Changes in antioxidative properties of hops in the course of drying, milling, pelletization and storage
2007
Krofta, K.,Chmelarsky Inst., Zatec (Czech Republic) | Mikyska, A.,Vyzkumny Ustav Pivovarsky a Sladarsky, Prague (Czech Republic) | Haskova, D.,Vyzkumny Ustav Pivovarsky a Sladarsky, Prague (Czech Republic)
The aim of this research was to compare antioxidant properties of fresh and dried hop cones, processed or not, and to evaluate the influence of cold and boiled water on the release of antioxidants from fresh cones. Different drying methods, milling and pelletization, aging and long-term storage were studied. The drying caused some loss of antioxidative activity which generally did not exceed 5% of the original radical 1,1-diphenyl-2-picryl-hydrazyl value. It also led to the decrease in polyphenol concentrations. The drying method (chamber or belt dryers) did not influence the antioxidative characteristics. The antioxidative activity in hot water extracts was similar when using either whole or ground hop cones. Pelletizing of ground cones did not significantly change their antioxidative activity either. The antioxidative activity declined during a long-term storage. The decrease depended on the temperature and form of the stocked hop cones. The storage had no detectable effect when the hop was stored in pellets packed in multilayer foils without air access.
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