Ultrasonic unit

Carotenoids were extracted from the tomato peels applying the protocol described by Bunea et al. [17 (link)]. Briefly, a mixture of methanol/ethyl: acetate/petroleum: ether (1:1:1, v/v/v) was used to extract total carotenoids from each powder sample (1 g). Falcon tubes containing the sample together with 10 mL solvent was placed in an ultrasonic unit (Elma Schmidbauer GmbH, Singen, Germany) for 10 min, centrifuged at 11,000 RPM and filtrated. The remained residue was re-extracted two more times by applying the same protocol. The extracts were collected in a separation funnel and were successively washed with sodium chloride solution (15%) and diethyl ether. The organic phase (upper layer), enclosing the targeted carotenoids, was dried over anhydrous sodium sulphate and the solvent was removed by a rotary evaporator (Rotavapor R-124, Buchi, Flawil, Switzerland) at 35 °C.

Ultrasound assisted extraction (UAE) was applied to recover carotenoids from the tomato peels due to the advantages related to processing time and to the possibility of using low processing temperatures in recovery of heat-sensitive compounds like carotenoids. The samples (0.5 g tomato peels from both processing lines) were placed in Falcon tubes with 5 mL mixture of methanol/ethyl: acetate/petroleum: ether (1:1:1, v/v/v), underwent sonication in an ultrasonic unit (Elma Schmidbauer GmbH, Singen, Germany) with an ultrasonic power of 60 W/g at 37 kHz frequency for 10 min and were centrifuged for separation 5 min at 11,000 rpm [29 (link)]. The supernatant was collected in a separation funnel and the pellet was re-extracted two more times by the same procedure. The collected extracts were washed successively with sodium chloride solution (15%) and diethyl ether. The organic phase, containing the targeted carotenoids, was dried over anhydrous sodium sulphate and the solvent was evaporated by a rotary evaporator (Rotavapor R-124, Buchi, Flawil, Switzerland) at 35 °C and further analyzed by HPLC with a diode-array detector (DAD).