Degradation of glycidyl esters in RBD palm oil as a function of storage conditions

Abstract

Storage of oil samples in a refrigerator results in the degradation of glycidyl fatty acid esters (G-FE). In the present work, the degradation rate for G-FE in RBD palm oil was determined at different temperatures with 0.4mg/kg per month (5°C), 0.3mg/kg per month (10°C), 0.2mg/kg per month (15°C), 0.1mg/kg per month (-20°C), and 0.0mg/kg per month (20°C). The crystallization process was identified for RBD palm oil as reason for this phenomenon. Isothermal differential scanning calorimetry measurements show that this process delivers enough energy to cleave the epoxy bonding of the G-FE (33.7J/g [5 and 15°C] and 41.5J/g [10°C]). Practical applications: The occurrence of glycidyl fatty acid esters is a big issue in oil processing industry especially for RBD palm oil. Short after the first announcement about the appearance of the esters in edible oils, a degradation of G-FE was observed when oil samples were stored in a refrigerator. This observation was of great interest for analytics since oil samples usually are stored in the refrigerator until use to avoid deterioration of the oil quality. Thus, the investigation of the rate and the reason for the degradation of G-FE during storage of RBD palm oil at lower temperatures is important to explain this phenomenon.