Effect of season and variety on the differentiation of geographic growing origin of pistachios by stable isotope profiling.

The objectives of this study were to demonstrate if seasonal or variety differences affected the feasibility of stable isotope profiling methods to differentiate the geographical growing regions of pistachios (Pistachia vera). Bulk carbon and nitrogen isotope analyses of approximately 150 pistachios samples were performed. Isotope ratios were determined using a stable isotope mass spectrometer. The pistachio samples analyzed were from the three major pistachio-growing regions: Turkey, Iran, and the United States (California). Geographic regions were well separated on the basis of isotope ratios. Seasonal effects were found to affect some isotopes for some regions. Pistachio varieties within specified geographic regions were not found to affect the discriminating power of stable isotopes, for the varieties tested. This paper reports the development of a simple chemical profiling method using bulk stable isotope ratios that may be widely applied to the determination of the geographic origin of foods.