Tocopherol Contents of Walnut Varieties Grown in Turkey and the Effect of Storage on Tocopherol Content

Tocopherol contents of seven popular walnut varieties grown in Turkey were determined. The effects of storage temperature, oxygen permeability of packaging material and walnut variety on the tocopherol content of vacuum‐packed walnut kernels were also examined during the 12 months of storage. α‐, γ‐ and δ‐tocopherol were identified and quantified in walnut varieties. α‐, γ‐, δ‐ and total tocopherol contents of walnuts ranged from 9.69 to 14.13, 298.75 to 470.02, 10.06 to 25.98 and 321.27 to 505.28 mg/kg walnut, respectively. The decrease in the amount of these compounds during the 12 months of storage was severe in packaging material having high oxygen permeability (63.40 ± 0.40 mL/m2/24 h [23C]) and at 30C. The present study concluded that it is possible to protect the tocopherol content of walnut kernels by packaging in polyamide/polyethylene laminate pouches having an oxygen permeability lower than 63.40 ± 0.40 mL/m2/24 h (23C) under vacuum at 10C up to 12 months. Practical Applications Walnut is a nut having high tocopherol content, especially γ‐tocopherol. γ‐Tocopherol has long been considered to be of minor importance compared with α‐tocopherol because of its lower plasma concentration and antioxidant activity. Recently, much research concerning γ‐tocopherol has shown that γ‐tocopherol is much more powerful than α‐tocopherol in detoxifying lipophilic electrophiles, inhibiting prostate cancer cell proliferation and protecting cardiovascular system. The results of this study provide guidance to protect tocopherol content of shelled walnut during long‐term storage.