Comparison of the most odour-active volatiles in different hop varieties by application of a comparative aroma extract dilution analysis

Application of a comparative aroma extract dilution analysis on the volatiles isolated from five different hops (Hallertau Perle, Hallertau Hersbrucker Spät, Slowenian Golding, Hallertau Smaragd, US Cascade) revealed linalool and myrcene with the highest Flavour Dilution (FD)-factors in all varieties, followed by 2-isopropyl-3-methoxypyrazine, 3-methylbutanoic acid and geraniol. Some odourants, however, showed high FD-factors only in certain varieties, for example, (5Z)-octa-1,5-dien-3-one and germacrene B in Hersbrucker Spät, (3E,5Z)-undeca-1,3,5-triene in Hersbrucker Spät and Cascade and nonanal in Cascade. The overall odour profile of the Cascade sample clearly differed from the other varietes, and was dominated by a black currant like odour note. The identification experiments revealed 4-methyl-4-sulfanylpentan-2-one, so far unknown as hop constituent, as key contributor to this odour. In addition, an odour-active undecatetraene was present, in particular, in Perle and Cascade. Synthesis and structural assignment of the four stereoisomers of (3E)-undeca-1,3,5,9-tetraene allowed the identification of the fresh, pineapple-like smelling compound as (3E,5Z,9E)-undeca-1,3,5,9-tetraene. Among the four isomers synthesised, this compound showed by far the lowest odour threshold of 0.01 ng/L in air.     

Thoracic and lumbar myelography with metrizamid (author's transl)

With the new x-ray medium Metrizamid it is possible to perform almost complication-free lumbar and thoracic myelography. In an experience the type of complications arising were reduced to moderate headaches, mild nausea occasional dissiness. No convulsions were seen. The number of complications are less than with other watersoluble contrast medium.     

Changes in odour-active compounds of two varieties of Colombian guava (Psidium guajava L.) during ripening

Changes in the concentrations of odour-active compounds in two varieties of Colombian guava (Psidium guajava L.) fruits during ripening were followed by application of stable isotopic dilution analyses (SIDA). The data revealed that, in particular, the concentration of C₆-aldehydes, as well as the amount of the sulphur compounds 3-sulphanylhexyl acetate and 3-sulphanyl-1-hexanol, decreased with ripening, while the concentrations of aliphatic esters and furanones increased during this process. A calculation of odour activity values indicated that although the C₆-aldehydes decreased during ripening, these still made the greatest contribution to the overall aroma at all stages of ripening. Changes in odour-active compounds in white- and pink-fleshed guavas showed the same behaviour.