The effect of extraction and isoelectric pH values on functional and thermal properties of tahini meal protein

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 pH11 and precipitated at pH6.5. On the other hand, thermal properties of TM protein including onset denaturation temperature (Tm), denaturation peak temperature (Td) and denaturation enthalpy (ΔHd) 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.