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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.
1

Evaluation of Pigments from a Purple Variety of Atriplex hortensis L. for Use in Food Applications

Vila Roa, Eva Graciela 01 June 2018 (has links)
Atriplex hortensis L., also known as orach, is a leafy vegetable from the Amaranthaceae family, which has historically been consumed as a potherb, like spinach. The brightly colored leaves are a source of high quality protein, but may also be of interest as a potential source of natural food pigments. An aqueous extraction was obtained from the freshly harvested leaves of the'Triple Purple' variety of A. hortensis. The extract was spray-dried into a powder, and individual pigments were analyzed using HPLC and LC-MS. The powder was also included as a color additive in a typical stabilizer/sweetener preparation and mixed into plain yogurt. Two batches of colored yogurt were held under light and dark conditions and tested for pH and color (L*a*b*) every 15 days. A visual sensory panel was performed on days 0, 45, and 90 to evaluate the color acceptance.A total of three types of betacyanins and six types of anthocyanins were tentatively identified by HPLC and/or LC-MS. Orach pigments in yogurt were not stable under full light exposure. The color of samples exposed to light degraded within days. There were statistically significant differences found in L*a*b* scores in the dark treatment, beyond 30 days; but these modest changes in dark-stored samples were not found to be statistically significant in the consumer sensory panel. The tentative identification of both anthocyanins and betacyanins in orach is a novel finding in botanical research, as the literature indicates that these two pigment classes are mutually exclusive. The application of heat during pigment extraction, spray drying, and yogurt color additive preparation, did not appear to appreciably affect stability of orach pigments, indicating that orach extract could be used as a color in different process applications, if protected from light.
2

Understanding the Thermal Stability and Environmental Sensitivity of Phycocyanin using Spectroscopic and Modelling Tools

Toong, Cally 25 October 2018 (has links) (PDF)
Phycocyanin (PC), a pigment-protein conjugate from Arthrospira platensis, is increasingly used in foods as a natural alternative to artificial blue dyes. Although PC has been classified as a color additive exempt from certification by the Food and Drug Administration, its limited stability has hindered its widespread application in food products. The objectives of this study were: a) to evaluate the photophysical properties of PC and their sensitivity to temperature, viscosity, and water activity, b) to monitor PC’s thermal degradation based on changes in the optical properties of its intrinsic fluorophores, namely its chromophores and aromatic amino acids, and c) to extract PC’s thermal degradation kinetics parameters from non-isothermal degradation profiles and validate their predictive ability. PC’s photophysical properties were monitored in solutions with viscosities from 1 to8000 mPa s and water activities, aw, from about 0 to 1. PC’s emission intensity showed high sensitivity to aw above 0.8 and mild sensitivity to the viscosity of its local environment. The effect of temperature on PC’s photophysical properties was tested in aqueous PC solutions (0.5 mM, pH: 6.1) subjected to non-isothermal temperature profiles with target temperatures from 42.5 to 80°C. The stability of PC was monitored in terms of its photophysical properties, i.e., fluorescence emission intensity, energy, and anisotropy (r) of its chromophore at set time intervals. Additionally, the photophysical properties of PC’s aromatic amino acids (AAs) tyrosine and tryptophan (lexc: 280 and 295 nm) were recorded. The thermal degradation kinetics of PC was assumed to follow a Weibullian model, and the temperature dependence of the degradation rate parameter, b(T), a logarithmic exponential model. Changes of PC fluorescence intensity under dynamic conditions were used to extract the degradation kinetics parameters using the endpoints method. Deviations between the estimated and experimental values were less than 10% for all temperature profiles. During thermal treatments, hypsochromic shifts of AAs’ emission spectra (from 340 to 315 nm) and significant increases in fluorescence anisotropy revealed that color losses were not solely associated with an alteration of the chromophore but with conformational changes and possible aggregation of the protein subunits. An increase in viscosity of the surrounding media provided a protected effect on discoloration during heating. Adequate modeling approaches and molecular spectroscopic techniques can help to develop effective strategies to enhance thermal stability, expand its use as a color and functional ingredient and operationalize it as an endogenous sensor of food quality.
3

The Language of Textiles : Description and Judgement on Textile Pattern Composition / Det Textila Språket : Beskrivning och bedömning av textila mönster

Homlong, Siri January 2006 (has links)
<p>The present study concerns ways to describe, judge and discuss aesthetic qualities of designed textile patterns. Specific aims were to study how colours and compositions used in Old Amish Quilts can be systematically described, to study how simple and complex patterns in printed textile fabrics are perceived and expressed verbally and to study judgements, concepts and values in relation to designed textile patterns as expressed by schoolchildren, consumers, teachers of textile handicraft and designers.</p><p>The study design is qualitative in order to collect concepts used by subjects from different user groups when describing textile patterns and of the reasons for their judgements of the designed patterns. A modified Repertory Grid Method was used. Describing colour design and composition using graphic models was also attempted.</p><p>The experience of aesthetic qualities in designed patterns is complex and not possible to describe using clear-cut concepts. Descriptions and choice of words are part of different language games outside the field of textile design and their contents are found in a dynamic interplay between a number of experiential contexts. The dominant inner contexts of individuals, basic perceptual patterns of apprehension, direct experiences of the surrounding world, and influences from the cultural context all give different and complex structures of attention. Different structures of attention lead to different perceptual choices and different descriptions, judgements, notions and values concerning designed printed patterns.</p><p>The present study shows that subjects make their judgements on the basis of formal, functional, cultural and emotional contents. These content categories are related to the multiple contexts of different dimensions of experience. For judgement and communication in the process of design and in design education, mutual understanding calls not only for concepts and notions in the field of design, but also consideration of conditions of experience and communication in life.</p>
4

The Language of Textiles : Description and Judgement on Textile Pattern Composition / Det Textila Språket : Beskrivning och bedömning av textila mönster

Homlong, Siri January 2006 (has links)
The present study concerns ways to describe, judge and discuss aesthetic qualities of designed textile patterns. Specific aims were to study how colours and compositions used in Old Amish Quilts can be systematically described, to study how simple and complex patterns in printed textile fabrics are perceived and expressed verbally and to study judgements, concepts and values in relation to designed textile patterns as expressed by schoolchildren, consumers, teachers of textile handicraft and designers. The study design is qualitative in order to collect concepts used by subjects from different user groups when describing textile patterns and of the reasons for their judgements of the designed patterns. A modified Repertory Grid Method was used. Describing colour design and composition using graphic models was also attempted. The experience of aesthetic qualities in designed patterns is complex and not possible to describe using clear-cut concepts. Descriptions and choice of words are part of different language games outside the field of textile design and their contents are found in a dynamic interplay between a number of experiential contexts. The dominant inner contexts of individuals, basic perceptual patterns of apprehension, direct experiences of the surrounding world, and influences from the cultural context all give different and complex structures of attention. Different structures of attention lead to different perceptual choices and different descriptions, judgements, notions and values concerning designed printed patterns. The present study shows that subjects make their judgements on the basis of formal, functional, cultural and emotional contents. These content categories are related to the multiple contexts of different dimensions of experience. For judgement and communication in the process of design and in design education, mutual understanding calls not only for concepts and notions in the field of design, but also consideration of conditions of experience and communication in life.

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