• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 23
  • 10
  • 3
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 44
  • 11
  • 8
  • 5
  • 5
  • 5
  • 5
  • 5
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 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.
41

An investigation of the association of colonic adenomatous polyps and nutritional status of retinol and carotene

Magnetti, Cecilia Ann January 1985 (has links)
The hypothesis was evaluated that lower dietary consumption of carotene or retinol or lower serum levels of beta carotene or retinol are associated with development of colonic adenomas. To evaluate this hypothesis, selected patients who were to undergo colonoscopy to determine polyps status were asked to undergo a battery of tests to assess nutritional status. These tests included a dietary and demographic questionnaire, serologic assessment of beta carotene and retinol, and a dark adaptation test. One hundred male subjects were evaluated. Fifty-seven were found to have colonic adenomatous polyps. Cases and controls appeared to be well matched for demographic characteristics. There were no statistically significant differences for any nutritional parameter between cases and controls, but cigarette smoking was more prevalent among cases than controls (p<0.05). Because nonsignificant negative associations with colonic adenomas were observed for some of the nutritional parameters, it is concluded that additional subjects should be studied, as planned. / M.S.
42

Desacidificação por via fisicade oleo de Buriti (Mauritia flexuosa) / Steam deacidification of Buriti oil (Mauritia flexuosa)

Silva, Simone Monteiro e, 1983- 12 August 2018 (has links)
Orientadores: Antonio Jose de Almeida Meirelles, Roberta Ceriani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-12T23:42:39Z (GMT). No. of bitstreams: 1 Silva_SimoneMonteiroe_M.pdf: 2957959 bytes, checksum: f87550c181a2c8385702e38ac3b23215 (MD5) Previous issue date: 2009 / Resumo: O óleo de buriti (Mauritia flexuosa), obtido do fruto de uma palmeira nativa do Brasil, é uma fonte rica em b-caroteno e tocoferóis. Sua alta acidez (geralmente superior a 2,0%, expressos em ácido oléico), em conjunto com seus baixos teores de fósforo (10 mg/kg), torna interessante o seu refino por via física. Dessa forma, o objetivo deste trabalho é estudar a desacidificação por via física do óleo de buriti, visando manter os compostos nutracêuticos. Na primeira fase deste trabalho foi avaliada variabilidade do óleo de buriti de diversas procedências, pois o valor nutricional do óleo bruto pode variar com a sazonalidade e também com o processo de extração. Foi verificado que os óleos obtidos artesanalmente possuem maior valor nutracêutico. Entretanto, eles não são produzidos em larga escala, e em quantidades suficientes para a utilização comercial. Por isso foi utilizado um blend formado por um óleo de buriti artesanal obtido em uma feira popular e um industrial adquirido da empresa BERACA-SABARÁ. A utilização desse blend foi a melhor combinação entre qualidade e quantidade. O blend de óleo de buriti foi completamente caracterizado em termos da composição em ácidos graxos, classes de acilgliceróis e características físico-químicas. Estas análises, além de permitir conhecer de fato o sistema em estudo, tornam possível a modelagem e simulação dos experimentos. Os experimentos de desacidificação foram realizados no desodorizador em batelada desenvolvido pelo grupo de pesquisa juntamente com a empresa MARCONI, seguindo planejamento fatorial completo com duas variáveis independentes, sendo elas temperatura e vazão de vapor. Foram retiradas amostras após 30 e 60 minutos de stripping, obtendo dois planejamentos. Em cada uma das amostras de óleo foram realizadas análises de acidez. Também foram determinados teor de carotenóides e tocoferóis totais por HPLC, seguindo metodologia desenvolvida durante este trabalho. Foram recolhidas as fases aquosas e oleosas do destilado, e determinadas acidez e teor de água. Estas análises possibilitaram a determinação por diferença da perda de óleo neutro no destilado e a realização de balanços de massa para averiguar a qualidade dos experimentos. Os dados experimentais foram comparados com os obtidos por um programa de simulação computacional desenvolvido no grupo de pesquisa, utilizando o software MatLabè, que descreve a desodorização em batelada. A desacidificação por via física se mostrou um processo interessante para reduzir a acidez do óleo de buriti. Para isso, deve-se priorizar a utilização de altas vazões de vapor para o óleo de buriti, pois minimiza a degradação de carotenos e a perda de tocoferóis. A simulação computacional desenvolvida foi eficiente na predição da acidez e tocoferóis no óleo final, e apresenta uma boa perspectiva auxiliar na melhora da qualidade do óleo final, através da definição dos parâmetros do processo de acordo com a matéria-prima e a especificação do produto final / Abstract: Buriti oil (Mauritia flexuosa), obtained from the fruit of a palm tree native to Brazil, is a rich source of b-carotene and tocopherols. Its high acidity (usually above 2.0%), in conjunction with their low levels of phospholipids (below 10 ppm), enables buriti oil to physical refining. This work aimed to investigate the physical refining of buriti oil maintaining nutraceuticals compounds. At the first step, the variability of oil from different proveniences was evaluated, because the nutritional value of crude oil may vary with the seasonality and also with the extraction process. It was found that the artisanal oils have greater nutraceutical value. However, they are not produced in large scale, and in sufficient quantities for commercial use. So we used a blend formed by an artesanal buriti oil obtained at a popular market and an industrial, acquired from BERACA SABARA company. The use of this blend was the best combination of quality and quantity. The blend of buriti oil has been completely characterized in terms of fatty acids composition, classes of acilglycerides, and physical and chemical characteristics. These analyses allows the study of a well know system and to make the modeling and simulation of the experiments. The experiments were conducted in batch deodorizer developed by the research group in cooperation with MARCONI Company, following a full factorial experimental design with two independent variables, which are temperature and steam flow rate. Samples were removed after 30 and 60 minutes of stripping, getting two plans. Acidity was determined in the samples of oil. Carotenoids and tocopherols content was determined by HPLC, following methodology developed during this work. The aqueous and oily phases of distillate were collected, and its acidity and moisture content was determined. These analyses allowed the determination of neutral oil loss in distillate by difference and to make mass balances to assure the quality of the experiments. Experimental data were compared with those obtained by a computer simulation program which describes a batch deodorizer, developed in the research group, using the software MatLab è. The physical refining was an interesting process to reduce the acidity of the buriti oil. For this, it should prioritize the use of high flow of steam to the buriti oil, because it minimizes carotenes degradation and tocopherols loss. The simulation was efficient in predicting the acidity and tocopherols in the final oil, and gives a good perspective to help the quality of the final oil improving, by defining the process parameters according to raw material and final product specification / Mestrado / Mestre em Engenharia de Alimentos
43

Variation B-carotene content and physicochemical properties of orange-fleshed sweet potato (Ipomoea batatas (L.) Lam) cultivars grown in Limpopo Province, South Africa

Silungwe, Henry 18 September 2017 (has links)
PhD (Agric) (Food Science and Technology) / Department Food Science and Technology / In recent years, there has been a lot of interest in orange fleshed sweet potato (OFSP) [Ipomoea batatas (L.) Lam] cultivar, as a cheaper source of vitamin A. In Southern Africa, reports have shown that one in every three children has deficiency in vitamin A. This study investigated the variations in β-carotene (vitamin A precursor) content among selected OFSP cultivars grown in Limpopo Province, South Africa. In addition, the study investigated the effects of location on functional properties, total carotenoids and antioxidant profile of the sweet potato flour as well as their physicochemical, functional and nutritional properties. Four (4) sweet potato cultivars [Dagga, Bophelo, Impilo (orange fleshed) and Mvuvhelo (cream fleshed)] were obtained from two locations, namely, University of Venda (Univen) agricultural experimental farm and Tshiombo irrigation scheme (Tshiombo) and analysed for pasting, functional, physicochemical and nutritional properties. The sweet potato flours from these two locations were also analysed by computed tomographic (CT) scans for flour particle density. Mineral and microstructure of OFSP flours were analysed by scanning electron microscope (SEM). All measurements, except the tristimulus L* a* b* and other colour parameters from five replicates, were performed in triplicate. Statistical analysis was performed using a one-way analysis of variance and means were separated using Duncan’s multiple range test; P < 0.05 was considered to be statistically significant. Pearson’s correlation coefficients were used to determine the correlation among functional, physicochemical, nutritional and pasting properties of sweet potato flour. β-carotene content varied significantly between the two locations from 70.98 ± 0.8 μg/g (Tshiombo) to 86.09 ± 2.0 μg/g (Univen), among cultivars from 1.71 ± 0.0 μg/g (Mvuvhelo) to 201.50 ± 1.0 μg/g (Dagga) and among orange fleshed (Dagga, Bophelo and Impilo) flours from 28.38 ± 0.2 μg/g (Impilo) to 201.50 ± 1.0 μg/g (Dagga). There was a similar trend in the contents of α-carotene to that of β-carotene from the two locations, which ranged from 0.63 ± 0.0 mol/L (Tshiombo) to 1.01 ± 0.0 mol/L (Univen). Mvuvhelo had significantly the lowest α-carotene content (0.50 ± 0.0 mol/L) and Impilo the highest (1.28 ± 0.0 mol/L). The total carotenoids was highest for Impilo (7.56 μg/g) and lowest for Mvuvhelo (1.33 ± 0.1 μg/g) but did not vary significantly (P > 0.05) between ii the locations. The antioxidant activity, based on 2, 2-diphenyl-1picrylhydrazyl (DPPH) free radical scavenging activity, was significantly highest in Bophelo (63.37 ± 0.8 mMAAE ml-1) and lowest in Dagga (26.93 ± 1.4 mMAAE ml-1) flours. The ferric reducing antioxidant power (FRAP) varied significantly across the locations and among the cultivars and ranged from 14.45 ± 0.3 μMTE ml-1 (Tshiombo) to 17.40 ± 1.1 μMTE ml-1 (Univen). FRAP was significantly highest in Impilo (21.12 ± 2.1 μMTE ml-1) and lowest in Mvuvhelo (8.16 ± 2.0 μMTE ml-1). Total carotenoid content positively correlated with DPPH (0.486*), FRAP (0.830**), β-carotene (0.370*), and α-carotene (0.424*). The antioxidant content and the radical scavenging activity were significantly correlated (0.563**). Vitamin A content was significantly lowest (6.88 ± 0.38 μg/g retinol) in Dagga flour and highest (7.97 ± 0.25 μg/g) in Impilo flour. Protein content varied significantly across the two locations and ranged from 4.23% (Tshiombo) to 7.16% (Univen). Dagga had significantly the lowest (3.47%) protein content while Impilo had the highest (7.53%). The fat content of the flours varied significantly between the two locations ranging from 0.63% (Tshiombo) to 1.01% (Univen). The protein content was positively correlated 0.594** and 0.421* to vitamin A and fat contents respectively. The Bophelo colour luminosity was significantly lower (L* 76.2) than the other two OFSP, Dagga (L* 83.51) and Impilo (L* 82.07). Bophelo a* (14.09) also differed significantly across all sweet potato cultivars. All cultivars differed significantly in b* values. Colour intensity (ΔE*) ranged from 15.87 to 38.48 for Mvuvhelo and Bophelo, respectively. Chroma ranged from 87.52 to 84.95 for Dagga and Mvuvhelo respectively. Total starch content was significantly different in all sweet potato cultivars and ranged from 244.07 μg/100 g (Bophelo) to 325.04 mg/g (Dagga). Resistant starch differed significantly in all sweet potato cultivars ranging from 1.21 μg/100 g dwb (Bophelo) to 7.07 μg/100 g dwb (Impilo). Ash content was significantly different in all cultivars and ranged from 3.17% (Dagga) to 3.79% (Bophelo). Water holding capacity (WHC) varied significantly across the two locations and ranged from 1.44 g H2O/g DM (Tshiombo) to 1.72 g H2O/g DM (Univen). Bophelo had significantly the lowest (1.27 g H2O/g DM) WHC and Impilo the highest (1.99 g H2O/g DM). The ash content negatively correlated to total starch (-0.928**) but positively iii correlated to WHC (0.654**). Peak viscosity differed significantly across all cultivars under study and ranged from 126.54 RVU (Bophelo) to 302.36 RVU. (Dagga). There was significant difference in trough viscosity across all cultivars ranging from 55.97 RVU (Impilo) to 280.78 RVU (Dagga). There were significant differences in the final viscosity across all cultivars ranging from 78.99 RVU (Impilo) to 319.26 (Dagga). Peak time viscosity varied significantly across all cultivars ranging from 3.87 min (Impilo) to 8.47 min. (Bophelo). Dagga cultivar had significantly the highest pasting temperature (94.16oC) and Bophelo the lowest (77.75oC). The setback viscosity was significantly highest 51.10 RVU (Mvuvhelo) and lowest 23.01 RVU (Impilo). All cultivars from the two locations consistently showed high potassium content ranging from 0.46% (Impilo) to 1.38% (Dagga) as compared to other minerals such as magnesium, calcium and chlorine which ranged from 0.16% (Impilo) to 0.34%. (Dagga). The CT scans revealed that there was a possibility of evaluating the effect of location on the density of granules of sweet potato flour and also the inherent differences in granular distribution of various sweet potato cultivars. SEM revealed high amounts of potassium, magnesium and chlorine. A profile of physicochemical and functional properties of flour of some of the OFSP cultivars produced in Limpopo province, South Africa has been drawn. This study also highlights the nutritional quality of the flour from four sweet potato cultivars and provides a ranking of flour to help the producers in the selection process. Bophelo flour was ranked the highest in terms of β- and, α-carotenes, total carotenoids and antioxidant capacity while Impilo was ranked highest in terms of functional properties and ash content. This study has highlighted significant differences in a number of parameters measured among the sweet potato cultivars. Therefore, in order to derive the maximum benefit from aIn recent years, there has been a lot of interest in orange fleshed sweet potato (OFSP) [Ipomoea batatas (L.) Lam] cultivar, as a cheaper source of vitamin A. In Southern Africa, reports have shown that one in every three children has deficiency in vitamin A. This study investigated the variations in β-carotene (vitamin A precursor) content among selected OFSP cultivars grown in Limpopo Province, South Africa. In addition, the study investigated the effects of location on functional properties, total carotenoids and antioxidant profile of the sweet potato flour as well as their physicochemical, functional and nutritional properties. Four (4) sweet potato cultivars [Dagga, Bophelo, Impilo (orange fleshed) and Mvuvhelo (cream fleshed)] were obtained from two locations, namely, University of Venda (Univen) agricultural experimental farm and Tshiombo irrigation scheme (Tshiombo) and analysed for pasting, functional, physicochemical and nutritional properties. The sweet potato flours from these two locations were also analysed by computed tomographic (CT) scans for flour particle density. Mineral and microstructure of OFSP flours were analysed by scanning electron microscope (SEM). All measurements, except the tristimulus L* a* b* and other colour parameters from five replicates, were performed in triplicate. Statistical analysis was performed using a one-way analysis of variance and means were separated using Duncan’s multiple range test; P < 0.05 was considered to be statistically significant. Pearson’s correlation coefficients were used to determine the correlation among functional, physicochemical, nutritional and pasting properties of sweet potato flour. β-carotene content varied significantly between the two locations from 70.98 ± 0.8 μg/g (Tshiombo) to 86.09 ± 2.0 μg/g (Univen), among cultivars from 1.71 ± 0.0 μg/g (Mvuvhelo) to 201.50 ± 1.0 μg/g (Dagga) and among orange fleshed (Dagga, Bophelo and Impilo) flours from 28.38 ± 0.2 μg/g (Impilo) to 201.50 ± 1.0 μg/g (Dagga). There was a similar trend in the contents of α-carotene to that of β-carotene from the two locations, which ranged from 0.63 ± 0.0 mol/L (Tshiombo) to 1.01 ± 0.0 mol/L (Univen). Mvuvhelo had significantly the lowest α-carotene content (0.50 ± 0.0 mol/L) and Impilo the highest (1.28 ± 0.0 mol/L). The total carotenoids was highest for Impilo (7.56 μg/g) and lowest for Mvuvhelo (1.33 ± 0.1 μg/g) but did not vary significantly (P > 0.05) between ii the locations. The antioxidant activity, based on 2, 2-diphenyl-1picrylhydrazyl (DPPH) free radical scavenging activity, was significantly highest in Bophelo (63.37 ± 0.8 mMAAE ml-1) and lowest in Dagga (26.93 ± 1.4 mMAAE ml-1) flours. The ferric reducing antioxidant power (FRAP) varied significantly across the locations and among the cultivars and ranged from 14.45 ± 0.3 μMTE ml-1 (Tshiombo) to 17.40 ± 1.1 μMTE ml-1 (Univen). FRAP was significantly highest in Impilo (21.12 ± 2.1 μMTE ml-1) and lowest in Mvuvhelo (8.16 ± 2.0 μMTE ml-1). Total carotenoid content positively correlated with DPPH (0.486*), FRAP (0.830**), β-carotene (0.370*), and α-carotene (0.424*). The antioxidant content and the radical scavenging activity were significantly correlated (0.563**). Vitamin A content was significantly lowest (6.88 ± 0.38 μg/g retinol) in Dagga flour and highest (7.97 ± 0.25 μg/g) in Impilo flour. Protein content varied significantly across the two locations and ranged from 4.23% (Tshiombo) to 7.16% (Univen). Dagga had significantly the lowest (3.47%) protein content while Impilo had the highest (7.53%). The fat content of the flours varied significantly between the two locations ranging from 0.63% (Tshiombo) to 1.01% (Univen). The protein content was positively correlated 0.594** and 0.421* to vitamin A and fat contents respectively. The Bophelo colour luminosity was significantly lower (L* 76.2) than the other two OFSP, Dagga (L* 83.51) and Impilo (L* 82.07). Bophelo a* (14.09) also differed significantly across all sweet potato cultivars. All cultivars differed significantly in b* values. Colour intensity (ΔE*) ranged from 15.87 to 38.48 for Mvuvhelo and Bophelo, respectively. Chroma ranged from 87.52 to 84.95 for Dagga and Mvuvhelo respectively. Total starch content was significantly different in all sweet potato cultivars and ranged from 244.07 μg/100 g (Bophelo) to 325.04 mg/g (Dagga). Resistant starch differed significantly in all sweet potato cultivars ranging from 1.21 μg/100 g dwb (Bophelo) to 7.07 μg/100 g dwb (Impilo). Ash content was significantly different in all cultivars and ranged from 3.17% (Dagga) to 3.79% (Bophelo). Water holding capacity (WHC) varied significantly across the two locations and ranged from 1.44 g H2O/g DM (Tshiombo) to 1.72 g H2O/g DM (Univen). Bophelo had significantly the lowest (1.27 g H2O/g DM) WHC and Impilo the highest (1.99 g H2O/g DM). The ash content negatively correlated to total starch (-0.928**) but positively iii correlated to WHC (0.654**). Peak viscosity differed significantly across all cultivars under study and ranged from 126.54 RVU (Bophelo) to 302.36 RVU. (Dagga). There was significant difference in trough viscosity across all cultivars ranging from 55.97 RVU (Impilo) to 280.78 RVU (Dagga). There were significant differences in the final viscosity across all cultivars ranging from 78.99 RVU (Impilo) to 319.26 (Dagga). Peak time viscosity varied significantly across all cultivars ranging from 3.87 min (Impilo) to 8.47 min. (Bophelo). Dagga cultivar had significantly the highest pasting temperature (94.16oC) and Bophelo the lowest (77.75oC). The setback viscosity was significantly highest 51.10 RVU (Mvuvhelo) and lowest 23.01 RVU (Impilo). All cultivars from the two locations consistently showed high potassium content ranging from 0.46% (Impilo) to 1.38% (Dagga) as compared to other minerals such as magnesium, calcium and chlorine which ranged from 0.16% (Impilo) to 0.34%. (Dagga). The CT scans revealed that there was a possibility of evaluating the effect of location on the density of granules of sweet potato flour and also the inherent differences in granular distribution of various sweet potato cultivars. SEM revealed high amounts of potassium, magnesium and chlorine. A profile of physicochemical and functional properties of flour of some of the OFSP cultivars produced in Limpopo province, South Africa has been drawn. This study also highlights the nutritional quality of the flour from four sweet potato cultivars and provides a ranking of flour to help the producers in the selection process. Bophelo flour was ranked the highest in terms of β- and, α-carotenes, total carotenoids and antioxidant capacity while Impilo was ranked highest in terms of functional properties and ash content. This study has highlighted significant differences in a number of parameters measured among the sweet potato cultivars. Therefore, in order to derive the maximum benefit from a given cultivar careful selection of sweet potato cultivars would be necessary.
44

Comparison of vacuum treatments and traditional cooking in vegetables using instrumental and sensory analysis

Iborra Bernad, María del Consuelo 21 October 2013 (has links)
Los objetivos de la presente tesis fueron comparar el efecto de tres técnicas de cocción en varios vegetales y su selección para cada producto estudiado. Para ello, los trabajos realizados han considerado los cambios en las propiedades físico-químicas, nutricionales, sensoriales y la microestructura. Asimismo, como respuesta al reto de aplicar tratamientos equivalentes en firmeza con diferentes técnicas de cocción se ha propuesto una metodología que combina los diseños experimentales de superficie respuesta (RSM) con análisis instrumentales y sensoriales. Los tratamientos térmicos estudiados fueron la cocción tradicional (TC¿ agua hirviendo a 100 °C) junto con dos tratamientos que utilizan el vacío en el procesado: el cook-vide (CV¿ cocción a vacío continuo donde los alimentos están en contacto con agua hirviendo a baja presión) y el sous-vide (SV¿ cocción de alimentos previamente embolsados a vacío donde el alimento está separado del agua de cocción). Los vegetales objeto de estudio fueron la patata morada (Solanum tuberosum L. var. Vitelotte), la judía verde (Phaseolus vulgaris L. cv. Estefania), la zanahoria (Daucus carota L. cv. Nantesa) y la col lombarda (o repollo colorado) (Brassica oleracea convar. capitata var. capitata f. rubra). Considerando muestras con firmeza instrumental similar y las propiedades nutricionales y sensoriales (especialmente aroma y sabor), incluyendo la aceptación del consumidor, se recomienda la cocción SV para los vegetales estudiados, excepto para la zanahoria. En el caso de este vegetal el cocinado tradicional (100 °C) mantiene la aceptabilidad del consumidor y aumenta la extracción de los ß-carotenos por lo que se considera más recomendable que el SV. / Iborra Bernad, MDC. (2013). Comparison of vacuum treatments and traditional cooking in vegetables using instrumental and sensory analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/32953 / TESIS

Page generated in 0.0341 seconds