No abstract

No abstract

No abstract

Rationale We report for the first time the top‐down lignomic analysis of the virgin released lignin (VRL) oligomers obtained from the Saudi date palm wood (SDPW), using a matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight (MALDI‐TOF/TOF) instrument. In addition, we are proposing new collision‐induced dissociation tandem mass spectrometry (CID‐MS/MS) fragmentation routes for this series of unreported VRL oligomers. Methods We have used direct MALDI‐TOF‐MS analysis of the mixture of lignin oligomers without any chromatographic pre‐separation. High‐energy CID‐MS/MS analyses were used to confirm the precursor ion structures. Results Six protonated lignin oligomer molecules were identified: [C19H24O8 + H]+ as H(8‐O‐4')G; [C50H52O19 + H]+ as H(8‐O‐4')H(8‐O‐4'')S(8‐O‐4''')S(8‐O‐4'''')G; [C58H54O18+ H]+ as H(8‐O‐4')H(8‐O‐4'')H(8‐O‐4''')G(8‐O‐4'''')S(8‐O‐4''''')G; [C58H54O19 + H]+ as H(8‐O‐4')H(8‐O‐4'')H(8‐O‐4''')S(8‐O‐4'''')S(8‐O‐4''''')G; [C61H68O25 + H]+ as H(8‐O‐4')G(8‐O‐4'')G(8‐O‐4''')S(8‐O‐4'''')S(8‐O‐4''''')G; and [C61H68O26 + H]+ as C(8‐O‐4')G(8‐O‐4'')G(8‐O‐4''')S(8‐O‐4'''')S(8‐O‐4''''')G units (H = coniferyl, S = sinapyl, and G = p‐coumaryl). Two distonic cations were identified as [C39H43O15 + H]+• and [C40H43O16 + H]+• deriving from two tetrameric lignin oligomers. The high‐energy MS/MS analyses allowed the confirmation of the proposed structures of this series of lignin oligomers. Conclusions To our knowledge, this is the first elucidation of the lignin structure of the Saudi seedling date palm wood that was accomplished using a top‐down lignomic strategy that has not previously been published. The complex high‐energy CID‐MS/MS fragmentations presented herein are novel and have never been described before.

The potential of date palm wood (DPW) as a new source of phenolic antioxidants was investigated in this contribution. The total phenolic content and antiradical activity of soluble and insoluble‐bound fractions of DPW was compared to those of maple wood (MW). Furthermore, salmon was smoked with DPW and MW. Irrespective of the wood type, volatile phenolic compounds were mainly methoxyphenols, with the highest contribution from eugenol followed by guaiacol and their corresponding derivatives, as evaluated by solid‐phase microextraction and gas chromatography–mass spectrometry. Salmon smoked with DPW showed a higher oxidative stability than that of MW during 21 days of storage at 4°C, which was explained by the higher content of volatile phenolic compounds in the smoke generated from DPW. Minor differences were detected for the instrumental color between both samples of smoked salmon. Therefore, smoking with DPW may be used for industrial meat and fish smoking purposes. Practical applications Smoking has long been used to preserve fish and meat products. The process changes the appearance and gives a desirable flavor to the product. However, high temperatures applied during smoking may also induce lipid oxidation, the extent of which is counterbalanced by the antioxidant action of phenolics in woodsmoke. In this sense, the desired interactions of the smoke volatiles in the food matrix dictates the quality of the final product. Volatile phenolics released upon smoking are dependent on the type of wood. Thus, use of a specific wood might provide unique products, hence date palm wood (DPW) used in this work may not only provide special smoked fish products but its use could be extended to other smoked products. Hence, this contribution extends the possible feedstocks for the preparation of smoked products.