This experiment is carried out typically for fruit powder. According to a number of researchers, Olive oil is suggested for this experiment. Kindly clarify why only olive oil is preferred?
There is no thumb rule to use oilve oil. As a matter of fact, many researchers replicated the already established protocol which might be attributed to ease of availability of olive oil and its better stabilization properties. I don not think the differences in physical attributes such as viscosity (minor difference among fresh oils) have much role to play in OHC. The best reason, which could be thought of, includes difference in fatty acid composition and unsaponifiable composition, among oils, which may lead to varied OHC.
In my logical opinion, you should experiment with palm oil and soybean oil as well and examine the difference.