PhD theses

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    Wageningen PhD theses


    This database contains bibliographic descriptions of all Wageningen University PhD theses from 1920 onwards. It is updated on a daily basis by WUR Library.

    Author abstracts and/or summaries are added to all descriptions. A link to the full text dissertation is added to the bibliographic description. In a few cases, no electronic version is available, mostly because of copyright issues.

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Record number 1833874
Title Characterisation of cell wall polysaccharides in bilberries and black currants
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Hauke Hilz
Author(s) Hilz, H.
Publisher [S.l. : s.n.]
Publication year 2007
Description 158 p
Description 1 online resource (158 p)
Notes Met lit. opg. - Met samenvatting in het Engels, Nederlands en Duitsshow all notes
Proefschrift Wageningen
ISBN 9085046246
Tutors Voragen, Prof. Dr. Ir. A.G.J. ; Schols, Dr. H.A.
Graduation date 2007-03-02
Dissertation no. 4147
Author abstract show abstract
Keywords: bilberries; Vaccinium myrtillus ; black currants; Ribes nigrum ; cell wall; polysaccharides; structure; rhamnogalacturonan II; xyloglucan;juice processing; high pressure processing

Cell wall polysaccharides play an important role during berry processing. Due to their polymeric character they can cause thickening after mashing of the berries and cause problems during extraction and clarification of fruit juices. Therefore, commercial enzyme preparations are used to degrade cell wall polysaccharides during processing. However, the berry cell wall composition of berries has never been studied in detail.

Aim of this thesis was to analyse cell wall composition and structure of bilberries and black currants to use the obtained data to monitor cell wall components during current processing and during high pressure processing.

A general characterisation of cell wall polysaccharides showed a higher pectin content with similar structure in black currants compared to bilberries. The major storage polysaccharides in black currant seeds were mannans and xylans in bilberry seeds. Rhamnogalacturonan II was enzymatically released in its dimeric form from all polymeric pectic populations of black currants and bilberries. Analysis of xyloglucans with different analytical techniques showed major differences between bilberries and black currants: while xyloglucan structure in black currants was simple, it was very complex in bilberries due to the presence of a rare side chain in partly novel building blocks.

During conventional processing using pectolytic enzymes, pectic poly­saccharides were degraded to a large extent. Some polymeric pectic elements were extracted into the juice. One third of these polysaccharides were monomeric and dimeric rhamnogalacturonan II, two thirds were modified hairy regions. During high pressure processing pectins become more calcium sensitive and more extractable, which leads to the formation of a strong gel that hinders juice pressing. When high pressure is combined with commercial enzyme preparations, pectins are, however, further degraded than at atmospheric pressure.

The detailed characterisation of cell wall polysaccharides in bilberries and black currants led to the identification of novel structures and showed the complexity of the plant cell wall. Influences of novel processing technologies were now substantiated. A higher viscosity and lower juice yield were assigned to changes in pectin structure and extractability. This opens the possibility to use high pressure together with commercial enzyme mixtures to obtain a synergistic effect.
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Keyword(s) bilberries / black currants / cell wall components / pectins / xyloglucans / characterization / enzymes / pressure treatment / berries
Categories Chemistry of Food Components / Plant Products
Publication type PhD thesis
Language English
About During berry juice production, polysaccharides are released from the cell walls and cause thickening and high viscosity when the berries are mashed. Consequences are a low juice yield and a poor colour. This can be prevented by the use of enzymes that degrade these polysaccharides. To use these enzymes most efficiently, the structure and composition of the cell walls had to be known. This thesis describes a detailed composition of the cell walls of bilberries and black currants. The obtained results were used to monitor changes in the cell walls during different treatments such as enzyme treatment and high pressure processing. A higher viscosity and lower juice yield after high pressure processing were assigned to changes in pectin structure and extractability. Based on this knowledge, a synergistic effect was obtained by combining high pressure processing with treatment with commercial enzyme preparations.
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