Valorization of black chokeberries (Aronia melanocarpa) pomace and chemical characterization by comprehensive two‐dimensional liquid chromatography coupled to mass spectrometry

Resumen del trabajo presentado al XVI Scientific Meeting of the Spanish Society of Chromatography and Related Techniques, celebrado en Sevilla (España) del 2 al 4 de noviembre de 2016.This work shows a new alternative for the downstream processing and valorization of black chokeberry pomace (Aronia melanocarpa) which could be potentially coupled to a biorefinery process. Biorefinery relies on the development of integrated production processes in which all kinds of materials and by‐products are converted in valuable endproducts, including energy, biofuels and chemicals. This new procedure is based on the application of pressurized liquid extraction (PLE) to the residue obtained after the supercritical fluid extraction (SFE) of the berry pomace. The main aim is to produce a valorization of this important food‐related by‐product. An experimental design is employed to study and optimize the most relevant extraction conditions in order to attain extracts with high extraction yields, total phenols content and antioxidant activity. Moreover, the obtained PLE extracts were characterized by using a new method based on the application of two‐dimensional comprehensive liquid chromatography coupled to mass spectrometry (LC×LC‐MS/MS) in order to correlate their activity with their chemical composition. A microbore amino column was used in the first dimension eluted at 18 μL min‐1 coupled to a short partially‐porous C18 column in the second dimension, using a flow rate of 3 mL min‐1. This approach provided with a good degree of orthogonality (as could be inferred from the peaks distribution obtained along the 2D plane, and high theoretical peak capacity, equal to 1693. Thanks to the use of this powerful analytical tool, 61 compounds could be separated being possible the tentative identification of different anthocyanins, proanthocyanins, flavonoids and phenolic acids. By using the optimized PLE approach (using pressurized 46% ethanol in water at 165 ºC containing 1.8% formic acid), extracts with high total phenols content (236.6 mg GAE g‐1 extract) and high antioxidant activities (4.35 mmol TE g‐1 extract and EC50 5.92 μg ml‐1) could be obtained with high yields (72.5%). Using those analytical conditions in combination with DAD and MS detectors, a good separation of the complex PLE extracts could be obtained.Peer reviewe