Investigation of the synergistic and antagonistic properties of Spirulina platensis and Moringa oleifera extracts on virgin olive oil

Virgin olive oil has high oxidative stability due to its special compounds, including large amounts of monounsaturated fatty acids (MUFAs) and a wide range of natural antioxidants. However, virgin olive oil is easily oxidized due to the presence of polyunsaturated fatty acids (PUFAs), mainly linoleic and linolenic acids. Lipid oxidation is the main cause of poor food quality; for this reason, the use of antioxidants is essential to prevent the onset and progression of oxidative damage and increase the shelf life of oils and fats. Because lipid oxidation occurs following a complex set of processes and no antioxidant alone can stop all the oxidation steps and keep oxygen away, a mixture of antioxidants can be used to create a synergistic effect. Spirulina is a dry biomass of Artrhrospira platensis cyanobacteria. Flavonoids, β-carotene, vitamin A and α- -tocopherol in spirulina are largely involved in the high antioxidant activity of this microalgae. The Moringa oleifera plant belongs to the Moringaceae family, the genus Moringa and the species Oleifera. This plant is considered as a high-potency natural antioxidant because it is rich in tocopherols, carotenoids, vitamin C, flavonoids and phenolic compounds. Therefore, the aim of this study was to investigate the synergistic and symbiotic effect of spirulina and M. oleifera extracts as natural antioxidants to increase the oxidation stability and shelf life of virgin olive oil.

To prepare the extracts of s. platensis and M. oleifera plant, both plants were dried in the shade at 30°C for 24 hours in the presence of air, then ground into a powder. Then, 5 g of s. platensis and M. oleifera powders were extracted with two solvent of ethanol (96%) and methanol. Antioxidant activity was evaluated by measuring the effect of free radical scavenging of ethanolic extracts of Algae Spirulina and Acacia on the synthetic radical DPPH. Determination of total phenol and flavonoid content of all extracts was performed using Folin-Ciocalteu reagent and aluminum chloride colorimetric method, respectively. Polyphenolic compounds of the extracts were identified by HPLC. Extracts were added separately (1000 ppm each) and in combination (500 ppm each) to 100g of virgin olive oil and a sample containing the synthetic antioxidant TBHQ and a sample of virgin olive oil were considered as control. Peroxide index, refractive index and color evaluation (L*, a*, b*) of virgin olive oil samples were measured. Statistical analysis was performed using SPSS software version 19 and the results were expressed as mean ± standard deviation.

Based on the results obtained from ethanolic and methanolic s. platensis extracts, the highest amount of total phenol in ethanolic extract was equal to 67.19±4.5 mg GA/g and the highest amount of flavonoids in methanolic extract was equal to 12/1±40/267 mg QU/g. In the study of the content of total phenol and flavonoids in ethanolic and methanolic extracts of M. oleifera plant, there was the highest levels of total phenols and flavonoids in ethanolic extracts of this plant, respectively, 43.43±0.71 mg GA/g and 23.78±1.57 mg QU/g. The results showed that the active compounds in the extracts of S. platensis and M. oleifera are polyphenolic compounds of rosmarinic acid, catechin, quercetin, vanillin, hesperidin, hesperetin. Changes in peroxide value from the time of production and addition of the extract for 8 hours at 2 hour intervals were investigated. According to the results, the lowest amount of peroxide value (0.38±0.005 meq O2/kg) was related to the sample containing M. oleifera extract at the third storage time. The highest amount of peroxide value was observed in the control and the sample containing TBHQ in the range of 15 meq O2/kg. Generally, Changes in peroxide value were reduced significantly in the 3 samples containing the extract compared to the control sample and the sample containing TBHQ (p<0.05). The presence of extracts in virgin olive oil reduced the parameters of L*a*b*, but the sample containing S. platensis extract was no significant difference from the control sample (p >0.05). According to the results of peroxide index of samples containing extracts, it can be stated that by recognizing the antioxidant effects of S. platensis and M. oleifera extract, they can be used for industrial use and replacement with synthetic antioxidants.