HS-GC-MS Volatile compounds recovered in freshly pressed and commercial Wonderful pomegranate juices

Authors: Beaulieu, John; Stein, Rebecca

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2015
Publication Date: 6/3/2015
Citation: Beaulieu, J.C., Stein, R.E. 2015. HS-GC-MS Volatile compounds recovered in freshly pressed and commercial Wonderful pomegranate juices. Food Chemistry. 190:643-656.

Interpretive Summary: Consumer awareness concerning the possible health benefits of consuming phytonutrient-rich fruits (generally highly colored), and keen marketing have created the demand for and availability of juices and functional beverages prepared from them. The juice and beverage industry has rapidly advanced several pomegranate containing products, driven by this consumer awareness that “superfruits” apparently confer to the diet. However, highly colored fruits and berries often have several constituents that make them bitter or astringent, even though their sugar contents might be very high; therefore, the long-term full potential of these fruits and their expanding markets may not be sustained if flavor changes and/or possible off-flavors associated with bitterness and astringency are not studied, understood, and ultimately resolved. There is insufficient information published regarding flavor and aroma compounds in processed 'Wonderful' pomegranate (Punica granatum) juices. Many investigative methods employed have involved blending (oxidation) during juice extraction prior to compound isolation. This can change the native flavor/aroma profile of the juice and create undesirable aroma/flavor changes. Although the seed-containing juice sacks (arils) have fruity and sweet characteristics, there are few publications describing actual volatile compounds responsible for their typical flavor. Since most commercial use of domestic U.S. pomegranates involves juices pressed from whole fruit, the volatile profiles in the most common U.S. cultivar, ‘Wonderful’ was investigated. During method development we took the liberty to assess different extraction techniques, and refine the possible volatile database by reviewing hundreds of analyses from fresh 'Wonderful', commercial samples and concentrates. That data is presented in the offered manuscript. Solid phase microextraction (SPME), polydimethylsiloxane stir bar sorptive extraction, and Tenax adsorption were performed with freshly pressed 'Wonderful' juices, commercial juices and concentrates. Using SPME, 36 compounds were isolated in whole pressed 'Wonderful' juices, including 18 of the 21 consensus compounds found in the literature. In arils-only juices, 41 compounds were isolated by SPME, including 17 of the consensus volatiles. Dramatic variation existed in volatiles recovered in commercial juices, and isolation of consensus compounds was sporadic. Data presented corroborates closely the key recent pomegranate volatile publications, indicating roughly 20 compounds of potential flavor/aroma and sensory interest. The data also established that there are marked differences between “endogenous” volatiles extracted in the laboratory versus a large suite of compounds recovered in various commercial products. Subsequently, this article and summary of the literature serves to deliver a volatile data base using a rapid method for fresh and partially processed (pressed) ‘Wonderful’ pomegranates, in advance of future reports illustrating the flavor/sensory effects encountered through industrial-like and commercial juice manufacturing processes.

Technical Abstract: Consumption and production of superfruits has been increasing. Highly colored fruits often have bitter and astringent components that may make them undesirable, especially when processed. Many pomegranate volatile reports involved commercial samples, complicated isolation methods, or blending and concentrating that were from arils only, cultivars other than Wonderful, or mixed cultivars. Solid phase microextraction (SPME), polydimethylsiloxane stir bar sorptive extraction, and Tenax adsorption were performed with freshly pressed Wonderful juices, commercial juices and concentrates. Using SPME, 36 compounds were isolated in whole pressed Wonderful juices, including 18 of the 21 consensus compounds. In arils-only juices, 41 compounds were isolated by SPME, including 17 of the consensus volatiles. Dramatic variation existed in volatiles recovered in commercial juices and isolation of consensus compounds was sporadic. This article and summary of the literature serves to possibly deliver an improved volatile data set via a rapid method for fresh and partially processed (pressed) Wonderful pomegranates.