Phenolic profile, antioxidant activity and thermo-oxidative stability of Brazilian chia seed oil (Salvia hispanica L.)

Chia seeds (Salvia hispanica L.) have interesting nutritional qualities, and their oil is known for its high levels of natural antioxidant compounds such as tocopherols, phytosterols, carotenoids, and phenolic compounds, associated with multiple biological effects, in addition to ω-3 among PUFAs. However, this composition favors a greater susceptibility to lipid oxidation. In this sense, the present study was carried out to analyze the phenolic profile, antioxidant activity and thermo-oxidative stability of chia oil. Chia seeds (Salvia hispânica L.) were produced in Entre-Ijuís-RS, purchased from Giroil Agroindústria Ltda and their oil extracted by cold pressing (~20 ºC), filtered and stored in headspace at 4°C. The phenolic profile was determined using HPLC, with peak identification using LabSsolutions software, and the antioxidant activity was determined by the DPPH method, expressed as EC50. The oxidative stability of chia oil was studied by the effect of the natural antioxidants α-tocopherol and myricetin, through a mixture experimental design using the synthetic antioxidant TBHQ as a reference and an oil sample without antioxidant as a control. Thermal analyses were performed using thermogravimetric curves (TG/DTG). The major phenolic compounds identified were myricetin, quercetin, kampferol, and synaptic acid. The seed oil also showed high antioxidant activity (EC50 of 22 µL), standing out among previous studies using other oils such as olive and soybean oil. Stability results show that the induction period (IP) ranged from 1.69 to 4.00 h in treatments with the addition of natural antioxidants, comparing these results with chia oil without antioxidants (0.6 h) and chia oil with the addition of the synthetic antioxidant TBHQ (9.01). Myricetin was more effective than α-tocopherol during accelerated oil oxidation at 110 °C, and TBHQ was undoubtedly the antioxidant with the greatest protective power. The results presented here demonstrated the significant presence of phenolic compounds that may be strongly associated with the high antioxidant activity found in Brazilian chia seed oil. However, the oxidative stability study showed that despite the presence of antioxidant compounds, the oil is highly susceptible to oxidation, requiring the use of methods to slow this process, such as antioxidant additives.