Optimization of aqueous extraction conditions for the recovery of phenolic compounds and antioxidants from lemon pomace

The aim of this study was to optimize the aqueous extraction conditions for the recovery of phenolic compounds and antioxidant capacity of lemon pomace using response surface methodology. An experiment based on Box–Behnken design was conducted to analyse the effects of temperature, time and sample-to-water ratio on the extraction of total phenolic compounds, total flavonoids, proanthocyanidins and antioxidant capacity. Sample-to-solvent ratio had a negative effect on all the dependent variables, while extraction temperature and time had a positive effect only on TPC yields and ABTS antioxidant capacity. The optimal extraction conditions were 95 oC, 15 min, and a sample-to-solvent ratio of 1:100 g/ml. Under these conditions, the aqueous extracts had the same content of TPC and TF as well as antioxidant capacity in comparison with those of methanol extracts obtained by sonication. Therefore these conditions could be applied for further extraction and isolation of phenolic compounds from lemon pomace.

Enhancing the total phenolic content and antioxidants of lemon pomace aqueous extracts by applying UV-C irradiation on the dried powder

Several studies have shown that UV-C irradiation promotes the bioactive compounds and antioxidants of fresh fruits and vegetables. The aim of this study was to apply UV irradiation in lemon pomace dried powder for enhancing its phenolic content and antioxidant properties, thus more bioactive compounds should be available for extraction and utilization. Lemon pomace dried powder was placed above the UV lamp and treated with dosages of 4, 19, 80 and 185 kJ m-2, while untreated powder was used as a control. UV-C irradiation significantly affected the total phenolic content, total flavonoid content, proanthocyanidins and antioxidant capacity measured by CUPRAC and FRAP of the lemon pomace dried powder, while it did not affect the vitamin C content. UV-C irradiation of 19 kJ m-2 resulted in 19% higher total phenolic content than the control, while UV-C irradiation of 180 kJ m-2 resulted in 28% higher total flavonoid content than the control. The antioxidant capacity was reduced when UV-C irradiation more than 4 kJ m-2 was applied. The results of this study indicate that UV-C treatment has the potential to increase the extraction of bioactive compounds of lemon dried pomace at relatively high dosages.