Title: Chemical composition and antioxidant properties of hull and core of Pistacia khinjuk stocks

Pistacia is a genus of the family Anacardiaceae. Among the 15 known species of pistachios, only 3 species grow in Iran, including Pistacia vera, Pistacia Khinjuk and Pistacia atlantica. P. Khinjuk is a native plant in Iran. The plant is known as Khenjuk or Kelkhong in Persian. Resin of this plant has been used as an indigestion, tonic, toothache and astringent. In addition, fruits of P. Khinjukare used as edible wild fruits in form of roasted or salted nuts. There are reports on extract obtained from wild pistachio. It has been shown that the extract is rich source of phenolic compounds and other antioxidant compounds. Oil obtained from wild pistachio also has high content of essential fatty acids which can reduce and prevent from different diseases. Extracts obtained from the wild pistachio tree has also been used in pharmaceutical and cosmetic industries. However, there is no scientific report on qualitative properties of wild pistacia species khinjuk. Therefore, the aim of this research was to study the chemical and nutritional composition hull and core of wild pistacia species khinjuk.

The Pistacia Khinjuk was collected during flowering stage from Southwest of Iran (KouhgiloyeBoyerahmad province) and identified by the Herbarium. Separate tests were performed on the hull and core of wild pistachio. First, the fruit hull was isolated from its core and then they were crashed and their core was separated. Moisture, oil, protein and ash content and pH of the hull and core of the fruit were determined. The hull and core of fruit were used for oil extraction. The hull and core were powdered and their oil was extracted by hexane. For fatty acids profile, extracted oil samples were methylated and obtained fatty acid methyl esters were analyzed by gas chromatography. Also, the extracted oil stored for three month at room temperature, and every thirty day peroxide value (PV), acid value (AV) and chlorophyll content were determined. PV and AV were determined by titration methods. Chlorophyll content was determined by spectrophotometer. Extract of the dried hull and core of fruit were obtained with percolation in ethanol and its total phenol content and DPPH free radical scavenging activity were determined. Phenolic content was determined using folinciocalteu method. Also, the extracts were added at percentages of 1, 2 and 3% to the rapeseed oil and extracts antioxidant properties were evaluated by rancimat.

Analysis showed that hull has more oil and ash content and lower protein content than core. Hull oil content (84%) was two times more compared to the core of the fruit (47%), but core protein content (7%) was almost twice compared to hull protein content (3%). The results showed that the percentage of major fatty acids in hull and core of fruit was oleic acid 33% and 41.2%, linoleic acid 10.6% and 21.5%, alpha-linolenic acid 6% and 3.1%, palmitic acid 17.2% and 11% and palmitoleic acid 13.1% and 3.1%, respectively. Results showed that oil extracted from hull and corehave high content ofmonounsaturatedand polyunsaturated fatty acids with relatively high amount of essential fatty acids. Total phenolic content of hull and core of the fruit were 25.6 and 6.3 mg gallic acid per 1 gram of dried sample, respectively. This results show that hull is a rich source of phenolic compound which can be important from nutritional point of view. Peroxide value and acid value increased during 4 month storage significantly. Increase in PV was higher in oil obtained from hull than core oil. Increase in PV can be result of fatty acid oxidation which is affected by several factors such as fatty acid composition, antioxidant content, peroxidant content and storage condition. AV of oil extracted from hull was higher than oil obtained from core. AV was increased in oils obtained from core and hull, but increases in hull were higher. Increase of AV can be result of hydrolyses of triacylglycerols which produce free fatty acids.Chlorophyll content was higher (7 times) in oil obtained from core compared with oil obtained from hull. Oil obtained from core had green color because of high chlorophyll content. Chlorophyll content reduced significantly (P≤0.01) during storage. It should be mentioned that chlorophyll content is an important factor in oil oxidative stability because chlorophyll act. as a sensitizer and enhance oil photoxidation.Evaluation of oil stability by rancimat showed that highest rapeseed oiloxidative stability was obtained by addition 3% of hull extract. Hullextract was more effective onfree radicalscavenging(88%) than core(75%).Hull of wild pistachio in comparison to its core has more phenolic content, therefore more antioxidant activity is also is expected. Phenolic compounds can act as antioxidant and make oils more stable against oxidation.

According to suitable fatty acid composition and total phenol content, wild pistachio need more attention in people’s diets as a cheap and useful nut.