No description available.

The provitamin A carotenoid β-carotene is an attractive candidate for the prevention of cancer. Indeed, abundant evidence suggests that β-carotene inhibits carcinogenesis. β-Carotene is thought to inhibit carcinogenesis by scavenging free radicals involved in tumor formation. However, there is no direct evidence that β-carotene traps radicals under conditions where it inhibits carcinogenesis. The overall objective of this dissertation research was to identify β-carotene oxidation products from β-carotene antioxidant reactions in model systems. Identification of such products will enable the direct measurement of β-carotene antioxidant activity in systems where it inhibits neoplastic transformation. In hexane solution, β-carotene was oxidized by peroxyl radicals to 5,6-epoxy-β, β-carotene, 15,15'-epoxy-β, β-carotene, a previously unreported product, and several unidentified polar products. Studies on the kinetics of product formation suggested that polar products are formed by both epoxide-dependent and -independent pathways. Because β-carotene may be localized within lipid bilayers in vivo, peroxyl radical oxidation of β-carotene in model membranes was examined. In soy phosphatidylcholine liposomes, β-carotene was oxidized by peroxyl radicals to the 5,6-epoxide and to unidentified polar products. β-Carotene antioxidant activity in the liposome system was the same at 15 torr and 160 torr O₂ and decreased at 760 torr O₂. These results suggest that β-carotene provides equal antioxidant protection in all tissues in vivo. The relative rates of product formation and β-carotene oxidation at different pO₂ suggested that β-carotene antioxidant activity is governed by the relative proportions of β-carotene radical trapping and autoxidation reactions, which do not contribute to radical trapping. Therefore, the loss of β-carotene antioxidant action at 760 torr O₂ may result from an increase in β-carotene oxidation by autoxidation pathways. The 5,6-epoxide was formed during both antioxidant reactions and autoxidation reactions and may be marker for the peroxyl radical oxidation of β-carotene. Attempts to study β-carotene antioxidant reactions in biological membranes were only partially successful. In vitro incorporation of β-carotene into microsomes was attempted by several methods. However, these efforts resulted in only modest β-carotene antioxidant activity in microsomes. These studies provide a basic understanding of β-carotene antioxidant chemistry in model systems. Their results will enable further investigation of β-carotene antioxidant action in biological systems.

No description available.

Beta-carotene presence or absence in muskmelon is controlled by two genes, green flesh gf and white flesh wf. In its dominant form the wf gene is responsible for orange flesh color; however, the epistatic interactions of gf and wf can create three flesh colors: orange, white and green. Two F2 populations, consisting of 77 greenhouse grown and 117 field grown plants, from the cross of ‘Sunrise’ (white fleshed) by ‘TAM Uvalde’ (orange fleshed), were used to examine the relationships of beta-carotene content, flesh color, and flesh color intensity. Bulk segregent analysis was used with RAPD markers to identify molecular markers associated with high beta-carotene content. Flesh color and flesh color intensity both had significant relationships with beta-carotene content. A significant correlation between total soluble solids and beta-carotene content was also found. Molecular markers were identified in both F2 populations and all significant, associated markers from ‘TAM Uvalde’ were linked with WF. A single QTL was also found to be linked with the WF locus. The identified QTL can be used to screen potential breeding lines for high beta-carotene. It was also confirmed that the visual ratings of flesh color intensity can be reliably used to select high beta-carotene content melons.

Genetic transformation is a useful tool to incorporate novel genes, potentially allowing sexual incompatibility and interspecific barriers to be circumvented. The purpose of this study was to improve beta-carotene levels in melon fruits by transferring a phytoene synthase (PSY) gene. At present, there are not sufficient regeneration and transformation studies reported on two commercially important melon types - western shipper cantaloupe and honeydew. To establish a high efficiency shoot regeneration system, we evaluated three types of explants in our elite breeding lines. A shoot tip with a hypocotyl and cotyledon fragments, regenerated shoots whereas a shoot tip with a hypocotyl without cotyledon, did not produce regenerants. Murashige & Skoog (MS) basal medium with 1 mg 1⁻¹ benzyladenine (BA), 0.26 mg 1⁻¹ abscisic acid (ABA) and 0.8 mg 1⁻¹ indole-3-acetic acid (IAA) was the best for regeneration from cotyledon explants in cantaloupe 'F39'. MS basal medium with 1 mg 1⁻¹ BA and 0.26 mg 1⁻¹ ABA was chosen for honeydew '150' to solve a curving-up problem of explants. Fifty to sixty percent of regenerants were found to be polyploids. To establish a reliable Agrobacterium-mediated transformation protocol, kanamycin sensitivity as well as Timentin[trademark] and Clavamox® were evaluated. Kanamycin 200 and 150 mg 1⁻¹ were chosen as the threshold levels for 'F39' and '150' respectively. No significant differences were found between Timentin[trademark] and Clavamox® in 'F39'; however, Clavamox® reduced the incidence of vitrification and increased the frequency of shoot elongation in '150'. A. tumefaciens strain EHA105, harboring pCNL56 carrying nptII and gusA genes, was used to establish a transformation protocol. The transformation efficiency was 0.3% from 'F39' and 0.5% from '150'. We introduced a watermelon PSY-C gene under the control of a fruit-specific promoter of a polygalacturonase gene into '150'. All the transgenic plants were tetraploids based on flow cytometry assays. Up to 32-fold of beta-carotene was elevated in the rind tissue of transgenic honeydew including phytoene increase. This is a very promising result for a further investigation to increase beta-carotene level in flesh tissue using the PSY-C gene with an appropriate promoter.

Vitamin A deficiency is recognized as a major health concern worldwide, especially in developing countries. Sweet potatoes are a cash crop that is abundantly grown and available, providing an excellent source of the carotenoid, beta-carotene. Carotenoids are precursors to vitamin A (retinol). Three sweet potato cookie products were developed: glutenree, wheat-containing, and glutenree with extra sweet potato. Products were evaluated by adults and pre-school aged children based on appearance, aroma, texture, flavor, and overall acceptability. Results showed that overall the children liked both the glutenree and wheat-containing cookies (p<0.05). Adults preferred (p<0.05) the glutenree with extra sweet potato and the wheat-containing products. The glutenree cookie contained 10.1 parts per million of beta-carotene as determined by high-performance liquid chromatography.

No description available.

Ho, Wing Ho. / On t.p. "beta" appears as the Greek letter. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 157-183). / Abstracts in English and Chinese. / Thesis committee --- p.ii / Statement --- p.iii / Acknowledgements --- p.iv / Abstract --- p.vi / 摘要 --- p.vii / Table of Contents --- p.viii / List of Tables --- p.xv / List of Figures --- p.xvii / List of Abbreviations --- p.xxiii / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter Chapter 2 --- Literature Review --- p.4 / Chapter 2.1 --- Vitamin A --- p.4 / Chapter 2.1.1 --- Genral and properties --- p.4 / Chapter 2.1.2 --- Biological importance of vitamin A --- p.6 / Chapter 2.1.3 --- Dietary source of vitamin A --- p.12 / Chapter 2.1.3.1 --- Plant-derived provitamin A and animal-derived vitamin A --- p.12 / Chapter 2.1.3.2 --- Dependence on the plant-derived provitamin A by the poor --- p.14 / Chapter 2.1.3.2.1 --- Plant-derived provitamin A --- p.14 / Chapter 2.1.3.2.1.1 --- General and properties --- p.14 / Chapter 2.1.3.2.1.2 --- Biosynthesis of provitamin A in plants --- p.17 / Chapter 2.1.3.2.1.2.1 --- Assembly of C40 backbone … --- p.17 / Chapter 2.1.3.2.1.2.2 --- Desaturation and cyclization --- p.26 / Chapter 2.1.3.2.1.2.3 --- Oxygenation --- p.29 / Chapter 2.1.3.2.1.2.4 --- Carotenogenic enzymes --- p.31 / Chapter 2.1.4 --- Metabolism of dietary vitamin A and provitamin A in human system --- p.35 / Chapter 2.1.4.1 --- Digestion and absorption --- p.35 / Chapter 2.1.4.2 --- Biocon version --- p.37 / Chapter 2.1.4.2.1 --- "Beta, beta '-carotene 15, 15'-monooxygenase (BCMO)" --- p.40 / Chapter 2.1.4.3 --- "Transport, uptake and storage" --- p.43 / Chapter 2.1.4.4 --- Provision or excretion --- p.46 / Chapter 2.2 --- Vitamin A deficiency (VAD) --- p.48 / Chapter 2.2.1 --- Green revolution --- p.48 / Chapter 2.2.2 --- Rice as the major staple food for feeding the poor --- p.49 / Chapter 2.2.3 --- Provitamin A content in processed rice seeds --- p.49 / Chapter 2.2.4 --- Symptoms of VAD --- p.51 / Chapter 2.2.5 --- Global prevalence of VAD --- p.53 / Chapter 2.3 --- Previous efforts for dealing with the deficiency --- p.55 / Chapter 2.3.1 --- The key for dealing with the deficiency --- p.55 / Chapter 2.3.2 --- Selective plant breeding --- p.55 / Chapter 2.3.3 --- Supplementation and post-harvesting fortification --- p.56 / Chapter 2.3.4 --- Bio-fortification by genetic engineering --- p.57 / Chapter 2.3.4.1 --- Advantages of genetic engineering --- p.57 / Chapter 2.3.4.1.1 --- Genetic engineering of non-cereal crops --- p.58 / Chapter 2.3.4.1.2 --- Genetic engineering of cereal crops --- p.62 / Chapter 2.3.4.1.2.1 --- Golden Rice 1 --- p.62 / Chapter 2.3.4.1.2.2 --- Golden Rice 2 --- p.64 / Chapter 2.4 --- Motivation for striking forward --- p.67 / Chapter 2.4.1 --- Recommended Dietary Amount of vitamin A --- p.67 / Chapter 2.4.2 --- Factors affecting the bioefficacy of provitamin A in human body --- p.68 / Chapter 2.4.2.1 --- Bioavailability --- p.68 / Chapter 2.4.2.2 --- Bioconvertibility --- p.69 / Chapter 2.4.2.3 --- Health and nutritional status --- p.71 / Chapter 2.4.3 --- Further improvement for dealing with the deficiency --- p.73 / Chapter 2.5 --- Hypothesis --- p.75 / Chapter Chapter 3 --- Materials and Methods --- p.78 / Chapter 3.1 --- Chemicals --- p.78 / Chapter 3.2 --- Bacterial strains --- p.78 / Chapter 3.3 --- Transient expression of BCMOs in plant system --- p.79 / Chapter 3.3.1 --- Choice of BCMOs --- p.79 / Chapter 3.3.2 --- Plasmids and genetic material --- p.79 / Chapter 3.3.3 --- Construction of chimeric genes for transient expression --- p.82 / Chapter 3.3.4 --- Microprojectile bombardment and GUS assay --- p.83 / Chapter 3.4 --- Construction of chimeric genes for rice co-transformation --- p.84 / Chapter 3.4.1 --- Choice of carotenogenic genes --- p.84 / Chapter 3.4.2 --- Choice of promoters --- p.84 / Chapter 3.4.3 --- Necessities and choice of transit peptide (TP) --- p.85 / Chapter 3.4.4 --- Arrangement of chimeric gene-cassettes --- p.86 / Chapter 3.4.5 --- Plasmids and genetic materials --- p.87 / Chapter 3.4.6 --- Construction of chimeric gene expressing PSY and PDS coordinately --- p.87 / Chapter 3.4.7 --- "Construction of chimeric gene expressing PSY, PDS and TP equipped CHBCMO coordinately" --- p.92 / Chapter 3.4.8 --- "Construction of chimeric gene expressing PSY, PDS and TP equipped ZEBCMO coordinately" --- p.98 / Chapter 3.4.9 --- Construction of chimeric gene expressing ZDS and LYCB coordinately --- p.103 / Chapter 3.4.10 --- Confirmation of sequence fidelity --- p.108 / Chapter 3.5 --- Rice co-transformation --- p.109 / Chapter 3.5.1 --- Plant materials --- p.109 / Chapter 3.5.2 --- Preparation of Agrobacterium tumefaciens --- p.109 / Chapter 3.5.3 --- Agrobacterium mediated co-transformation --- p.110 / Chapter 3.5.3.1 --- Callus induction from mature rice seeds --- p.110 / Chapter 3.5.3.2 --- Callus induction from immature rice seeds --- p.110 / Chapter 3.5.3.3 --- "Co-cultivation, selection and regeneration" --- p.111 / Chapter 3.6 --- Detection of transgene expression --- p.112 / Chapter 3.6.1 --- Detection at DNA level --- p.112 / Chapter 3.6.1.1 --- Genomic DNA extraction --- p.112 / Chapter 3.6.1.2 --- PCR screening --- p.112 / Chapter 3.6.1.3 --- Synthesis of DIG-labeled DNA probes --- p.114 / Chapter 3.6.1.4 --- Southern blot analysis --- p.115 / Chapter 3.6.2 --- Detection at RNA level --- p.116 / Chapter 3.6.2.1 --- Total RNA extraction --- p.116 / Chapter 3.6.2.2 --- Northern blot analysis --- p.116 / Chapter 3.6.3 --- Detection at product level --- p.117 / Chapter 3.6.3.1 --- Phenotypic identification --- p.117 / Chapter 3.6.3.2 --- HPLC analysis --- p.117 / Chapter 3.6.3.2.1 --- Extraction of total carotenoids and retinoids --- p.117 / Chapter 3.6.3.2.2 --- HPLC identification --- p.118 / Chapter 3.6.3.2.3 --- HPLC quantification --- p.118 / Chapter Chapter 4 --- Results --- p.119 / Chapter 4.1 --- Transient expression of BCMOs in plant system --- p.119 / Chapter 4.1.1 --- Construction of chimeric genes for transient expression --- p.119 / Chapter 4.1.2 --- Microprojectile bombardment and GUS assay --- p.120 / Chapter 4.2 --- Construction of chimeric genes for rice co-transformation --- p.121 / Chapter 4.3 --- Rice co-transformation --- p.123 / Chapter 4.3.1 --- Callus induction from mature and immature rice seeds --- p.123 / Chapter 4.3.2 --- "Co-cultivation, selection and regeneration" --- p.124 / Chapter 4.4 --- Detection of transgene expression --- p.126 / Chapter 4.4.1 --- Detection at DNA level --- p.126 / Chapter 4.4.1.1 --- PCR screening --- p.126 / Chapter 4.4.1.2 --- Southern blot analysis --- p.129 / Chapter 4.4.2 --- Detection at RNA level --- p.133 / Chapter 4.4.2.1 --- Northern blot analysis --- p.133 / Chapter 4.4.3 --- Detection at product level --- p.135 / Chapter 4.4.3.1 --- Phenotypic identification --- p.135 / Chapter 4.4.3.2 --- HPLC identification --- p.137 / Chapter 4.4.3.3 --- HPLC quantification --- p.147 / Chapter Chapter 5 --- Discussion --- p.150 / Chapter Chapter 6 --- Conclusion --- p.156 / References --- p.157

A utilização de bioativos naturais como ingredientes está em constante expansão na indústria alimentícia, devido ao aumento das exigências pelos consumidores por alimentos mais saudáveis. Por isso, há uma busca constante de tecnologias que possibilitem a incorporação de tais substâncias em alimentos. O &#946;-caroteno é uma substância hidrofóbica, cujos benefícios estão relacionados principalmente à sua ação antioxidante. Devido à sua característica hidrofóbica, a utilização deste pigmento implica em desafios tecnológicos para ser incorporado em formulações alimentícias de base aquosa. Por este motivo, a encapsulação em lipossomas pode ser uma ótima alternativa, devido à capacidade de englobar tais substâncias em sua bicamada lipídica. Além da proteção, essas matrizes encapsulantes podem proporcionar a liberação controlada dos ingredientes encapsulados, bem como aumento de sua biodisponibilidade. O objetivo deste trabalho foi produzir e caracterizar dispersões de lipossomas encapsulando &#946;-caroteno estabilizadas com a adição de hidrocolóides(goma xantana ou mistura de goma xantana e goma guar). O diâmetro médio hidrodinâmico, a distribuição de tamanho das partículas e a morfologia foram avaliadas. Os lipossomas produzidos foram vesículas multilamelares (MLV), as distribuições de tamanho dos lipossomas apresentaram-se heterogêneas e as micrografias revelaram a forma esférica dos lipossomas dispersos no meio aquoso, assim como a integridade da sua bicamada lipídica. Foram realizadas análises de quantificação do &#946;-caroteno e colorimetria instrumental, sendo que todas as dispersões mostraram-se eficientes na preservação do &#946;-caroteno ao longo do período de armazenamento. Os hidrocolóides adicionados foram eficazes no aumento da viscosidade da fase contínua, evitando a agregação das vesículas ao longo do tempo, exceto para dispersão estabilizada com a mistura de goma xantana e goma guar, com 0,15% de goma total. Em relação à adição das dispersões de lipossomas em iogurte, as formulações mostraram-se homogêneas, com ausência de grumos ou qualquer tipo de separação de fases, e também foram aprovados por uma parcela de painelistas na análise sensorial. / The use of natural bioactives as ingredients is in constant expansion in the food industry, due to increasing consumer demands for healthier foods. Therefore, there is a constant search for technologies capable of incorporating such substances in food. &#946;-carotene is a hydrophobic substance, whose benefits are mainly related to its antioxidant action. Because of its hydrophobic characteristics, the use of this pigment implies technical challenges to be incorporated into aqueous-based food formulations. For this reason, encapsulation in liposomes may be a good alternative, because of their ability to incorporate such substances in their lipid bilayer. Besides the protection, these encapsulants matrix can provide controlled release of the encapsulated ingredients, as well as increasing its bioavailability. The objective of this study was to produce and characterize dispersions of liposomes encapsulating &#946;-carotene, which were stabilized with the addition of hydrocolloids: xanthan gum or a mixture of xanthan gum and guar gum. The mean hydrodynamic diameter, distribution of particle size and its morphology were studied. The obtained dispersions were multilamellar vesicles (MLV), the liposomes size distributions were heterogeneous and the micrographs revealed the liposomes spherical shape dispersed in aqueous medium, as well as the integrity of their lipid bilayer. The quantification of &#946;-carotene and instrumental colorimetry analyses indicated the liposomes were efficient in the preservation of &#946;-carotene during the storage period. The hydrocolloids added in the dispersions were highly efficient to increase the viscosity of the continuous phase. Therefore, the hydrocolloids were responsible for the prevention of aggregation of the vesicles during the storage period, except for stabilized dispersion with the mixture of xanthan gum and guar gum, with 0.15% gum total. Regarding the dispersions of liposomes added in yoghurt, the formulations were homogeneous, with absence of lumps or any phase separation, and also have been approved by a significant number of the panelists.

Molecules of anthocyanins and quinones possess distinctive electrophilic character, which is demonstrated by their facile reactions with nucleophiles such as sulfite, thiols, amines and water. In food systems, one of their likely targets would be nucleophilic centers in the side chains of amino acids. Our experiments revealed that on a short-term exposure (1 72 h) to free amino acids in solutions with pH < 7 glycosides of cyanidin and quinones of phenolic acids did not yield nucleophilic addition products with most of the amino acids. A notable exception was cysteine, which reacted with oxidized phenolic acids and caused anthocyanin bleaching at elevated temperature. Thermodynamic aspects of the nucleophilic addition reactions were investigated with the aid of computational chemistry. We have also found that enzymatic browning in apricot puree does not lead to trans-cis -carotene isomerization, contrary to some previous reports. Increased availability of -carotene for extraction was recorded for browned apple- and pear-apricot purees in comparison with the non-browned purees. / Food Science and Technology