Brachmann, Sonja: Analysis of the Storage Stability of Grape and Apple Juices in Terms of Antioxidative Capacity and Their Polyphenols, Hydroxymethylfurfural and Ascorbic Acid Content. - Bonn, 2008. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5N-16027
@phdthesis{handle:20.500.11811/3706,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5N-16027,
author = {{Sonja Brachmann}},
title = {Analysis of the Storage Stability of Grape and Apple Juices in Terms of Antioxidative Capacity and Their Polyphenols, Hydroxymethylfurfural and Ascorbic Acid Content},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2008,
note = {The aim of this work is to determine the storage stability of commercial grape and apple juices. Two storage studies are performed to provide extensive knowledge about the changes of the selected juices under different storage conditions. The analysis of fruit juice stability is of certain interest not only for the juice production but also for the development of new materials and composites for food packaging.
Deterioration of each juice is observed during one year of storage (i.e. usual period of shelf-life). Sensory quality as well as antioxidative capacity and concentrations of single juice compounds (especially antioxidants like polyphenols or ascorbic acid) are determined to clarify whether the antioxidative status of a juice can provide useful information concerning its storage stability.
In addition to the optimisation of the HPLC analysis of several juice compounds a new test is developed to determine the antioxidative capacity of a juice via electrochemical reactions of antioxidants. The voltammographic analysis of the reducing potential (VARP) assay uses the coulometric electrode array detector (CEAD) without prior HPLC separation.
The resulting voltammogram shows the ability of the sample to reduce other molecules and thus, provides an indication of the antioxidative capacity of the sample. It is shown that this fast, simple and sensitive method enables the detection of minor changes of the antioxidative status of the stored juice.
In conclusion, the storage studies demonstrate which parameters are mainly influenced by storage time, temperature and oxygen permeation of the packaging. They also point out how to ensure adequate storage stability.
Furthermore, for fruit juices with considerable amounts of antioxidants strong correlations are revealed between VARP data and sensory evaluations under different storage conditions. These findings indicate that antioxidative capacity might be associated with sensory color and taste evaluation.
In contrast, a juice with low amounts of antioxidants is less affected by storage temperature and an oxygen permeable packaging. The results indicate that such a juice might obtain an adequate storage stability when filled in packaging with considerable oxygen permeability. The use of this packaging could reduce the production costs since the aluminium foil accounts for a considerable share.},

url = {https://hdl.handle.net/20.500.11811/3706}
}

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