Investigation of the effect of packaging film, temperature and storage time on biochemical characteristics of Rosmarinus officinalis L.

Effects of packaging film, temperature, and storage time on the biochemical properties of dried leaves of Rosmarinus officinalis L. were investigated in a factorial experiment based on a completely randomized design at Gorgan University of Agricultural Sciences and Natural Resources during 2017-2018. Plant samples were collected and shade-dried from the newly grown branches of eight-year-old plants in June. Then, the samples were packed in packaging films including control (without coating), polyamide 80, 90, and 120 µ, polyethylene 90 µ and common plastic, before they were stored at 4 ℃ and 25 ℃ for one year. The biochemical compounds of the plant were measured every three-months. Chlorophylls and carotenoids were measured using dimethyl sulfoxide method. Phenols, flavonoids, and antioxidant activity were assayed by Folin-Ciocalteu, aluminum-chloride, and DPPH method. Findings showed that chlorophylls and carotenoids decreased over time; however, 4 ℃ preserved the pigments better than 25 ℃. The highest phenol content (4.5 mg/g) was observed in common plastic after 6 months, and the highest flavonoids (2.87 mg/g) was observed in polyamide 90 µ and polyethylene 90 µ stored for 3 months at 4 ℃. Total phenols and flavonoids in treatments were 1.78 and 3 times higher than the samples without coating stored for 12 months at 25 ℃. The highest antioxidant activity was observed in all packages at the beginning of the experiment, and the antioxidant activity decreased by 30.8% after 12 months storage at 25 ℃ without coating. According to the findings of the study, in order to preserve the quality of dried rosemary leaves, they are recommended to be stored in polyamide 90 and 120 µ and polyethylene 90 µ at 4 ℃ for 3 months, because in these treatments, in addition to the increase in total phenols and flavonoids (1.2-1.3 times compared to the beginning of the experiment), the content of total chlorophylls, carotenoids, and antioxidant activity did not increase highly.