Hi, Philip!

Do you want to test hydrolytic activity? If that, you can use triolein as substrate. The reaction mixture consist of triolein (0.5 g), triton X-100 (2.5 g), buffer Tris – HCl 1 M dilution 0.1 in water (5 g), and distilled water (2 g). The mixture is pre-incubated at 45°C for 10 min with continuous stirring at 1000 rpm. Then, a proper amount of the target sample is added and the reaction starts. After 5 min of reaction, hydrolysis is quenched by addition of ethanol (20 mL). Enzymatic activity is calculated by determination of liberated fatty acid through titration with 0.05N KOH and using phenolphthalein as end-point indicator. 

However, if you want to use olive oil, you have to probe esterification activity... I have never been used olive oil, but I used oleic acid to test synthesis of ethyl oleate catalyzed by lipase in a solvent-free system.  For that, you have to use a stoichiometric mixture of oleic acid and ethanol with no solvents added.  The reaction mixture includes oleic acid (3 g), ethanol (0.5 g) and water (20% w/w considering the weight of oleic acid). The initial concentration of oleic acid in the reaction medium is near 2.96 M, which implies a highly concentrated medium and thus the potential for high production  of  ester.  Proper  aliquots  of  enzyme  can be added  to  the  reaction  vial,  which  is  kept  at  45°C  with  constant  magnetic stirring (350 rpm) for 3 hours. After that time, 10 mL of a mixture ethanol/ether (50% v/v) is  added  for  quenching  the  reaction.  The  esterification  was  monitored  every  hour  by titration of withdrawn samples with KOH.

I hope that the information helps you

I agree with Pilar answers ...good luck.

Pilar Guauque has given reliable information.

We used tripalmitin, p-nitrophenyl acetate and Tween 80 as substrates in different experiments.

Thank you all  for the information !