Effect of ultrasounds and high pressure homogenization on the extraction of antioxidant polyphenols from lettuce waste

The possibility to exploit ultrasound (US) and high pressure homogenization (HPH) to obtain ethanolic antioxidant extracts from lettuce waste was studied. The application of US (400 W, 24 kHz) for 120 s led to polyphenol extraction yield (81 mu g/mL) and antioxidant activity (101 mu g TE/mL) significantly higher than those obtained by traditional solid-liquid extraction at 50 degrees C for 15 min. Despite the intense cell rupture effect, the application of HPH pre-treatments resulted in 25% lower phenolic yields as compared to US solely, possibly due to the 40% activation of polyphenoloxidase (PPO) upon HPH treatment. Industrial relevance: The waste generated by fresh-cut processing of lettuce poses environmental and economic issues to companies, leading to the need for alternative strategies for its management. US can be successfully exploited as time-saving extraction procedure for obtaining antioxidant extracts from lettuce waste.