Enhancing bioactive compound stability of stinging nettle (Urtica dioica L.) leaves via advanced packaging techniques

Abstract

Stinging nettle (Urtica dioica L.) is a highly nutritious plant, as it contains a variety of phytochemicals that contribute to the health-promoting properties of the human organism. However, preserving these valuable compounds and maintaining the organoleptic properties of fresh nettle leaves over a certain period of time is a problem given their perishable nature. Therefore, modified atmosphere packaging and the selection of polymeric materials during the 14-day storage period were investigated as possible strategies for the preservation of the bioactive compounds of fresh nettle leaves. Two packaging materials, biaxially oriented polypropylene (BOPP) and low-density polyethylene (LDPE), and different gas compositions of the modified atmosphere: (A) – 5% O₂ and 5% CO₂; (B) – 5% O₂ and 10% CO₂, were tested. The control samples were packaged in packaging materials without modification of the atmosphere. The content of ascorbic acid, phenolic compounds, photosynthetic pigments and the antioxidant capacity of fresh nettle leaves were investigated after 7 and 14 days of storage of nettle in the cold (temperature 4°C). The results show a strong influence of the modified atmosphere, the packaging material and the storage time on the bioactive components of the nettle. The highest content of ascorbic acid (91.85 mg/100 g) was found in samples stored for 7 days in LDPE and 5% O₂ and 5% CO₂. The highest content of total phenolic compounds (635.8 mg/100 g) and caffeoylmalic acid (469.75 mg/100 g) and the highest antioxidant capacity according to the ABTS method were found in samples stored in BOPP and 5% O₂ and 5% CO₂ for 7 days.