Currently, the authentication of virgin walnut oil (VWO) has become very important due to the possible adulteration of VWO with cheaper plant oils such as soybean oil (SO), puer tea seed oil (PO), and sunflower oil (SFO). Methods involving Fourier transform infrared (FT-IR) spectroscopy combined with chemometric techniques (partial least square) were developed for quantification of SO, PO, and SFO in VWO. IR spectra of oil samples were recorded at frequency regions of 4000–650？cm？1 on horizontal attenuated total reflectance (HATR) attachment of FT-IR. PLS model correlates the actual and FT-IR estimated values of oil adulterants (SO, PO, and SFO) with coefficients of determination ( ) of 0.9958, 0.9925, and 0.9952, respectively. The obtained RMSEC values of SO, PO, and SFO in VWO are 1.35%, 1.85%, and 1.43% (v/v), respectively. The method, therefore, has potential as a rapid method for quantification of product adulteration. 1. Introduction In the recent years, walnut oil has received great attention because of its biological activities and sensory qualities and has become a very important agricultural product for many countries. The unsaturated fatty acid in walnut oil is 90%. There is about 47.4% of linoleic acid and 15.8% of linolenic acid [1]. Epidemiological studies show that walnut oil not only reduces serum cholesterol but at the same time has nutritional cranial nerve cells which can adjust plant nerve function. Other experts discovered that walnut oil does not only act as officinal, but also can be used as the “old man and the infant nutrition oil” as well as aerial work and flight personnel’s senior health care oil [2]. Due to its higher price in the market, WO can be a target of adulteration with the cheaper oils such as soybean oil in order to gain economical profit. Therefore, the development of rapid and nonexpensive analytical techniques capable of detecting such adulterations in walnut oil is currently highly demanded. In fact, the adulteration is a serious problem in trade of fats and oils for a long time, and it is of primary importance for consumers, food processors, and industries, because there is a great difference in quality and price for different oil products. The adulteration is increasingly more difficult to detect when the oil adulterant has similar chemical composition to the authentic oil [3, 4]. In addition, chemical methods traditionally employed for the control of authenticity of virgin edible oil as gas chromatography and high performance liquid chromatography are expensive, time-consuming, require skilled operators, and
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