Die Differential Scanning Calorimetry (DSC) wurde angewendet zur Charakterisierung der Vorgange bei der Verkleisterung von Starken und der Reorganisation von Starkepolymeren (Retrogradation). Besonderer Wert wurde dabei auf die Optimierung des Menverfahrens gelegt. Aufgrund einer spez. Detektoranordnung des verwendeten Kalorimeters wird eine hohe kalorische Empfindlichkeit, bezogen auf das Probenvolumen, erzielt. Dadurch konnten neben den bekannten endothermen Umwandlungsenthalpien bei der Verkleisterung einiger Starken weitere Peaks aufgelost werden, die der Desintegration des Amylose-Lipid-Komplexes zugeschrieben werden. In Mischungen aus Amylose und Amylopektin werden unter bestimmten Umstanden deren Retrogradationsprodukte als diskrete Peaks beobachtet , die sich in ihrer Umwandlungstemperatur deutlich unterscheiden. Zum Schluf3 wird auf die Verkleisterung bei limitierten Wassergehalten eingegangen. Die Untersuchungen bestatigen kiirzlich veroffentlichte Ergebnisse. Die Differential Scanning Calorimetry ist damit zu einer nutzlichen analytischen Methode gereift, mit der Fragen der Starkechemie beantwortet werden konnen.DSC Investigations of Starches. Part 1. Feasibility of Thermoanalytical Methods to Characterize Starches. In this paper results on the application of Differential Scanning Calorimetry upon the gelatinization and reorganization of starch polymers (retrogradation) are discussed. Considerable emphasis was layed on optimization of the analytical method. A high caloric sensitivity related to the sample volume was accomplished based on a specific detector system of the used calorimeter. Due to these optimized conditionsbesides known endothermal enthalpy changes during gelatinizationfor some starches additional peaks could be detected that are attributed to the desintegration of the amylose-lipid-complex. Usingmixtures of amylose and amylopectin, discrete peaks from their retrogradation products are observed under certain circumstances. These differ clearly by transition temperature. Finally, gelatinization effects are discussed using limited water supply. Recently published results could be confirmed. Differential Scanning Calorimetry has been fully developed to an useful analytical method to answer questions within starch chemistry.
Branehed-chain Sugars, XI')
Epoxide Rearrangements with Branched-chaii SugarsIn 2.3-epoxy-1-propanols (1 -8) factors controlling the state of equilibrium are determined and applied to the equilibria of epoxide rearrangements in branched-chain sugars. The four epoxy ketoses 10,17, 24, and 31 react with methyllithium to yield the four branched-chain epoxy sugars 14,21,28, and 35 which can be rearranged. Equilibration studies show that the species in which the branching point is part of the epoxide ring is stabilized. In comparison to unbranched sugars this substituent effect is demonstrated. It can be applied to direct epoxide rearrangements. With respect to all conformations of epoxy sugars this substituent effect can be estimated to be approximately 1.5 kcal/mol.
Epoxidumlagerung an offenkettigen Modellsubstanzen
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