Troebel appelsap veel
gezonder.*
Uit
een Pools onderzoek blijkt dat troebel appelsap wel 4x meer gezonde bioactieve
stoffen, polyfenolen bevat dan helder sap. Polyfenolen worden ook gevonden in
o.a. donkere chocolade, druiven en rode wijn en hebben volgens allerlei
wetenschappelijke onderzoeken duidelijke anti-kanker eigenschappen. Meestal
wordt helder appelsap verkocht omdat de houdbaarheid veel langer is. Blijkbaar
wordt door het helder maken van appelsap de meeste gezonde stoffen verwijderd.
Overigens vinden de onderzoekers dat men het beste de appel zelf, met schil en
al, kan eten om de meeste gezonde stoffen binnen
te krijgen.
Comparative
study of polyphenolic content and antiradical activity of cloudy and clear apple
juices Jan Oszmianski
1 *, Michal
Wolniak
2, Aneta
Wojdylo
1, Iwona Wawer
2
1Department of Fruit and Vegetable Processing, Agricultural University of
Wroclaw, 25 Norwida Street, PL-50-375 Wroclaw, Poland
2Department
of Physical Chemistry, Faculty of Pharmacy, Medical University of Warsaw, 1
Banacha Street, PL-02-097 Warsaw, Poland
*Correspondence to Jan Oszmianski, Department of Fruit and Vegetable
Processing, Agricultural University of Wroclaw, 25 Norwida Street, PL-50-375
Wroclaw, Poland
Funded
by: State Committee for Scientific Research of Poland (KBN); Grant
Number: PBZ-KBN-94/P06/2003/24
Abstract
Clear and cloudy apple juices from Idared and Champion varieties were studied for their radical-scavenging effects. The polyphenolic content and composition of the juices before and after thiolysis were determined by high-performance liquid chromatography with diode array detection. Cloudy juices, especially that prepared from Champion variety, had a higher content of procyanidins than clear juices. Radical-scavenging activity was measured by electron paramagnetic resonance (EPR) spectroscopy using the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. All juices showed long-lasting radical-scavenging activity, and EPR spectra were recorded over time to follow the reaction kinetics. Scavenging of DPPH showed pseudo-first-order kinetics, which might be expected in the presence of polymerised antioxidants that prevent closer contact between the DPPH radical and hydroxyl groups. The content of polymeric procyanidins showed a linear dependence on the rate constant, suggesting that these compounds are mainly responsible for time-extended radical-scavenging activity. The antioxidant properties of apple juices were much better reproduced by EPR spectroscopy than by UV-visible measurements. The former method is especially sensitive to the concentration of polymerised or bound procyanidins, whilst the latter method requires transparent (clear) samples. Apple juices, especially cloudy ones, are a rich source of natural antioxidants that may be used in the pharmaceutical or food industry. The research is published in the SCI's Journal of the Science of Food and Agriculture (DOI: 10.1002/jsfa.2707). (Jan. 2007)