Abstract
Abstract Edible flowers are increasingly used in food preparations, requiring new approaches to improve their conservation and safety. Food irradiation, particularly electron beam and gamma irradiation, is legally recognized to extend shelf life, improve hygienic quality and disinfest foods. Garden nasturtium (Tropaeolum majus L.) flowers are widely used in food preparations, being also known for their antioxidant properties and high content of phenolics. The purpose of this study was to evaluate the dose–response effects of gamma and electron beam irradiation (unirradiated and doses of 0.5, 0.8 and 1 kGy) on its antioxidant activity and phenolic compounds. Kaempferol-O-hexoside-O-hexoside was the most abundant compound, while pelargonidin-3-O-sophoroside was the major anthocyanin. The flowers showed high antioxidant activity, in particular as reducing agents. The interaction among the effects of irradiation dose and irradiation technology was a significant source of variation for all parameters. In general, irradiated samples gave higher antioxidant activity, maybe due to their higher amounts of phenolic compounds. Anthocyanins were the sole compounds negatively affected by irradiation. These differences were reflected in the linear discriminant analysis, which allowed the perfect separation of the applied doses, as also both irradiation technologies. Accordingly, irradiation represents a feasible technology to preserve the quality of edible flowers. Industrial relevance The increasing application of edible plants in several food commodities demands new technological approaches to improve their distribution and marketing as fresh products. Prolonging post-harvest storage, while preserving the whole quality of plants, these facts will benefit their industrial development, as well as the consumers' health. This study applied irradiation technologies, using electron-beam and gamma-irradiation in different doses, to a widespread and highly appreciated edible flower species, T. majus, and demonstrated that these technologies/doses did not compromise the phenolic compounds composition and antioxidant activity.
Highlights
Edible flowers have been used in the culinary arts to add flavour and garnish for hundreds of years
UV and mass spectra obtained by HPLC-diode array detector (DAD)-ESI/mass spectrometer (MS) analysis showed that this Tropaeolaceae species is characterized by the presence of phenolic acids and flavonoids
The presence of hydroxycinnamoyl derivatives and flavonoid glycosides is coherent with the results obtained in Polish varieties of this species (Bazylko et al, 2013)
Summary
Edible flowers have been used in the culinary arts to add flavour and garnish for hundreds of years. People use various shapes, colours and flavours of flowers in order to enhance the sensory and nutritional qualities of foods, and many of them have biologically active substances (Mlcek & Rop, 2011). The increasing application of edible flowers in various branches of food technology requires new approaches to improve conservation and safety of these products. Edible flowers are highly perishable products and must be free from diseases and insect pests, which represents a challenge because they must grow without the use of any chemical pesticide (Newnam & O’Conner, 2009). Food irradiation is a method that can be used for the extension of shelf life of perishable commodities, improvement of hygienic quality, disinfestation of insects and food safety (Farkas, 2006). Safety and efficiency of food irradiation have been recognized by several authorities such as World Health Organization- WHO, International Atomic Energy Agency- IAEA and Food Agriculture Organization- FAO (Farkas, 2006; Farkas & Mohácsi-Farkas, 2011)
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