During the industrial manufacturing of pomegranate juice, large amounts of pomace are produced. The aim of this work was to find the effective method to dry pomegranate pomace to open new commercial applications for this co-product. The effects of three drying methods: (i) convective drying (CD) at 50, 60, and 70 °C; (ii) vacuum microwave drying (VMD) at 240, 360, and 480 W, and (iii) a combined method (CPD–VMFD); convective pre-drying (60 °C) followed by vacuum microwave finish drying (360 W), on drying kinetics and quality of PomP (pomegranate pomace obtained after preparing pomegranate juice by squeezing only arils) were evaluated. The shortest treatments were VMD at 240 and 360 W (52 and 33 min, respectively); besides, these treatments led to interesting values of the green–red coordinate, a*, (12.2 and 4.1, respectively), total phenolic content (4.0 and 4.1 mg eq gallic acid g−1 dry weight, respectively), and antioxidant activity (30.8 and 29.0 µmol g−1 dry weight, respectively). On the other hand, this study demonstrated that this co-product is a rich source of punicic acid (average value = 66.4%), being a good opportunity for the pharmaceutical and nutraceutical industries. Moreover, no significant changes in the fatty acid profile was observed as affected by the drying treatments, and no off-flavors were generated by any of the drying methods.
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The authors are grateful to the project AGL2013-45922-C2-2-R (Ministerio de Economía y Competitividad, MINECO, Spain). Author Marina Cano-Lamadrid was funded by a FPU grant (FPU15/02158) from the Spanish Ministry of Education..
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