Effect of different drying methods on antioxidant and phytochemical yield of Allium hirtifolium Boiss.

Allium hirtifolium Boiss. is a native plant of Iran and has medicinal uses due to its organosulfur compounds, in addition to consuming edible. The experiment was designed to investigate the effect of different drying methods on the quality of Allium hirtifolium. Allium hirtifolium slices were dried by using ten methods, which were sun and shade drying, soaking Allium hirtifolium in water for 24 hours and then sun drying (traditional method), oven drying (50, 60 and 70 °C), microwave drying (360, 540 and 720 W) and freeze-drying. The effect of different drying methods on antioxidant capacity (DPPH assay), total phenol content (Folin-Ciocalteu method), flavonoids (aluminum chloride colorimetric assay), allicin (4-mercaptopyridine method) and soluble and storage carbohydrates (anthrone method) as well as Allium hirtifolium color quality (image processing analysis) were investigated. The initial moisture content of the samples was 69.41% based on fresh weight. The highest antioxidant activity belonged to the extracts obtained by maceration of fresh samples followed by the shade-dried samples with methanol. The total phenolic content was found to be highest in the freeze-dried samples macerated with methanol. The greatest flavonoid content was observed in fresh samples followed by the freeze dried samples extracted by ultrasound. Shade- dried samples, next to fresh Allium hirtifolium, had the highest allicin. The maximum levels of soluble and storage carbohydrates were found in freeze-dried samples and microwave-dried samples at 720 W power, respectively. After the drying process, the lowest browning index was observed in freeze-dried samples. Among the drying methods, shade drying was introduced as the most suitable method to maintain the quality of Allium hirtifolium and it was found that the traditional method of drying Allium hirtifolium causes the loss of its bioactive compounds.