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Library Catalogue

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    Union Catalogue of Agricultural Libraries in the Netherlands

    The WUR Library Catalogue contains bibliographic data on books and periodicals held by the libraries of Wageningen University and Research Centre and some 15 associated libraries. Holding data are added to each record.

    Subjects covered include Agrotechnology, Food and Food Production, Plant and Animal Sciences, Soil Science, Geo-information, Landscape and Spatial Planning, Water and Climate, Ecosystem Studies, Economics and Society.

    The joint collections of the participating libraries cover a substantial part of the internationally available scientific literature in these disciplines.

    As far as Dutch scientific literature in these fields is concerned, coverage can be considered near 100%, including much of the so-called "grey literature".

    All titles are entered in their original language. Keywords are added to facilitate subject searching.

    The database is updated every day and now contains over 830.000 records.

Record number 104301
Title Electrometrisch onderzoek der thee-fermentatie in verband met de kwaliteit
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door J.E. Tjia (Tjia Bing-Sien)
Author(s) Tjia, J.E.
Publisher Wageningen : Verweij
Publication year 1948
Description 130 p
Notes Proefschrift Wageningen
Tutors Tendeloo, Prof. Dr. H.J.C. ; Wassink, Prof. Dr. E.C.
Graduation date 1948-03-03
Dissertation no. 143
Author abstract show abstract
Fermentation of tea-leaf was compared with different leaf ages, grades of leaf withering, temperatures and aerations. Fermentation was known to be very important for the final quality of tea. Careful estimation of redox potential proved suitable for study of fermentation in a single leaf. Potentiometric titration under aerated water (so not as normally in factories) showed that 'Buds' ('Pecco': best quality leaves) contained more ascorbid acid (AA) and fermented more rapidly than older leaves. More withered leaves fermented more actively and completely. Optimum temperature for fermentation was found to be about 26°C. Aeration to a certain point encouraged fermentation strongly. Thorough grinding promoted fermentation most. AA had to be oxidized to allow reddish brown discoloration of fermenting tea-leaves. 'Buds' oxidized AA much quicker than older leaves.

It was assumed that 'potential quality' of a fresh leaf was correlated with active fermentation. So in practice leaves had to be rolled often but briefly, while the rolling and fermenting rooms should be thoroughly aerated, although the leaves should not be allowed to dry. Ascorbic dehydrogenase, polyphenol oxidase and peroxidase were involved in the oxidation of AA. Traces of CU2 +(occurring in the prosthetic groups of ascorbic dehydrogenase and polyphenol oxidase) accelerated oxidation of AA in leaf extracts. Fe3 +less so. By rectilinear adjustment fermentation activity could be calculated. It was higher for 'Buds' than for older leaves.


Online full textINTERNET
On paper FORUM ; STACKS ; 290A13
FORUM ; STACKS ; NN08202,143
Keyword(s) (cab) camellia sinensis / tea / fermentation / quality
Categories Stimulant Crops
Publication type PhD thesis
Language Dutch; Flemish
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