Effect of dehydration on several physico-chemical properties and the antioxidant activity of leeks (Allium porrum L.)

Abstract

This study investigated the changes in some physico-chemical properties and variations in antioxidant compounds of leeks (cv. Inegol-92') caused by the drying process. The dry matter and ash contents of the fresh leek samples were:3.06 and 0.58 g 100 g(-1), respectively. The pH of the fresh leek samples was 6.02, and the titritable acidity in terms of citric acid was 0.14%. As expected, application of hot-air drying significantly increased the dry matter and ash values due to removal of water from the leek slices. The rehydration ratio of dried leeks at 45 degrees C was 5.41, and the coefficient of rehydration was 0.47. The contents of chlorophyll a and b were higher in the dried leeks than in the fresh leeks. The dehydrated leeks showed a high total color difference (Delta E=12.53) mainly due to the effect of temperature on heat-sensitive compounds. As expected, both fresh and dried leek samples exhibited antioxidant activity with fresh leeks showing a higher capacity of antioxidant activity. Drying the leeks resulted in some ascorbic acid loss. Fresh leeks had much higher phenolic values (26.33 mg rutin eq 100 g DM-1) than the dehydrated samples. The antioxidant capacity of leeks was decreased by more than 50% during the drying process. Although being the most applied method of thermal dehydration, hoc air drying causes the degradation of sensitive components, which results in significant losses in sensorial and physico-chemical properties of the dried products.