Caffeic and ferulic acids: An investigation of the effect of antioxidants on the stability of soybean biodiesel during storage

Soybean oil is widely used in many countries and its application for the synthesis of biodiesel is usual. The drawback of this raw material is its susceptibility to oxidative rancidity leading to the need of the development of antioxidants. In this paper, different antioxidants, caffeic acid, ferulic acid, and tert-hydroquinone, were added into soybean biodiesel during storage period with evaluation of its stability by accelerated techniques: Rancimat, PetroOXY and P-DSC (pressurized differential scanning calorimetry). According to the values of induction period (IP) by standard Rancimat method, the three antioxidants were effective in retarding the oxidation processes at the initial time of storage. Using the parameters assessed, the efficiency of the antioxidant took the following efficiency order: caffeic acid > ferulic acid > tert-butylhydroquinone. The efficiency of caffeic acid in maintaining the IP values during the entire storage period (6.66 h at 90 days) was noticeable, fulfilling the limit specified by EN 14214.