National Repository of Grey Literature 3 records found  Search took 0.00 seconds. 
Isotopic characterization of selected fruit juices - determination of authenticity on the basis of deuterium content by SNIF-NMR
Vyčítalová, Lucie ; Kolář, Kamil (referee) ; Sečkářová,, Pavlína (advisor)
The deuterium content of sugar in fruits is influenced mainly by two factors – the botanical and also the geographical origin of the fruit. The information of the fruit origin is kept even after fermentation of the sugar, in the molecules of ethanol. The deuterium content on the methyl group of ethanol then varies depending upon the botanical origin of the fruit. SNIF-NMR (Site-specific Natural Isotope Fractionation – Nuclear Magnetic Resonance) is a specific method for determination of the deuterium isotopic ratio (D/H) in small molecules, e.g. ethanol. This isotopic technique is widely used for determination of sugar adulteration of fruit-based beverages (wines, fruit juices..). In this thesis, the authentic samples of five different fruits (apples, oranges, grapefruits, pineapples and grapes) available in the Czech market have been collected and analyzed by SNIF-NMR. The results are presented as well as the comparison to some commercially available fruit juices and nectars.
Analýza džusov metódou „UV-odtlačkov prstov”
Saganová, Sabrina
Nowadays, people's interest in healthy food is increasing. These are mainly food ingredients as much as possible in their natural form. Such foods also include fruit juices, which, in addition to quenching thirst, also contain substances beneficial to health - vitamins, minerals, carbohydrates, proteins and others. By taking fruit juice, we support the immune system, intestinal peristalsis, strengthen bones, and even consumption of fruit can serve as a means of preventing cancer. However, with the increase in the consumption of fruit juices (especially orange and apple), the risk of adulteration of these drinks also increases. It is precisely in this context that it is ne-cessary to constantly look for new and fast methods with which to guarantee the quali-ty and safety of food. In the first part of this thesis, I focused on the composition of fruit juices, their health benefits for the human body, production, methods of counter-feiting. The second part of this work consists of a study in which the new method of "UV-fingerprints" was used as a quick tool for verifying the quality of fruit juices. The method is based on the spectral properties of the sample before and after irradiation with high-energy ultraviolet radiation (λ = 254 nm). During the irradiation, photoche-mical changes will occur, which serve to identify the sample. I optimized the method by placing the samples in different temperature environments (laboratory temperature, refrigerator, freezer). Subsequently, using boxplots - statistical evaluation, I tried to find differences both within individual types of fruit, but also between individual brands of one type of fruit.
Isotopic characterization of selected fruit juices - determination of authenticity on the basis of deuterium content by SNIF-NMR
Vyčítalová, Lucie ; Kolář, Kamil (referee) ; Sečkářová,, Pavlína (advisor)
The deuterium content of sugar in fruits is influenced mainly by two factors – the botanical and also the geographical origin of the fruit. The information of the fruit origin is kept even after fermentation of the sugar, in the molecules of ethanol. The deuterium content on the methyl group of ethanol then varies depending upon the botanical origin of the fruit. SNIF-NMR (Site-specific Natural Isotope Fractionation – Nuclear Magnetic Resonance) is a specific method for determination of the deuterium isotopic ratio (D/H) in small molecules, e.g. ethanol. This isotopic technique is widely used for determination of sugar adulteration of fruit-based beverages (wines, fruit juices..). In this thesis, the authentic samples of five different fruits (apples, oranges, grapefruits, pineapples and grapes) available in the Czech market have been collected and analyzed by SNIF-NMR. The results are presented as well as the comparison to some commercially available fruit juices and nectars.

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