Application of pulsed electric fields (PEF) on pecan nuts [Carya illinoinensis (Wangenh. K. Koch)]: Oil extraction yield and compositional characteristics of the oil and its by-product
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Pecan nut oil is conventionally obtained by mechanical extraction characterized by a low oil extraction yield (OEY) compared to solvent extraction. Pulsed electric fields (PEF) have been employed as a pretreatment to enhance OEY from several oilseeds, but no studies have been found regarding tree nut oil. Hence, PEF was applied at different specific energy inputs (0.5-17.6 kJ kg−1) to evaluate its impact on OEY, oil acidity, and antioxidant capacity (AC), along with total phenolics (TP), condensed tannins (CT), and AC of the by-product generated from oil extraction. Kernels treated by PEF were compared against untreated and soaked kernels due to sample water immersion during PEF processing. The water immersion reduced the initial oil content of soaked and PEF-treated kernels (7.3-11.7%), transferring between 3.8 ± 0.0 and 6.2 ± 0.1 g of oil into the soaking water (oSW). OEYTOTAL of soaked and PEF-treated samples was calculated considering oSW. The application of 0.5 kJ kg−1 increased OEYTOTAL by 21.4 and 17.6% compared to untreated and soaked kernels, respectively, while oil acidity and AC of PEF-treated kernels were within values reported for pecan nut oil. The highest concentration of TP and CT in the by-product was achieved at 0.8 kJ kg−1, increasing 9.5 and 30.1%, respectively, compared to untreated kernels. Results evidenced that PEF processing might be a suitable technology to increase OEY from pecan nuts, but the oil extracted during kernels water immersion must be recovered. Furthermore, the by-product of PEF-treated kernels displayed an enhanced content of phenolic compounds increasing its potential as food ingredient.