Irradiation as a novel approach to improve quality of Tropaeolum majus L. flowers: Benefits in phenolic profiles and antioxidant activity

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.

The influence of electron beam radiation in the nutritional value, chemical composition and bioactivities of edible flowers of Bauhinia variegata L. var. candida alba Buch.-Ham from Brazil

“…The irradiation was able to increase the antioxidant activity, especially when applying the dose of 0.5 kGy, which is in agreement with the highest concentration of phenolic compounds found in this sample (Table 3). Koike and co-authors reported an increase in the antioxidant activity of V. tricolor (Koike et al, 2015a) and T. majus (Koike et al, 2015b) subjected to irradiation treatment, especially at the dose of 1 kGy, which also gave the highest amount in phenolic compounds. Concerning the cytotoxic activity (Table 4), B. variegata L. var.…”

“…Moreover, extractability increase could also be explained by the capacity of irradiation to break chemical bonds that link polyphenols to other molecules, thereby releasing soluble phenols of low molecular weight and leading to an increase of antioxidant-rich phenolics (Alothman, Bhat, & Karim, 2009). Koike and co-authors evaluate the dose-response effects of gamma and electron beam irradiation (0.5, 0.8 and 1 kGy) of Viola tricolor L. (Koike et al, 2015a) and Tropaeolum majus L. (Koike et al, 2015b), verifying that electron beam was the most efficient technique to be applied at the dose of 1 kGy. However, this dose was not the most efficient in the flower samples studied in this work, which showed to be more susceptible to degradation when higher doses are applied.…”

“…The irradiation process was performed at the Nuclear and Energy Research Institute -IPEN-CNEN/SP (São Paulo, Brazil), using an electron beam accelerator (Dynamitron, Radiation Dynamics Inc., Edgewood, NY, USA) and following a procedure reported by Koike et al (2015aKoike et al ( , 2015b. The Flowers samples were irradiated using the doses of 0.5 kGy (dose rate: 1.11 kGy/s, energy: 1.400 MeV, beam current: 0.3 mA, tray speed: 6.72 m/min), 0.8 kGy (dose rate: 1.78 kGy/s, energy: 1.400 MeV, beam current: 0.48 mA, tray speed: 6.72 m/min) and 1.0 kGy (dose rate: 2.23 kGy/s, energy: 1.400 MeV, beam current: 0.6 mA, tray speed: 6.72 m/min).…”

“…The phenolic compounds were determined using an Hewlett-Packard 1100 from Agilent Technologies, (Santa Clara, CA, USA), equipped with DAD (280, 330 and 370 nm as preferred wavelengths), and a mass detector (API 3200 Qtrap, Applied Biosystems, Darmstadt, Germany) (Koike et al, 2015a(Koike et al, , 2015b. The phenolic compounds were identified by using reported data from literature or by comparison with the available commercial standards (Extrasynthèse, Genay, France).…”

“…The extracts descried above in Section 2.3.6, phenolic compounds, were dissolved in ethanol at a final concentration of 50 mg/mL and successive dilutions were prepared (0.156-50 mg/mL) in order to be submitted to the following in vitro assays: reducing power by the ferricyanide Prussian blue assay; scavenging activity by the 2,2-diphenyl-1-picrylhydrazyl (DPPH, Alfa Aesar, Ward Hill, MA, USA) assay; and lipid peroxidation inhibition by the β-carotene/linoleate assay, according to Koike et al (2015aKoike et al ( , 2015b. The sample concentrations presenting 50% of antioxidant activity (EC 50 ) or 0.5 of absorbance (EC 0.5 ) were obtained using the graphs of antioxidant activity percentages (DPPH and β-carotene/linoleate assays) or absorbance at 690 nm (reducing power assay) against sample concentrations.…”