Freeze dried pomegranate juices of Moroccan fruits: main representative phenolic compounds

BACKGROUND The pomegranate (Punica granatum) is an ancient perennial plant species of the Punicaceae family. Its seeds are consumed as food or as juice. Previous studies have noted that pomegranate juice encompasses many active compounds with beneficial effects. The main goals of this work were to study the phenolic components of freeze-dried and reconstituted pomegranate juices obtained from 13 pomegranate genotypes growing in Morocco. RESULTS We analyzed several pomegranate juices using high-performance liquid chromatography and high-resolution mass spectrometry to determine phenolic compounds. Twenty-seven bio-phenols, belonging to four different classes (phenolic acids, hydrolyzable tannins, anthocyanins, and flavonoids), were identified based on their accurate mass measurements, and quantified. Some encouraging results were obtained. Even though the freeze-drying process introduced a marked degradation of bio-phenols, substantially lowering their levels in the reconstituted fruit juices, these fruit juices were still rich enough in bio-phenols to compete with some fresh fruit juices. The reconstituted juices obtained by rehydration of the lyophilized material still differed enough to enable a statistical classification based on their polyphenol content. A correlation analysis was applied to the polyphenol data to explore correlations and similarities between genotypes. CONCLUSIONS The results showed that freeze-drying and reconstitution of juices introduced some degradation of the polyphenol content. The overall polyphenolic pattern within the same cultivar, in two different harvesting years, was maintained, however, suggesting the composition stability of the freeze-dried juices produced in this time span