Modified atmosphere in head space of extra virgin olive oil tanks: Testing a prototype integrated storage system

The maintenance of the quality of oil is a very complex operation, due to the storage conditions of the oil after the extraction step. The storage of oil must ensure the conditions necessary to avoid the increase of acidity, and consequently the onset of rancidity, or problems related to the anaerobic fermentation of suspended matter in the oil or deposited on the bottom of storage vessels. This work describes the development of a prototype integrated storage system. The storage system consists of a nitrogen gas generator, three stainless steel tanks, and a feedback controller of nitrogen concentration and tank temperature. In the experimentation, three tanks were used in order to test the functionality of the system. The experimental design is based on the creation of different modified atmospheres on the head space of steel tanks, using the nitrogen gas generator and feedback controller of head space composition of each tank. The results show that the prototype performs well in terms of its ability to detect and adjust the atmosphere of tank headspace. The oxygen percentage in the headspace of the three tanks remained between 0.7 and 0.9%. Chemical analyses of acidity, total phenol content and peroxides index show that the controlled headspace maintained acidity levels within the range 0.32-0.36% during the experiment, total phenol content in the range 152-146 ppm (gallic acid equivalent) and peroxides index values in the range 7.9-8.2 meq O2/kg of oil. The proposed prototype performs a function of effective control and regulation of the concentration of the headspace of tanks and can help to maintain the chemical characteristics of extra virgin olive oil over time. The experimental evidences confirmed that the prototype storage system was able to maintain the chemical characteristics of the extra virgin olive oils stored for 3 months.