Outer green leaves of white head cabbage (Brassica oleracea convar. capitata var. alba L.) represent a significant (40%) discharged fraction of cabbage crops, plowed after heads harvest or used as compost or to feed animals. Waste cabbage leaves constitute also an interesting source of bioactive compounds that can be recovered and used as food additives. To improve the value of the cabbage waste fraction, the removed outer leaves were treated with short-term low-doses of UV radiation to test if the enhancement of bioactive phytochemicals could be achieved. Cabbage leaves were irradiated by a single TL 100W/12 RS UVB Broadband lamp (Philips) in a storage room at 17 °C. A sodium white lamp provided a PPFD of about 20 µmol m-2 s-1 at the samples surface. The UVB treatment, with irradiance of 0.5 W m-2, was applied continuously 12 hours per day, for a total of 3 days. The effect of the UVB treatment in increasing leaf phenolics was monitored non-destructively on the apical and basal part of each leaf by using daily the Dualex sensor, which can quantitatively estimate flavonols thanks to a previously performed calibration. Additional cabbage leaves covered by a UV-filtering plastic film (LEE 226) were kept in the same storage room and used as controls. At the end of the UV treatment, the apical and basal leaf parts were collected separately and freeze-dried for the following extraction and HPLC analysis of polyphenols. The UVB-treated leaves showed a large increase in the flavonols content in the basal part as estimated by the Dualex sensor, recording a 5.7-fold rise as average with respect to the same leaves measured before UVB exposure. Flavonols in the apical leaf part increased only by a factor of 1.4 as average. Changes in the control leaves were small, within 10%. HPLC analysis showed that total flavonols content in the UVB-treated leaves was higher than controls, by 40% and 90% in the apical and basal leaf parts, respectively. Flavonols concentrations after UVB irradiation were 4.0 ± 0.6 and 1.0 ± 0.1 mg g-1 DW for apical and basal regions respectively, while the respective values in the controls were 2.8 ± 0.4 and 0.5 ± 0.1 mg g-1 DW. Our present investigation indicates that postharvest treatment of waste cabbage leaves by UVB radiation can be a useful tool to add value to discharged vegetables and stimulate waste reutilization for the recovery of bioactive phytochemicals.
Valorization of waste cabbage leaves by UV postharvest treatments
Giovanni Agati;Lorenza Tuccio;
2017
Abstract
Outer green leaves of white head cabbage (Brassica oleracea convar. capitata var. alba L.) represent a significant (40%) discharged fraction of cabbage crops, plowed after heads harvest or used as compost or to feed animals. Waste cabbage leaves constitute also an interesting source of bioactive compounds that can be recovered and used as food additives. To improve the value of the cabbage waste fraction, the removed outer leaves were treated with short-term low-doses of UV radiation to test if the enhancement of bioactive phytochemicals could be achieved. Cabbage leaves were irradiated by a single TL 100W/12 RS UVB Broadband lamp (Philips) in a storage room at 17 °C. A sodium white lamp provided a PPFD of about 20 µmol m-2 s-1 at the samples surface. The UVB treatment, with irradiance of 0.5 W m-2, was applied continuously 12 hours per day, for a total of 3 days. The effect of the UVB treatment in increasing leaf phenolics was monitored non-destructively on the apical and basal part of each leaf by using daily the Dualex sensor, which can quantitatively estimate flavonols thanks to a previously performed calibration. Additional cabbage leaves covered by a UV-filtering plastic film (LEE 226) were kept in the same storage room and used as controls. At the end of the UV treatment, the apical and basal leaf parts were collected separately and freeze-dried for the following extraction and HPLC analysis of polyphenols. The UVB-treated leaves showed a large increase in the flavonols content in the basal part as estimated by the Dualex sensor, recording a 5.7-fold rise as average with respect to the same leaves measured before UVB exposure. Flavonols in the apical leaf part increased only by a factor of 1.4 as average. Changes in the control leaves were small, within 10%. HPLC analysis showed that total flavonols content in the UVB-treated leaves was higher than controls, by 40% and 90% in the apical and basal leaf parts, respectively. Flavonols concentrations after UVB irradiation were 4.0 ± 0.6 and 1.0 ± 0.1 mg g-1 DW for apical and basal regions respectively, while the respective values in the controls were 2.8 ± 0.4 and 0.5 ± 0.1 mg g-1 DW. Our present investigation indicates that postharvest treatment of waste cabbage leaves by UVB radiation can be a useful tool to add value to discharged vegetables and stimulate waste reutilization for the recovery of bioactive phytochemicals.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
