Subcritical extraction of phenolic compounds from pecan nut shells to add value

RODRIGUEZ CAROLINA; MIGUEL ESTEBAN CARDONA JIMENEZ; VELEZ ALEXIS; LINA MARCELA AGUDELO LAVERDE; PATRICIO SANTAGAPITA; BODOIRA ROMINA

Los cocos, Córdoba

Conferencia; VI Iberoamerian Conference of Supercritical fluids; 2023

UNC/Univ.federal santa Catarina/Univ. de Coimbra/Univ. de Castilla la mancha/Univ. Nacional del sur

Changes in food trends such as the enhancement of consumer’s awareness regarding thenutritional properties of food products, have caused an increase in the consumption of nuts,particularly pecan nuts. According to data from the Pecan Cluster in Argentina, pecan nutproduction [Carya illinoinensis (Wangenh) K.Koch], is estimated to be over 2000 tons peryear. The shell, which is produced during walnuts shelling, is equivalent to 40-50% of thewaste generated by this productive system, and it is only used for energy generation.Many authors have reported the presence of bioactive components in pecan nutshells, including phenolic compounds with antioxidant, antiradical, or chelating capacity. This has generated a growing interest in studying this by-product and determining the best extraction method for recovering these compounds. Among the so-called green techniques, subcritical extraction stands out utilizing water or ethanol + water mixtures at temperatures between 100 and 374 °C, and pressures above atmospheric to maintain the solvent in a liquid state. It is a safe and fast technique that achieves high extraction yields of medium and high polarity compounds from a solid matrix.Considering these aspects, the use of water + ethanol mixtures at subcritical conditions for the extraction of phenolic compounds from pecan nutshells was evaluated in the present work. The pecan nutshell obtained as result of the peeling process was donated by Producor S.A (San Jerónimo, Santa Fe, Argentina). They were washed, disinfected, dried, milled and sifted before extraction. The pecan nutshell powder (PNSP) was subjected to different extraction conditions.The studied variables were temperature (T: 100, 140, 180, and 220°C), ethanol composition in the solvent mixture (S: 0, 25, 50, 75, and 100 %w/w), and solvent mass flow rate (F: 2.5, 5.0, and 7.5 g/min). The total phenolic content (TPC) expressed as mg gallic acid equivalents (GAE)/ g dry PNSP, and antioxidant activity by FRAP and ABTS methods expressed as mmol Trolox equivalents (Tx eq)/ g dry PNSP of each extract were measured.The TPC of the extracts varied between 165.93 and 454.61 mg GAE/g dry PNSP, and theantioxidant activity with a range between 2.41 to 7.63 mmol Tx eq/g dry PNSP, and 1.92 to5.50 mmol Tx eq/g dry PNSP for FRAP an ABTS, respectively. It was observed that increasing the extraction temperature enhances the recovery of phenolic compounds, while the opposite effect is observed with an increase in the ethanol content in the solvent mixture, which leads to a reduction in TPC values and antioxidant activities. Thus, regarding the bioactive content, the best extraction conditions were T 200°C, F 2.5 g/min, and S 50% w/w of ethanol.The results showed that the selected variables were influential in the extraction of bioactivecompounds. The ethanol + water subcritical extraction is an alternative for recovering phenolic compounds and adding value to pecan nutshell