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Influence of drying temperature on the preservation of organoleptic properties, antioxidant activity and polyphenol content in dried leaves of Allium ursinum L. subsp. ucrainicum

Introduction. The short vegetative occurrence of Allium ursinum limits its availability. Therefore, drying seems to be an excellent method for year- round preservation. The aim of the present study was to determine the influence of drying temperature on antioxidant activity and polyphenol content in dried leaves of Allium ursinum L. subsp. ucrainicum and their organoleptic properties. Materials and methods. The effect of three drying temperatures (40, 50 and 60 °C) on the organoleptic properties (colour, dehydration and rehydration ability), antioxidant activity and polyphenol content in the dried leaves of A. ursinum was evaluated. The colour of the samples was measured using the computer vision system. The total phenolic content was determined spectrophotometrically and the antioxidant activity was determined using the 2, 2-diphenyl-1- picrylhydrazyl method. Results and discussion. Significant differences were found between the fresh, dehydrated and rehydrated A. ursinum samples for all the colour parameters analysed (dried leaves showed a much lower intensity of green colour than fresh). Drying at higher temperature results in greater colour change, which is more pronounced at higher drying temperatures (60 °C) due to chlorophyll degradation. The drying temperatures had a statistically significant effect on the dehydration and rehydration capacity of the dried samples. The higher drying temperature resulted in the higher degree of dehydration and rehydration (the pores of the dried food allowed water to re- enter the cells). Convection air-drying resulted in considerable moisture removal from the fresh leaves of A. ursinum (more than 91%), but the organoleptic quality of the A. ursinum leaves was maintained. The drying conditions tested had a significant effect on the total phenolic content and antioxidant activity of A. ursinum leaves. An increase of temperature drying decreased the total polyphenol content in the dried A. ursinum leaves. Across the range of measurements, the samples dried at lower temperatures had the higher antioxidant capacity, while the higher drying temperatures resulted in a greater decrease in the antioxidant activity of the dried plant material. A. ursinum is considered one of the functional foods for human consumption due to its high nutritional value and prophylactic or therapeutic effects in various diseases. To obtain a high quality dried product, the drying process should ensure a quality comparable to fresh vegetables. Conclusions. Air drying showed a significant effect on the colour, drying properties, total polyphenol content and antioxidant activity of the leaves of A. ursinum. The losses were significantly dependent on the drying temperature and were more pronounced at higher process temperatures.

Allium ursinum L. subsp. ucrainicum ; image analysis ; drying ; phenolic ; antioxidant

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