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Melting Properties (melting + property)

Distribution by Scientific Domains
Chemistry83%

Selected Abstracts

Screening the Structural Space of Bicyclo-DNA: Synthesis and Thermal Melting Properties of bc4,3 -DNA

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2009
Andrea Stauffiger
Abstract In attempts to screen the structural and functional properties of bicyclo-DNA, in which the ribose C(3,) and C(5,) centers are integrated into an additional five-membered carbocyclic ring ([3.3.0]-series) we have now synthesized and investigated a ring enlarged analogue in which C(5,) and C(3,) are spanned by a six-membered carbocyclic ring ([4.3.0]-series). The synthesis of the corresponding bc4,3 -T nucleoside 13 was performed in 12 steps by starting from known allyl furanose 1. X-ray analysis of its benzyl protected precursor 12 showed the cyclohexane ring to adopt a chair conformation with the O(5,) substituent in an axial position. The furanose part shows clearly S-type sugar pucker. This nucleoside was converted into the corresponding phosphoramidite building block 15 and incorporated into oligodeoxynucleotides by standard phosphoramidite chemistry. The thermal stabilities of oligonucleotides with single or double incorporations of bc4,3 -T residues, paired to complementary DNA or RNA, were found to be similar to those of unmodified oligonucleotides (,2.3 to +0.7 °C per modification) and to those with the known bc-T modifications. We also found that mismatch discrimination in the bc4,3 -T series was similar to that of the natural series but less discriminative in comparison to the known bc-T series.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Effects of hydrogenation parameters on trans isomer formation, selectivity and melting properties of fat

EUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 3 2008
Anar Musavi
Abstract Effects of hydrogenation conditions (temperature, hydrogen pressure, stirring rate) on trans fatty acid formation, selectivity and melting behavior of fat were investigated. To this aim, soybean oil was hydrogenated under various conditions and fatty acid composition, trans isomer formation, slip melting point (SMP), solid fat content (SFC) and iodine number (IV) of the samples withdrawn at certain intervals of the reactions were monitored. A constant ratio (0.03%) of Nysosel 222 was used in the various combinations of temperature (150, 165 and 180,°C), stirring speed (500, 750 and 1000,rpm) and hydrogen pressure (1, 2 and 3,bar). Raising the temperature increased the formation of fatty acid isomers, whereas higher stirring rates decreased this formation, while changes in hydrogen pressure had no effect or slightly reduced it, depending on other parameters. Results also indicated that the trans fatty acid ratio increased with IV reduction, reached the highest value when the IV was about 70 and decreased at IV < 70 due to saturation. Selectivity values (S21) at that point ranged between 5.78 and 11.59. Lower temperatures and higher stirring rates decreased not only the trans isomer content but also the S21 values at significant levels. However, same effects were not observed with the changes in hydrogen pressure. It was determined that a high SMP does not necessarily mean a high SFC. Selective conditions produced samples with higher SFC but lower SMP, which is possibly because of higher trans isomer formation as well as lower saturation. [source]

Influence of residual milk-clotting enzyme and proteolysis on melting properties of soft cheese

INTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 3 2007
M C CANDIOTI
In this work, we assessed the influence of coagulant residual activity and primary proteolysis on Cremoso Argentino cheese melting properties. For that purpose, we made Cremoso soft cheeses using different amounts of coagulant, and also obtained samples in which milk-clotting enzyme was inactivated. Primary proteolysis correlated with residual activity of coagulant in early stages of cheese ripening; however, it was similar in all cheeses after 30 days. The hydrolysis of caseins did not significantly affect the melting ability of the cheeses, expressed as the area increase after heating samples under standardized conditions. Samples with similar proximate composition showed some changes in meltability; those seemed related to pH evolution during ripening. [source]

Rheological, textural and melting properties of commercial samples of some of the different types of pasteurized processed cheese

INTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2007
YANJIE LU
The detailed rheological and textural properties of commercially available samples of the three major categories of pasteurized processed cheese in the USA, that is, pasteurized process American cheese (PPA), pasteurized process cheese product (PPP) and pasteurized process cheese food (PPF), were analysed. All samples had similar pH values, ranging from 5.65 to 5.87, but most were ,5.7. Even within each of the categories considerable differences were observed in textural and melting behaviour. The samples with the lowest melt and the lowest loss tangent parameter from the rheological tests were two PPF and one PPA samples. These two PPF samples also had the highest hardness and adhesiveness force. Significant correlations were observed between several textural, rheological and melting properties. [source]