Metabolic Profiles and Juice Quality Parameters of 14 USDA-ARS Pomegranate (Punica granatum L.) Cultivars As Determined By 1H NMR, Spectrophotometry, Ion Chromatography, and Refractometry

Pomegranate (Punica granatum L.) juice is a highly valued beverage worldwide that has been demonstrated and marketed to have relatively large quantities of polyphenolic compounds with powerful antioxidant properties.  The USDA-ARS National Clonal Germplasm Repository, Davis, CA pomegranate collection conserves approximately 300 cultivars, many of which have yet to be evaluated for the food and beverage industries.  The purpose of this work was to evaluate high, medium and low acid pomegranates using analytical chemistry methods to look for candidates that meet the metabolic and juice quality profiles of ‘Wonderful’ pomegranate juice.  In this investigation, pomegranate juices from 14 different cultivars were analyzed using Nuclear Magnetic Resonance (NMR), spectrophotometry, ion chromatography and refractometry. The cultivars evaluated in this work included ‘Al Sirin Nar,’ ‘Ambrosia,’ ‘Blaze,’ ‘Desertnyi,’ ‘Eversweet,’ ‘Golden Globe,’ ‘Green Globe,’ ‘Haku Botan,’ ‘Loffani,’ ‘Parfianka,’ ‘Phoenicia,’ ‘Purple Heart,’ ‘Sakerdze,’ and ‘Wonderful.’ This work represents the genotypic diversity of approximately five percent of the USA pomegranate germplasm and provides deep, previously unseen values regarding the nutritional and postharvest qualities of pomegranate juice from a diversity of cultivars.  Metabolic and juice quality profiles were determined by analyzing for important juice quality parameters and metabolites, including concentrations of ethanol, glucose, fructose, citrate, malate, glutamate, glutamine, potassium, pH, total phenolics, antioxidant activity, titratable acidity and harvest index.  There were significant differences among cultivars for most of the parameters.  ‘Al Sirin Nar,’ ‘Ambrosia,’ ‘Blaze,’ ‘Desertnyi,’ ‘Eversweet,’ ‘Purple Heart,’ ‘Sakerdze,’ and ‘Wonderful’ had significantly higher glucose mean concentration than 'Haku Botan,' with 404.5, 409.4, 422.6, 385.8, 394.0, 379.8, 389.5, 417.1 and 301.6 mM, respectively.  'Eversweet' was the only cultivar which had a higher mean concentration of malate than citrate.  Several candidate cultivars meeting ‘Wonderful’ postharvest juice quality specifications were identified.