The effect of storage on quality of herbs genus Origanum

Abstract

Herbs of Origanum genus are rich in essential oils and contain large amounts of phenols, lipids, fatty acids, flavonoids and anthocyanins. Antioxidant activity of these herbs depends on many factors, including the type herbs, post-harvest processing and subsequent processing. The aim of this study was therefore to confirm the hypothesis that the composition of oils of these two herbs of the Origanum genus depends on the post-harvest treatment of herbs and that the dried herb antioxidant activity is higher for fresh than that of frozen herbs. Lamiaceae family herbs: oregano (Origanum vulgare L.) and Greek oregano (Origanum heracleoticum L.) were planted and analyzed. Herb samples were extracted by hot demineralised water. DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method was used for antioxidant activity assessment. The total phenolic content was determined spectrophotometrically by using Folin-Ciocalteu reagent. Steam distillation of essential oils was carried out via Clevenger Apparatus. The obtained essential oils were analysed by GC-MS technique. Results of tested fresh, dried and frozen herbs showed a considerable potential for quenching the free DPPH radical. Significantly higher antioxidant activity was found in dried herbs comparing to fresh and frozen, but only in case of values calculated per 100 g of the sample. However, the differences were not statistically significant after recalculation when expressed on dry matter content. There was no difference between fresh and frozen samples. The content of total phenols was significantly higher in dried than in frozen herbs in values recalculated per 100 g of sample. A strong correlation between the results of DPPH and TPC was found again only for values expressed per 100 g of the sample. Postharvest treatment of herbs affects the composition of their essential oils. The dominant essential oil component of Greek oregano is carvacrol with a proportion of 60% or more. On the contrary, there is no such dominating component in oregano essential oil but there are more components with a share of 10 to 20%.