• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 70
  • 63
  • 60
  • 15
  • 8
  • 8
  • 5
  • 4
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 275
  • 135
  • 97
  • 67
  • 49
  • 47
  • 43
  • 42
  • 40
  • 38
  • 32
  • 31
  • 28
  • 25
  • 24
  • 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.
171

Vliv podmínek skladování na obsah aromaticky aktivních látek v tavených sýrech / The effect of a storage conditions on aroma compounds in processed cheese

Štouračová, Anna January 2008 (has links)
The aim of this diploma thesis was to monitor influence of storage conditions (temperature and time) on content of aroma substances in sterilized processed cheeses and also on their flavour. The part of cheeses was stored at 6°C, second part at room temperature 23 °C and third part at 40 °C. Processed cheeses were produced by Madeta, a. s., sterilized at 117 °C 20 min. The analysis was made at regular intervals, cheeses stored 16 and 23 months were analysed in this work. The aroma compounds were isolated by SPME and subsequently identified and quantified by gas chromatography. In total 37 aroma compounds were identified and quantified, 7 aldehydes, 7 ketones, 6 acids, 12 alcohols and 5 esters. Total content of aroma compounds increases with higher storage temperature. The time of storage has also influence on content of aroma compounds, we may say, that content is increasing, although sharp growth was registered only after 23 months, namely in the thermostat. Simultaneously sensory analysis of cheeses was made. Ranking test and evaluation using scale were used. Cheeses from a fridge were always evaluated as the best in all categories. Cheeses stored at room temperature were evaluated worse and cheeses from thermostat were the worst. So it is apparent, that high temperature supports undesirable chemical changes in cheeses and certainly is related to their flavour.
172

Vliv aromaticky aktivních látek na chutnost kysaných mléčných výrobků / Influence of aroma active compounds on flavour of fermented dairy products

Tvrdková, Denisa January 2010 (has links)
The theme of this thesis is to determine the aroma active compounds in fermented dairy products. These substances significantly influence the palatability of these dairy products. Five kinds of dairy products were analyzed. Two types of creamy yogurts, and three types of yoghurt milks were produced at the dairy Ekomilk Ltd. in Frydek - Mistek and four types of acidified milk, five kinds of creamy yogurts, two kefir milks and two clabbered milks come from production of the company Kunin, Inc. Ostrava - Martinov. The SPME extraction method was used for the determination of aromatics, subsequent analysis was performed using gas chromatography. Compounds contained in fermented milk products were identified and quantified on the basis of the measured standards. Total 39 compounds, including 16 alcohols, 7 acids, 6 aldehydes, 6 ketones and 4 esters were identified. Fermented dairy products were twice subjected to sensory evaluation by the ranking test and scale test. The assessors were chosen from students, postgraduate students and staff of faculty of chemistry BUT. Consumers evaluated very positively yogurts, yogurt drinks and acidified milks, while kefir milks and clabbered milks did not suit in some aspects.
173

Analýza vybraných alergenů ve vonných kompozicích / Analysis of selected allergens in fragrances

Koláčková, Adéla January 2010 (has links)
This thesis is focused on potentially allergenic substances (PASs) in cosmetics. Their specific features, methods of control and observation are described. There are also mentioned dermatology problems connected with usage of perfumed cosmetic products in which the allergenic ingredients can be found and possibilities of their regulation. Fragrances are mixtures of natural or synthetic character which give the aroma. In nature, fragrances are produced mainly by plants. More than one hundred fragrances have been identified as allergens. Twenty six of them were declared as PASs. Allergenic components of perfume compositions are the main cause of allergic contact dermatitis. Experimental part of the thesis is focused on the procedure of analysis of specific allergenic fragrances (?-Amylcinnamaldehyde, Anisealcohol, Benzylsalicylate, Cinnamaldehyde, ?-Hexylcinnamaldehyde, 7-Hydroxycitronellal and Methyl-2-octynoate). Headspace-Solid Phase Microextraction connected with Gas Chromatography-Flame Ionisation Detector (HS-SPME-GC-FID) was used for extraction, analysis and identification of these substances. The method was validated and applied on the spectrum of real samples of cosmetic products.
174

Problematika produktů osobní péče ve složkách životního prostředí / Personal care products as environmental contaminants

Babuš, Ondřej January 2010 (has links)
Synthetic musk compounds were first prepared artificially in the late 19th century. They have been used to perfume cosmetics, detergents and personal care products. The attention of many researchers has been focused on it recently, due to its high penetration into the nature which is a logical consequence of its great use. The main goal of this thesis is to determine the effect of the ultrafiltration on the concentration reduction of substances mentioned above in the industrial waste waters produced by the cosmetic company. Analytes from the sample were extracted using solid phase microextraction (SPME) and on gas chromatography analysis with mass spectroscopy (GC / MS) has been performed. The whole method was optimized and evaluated. Determination of the average efficiency of the ultrafiltration was made based on data obtained before and after ultrafiltration. Such efficiency determines the suitability of use of this method for removal of synthetic musk compounds from waste waters.
175

Stanovení aromaticky aktivních látek ve vybraných typech ovoce / Assessment of aroma active compounds in chosen fruit types

Frechová, Vendula January 2011 (has links)
This diploma thesis deals with the determination of aroma compounds in selected species of less known fruits (sea buckthorn, cornelian cherry, rowanberry, medlar, japanese quince and chokeberry). The theoretical part is focused on the description of these plants, their chemical composition, possibility of utilization and processing. Aroma compounds were identified and quantified in experimental parts. The aroma compounds were extracted by solid-phase microextraction and analysed by gas chromatography. A total of 45 compounds were identified. This compounds included 17 alcohols, 9 ketons, 8 aldehydes, 6 acids and 5 esters. Concurrently, the sensory evaluation of these fruits was carried out. The profile test and evaluation using graphical scales were used for evaluation of pleasantness and intensity of taste and odour.
176

Stanovení syntetických vonných látek v odpadních vodách / Assessment of synthetic musk compounds in waste waters

Štefka, Michal January 2012 (has links)
The synthetic aromatic substances are present in the products of personal hygiene, detergents and cosmetics. After the application these compounds are drained away into the waste water. But the technological process used in sewage works is not able to eliminate these substances and these ones influence the particular items of the environment. The aim of the degree work is the determination of four selected items of the linear musk compounds (2-cyclohexylethanole, Fresco Menthe, Citronellol and Isobornyl acetate) in the wastewater. The real patterns were taken on the place of affluent of the sewage discharge and on the place of the draining off in the sewage plant in VFU Brno. On the basis of measurements and subsequent evaluation on of obtaining data it was possible to express the measurement of efficiency of the elimination of the present musk compounds. Firstly it was necessary to adapt the selected analytical method to the physical and chemical qualities of the prescribed analytes. The analytes were extracted from the patterns by the method of the micro extraction for the consistent phase so called solid phase microextraction (SPME). The gas chromatography in the tandem connection with the mass spectrometry makes the identification and quantification possible.
177

Stanovení aromaticky aktivních látek bezu černého / Assessment of aroma active compounds in elderberries

Kolibačová, Silvie January 2012 (has links)
The aim of this diploma thesis was to determine the aroma active compounds in different varieties of black elderberry (Sambucus nigra L.) and in elder juices that were mixed in different proportions with grape juice. The sensory analysis of these juices was subsequently performed with focusing on their tastiness. The theoretical part deals with the description of the black elderberry, its occurrence, composition and use at home and in industrial processing, as well as a description of aroma active compounds, which have been previously identified in elder by various authors. In the experimental part aroma active substances were identified and quantified in seven selected varieties of elder. Solid Phase Microextraction method was used for their isolation and subsequent analysis was performed by gas chromatography. 39 aroma active compounds were identified totally in fruits of the black elderberry, of which 15 alcohols, 11 aldehydes, 7 ketones, 5 esters and 1 acid. 45 aroma active compounds were identified totally in elderberry juices, of which 19 alcohols, 8 aldehydes, 5 ketones, 7 esters and 6 acids. The sensory analysis of elder juices was performed using ranking test and evaluation using the scales.
178

Aromatický profil vybraných druhů ovocných šťáv / Aroma profile of selected types of fruit juices

Baštová, Daniela January 2012 (has links)
This diploma thesis is focused on determination the aroma profile of selected species of fruit juices (apple, grape, carrot, orange, blackcurrant and elderberry juice). The theoretical part deals with the composition and properties of selected species of fruits and their juices, then deals with juice‘s technological process and selected methods for the determination of aroma active compounds. The experimental part describes the instrumental and sensory analysis. The six pure fruit juices and five mixed fruit juices were used for instrumental evaluation. The aroma active compounds were extracted by SPME and subsequently identified and quantified by gas chromatography. The sensory evaluation was performed by ranking test and evaluation using hedonic scale.
179

Stanovení aromaticky aktivních látek v plodech rybízu / Assessment of aroma active compounds in currant

Lišková, Michaela January 2014 (has links)
This master thesis deals with the assessment of aroma active compounds in fruits of currant (Ribes spp.). The theoretical part was focused on basic characteristics and chemical composition of currants, as well as the basic principles of techniques used: solid phase micro extraction (SPME), gas chromatography (GC) and sensory analysis. The main aim of the experimental part was to determine aroma active compounds in currants using SPME-GC-FID method. The profile and scale tests were used for assessment of sensory quality and tastiness of fruits. In total 18 varieties, among them 6 white, 6 red and 6 black currants, were evaluated. Fifty aroma active compounds were identified including 21 alcohols, 10 aldehydes, 2 acids, 8 ketones and 9 esters. The results were statistically evaluated using principal component analysis (PCA) to investigate the influence of single compounds on sensory quality of fruits.
180

Stanovení vybraných vonných látek v potravinách a kosmetických výrobcích / Assessment of chosen aroma compounds in foods and cosmetics

Obrdlíková, Blanka January 2014 (has links)
This diploma thesis is focused on the problematic of assessment of allergenic aroma compounds in various matrices. In the frame of European legislation 26 of potentially allergenic compounds are stated, whose content in cosmetic products is limited. In the case of foods there is not such restriction so far. In the experimental part, the allergenic aroma compounds in chosen samples of cosmetic and food samples were identified and quantified using Solid phase microextraction in conjunction with gas chromatography. Sensory evaluation of aroma or taste is also included.

Page generated in 0.1542 seconds