Browsing by Author "Yilmaz, Ozay Mentes"

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Changes in the Phenolic Content and Free Radical-Scavenging Activity of Vacuum Packed Walnut Kernels During Storage
(Karger, 2013) Bakkalbasi, Emre; Yilmaz, Ozay Mentes; Yemis, Oktay; Artik, Nevzat
In this study, the effects of storage temperature, O-2 permeability of packaging materials and variety on phenolic content and free radical-scavenging activity of vacuum-packaged walnut kernels were studied over a 12 months storage period. Methyl gallate (23.70 - 93.75 mg/kg), ellagic acid (137.95 - 569.22 mg/kg), and an ellagic acid pentoside (270.59 - 637.17 mg ellagic acid equivalent/kg) were identified in walnut varieties. While a slight decrease in the amount of ellagic acid was observed during 12 months storage, decreases in the amount of ellagic acid pentoside, total phenolic content and free radical-scavenging activity were severe. The present study concluded that it is possible to protect the phenolic content and antiradical activity of walnut kernels by packaging in Polyamide/Polyethylene laminate pouches having an oxygen permeability lower than 63.40 +/- 0.40 (mL/m(2)/24h at 23 degrees C) under vacuum at 20 degrees C up to twelve months.
Effects of Packaging Materials, Storage Conditions and Variety on Oxidative Stability of Shelled Walnuts
(Elsevier Science Bv, 2012) Bakkalbasi, Emre; Yilmaz, Ozay Mentes; Javidipour, Issa; Artik, Nevzat
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.
Phenolic Acid Contents and Antioxidant Activities of Wheat Milling Fractions and the Effect of Flour Extraction Rate on Antioxidant Activity of Bread
(Wiley, 2018) Yilmaz, Ozay Mentes; Bakkalbasi, Emre; Ercan, Recai
The amounts of free and bound phenolic contents, antioxidant activity and phenolic acids of nine different wheat varieties grown in Turkey and of their milling fractions (thick bran, thin bran, and flour) were determined. Furthermore, total phenolic content and antioxidant activity of the different extraction rate flours (65%, 75%, and 100%) and breads made from those flours were evaluated. The free and bound phenolic content of wheat varieties ranged from 656.80 to 900.64 and 1095.73 to 1376.33 mg GAEq./kg defatted wheat dm, respectively. In wheat, thick bran fraction has shown the highest phenolic content and antioxidant activity. Ferulic and vanillic acids were determined in free phenolic extracts obtained from the studied wheat varieties and their milling fractions. Syringic and p-coumaric acids were determined as well as ferulic and vanillic acids in bound phenolic extracts. Total phenolic content and antioxidant activity of breads increased with an increase in flour extraction rate.
Tocopherol Contents of Walnut Varieties Grown in Turkey and the Effect of Storage on Tocopherol Content
(Wiley, 2014) Bakkalbasi, Emre; Yilmaz, Ozay Mentes; Poyrazoglu, Ender Sinan; Artik, Nevzat
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. alpha-, gamma- and delta-tocopherol were identified and quantified in walnut varieties. alpha-, gamma-, delta- 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/m(2)/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/m(2)/24 h (23C) under vacuum at 10C up to 12 months.