Effects of packaging materials, storage conditions and variety on oxidative stability of shelled walnuts

The effects effects of storage temperature, oxygen permeability of packaging material and variety on oxidative stability of vacuum-packaged walnut kernels were studied over a 12 months storage period. The oxidation experiments applied to two popular walnut varieties (Yalova-1 and Yalova-3) grown in Turkey. The peroxide values and hexanal contents of walnut samples significantly increased (p < 0.01) during storage at 30 degrees C. The highest hexanal content (4464.5-6406.9 mu g/kg) were observed in Yalova-3 variety stored at 30 degrees C for 12 months in Polyamide/Polyethylene film pouches (oxygen permeability: 63.4 +/- 0.4 mL/m(2)/24 h (23 degrees C)) with 90 mu m total thickness. The effect of storage temperature and variety on lipid oxidation was found to be higher than the effect of oxygen permeability of the packaging material. It was concluded that for vacuum-packed walnut kernels in PA/PE film pouches having 63.4 +/- 0.4 mL/m(2)/24 h (23 degrees C) oxygen permeability, 20 degrees C is sufficient to protect against oxidation for 12 months. (C) 2011 Elsevier Ltd. All rights reserved.