Iran Agricultural Research (2020) 39 (2) 91-98 Research Article The effect of extraction and isoelectric pH values on functional and thermal properties of tahini meal protein N. Koushki 1 , T. Najafi Mirak 2 *, M. H. Haddad Khodaparast 1 , F. Naghipour 2 , M. Vazifedoost 1 1 Department of Food Science and Technology, Neyshabur Branch, Islamic Azad University, Neyshabur, I. R. Iran 2 Seed and Plant Improvement Institute, Agriculture Research, Education and Extension Organization (AREEO), Karaj, I. R. Iran * Corresponding Author: tnmirak@yahoo.com tnmirak@spii.ir DOI: 10.22099/IAR.2021.36663.1385 ARTICLE INFO ABSTRACT - Tahini is an important product of peeled sesame. As a byproduct of oil extraction from tahini, tahini meal (TM) is a valuable protein source. However, it is only used to feed livestock. TM can be used as an affordable protein source in human diet. In this research work, the effects of extraction pH (10, 11 and 12) and isoelectric pH (4.5, 5.5 and 6.5) on functional and thermal properties of proteins isolated from TM were studied. Functional properties of extracted proteins including water and oil absorption, foaming capacity and foam stability as well as thermal properties were measured. The results showed that the highest protein extraction efficiency (87%) was obtained in extraction pH at pH≥11 and isoelectric pH 6.5. In addition, the highest levels of water and oil absorption capacity were obtained in proteins precipitated at pH 6.5 (P≤0.05). The highest level of foaming capacity and stability was observed in proteins extracted at pH 11 and precipitated at pH 6.5. On the other hand, thermal properties of TM protein including onset denaturation temperature (T m ), denaturation peak temperature (T d ) and denaturation enthalpy (ΔH d ) were affected by sediment pH and pH 6.5 led to the highest thermal characteristics. Since the optimum characteristics of proteins isolated from TM were obtained at isoelectric pH 6.5 and extraction pH 11, these pH values are recommended for the extraction and precipitation of TM proteins, respectively. Article history: Received 28 November 2017 Accepted 7 April 2018 Available online 13 March 2021 Keywords: Functional properties Protein extraction yield Tahini meal Thermal properties. INTRODUCTION Now a day, plant based proteins play a vital role in human nutrition, especially in developing countries where the mean protein intake does not satisfy the minimum requirements of the body (Kanu et al., 2007). The shortage of animal based protein sources has intensified attempts made to find new protein sources with suitable functional properties and nutritional value (Egorova et al., 2017). On the other hand, it has been reported that consuming plant based proteins is more cost effective compared to animal based proteins (Muhamyankaka et al., 2013). Sesame, Sesamum Indicum, Linn, is the seed of an herbaceous plant of the family, Pedaliaceae. In 2019, the total production rate of sesame was 6,549,725 million tons (FAOSTAT, 2019). It ranks 8th in the global ranking in terms of production rate The contribution of Iran to the production of sesame is 29 thousand tons (FAOSTAT, 2019). Sesame is a rich source of protein with a high nutritional value. The protein content of sesame seed is approximately 25% varying from 17% to 31%, depending on the seed source. Protein is mainly stored in sesame seed as globulin (67.3%), albumin (8.6%), prolamin (1.4%) and glutelin (6.9%) (Achouri et al., 2012; Inyang and Iduh, 1996). It is having fat contents of about 80% unsaturated and 20% saturated fatty acids (Onsaard et al., 2018). Tahini is a processed product of sesame. Traditionally, it is consumed with sweet substances such as honey and grape syrup in the Middle East countries and it is an important ingredient of Halva (one kind of dense, sweet confection with roots in the Middle East, Central Asia, and India). Tahini is actually an oily liquid which is derived from peeled sesame. It constitutes from 24.7% protein, 59% fat, 2.3% fiber and 3% mineral substances (Torlak et al., 2013). It has been reported Shiraz University