**4. Discussion**

Dry pecan nuts used as reference kernels displayed moisture and oil content within ranges reported in other studies [10]. Regarding kernels- immersion in water, moisture reductions observed in kernels pretreated at 7.8 and 15.0 kJ/kg could be associated with the release of intracellular water as a result of electroporation of the cell membrane during PEF processing [33,34]. Oil content reductions along with oSW values were comparable to those reported for fresh kernels pretreated by PEF [18], being related to the exposure of kernels cotyledon tissue to the soaking water provoking oleosomes release. An increment of oleosomes extraction was expected for dry kernels compared to the fresh ones as a result of the drying effect on kernels- microstructure [11]. However, given that the oSW was comparable among pecan nuts, it is proposed that kernels rehydration and water-soluble compounds release were favored over oleosomes extraction.

Concerning oil extraction from dry pecan nuts, the OEY of reference kernels (88.7%) was higher than those reported for pecan nut oil extracted by hydraulic pressing (56.4–58.9%) [9,35,36] and higher than the OEY of fresh pecan nut kernels used as a reference in the previous study (63.8%) [18]. Dry kernels differed from fresh kernels in moisture and oil content but also in kernels microstructure displaying more structural damage compared to fresh pecan nuts [37–39]. Savoire et al. evaluated oil extraction processes comparing seeds from the same type that only differed in moisture and oil content. The authors reported an overall improvement of OEY in seeds with lower moisture and higher oil content [40]. They also stated that varietal differences that influence seed characteristics (moisture and oil content, hull and testa thinness, and pore number and size) could affect oil extraction by modifying seed pressing behavior, oil flow and kernels permeability.

The PEF pretreatments did not increase oil extraction from dry pecan nut kernels, contrasting with previous findings where the application of 0.8 kJ/kg increased OEYTOTAL of fresh kernels up to 74.8% being higher than OEY of kernels without soaking nor PEF pretreatment [18]. Sarkis et al. reported similar results where drying and grinding of sesame seeds yielded higher values than the seeds pretreated by PEF [4]. Nikiforidis stated that soaking of seeds causes cell swelling, changing oleosomes shape and diffusion kinetics [12]. Consequently, the soaking of dry pecan nuts might hinder oil extraction by the initial reduction of oil content caused by oleosomes release and the reorganization of the remaining oleosomes within the cotyledon tissue trapping them within kernels microstructure.

The analysis of oil stability showed that oils extracted from dry pecan nuts were within the acidity range accepted by the Food and Agriculture Organization for coldpressed oils [41]. Furthermore, the AC of extracted oils was slightly lower than those achieved in the study employing fresh kernels but higher than those reported for pecan nut oil obtained by solvent extraction [18,28]. Regarding OSI values, Oro et al. reported a similar OSI value for pecan nut oil also extracted by mechanical pressing [42]. Phytosterols concentration of oil extracted from reference kernels was lower in comparison with other studies where pecan nut oil was characterized [8,43,44]. Differences in acidity, AC, OSI and phytosterols concentration might be related to varietal differences between pecan nuts as well as tocopherols concentration since these compounds have been associated to the antioxidant capacity of pecan nut oil [40,44]. Concerning the LOX activity of reference kernels, this value was similar to those reported for different cultivars of walnuts [45]. In tree nuts, LOX inactivation has been associated to moisture reduction [11,46]. Thus, it is possible that the increment of LOX activity observed in control kernels could be related to moisture increase by modifying cell and organelle structure. Instead, LOX activity maintenance observed in PEF-treated kernels compared to control kernels might be due to the improvement of condensed tannins which have been reported to inhibit LOX [47–49].

Total phenolics, condensed tannins, and antioxidant capacity of cakes generated from dry kernels were lower than those reported for fresh kernels [18]. These differences could be due to the effect of drying as this process has been demonstrated to decrease TP, CT and AC of pecan nuts [50]. Despite that, the application of PEF increased not only the

CT concentration but also enhanced AC of the cakes. Considering that pecan nuts AC is closely related to their CT concentration, the increment of AC in cakes from PEF-treated kernels might be attributed to the release of simple phenolic compounds while condensed tannins are retained in the cake increasing its AC [50,51].
