Effect of PEF pre-treatment and extraction temperature on the recovery of carotenoids from tomato wastes

In this work, the influence of pulsed electric fields (PEF) pre-treatment and extraction temperature on the recovery of carotenoid compounds from tomato peels, achieved after peeling of steam blanched whole tomato fruits, was investigated. PEF pre-treatments were carried out at different field strengths (E = 0.5–5 kV/cm) and total specific energy input (WT = 0.5-20 kJ/kg). The cell disintegration index (ZP) was used to identify the optimal PEF processing conditions for the pre-treatment of tomato peels before the extraction with acetone at different temperatures (20-50°C). Extracts from untreated and PEF treated samples were analysed in terms of content and composition of carotenoids and antioxidant power. According to the ZP values, an energy input of 5 kJ/kg was enough for reaching the maximal permeabilization of tomato peel tissues at any investigated field strength. At this optimal energy input, only the extracts obtained from PEF pre-treated peels at 5 kV/cm showed a significantly higher total carotenoids content (47.3%) and antioxidant power (68%), as compared to the untreated samples. Regardless of the application of a PEF pre-treatment, the increase of the extraction temperature did not lead to further intensification in the recovery yield of total carotenoids in the extracts. Moreover, HPLC analyses revealed that lycopene was the main carotenoid extracted and no degradation/isomerization phenomena occurred. Results obtained in this work demonstrated that the PEF pretreatment of tomato processing wastes coupled with room or moderate extraction temperature could add new value to the tomato processing chain, improving economic performances and decreasing waste problems.