Refrigeration may cause olive oil to crystallize. Crystallization is not a condition for or an indication of the quality of the oil. The reason for the difference in the tendency of different varieties to crystallize is the order and location of the fatty acids in the triglycerides, in addition to structural symmetry.
The purity of the oil is tested by qualified laboratories. Yad Mordechai performs the most stringent tests and conforms to all sections of the international standard.