After synthesis of fluorine-18 labelled analogues by [18F]fluorobenzoylation at the alpha-amino group, biodistribution and elimination of individual advanced glycation endproducts, namely N epsilon-carboxymethyllysine and N epsilon-carboxyethyllysine, were studied in comparison to lysine in rats after intravenous injection using positron emission tomography (PET). The [18F]radiofluorinated amino acids were fast distributed via the blood, followed by a rapid excretion through the kidneys. Elimination kinetics were similar for both AGEs and lysine. For CML and CEL, but not for lysine, a temporary liver accumulation could be observed, which was not connected with any metabolisation or enterohepatic circulation. No further accumulation in any tissues was observable, indicating that increased tissue levels of CML or CEL, which have been described for certain disorders, are exclusively derived from endogenous origin and should not depend on a dietary intake. However, under uremic conditions, an impaired kidney function might result in a significant increase of the AGE-load of blood and tissues. PET based on 18F-labelled AGEs proved to be a promising tool to elucidate the physiological fate of post-translationally modified amino acids and to clarify the role of AGEs as possible "glycotoxins".

Heat treatment of inulin at 135 to 190°C leads to a decrease in the measurable amount of the fructan, when quantified as fructose after enzymatic hydrolysis. Using high-performance anion-exchange chromatography with pulsed amperometric detection, degradation of the fructan chains and concomitant formation of low-molecular products was observed, most likely representing di-D-fructose dianhydrides. Heat-induced degradation of inulin during thermal processing of foods like bakery products must be taken into account within the discussion about possible prebiotic properties of the fructan.

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After storage of UHT milk at 37 degrees C resp. 50 degrees C, yoghurt was prepared. For a storage temperature of 37 degrees C, breaking strength of the yoghurt samples increased from 2.7 to 5.8 N with increasing storage duration of the UHT milk. A plateau is reached after 17 days of storage. This increase in breaking strength correlates with a significant increase in non-reducible casein oligomerization from 14% for fresh UHT milk to 25% measured using size exclusion chromatography under reducing and denaturing conditions and calculated as sum of predominantly formed dimers and trimers at the total casein fraction. At a storage temperature of 50 degrees C, a less increase in breaking strength from 2.7 to 4.6 N with a plateau after 17 days was observed while casein oligomerization increased to 63%. After acid hydrolysis, only lysinoalanine and histidinoalanine were detected in the caseinate samples via amino acid analysis. The quantified concentration of lysinoalanine and histidinoalanine could not explain the observed casein oligomerization. Thus, unknown crosslinked amino acids must have been formed during storage, inducing significant changes in the functional properties of milk proteins.

No abstract