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  • 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.
31

Stevia the ideal sugar substitute and dental caries prevention

Cojocaru, Daniela 20 February 2021 (has links)
Dental caries affects people worldwide. The oral microflora has been found to be less responsible than the carbohydrate diet, which is considered the main cause of dental caries. Carbohydrates from sucrose are processed by oral bacteria and acids are produced as a byproduct. High sugar intake is a risk factor for systemic health and for overall health of the oral cavity. Artificial sweeteners are considered a healthy alternative for people who prefer the sweet taste but renounce sucrose. In the United States there are several artificial sweeteners approved by the Food and Drug Administration. Among these, stevia is the only natural sweetener. Stevia is extracted from the Stevia rebaudiana plant. Steviol glycosides are extracted from the stevia leaf and refined to get the best taste quality. There are many types of steviol glycosides that are extracted from the stevia plant and the most important steviol glycosides will be discussed in the thesis. Scientific research (PubMed, EMBASE), appropriate websites (Colgate, Pure Circle Stevia Institute), the World Health Organization, HealthInfo Clinical Advisers and vectorstock as well as books in English and in Russian (The Stevia Deception: The Hidden Dangers of Low Calorie Sweeteners By Bruce Fife, and Puti Izbavlenie of Bolezne by Neumyvakin) were consulted. Electronic searches were limited to publications in the past five years. The scope of the thesis is to review the basic statistics on dental caries, the types of caries and the number of people affected, discuss the advantages and benefits of stevia relative to other artificial sweeteners, review the safety of stevia including side effects and potential as an addictive sugar substitute and lastly, to assess and recommend which form of stevia is most effective against dental caries.
32

Technologie výroby mrazených krémov s náhradnými sladidlami

Sabotová, Michaela January 2018 (has links)
The theme of this thesis is Technology of production of ice cream with alternative sweeteners. This work was divided into two parts. The theoretical and practical part. In the theoretical part, there are described general information about the ice cream related to basic materials, technological process of production and rheological characteristics. The chapter about sugar and sweeteners is described in more detail. The main point of it are sweeteners which can replace sucrose. Information related to history of sweeteners, division of alternative sweeteners, allowed sweeteners in the EU and their use. In detail is described plant Stevia rebaudiana, it is origin, content substances, sweetening substances and the use of stevia as a sweetener for a production of the ice cream. In the practical part, there was the main aim to product an ice cream with alternative sweeteners. As a standard was used fructose, which was replaced with many others. In this experiment I made the sample in two flavours: vanilla and cacao. Ice cream was produced with sweetener stevia, next ice cream with sweetener stevia, wchich was enriched by fiber. In next experiments was produced ice cream with the sweetener DiaChrome with sucralose, date syrup, coconut sugar, xilovit and agave syrup. I had 14 samples which where divided into two halves. The first half was with vanilla flavour and the second half was with cacao flavour. They were rated right after the production. The results were received by sensorican analysis and drain tests and it was graphically evaluated. The main aim was to formulate a suitable recipe for the production of ice cream with sweeteners. To focus on new materials used in production of ice cream, including using the alternative sweeteners in production of ice cream, including their influence on the sensoric quality of the finished products. To evaluate their influence on rheological properties and sensory quality.
33

Vliv podmínek prostředí na pěstování Stévie sladké (Stevia rebaudiana Bertoni)

HAVLOVÁ, Martina January 2017 (has links)
Stevia or Stevia rebaudiana Bertoni are two of the numerous names of this subtropical plant with a sweetening power as much as 300 times higher than in case of sucrose. Stevia is a plant with a very interesting, but up to this date not very utilised potential. The fields of its application, processing, cultivation and wintering options have not been explored very extensively, and therefore I have decided to elaborate this topic related to the impact of the environmental conditions for growing of Stevia rebaudiana. The resources for the text of the diploma thesis were formed by available specialised publications and the Internet. The first part of the thesis represents a brief overview of the whole issue concerning the topic of Stevia rebaudiana. The objectives, hypotheses and methodology of the conducted research, including the findings based on the plant growing as well, and the evaluation of the experiment results have been included in the second part. The purpose of the thesis was to expand the knowledge regarding cultivation, reproduction methods and wintering options of the stevia plants. A field and a greenhouse experiments were staged with a focus on temperature indicators during the growing season and their impact on the total number of wintered plants. Simultaneously, an evaluation of the dry matter yield of the plants per an area unit and statistical processing and evaluation of the experiment results have been performed. Further, a determination of seed germination for Stevia rebaudiana in laboratory conditions has been conducted. The research results have shown that the plants obtained vegetatively are more suitable for cultivation due to a higher yield of the dry matter in both greenhouse as well as field conditions. The only pests invading stevia were the whiteflies appearing only in the greenhouse environment. Variable conditions were arranged for the wintering of the Stevia rebaudiana plants within the experiment; and in spite of the various materials and thermal insulation layers, the plants have not successfully wintered in an unheated environment. On the contrary, in the heated greenhouse space, most of the plants have successfully wintered. The stevia seed germination was low and proves the opinion of the majority of authors. The dry matter yields also matched the yields mentioned in the specialised literature.
34

Antimikrobiální účinky extraktů ze stévie cukrové / An antimicrobial activity of Stevia rebaudiana extracts

Mlatečková, Tereza January 2008 (has links)
This master thesis is oriented on study antimicrobial effects extracts and macerates from cure Stevia rebaudiana Bertoni. Teoretical part describes basic information about plant Stevia, summary of health significant matters contained in Stevia and posobilities preparing extracts from Stevia. Antimicrobial effects extracts and macerates from cure Stevia were testing on food-borne bacteria (Bacillus cereus and Micrococcus luteus) and yeasts (Geotrichum candidum and Hansenula anomala). Microorganism, extracts and macerates were chosen on basis previous study (Study of antimicrobial effects Stevia Rebaudiana extracts, Eva Rakovská). For screening antimicrobial activity were determined the growth curves by using turbidimetrie for bacteria and direct treetment metod of cells number for yeasts. Antimicrobial effects were confirmed aplication with diffusion pit method on the agar ranges. From the results flow the testing extracts and macerates from stevia analysed antimicrobial effects. The best effect was demostrated on macerates and the most sensitive was bacteria Micrococcus luteus with the best inhibitoring effects.
35

Analýza nápojů slazených extrakty stévie cukerné / Analysis of drinks sweetened with stevia extracts

Procházka, Václav January 2013 (has links)
The steviolglycosides are the natural, sweet substances from Stevia rebaudiana Bertoni. It affect human health positively and its sweetness is 300x stronger than the sweetness of sucrose. That's why it's used to sweetening the commercial products. Because of its potential properties it's good to have an appropriate method to isolate it. High performance liquid chromatography ( HPLC) is based on the separation of analyte between two immiscible phases with high pressure pump and appropriately chosen stationary phase in the column. Than the analytes come out from the column in different retention times. This master´s thesis follows up selection of the best HPLC system for isolation of the main steviolglycosides and its analysis in commercial products. In the theoretical part of the thesis is described the origin, basic characteristics, botanical description, cultivation and affect to the human health of Stevia rebaudiana Bertoni and its use in food industry. There are also concisely characterized the sweet substances contained in the plant, so called steviolglycosides. Than there are given the theoretical basics of high performance liquid chromatography, HPLC instrumentation and its specific applications at sleviolglycosides with the basic chromatographic parameters. The object of the first experimental part was to research the optimum conditions for time and separation effective chromatographic analysis and select the best chromatographic system for isolation of steviolglycosides. In the second experimental part, I have compared and defined the main steviolglycosides (stevioside, rebaudioside A) in nine selected products, commercially available in Czech republic, with the best chromatographic method. In these products was the contain of the stevioside or rebaudioside A confirmed or refused.
36

Stanovení antioxidační aktivity v méně známých druzích zeleného koření

Ištvánková, Barbora January 2017 (has links)
The diploma thesis deals with content substances with antioxidant effects in green spice. In the literary part, green spices, antioxidants are defined, and lesser known species are introduced, as well as the determination methods used in the practical part. In the practical part are given the individual determinations. The DPPH method was used to determine the antioxidant capacity, to determine the nitrate content ISE method was used, the flavonoids were determined using the Folin-Ciocalteaue reagent, and the standard in the phenols was gallic acid. Vitamin C was determined by liquid chromatography.
37

STEVIA Y OTROS EDULCORANTES SALUDABLES EN LA FORMULACION DE GOLOSINAS FUNCIONALES: IMPLICACIONES TECNOLÓGICAS Y DE CALIDAD

Periche Santamaría, Angela 24 November 2015 (has links)
Pese a que las golosinas no son un producto imprescindible en la dieta, no hay que duda de que su consumo está muy generalizado tanto en la población infantil como en la adulta. Sin embargo, su ingesta elevada está relacionada con problemas de sobrepeso, caries y elevado índice glicémico. Para contrarrestar estos problemas se ha invertido mucho esfuerzo en el desarrollo de productos dietéticos. Para ello, se sustituyen los azúcares convencionales por edulcorantes artificiales que dan lugar a productos hipocalóricos, pero que presentan otros problemas relacionados con su efecto laxante y con una posible mayor incidencia de determinados cánceres. Actualmente existen en el mercado azúcares y edulcorantes naturales alternativos a la sacarosa con propiedades funcionales muy interesantes, como es el caso de la Isomaltulosa y la estevia. En el primer caso se trata de un azúcar no cariogénico, que aporta energía de forma gradual (bajo índice glicémico) y en el caso de la estevia se trata de un intenso edulcorante natural acalórico. Estudiar la sustitución total o parcial de los azúcares convencionales de las golosinas por este tipo de azúcares y edulcorantes más saludables y su influencia sobre la calidad de los productos es el objetivo general de este proyecto. Cabe resaltar que no se pretende formular un producto dietético sino un producto energéticamente similar a las golosinas tradicionales pero que aporten energía saludable. La sustitución de ingredientes implica cambios en las características de los productos que deben ser evaluados para optimizar el nivel de sustitución, por lo que es necesario abordar estudios sobre la influencia de estos ingredientes en las propiedades ópticas, mecánicas, sensoriales así como sobre la aceptación del producto y su estabilidad a lo largo del almacenamiento. / Periche Santamaría, A. (2014). STEVIA Y OTROS EDULCORANTES SALUDABLES EN LA FORMULACION DE GOLOSINAS FUNCIONALES: IMPLICACIONES TECNOLÓGICAS Y DE CALIDAD [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/45995 / Alfresco
38

光環境調節によるステビア甘味成分の向上に関する研究

米田, 有希 26 March 2018 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21146号 / 農博第2272号 / 新制||農||1058(附属図書館) / 学位論文||H30||N5120(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 清水 浩, 教授 近藤 直, 教授 田中 千尋 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM
39

Influencia de fungos micorrizicos arbusculares, sistemas de cultivo e parametros pos-colheita na concentração de esteviosideos e desenvolvimento de Stevia rebaudiana (BERT.) Bertoni / Influence of arbuscular mycorrhizal fungi, cultivation systems and postharvest parameters in the concentration of steviosides and development of Stevia Rebaudiana (BERT.) Bertoni

Portugal, Edilberto Princi 20 December 2006 (has links)
Orientador: Sylvio Luis Honorio / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola / Made available in DSpace on 2018-08-08T08:41:42Z (GMT). No. of bitstreams: 1 Portugal_EdilbertoPrinci_D.pdf: 3108115 bytes, checksum: 834974ae808b2dc8cae3ca812f9976ba (MD5) Previous issue date: 2006 / Resumo: A Stevia rebaudiana, um arbusto que tem na produção de esteviosídeos seu principal produto de interesse, foi objeto deste trabalho. Considerando sua cadeia produtiva, existem lacunas que necessitam pesquisas, tanto no aspecto agronômico, como o emprego de espécies fúngicas micorrízicas, quanto procedimentos pós-colheita, dos quais a secagem é um dos fatores. O presente trabalho teve como objetivos, identificar uma espécie de fungo micorrízico arbuscular eficiente e sua relação com o desenvolvimento e concentração de esteviosídeos em plantas de estévia, cultivadas em campo, hidroponia e aeroponia, selecionar substrato adequado para o desenvolvimento da colonização micorrízica, avaliar sistemas de secagem no teor de esteviosídeos e determinar as isotermas de sorção da estévia. Para seleção de fungo micorrízico foram testadas sete espécies, sendo cinco de um banco de culturas e duas isoladas da própria cultura da estévia. O ensaio foi conduzido em casa de vegetação em vasos com solo esterilizado e cinco repetições. Foram determinados a massa seca total da parte aérea e de folhas, teor e quantidade acumulada de esteviosídeos nas folhas e colonização micorrízica. Para seleção de substratos, foram testados nove produtos comerciais, utilizando-se como planta indicadora uma gramínea (Brachiaria humidicola) e como parâmetro avaliado a taxa de colonização fúngica no sistema radicular. Plantas de estévia inoculadas ou não com o fungo micorrízico Glomus intraradices foram cultivadas em três sistemas distintos, campo, aeroponia e hidroponia. Foram realizadas três colheitas em épocas distintas e determinada a massa da matéria seca total da parte aérea e de folhas, teor e acúmulo de esteviosídeos nas folhas e colonização micorrízica. Foram testados três processos de secagem, ao sol, secador a gás e estufa elétrica com circulação forçada de ar, à temperatura de 45oC. Os processos foram avaliados em função do teor de esteviosídeos nas folhas. A determinação da umidade de equilíbrio nas folhas de estévia foi realizada nas temperaturas de 30 e 45oC e, as isotermas de sorção foram tratadas com os modelos matemáticos de BET, BET linear, Peleg, GAB, Halsey, Langmuir, Oswin, Henderson e Chung e Pfost. A espécie Glomus intraradices foi a mais eficiente para o desenvolvimento da estévia e acumulação de esteviosídeos. O substrato Rendmax Citrus sem adubação propiciou as melhores condições para a colonização micorrízica nas raízes da gramínea. Dentre os sistemas de cultivo estudados a hidroponia mostrou-se o menos eficiente para o cultivo de estévia. Em aeroponia obteve-se maior produtividade em termos de matéria seca da parte aérea, enquanto no campo maior quantidade acumulada de esteviosídeos. Não se observou diferença entre a secagem na estufa e no secador para qualquer das épocas de colheita. O teor de esteviosídeos nas folhas de plantas secadas ao sol foi sempre inferior, com perda de até 20% em relação aos outros dois sistemas. Os modelos que apresentaram melhor ajuste, nas temperaturas de 30 e 45oC, foram GAB e HALSEY. O modelo BET LINEAR também mostrou bom ajuste, mas somente para a temperatura de 45oC / Abstract: Stevia rebaudiana, a shrub mostly interesting for its production of steviosides, was the object of this work. In regard to its productive chain, further researches must be done, not only in agronomical aspects, but also in the utilization of mycorrhizal fungal species, as well as in the post-harvest processes, namely the drying one. The present work aimed at the identification of an efficient arbuscular mycorrhizal fungal species and its influence in the development and concentration of steviosides in stevia plants grown in hydroponic and aeroponic systems; to select an adequate substrate for the development of mycorrhizal fungi; to evaluate drying systems in steviosides rates and to determine stevia?s isotherms of sorption. For the mycorrhizal fungi selection seven species were tested, five from a germplasm bank and two were isolated from their own stevia culture. Five assays in pots with sterilized soil were carried out in a greenhouse. The total dry mass of the aerial parts and of the leaves, the rate and accumulated quantity of steviosides in the leaves as well as the mycorrhizal colonization were determined. Nine commercial substrates were tested for the rate of colonization of the root system of an indicating gramineous plant (Brachiaria humidicola). Stevia plants that were inoculated (or not) with the mycorrhizal fungus Glomus intraradices were cultivated in three different growing systems, field, aeroponic and hydroponic. Three harvests were carried out in different periods and the total dry mass of the branch and leaves sections, contents and accumulated steviosides in the leaves and mycorrhizal colonization were determined. Three processes for drying leaves were tested: by sunlight, gas dryer and electrical stove with forced air circulation, at 45oC. The processes were evaluated in relation to the steviosides rate of the leaves. The equilibrium moisture content for stevia leaves was done at 30oC and 45oC, while the isotherms of sorption were tested for the best fit by mathematical models of BET, BET linear, Peleg, Gab, Halsey, Langmuir, Oswin, Henderson and Chung and Pfost. The Glomus intraradices species was the most efficient for the stevia development and accumulation of steviosides. The Rendmax Citrus substrate without manure rendered the best conditions for the mycorrhizal colonization in the gramineous roots. Among the growing systems studied, hydroponics turned out to be the least efficient for stevia cultivation. Aeroponics brought the highest production in terms of dry mass from the aerial parts, while in the field a larger accumulated quantity of steviosides was obtained. No difference was observed between the stove and gas drying processes at any of the harvesting periods. The steviosides rate from the leaves dried by sunlight was always inferior, coming to a loss of 20% in relation to the others. The best fit models were GAB and HALSEY. The BET LINEAR fitted by 45ºC / Doutorado / Tecnologia Pós-Colheita / Doutor em Engenharia Agrícola
40

PSE extrakce rostlinného materiálu pro potravinářské účely / Pressurized solvent extraction of plant material for food industry use

Holasová, Petra January 2009 (has links)
Flavonoids were identified and quantified in samples of dry leaves of plant Stevia rebaudiana Bertoni. Content of flavonols (kaempherol, quercetin, myricetin, rutin) and flavons (apigenin, luteolin) were compared in three samples (standard leaves of Stevia rebaudiana Bertoni, Stevia rebaudiana Bertoni origin from Ukraine and from Czech republic), that were extracted by three extraction methods (PSE, ultrasonic extraction, Soxhlet extraction) with two polar solvents, methanol and ethanol, in combination with non-polar hexane. Extracts were analyzed by HPLC with detection UV-VIS. Antioxidant activity and total content of flavonoids in extracts were measured by spectrometry. Stable free radical DPPH. was used for determination of scavenging effect in extracts. PSE was the most effective extraction method with this conditions – 120 °C, dynamic mode and with methanol like solvent.

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