diffusion de chaînes de dextran marquées par des fluorophores dans des solutions d’agrégats et des gels de WPI. Une diffusion brownienne estobservée dans des suspensions d’agrégats et des gels faibles formés juste au-delà de Cg avec un coefficient de diffusion (D) qui diminue avec l'augmentation de la concentration mais, avec une dépendance plus faible que celle de la viscosité (). A des concentrations plus élevées, des gels densément réticulés sont formés, ce qui induit une forte diminution de la mobilité des chaînes de dextran. Pour ces systèmes, la recouvrance de la fluorescence est logarithmique avec le temps,suggérant une distribution exponentielle des coefficients de diffusion. La diffusion des chaînes de dextran a également été étudiée en fonction de la concentration en protéines pour les suspensions de trois types d'agrégats de WPI (petits et grands fractals et microgels). / Polydisperse fractal aggregates of varying average sizes were formed when solutions of whey protein isolate and soy protein isolate were heated at different protein concentrations and at neutral pH. The structure of these fractals aggregates solutions was analyzed by light scattering as a function of protein concentration. In dense suspension, the osmotic compressibility and the correlation length decreases with increasing concentration and become independent of the initial aggregate size. In this concentration regime, the aggregates are strongly interpenetrated and can be visualized as a set of "blobs". For a fixed aggregate size, the viscosity initially increases exponentially with increasing concentration and then diverges at the gel point. Larger fractal aggregates show a more important increase of the viscosity with increasing concentration than smaller aggregates, because they are less dense. The increase of the viscosity was much stronger for large fractal aggregates than for homogeneous microgels (microgels were formed by heating the WPI solution in present of CaCl2) of the same size.Dynamic light scattering, rheology and FRAP measurements were performed to investigate mixtures of different type of aggregates of WPI (fractals/fractals, fractals/microgels) and fractals of mixtures of WPI and SPI. Flow measurements were used to characterise the rheological properties of the aggregate suspension whereas Fluorescence recovery after Photobleaching (FRAP) was used to determine the self diffusion of fluorophore-labelled dextrans chains in mixtures over a wide range of concentrations. The results were compared to the concentration dependence of zero shear viscosity, gel stiffness, osmotic compressibility and correlation length. Brownian diffusion of the dextran chains was observed in aggregate suspensions and weak gels formed just above the gel point with a diffusion coefficient that decreased with increasing concentration, but the dependence was weaker than that of the viscosity. At higher concentrations, densely crosslinked gels were formed, which induced a sharp decrease in the mobility of the dextran chains. For these systems, the recovery of fluorescence was logarithmic over time, suggesting an exponential distribution of diffusion coefficients.
105

Características do leite e sanidade da glândula mamária de bovinos curraleiro pé-duro e pantaneiro / Milk characteristics and mamary glands sanity of curraleiro pé-duro and pantaneiro catte

Sola, Marília Cristina 02 October 2015 (has links)
Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2016-01-28T16:09:59Z No. of bitstreams: 2 Tese - Marília Cristina Sola - 2015.pdf: 1799194 bytes, checksum: 1cc96734092d165f83412bce38881a2c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-01-29T11:32:22Z (GMT) No. of bitstreams: 2 Tese - Marília Cristina Sola - 2015.pdf: 1799194 bytes, checksum: 1cc96734092d165f83412bce38881a2c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-01-29T11:32:23Z (GMT). No. of bitstreams: 2 Tese - Marília Cristina Sola - 2015.pdf: 1799194 bytes, checksum: 1cc96734092d165f83412bce38881a2c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-10-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study aimed to analyze the health aspects of the mammary gland, whey protein profile, and quality of milk produced by the breeds Curraleiro Pe-Duro and Pantaneiro. We evaluated 226 milk samples from a Curraleiro Pé-Duro herd, in the municipality of Cocalzinho, Goiás, and 107 milk samples from a Pantaneiro herd, belonging to the Nhumirim farm - Embrapa Pantanal experimental unit, municipality of Corumbá, Mato Grosso do Sul, from January 2013 to May 2014. We determined values related to the milk chemical composition (fat, protein, lactose, degreased, and total dry extract) and physical aspects (acidity, pH, electroconductivity). According to the results of this study, we determined the values related to the chemical composition (fat, protein, lactose, total solids, and degreased) and physical aspects of milk (acidity, pH, electroconductivity). Cases of clinical and subclinical mastitis were identified in herds with the involvement of bacteria of the genera Staphylococcus, Streptococcus, Bacillus, Corynebacterium, Escherichia, Serratia, Enterobacter, Klebsiella, Citrobacter, Proteus, Yersinia, and Shigella. There was no presence of antibiotic residues in the milk of both breeds. It was possible to characterize the main proteins present in whey as the concentration, molecular weight, and gel migration time due to microfluidic electrophoresis assays, besides the evidence of mastitis effect on whey proteins regarding the increase in the concentration of albumin, immunoglobulin G, and lactoferrin. The results of this study suggest that Curraleiro Pé-Duro and Pantaneiro showed good conditions of milk quality and sanity of the mammary gland in most animals evaluated, justifying the importance in the conservation of these genetic resources for future contribution to the development of the national livestock. / O presente estudo teve por objetivo analisar os aspectos sanitários da glândula mamária, perfil de proteínas no soro lácteo e a qualidade do leite produzido pelas raças Curraleiro Pé-Duro e Pantaneiro. Foram avaliadas 226 amostras de leite obtidas de um rebanho da raça Curraleiro Pé-Duro, localizados no município de Cocalzinho, Goiás e 107 amostras de leite de bovinos Pantaneiro, pertencentes à Fazenda Nhumirim -unidade experimental da Embrapa Pantanal, município de Corumbá, Mato Grosso do Sul, no período de janeiro de 2013 a maio de 2014. De acordo com os resultados encontrados neste estudo, foi possível determinar os valores relacionados à composição centesimal do leite (gordura, proteína, lactose, extrato seco total e desengordurado) e aspectos físicos (acidez, pH e eletrocondutividade). Foram identificados casos de mastite clínica e subclínica nos rebanhos com o envolvimento dos gêneros bacterianos Staphylococcus, Streptococcus, Bacillus, Corynebacterium, Escherichia, Serratia, Enterobacter, Klebsiella, Citrobacter, Proteus, Yersinia e Shigella. Não foi observada a presença de resíduos de antimicrobianos no leite de ambas as raças. A partir da realização da técnica de eletroforese microfluídica foi possível caracterizar as principais proteínas presentes no soro do leite quanto a concentração, peso molecular e tempo de migração em gel, além de evidenciar a efeito da mastite sobre as proteínas presentes no soro lácteo, a partir da elevação na concentração de albumina, imunoglobulina G e lactoferrina. Os resultados obtidos neste estudo sugerem que as raças Curraleiro Pé-Duro e Pantaneiro apresentaram boas condições quanto à qualidade do leite e sanidade da glândula mamária na maioria dos animais avaliados, justificando a importância na conservação destes recursos genéticos para futura contribuição ao desenvolvimento da pecuária nacional.
106

Retenção de óleo de café verde em complexos coacervados de proteínas concentradas do soro de leite ou soja e goma arábica / Retention of green coffee oil in complex coacervates of whey proteins concentrate or soy and gum arabic

Maggioli , Mirtza Fúlvia 09 May 2014 (has links)
Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2016-11-23T16:13:22Z No. of bitstreams: 2 Dissertação - Mirtza Fúlvia Maggioli - 2014.pdf: 10959485 bytes, checksum: 5397bb78460f4fbc15b15f9f9dd335a5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2016-11-30T15:44:44Z (GMT) No. of bitstreams: 2 Dissertação - Mirtza Fúlvia Maggioli - 2014.pdf: 10959485 bytes, checksum: 5397bb78460f4fbc15b15f9f9dd335a5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-11-30T15:44:44Z (GMT). No. of bitstreams: 2 Dissertação - Mirtza Fúlvia Maggioli - 2014.pdf: 10959485 bytes, checksum: 5397bb78460f4fbc15b15f9f9dd335a5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2014-05-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work shows the green coffee oil coacervation processes, as core material, in two different systems: whey protein / gum arabic and soy protein / gum arabic, as biopolymer wall. The biopolymers concentration were fixed in 4% (weight / weight) of the emulsion, and the proportion between then was respectively 2:1 and 1,4:1. Different emulsions were made, each one with a different green coffee oil concentration (0%, 10%, 17.5% and 25%) compared with wall materials. From these emulsions with adjusted pH, the system presented phase separation (coacervation). The following system characteristics were studied: maximum interation pHs, emulsions rheological behavior, emulsions sizes, physico-chemical characterization of the phases (coacervate and supernadant), process mass balance, coacervate rheology, microparticles morphology after lyophilization, the powder density, the powder stability and the microencapsulation process efficiency. The results confirmed that there is an optimum range of particle formation, depending on pH. The emulsions presented typical Newtonian fluid behavior and the viscosity increased with incresing the oil concentration. That behavior does not depend on wall materials. It was also observed that wet coacervates were better fitted to Power Law, presenting pseudoplastic behavior. Concentrate soy protein / gum arabic showed thixotropy. The emulsion gout showed an surface average diameter between 2,24 µm e 14,42µm. The microparticles exhibited slightly spherical, rough surface and pores, probably influenced by drying process. The process efficiency showed no dependence on the oil concentration at studied systems. The adsorption isotherms (at 30°C) of the obtained powders were best fitted to the GAB model and the e moisture content of monolayer (xm) for this model were between 2.5% to 5.1% for CPSL and GA microparticles and between 5.1% and 6.1% for IPS and GA / Neste trabalho foram estudados os processos de coacervação complexa de óleo de café verde, como material de recheio, em dois tipos de sistemas: concentrado proteico de soro de leite (CPSL)/ goma arábica (GA) e isolado proteico de soja (IPS) / goma arábica (GA), como biopolímeros de parede. Estes sistemas foram preparados com concentração de biopolímeros fixa em 4% (massa / massa) da emulsão e a proporção entre eles foi respectivamente 2:1 e 1,4:1. Emulsões com diferentes concentrações de óleo de café verde (0%; 10%; 17,5% e 25%), em relação aos materiais de parede, foram preparadas. A partir destas emulsões com os pHs ajustados, o sistema apresentou separação de fases (coacervação). Foram avaliados os pHs de máxima interação entre os pares de biopolímeros estudados, o comportamento reológico das emulsões, o tamanho de gota das emulsões produzidas, a caracterização fisicoquímica das fases (sobrenadante e coacervado), o balanço de massa do processo, a reologia do coacervado, a morfologia das micropartículas após liofilização, a densidade dos pós obtidos, a estabilidade do pó e a eficiência do processo de microencapsulação. Os resultados obtidos confirmaram que existe uma faixa ótima de formação de partículas dependente do pH. As emulsões apresentaram comportamento típico de fluidos newtoniano e a viscosidade aumentou com a concentração de óleo independente dos materiais de parede estudados. Já os coacervados úmidos ajustaram-se melhor à Lei da Potência apresentando comportamento pseudoplástico. Os coacervados de isolado proteico de soja / goma arábica apresentaram tixotropia. As emulsões apresentaram gotas com diâmetro superficial médio entre 2,24 µm e 14,42µm. As micropartículas apresentaram forma levemente esférica, superficie rugosa e com poros provavelmente influenciada pelo processo de secagem. A eficiência do processo não mostrou dependência com a concentração de óleo nos sistemas estudados. As isotermas de adsorção (a 30°C) dos pós obtidos ajustaram-se melhor ao modelo GAB e os teores de umidade da monocamanda (xm) para este modelo ficaram entre 2, 5 % e 5,1% para as micropartículas de CPSL e GA e entre 5,1% e 6,1% para as micropartículas de IPS e GA
107

Réhydratation des protéines laitières dans un milieu complexe : influence de l'état d'hydratation sur les propriétés texturales des gels acides / Dairy proteins powders rehydration into a complex media : effects of rehydration state on textural properties of acid milk gels

Karam, Marie-Céleste 13 September 2013 (has links)
L'objectif de la thèse a été d'élucider le processus de réhydratation des caséines micellaires et des protéines solubles dans un milieu complexe et opaque : le lait. L'influence de l'état d'hydratation de ces ingrédients laitiers en fonction du temps (5, 120, 180, 240, 300, 480, 900 et 1440 min de réhydratation) sur les propriétés rhéologiques, texturales, physiques ainsi que la microstructure des gels laitiers acides a également été étudiée. Il en résulte que le processus de réhydratation des caséines micellaires diffère de celui des protéines solubles, et est extrêmement long avec trois étapes : une étape de mouillage des particules, suivie d'une étape de gonflement caractérisée par une augmentation de la taille des particules et enfin une étape de dispersion marquée par la diminution de la taille des particules. La réhydratation des protéines solubles est caractérisée par une grande rapidité, avec deux phases : le mouillage et la phase de dispersion (superposée). D'autre part, l'allongement de la durée de réhydratation des caséines micellaires est associé à une augmentation du point de gélification ainsi qu'à une nette amélioration des propriétés physiques, texturales et rhéologiques des gels : augmentation de leur fermeté et de leur force, diminution de la synérèse et de la formation de grumeaux. La durée de réhydratation des protéines solubles n'a pas d'influence sur ces paramètres. En revanche, leur dénaturation (par chauffage à sec) est associée à une dégradation des propriétés texturales des gels acides. Finalement, il s'avère que les gels acides formulés à partir des protéines solubles sont de meilleure qualité texturale (à l'exception de la formation de grumeaux) que ceux préparés à partir des caséines micellaires / The main objectives of this work were to elucidate the rehydration mechanism of the two major milk proteins (micellar casein and whey protein) into a complex and opaque medium such as milk and to assess the influence of hydration state (defined as a function of rehydration length after 5,120,180,240,300, 480, 900 and 1440 minutes of rehydration) on the rheological, textural, physical properties and microstructure of the obtained acid milk gels. Whereas, micellar casein presented a long rehydration process into milk characterized by three stages: a wetting, swelling and dispersion phase, whey protein displayed a quick rehydration process characterized by an overlapping of wetting and dispersion phase. Furthermore, an extended rehydration time of micellar casein powder into the milk base was associated with a postponed onset of gelation and enhanced physical, textural as well as rheological properties of the obtained acid milk gels characterized by increases in gel firmness, strength, and decreases in syneresis susceptibility and grains formation. In contrast, acid milk gels prepared with whey protein powder exhibited comparable overall textural properties regardless the different rehydration times. Nevertheless, denaturation of whey protein powder (by dry heating) was associated with a deterioration of the textural properties of the acid milk gels. Finally, acid gels prepared with whey proteins displayed better overall textural quality than those prepared with micellar casein (except for grains formation)
108

Metabolomic Assessment of Dietary Interventions in Obesity by Capillary Electrophoresis Mass Spectrometry

Lam, Karen Phoebe January 2018 (has links)
Capillary electrophoresis mass spectrometry (CE-MS) is a versatile instrumental method for metabolomics, which allows for comprehensive metabolite profiling of volume-limited biological specimens in order to better understand the molecular mechanisms associated with chronic diseases, including an alarming epidemic of obesity worldwide. Multiplexed CE separations enable high-throughput metabolite screening with quality assurance to prevent false discoveries when combined with rigorous method validation, robust experimental designs, complementary statistical methods, and high-resolution tandem mass spectrometry (MS/MS) for unknown metabolite identification. In this thesis, multiplexed CE-MS technology is applied for both targeted and untargeted metabolite profiling of various biological fluids, including covalently bound thiol-protein conjugates, as well as free circulating metabolites in serum and plasma, and excreted/bio-transformed compounds in urine due to complex host-gut microflora co-metabolism. This work was applied to characterize aberrant metabolic responses of obese subjects in response to dietary challenges, and measure the benefits of dietary interventions that reduce adiposity without deleterious muscle loss. Chapter 2 presents, a simple, sensitive yet robust analytical protocol to expand metabolome coverage in CE-MS for the discovery of labile protein thiols in human plasma using a rapid chemical derivatization method based on N-tert-butylmaleimide (NTBM). Chapter 3 describes targeted metabolite profiling of serum and plasma to investigate the differential metabolic responses between healthy and unhealthy obese individuals before and after consumption of a standardized high-caloric meal, respectively. Chapter 4 of this thesis describes an untargeted metabolite profiling strategy for urine using multisegment-injection (MSI)-CE-MS for elucidating the effects of protein supplementation following a short-term dietary weight-loss intervention study. This work revealed six urinary metabolites that were classified as top-ranking treatment response biomarkers useful for discriminating between subjects consuming carbohydrate (control), soy, and whey supplemented diets. In summary, this thesis demonstrated the successful implementation of multiplexed CE-MS technology for biomarker discovery in nutritional-based metabolomic studies as required for more effective treatment and prevention of obesity for innovations in public health. / Thesis / Doctor of Philosophy (PhD)
109

Effect of processing on the physicochemical, sensory, nutritional and microbiological quality of fresh-cut 'Rojo Brillante' persimmon

Sanchís Soler, Elena 15 April 2016 (has links)
[EN] Persimmon (Diospyros kaki L.) 'Rojo Brillante' is an astringent variety characterised by good growing conditions, excellent colour, size, sensory characteristics and good nutritional properties. In the last decade, its production has grown substantially in Spain given the application of high levels of CO2 to remove astringency while firmness is preserved. This technology has also increased its potential as a fresh-cut commodity. However, physical damage during processing result in degradation of the colour and firmness of the product and a higher susceptibility to microbial spoilage that significantly reduces the fruit's shelf life. The objective of the present thesis was to develop optimum procedures for processing and marketing 'Rojo Brillante' persimmon into a fresh-cut product with the maximum shelf life and best physicochemical, nutritional, sensory and microbiological quality. Firstly, the objective was to evaluate the effect of the maturity stage (MS) at harvest, storage time at 15 ºC before processing, and the application of different antioxidant treatments on enzymatic browning, sensory and nutritional quality of fresh-cut 'Rojo Brillante' persimmon during storage at 5 ºC. Concentrations of 10 g L-1 ascorbic acid (AA) or 10 g L-1 citric acid (CA) controlled tissue browning and maintained the visual quality of fresh-cut persimmon above the limit of marketability for 6-8 storage days at 5 ºC, depending on the MS. However, these acidic solutions reduced fruit firmness as compared to control samples. Further studies showed that the combination of these antioxidants with 10 g L-1 CaCl2 maintained firmness of the persimmon slices within the same range as the control samples. In another work, the application of 1-methylcyclopropene (1-MCP) allowed to process fruits after 45 days of storage at 1 ºC with commercial firmness and the antioxidant solution (10 g L-1 CA + 10 g L-1 CaCl2) extended the limit of marketability up to 9 days of storage at 5 ºC. Different controlled atmosphere conditions in combination with AA or CA dips were also evaluated as a first step to select optimum O2 and CO2 concentrations for modified atmosphere packaging (MAP) of fresh-cut 'Rojo Brillante' persimmons. Overall, the combination of antioxidant dips and a controlled atmosphere composed of 5 kPa O2 (balance N2) was proved to be the most effective combination to control enzymatic browning. This atmosphere maintained the visual quality of persimmon slices within the limit of marketability during 7- 9 days at 5 ºC. On the contrary, high CO2 concentrations (10 or 20 kPa) induced darkening in some tissue areas, associated with a flesh disorder known as 'internal flesh browning'. Later studies confirmed the beneficial effect of an active MAP in 5 kPa O2 compared to passive MAP to improve the visual quality of fresh-cut 'Rojo Brillante' persimmon, showing a synergic effect with the antioxidant dip (10 g L-1 CA + 10 g L-1 CaCl2). Antioxidant edible coatings were prepared from whey protein isolate (WPI), soy protein isolate (SPI), hydroxylpropyl methylcellulose (HPMC) and apple pectin as the polymeric matrix. All edible coatings were amended with the antioxidant combination selected (10 g L-1 CA + 10 g L-1 CaCl2). All the edible coatings tested proved effective to control enzymatic browning of persimmon slices. However, the samples treated with the HPMC- and pectin- based coatings were scored with a better visual quality that the rest of the treatments. In general, free radical scavenging activity and total carotenoid content increased in late-season persimmons; whereas, processing (cutting and storage at 5 ºC), antioxidant dips, controlled atmosphere storage or edible coatings had no clear effect on nutritional quality (vitamin C, free radical scavenging activity, total phenolic content, and carotenoids) of fresh-cut persimmons. / [ES] El caqui persimmon (Diospyros kaki L.) 'Rojo Brillante' es un cultivar astringente que presenta unas propiedades organolépticas y nutricionales excelentes. En la última década, su cultivo en el área mediterránea de España se ha incrementado de manera exponencial con el desarrollo de la tecnología que permite eliminar la astringencia, manteniendo la firmeza del mismo. Esta nueva forma de presentación, aporta numerosas ventajas, entre la que se incluye la posibilidad de ser comercializado como fruta fresca cortada. Sin embargo, el éxito comercial del producto está limitado por el pardeamiento enzimático, la pérdida de firmeza y al crecimiento microbiano. En este contexto, el objetivo de la Tesis ha sido el desarrollo de caqui 'Rojo Brillante' fresco cortado mediante un enfoque que integra el estudio de las características del producto en el momento del procesado y de distintas tecnologías que mantengan la calidad físico-química, sensorial, nutricional y microbiológica del producto durante un periodo que permita su comercialización. En primer lugar, se evaluó el efecto del estado de madurez (MS) en el momento de recolección, el tiempo de almacenamiento a 15 ºC antes del procesado y la aplicación de diferentes antioxidantes en el pardeamiento enzimático y la calidad sensorial y nutricional del caqui 'Rojo Brillante' cortado y almacenado a 5 ºC. La aplicación de 10 g L-1 de ácido ascórbico (AA) ó 10 g L-1 ácido cítrico (CA) controló el pardeamiento enzimático y mantuvo la calidad visual del caqui por encima del límite de comercialización entre 6 y 8 días de almacenamiento a 5 ºC, dependiendo del MS. Sin embrago, la aplicación de estos antioxidantes redujo de manera significativa la firmeza del fruto respecto al control. La combinación de estos antioxidantes con 10 g L-1 de CaCl2 permitió mantener la firmeza en el mismo rango que las muestras control. En un trabajo posterior, la aplicación de 1-metilciclopropeno (1-MCP) permitió procesar caqui almacenado 45 días a 1 ºC con una buena firmeza comercial y el tratamiento antioxidante (10 g L-1 CA + 10 g L-1 CaCl2) consiguió alcanzar un límite de comercialización del producto de 9 días a 5 ºC. La evaluación de distintas atmósferas controladas en combinación con tratamientos antioxidantes (AA o CA), como paso previo al envasado en atmósfera modificada (MAP) del caqui, mostró como más efectiva en el control del pardeamiento enzimático la atmósfera compuesta por 5 kPa O2 (balance N2). Esta atmósfera mantuvo la calidad visual del caqui cortado dentro del límite de comercialización durante 7-9 días a 5 ºC. Por el contrario, la aplicación de altas concentraciones de CO2 (10 ó 20 kPa) dio lugar a un pardeamiento en ciertas zonas de la pulpa que se conoce como 'internal flesh browning'. Estudios posteriores confirmaron el efecto beneficioso del envasado de caqui cortado y tratado con solución antioxidante (CA-CaCl2) en una MAP activa de 5 kPa O2 en la calidad visual del fruto frente a la aplicación de una MAP pasiva. El desarrollo de recubrimientos comestibles con capacidad antioxidante se realizó mediante la incorporación de antioxidantes (10 g L-1 CA + 10 g L-1 CaCl2) a formulaciones a base de proteína de suero lácteo (WPI), proteína de soja (SPI), hidroxipropilmetilcelulosa (HPMC) y pectina. Todos los recubrimientos fueron efectivos controlando el pardeamiento enzimático del caqui cortado, siendo las muestras recubiertas con HPMC y pectina las mejor evaluadas visualmente. En general, el procesado, la aplicación de antioxidantes, el envasado en atmósferas controladas y los distintos recubrimientos comestibles estudiados, si bien no mostraron un efecto claro en los parámetros de calidad nutricional evaluados, no tuvieron un efecto negativo en los mismos. Por otra parte, los frutos cosechados a final de campaña tuvieron mayor actividad antioxidante y contenido en carotenoides. / [CAT] El caqui persimmon (Diospyros kaki L.) 'Rojo Brillante' és un cultiu astringent que presenta unes propietats organolèptiques i nutricionals excel¿lents. En la última dècada, el seu cultiu en l'àrea mediterrània d'Espanya s'ha incrementat de manera exponencial amb el desenvolupament de la tecnologia que permet eliminar l'astringència, mantenint la fermesa del mateix. Esta nova forma de presentació, aporta un gran nombre d'avantatges, entre els quals s'inclou la possibilitat de comercialitzar-lo com fruita fresca processada. No obstant, l'èxit comercial del producte està limitat per pardetjament enzimàtic, la pèrdua de fermesa i el creixement microbià. L'objectiu de la Tesis ha estat en el desenvolupament de caqui 'Rojo Brillante' tallat en fresc mitjançant un enfocament que integra l'estudi de les característiques del producte en el moment del processat i de diferents tecnologies en el manteniment de la qualitat físico-química, sensorial, nutricional i microbiològica del producte durant un període que permeta la seua comercialització. En primer lloc, es va avaluar l'efecte de l'estat de maduresa (MS) en el moment de recol¿lecció, el temps d'emmagatzemament a 15ºC abans del processat i l'aplicació de diferents tractaments antioxidants en el pardetjament enzimàtic i la qualitat sensorial i nutricional del caqui 'Rojo Brillante' tallat i emmagatzemat a 5 ºC. L'aplicació de 10 g L-1 d'àcid ascòrbic (AA) o 10 g L-1 d'àcid cítric (CA) va controlar el pardetjament enzimàtic i va mantenir la qualitat visual del caqui per damunt del límit de comercialització entre 6-8 dies d'emmagatzemament a 5 ºC, depenent del MS. No obstant, l'aplicació d'antioxidants va reduir de manera significativa la fermesa del fruit comparat amb el control. La combinació d'aquestos antioxidants amb 10 g L-1 de CaCl2 va permetre mantenir la fermesa en el mateix rang que les mostres control. En un treball posterior, l'aplicació de 1-metilciclopropeno (1-MCP) va permetre processar caqui emmagatzemat 45 dies a 1 ºC amb una bona fermesa comercial i a més, el tractament antioxidant (10 g L-1 CA + 10 g L-1 CaCl2) va aconseguir un límit de comercialització del producte tallat de 9 dies a 5 ºC. L'avaluació de diferents atmosferes controlades en combinació amb tractaments antioxidants (AA o CA), com a pas previ a l'envasament en atmosfera modificada (MAP) del caqui 'Rojo Brillante, va mostrar com a més efectiva en el control del pardetjament enzimàtic l'atmosfera composta per 5 kPa O2 (balanç N2). Aquesta atmosfera va mantenir la qualitat visual del caqui tallat dins del límit de comercialització durant 7-9 dies a 5 ºC. Per contra, l'aplicació d'altes concentracions de CO2 (10 ó 20 kPa) va donar lloc a un pardetjament en certes zones de la polpa, el qual és conegut com 'internal flesh browning'. Estudis posteriors van confirmar l'efecte beneficiós de l'envasament de caqui tallat i tractat amb solució antioxidant (CA-CaCl2) en una MAP activa de 5 kPa O2 millorant la qualitat visual de la fruita front a l'aplicació de una MAP passiva. El desenvolupament de recobriments comestibles amb capacitat antioxidant es va realitzar mitjançant la incorporació d'antioxidants (CA-CaCl2) en formulacions a base de proteïna de sèrum làctic (WPI), proteïna de soia (SPI), hidroxipropilmetilcel-lulosa (HPMC) i pectina. Tots els recobriments van ser efectius controlant el pardetjament enzimàtic del caqui tallat. No obstant, les mostres recobertes amb HPMC i pectina van ser millor avaluades visualment que la resta de tractaments. En general, el processat, l'aplicació d'antioxidants, l'envasament en atmosferes controlades i els distints recobriments comestibles estudiats, si bé no van mostrar un efecte clar en els paràmetres de la qualitat nutricional avaluats, no van tindre un efecte negatiu en els mateixos. Per altra banda, els fruits recol¿lectats a final de temporada van tenir major activitat antioxidant i contingut en / Sanchís Soler, E. (2016). Effect of processing on the physicochemical, sensory, nutritional and microbiological quality of fresh-cut 'Rojo Brillante' persimmon [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62588 / TESIS

Page generated in 0.0562 seconds