Green extraction of carotenoids from tomato by‑products using sodium dodecyl sulphate

Abstract

Tomato peel by-products contain high levels of lycopene, which has traditionally been extracted using organic solvents. This research focuses on the optimisation of a sustainable method to obtain a lycopene-rich extract using the biodegradable anionic surfactant sodium dodecyl sulphate (SDS). A Plackett–Burman experimental design was used to investigate the effect of seven factors on the extraction of carotenoids from tomato peels using sodium dodecyl sulphate (SDS volume and concentration, homogenisation intensity and time, sonication phase, extraction time and ultracentrifugation intensity). Based on the responses of total carotenoid extraction, the SDS volume, the use of ultrasound and the extraction time significantly influenced the extraction yield and were selected for optimisation using a Box–Wilson experimental design. The final green extraction protocol (1 g sample+11.9 ml SDS 0.3%, homogenisation at 13,500 rpm for 2 min, ultrasound phase, agitation for 8.2 h and ultracentrifugation) was selected after quantification of total carotenoids by UV–VIS and HPLC-DAD. Finally, we used nuclear magnetic resonance to demonstrate a high lycopene purity in the carotenoid extract obtained. Furthermore, using transmission electron microscopy, we observed the presence of intact chromoplasts in the extract, protecting the carotenoids from the exposure to external agents. Thus, this work reports an optimised method for the sustainable extraction of carotenoids and demonstrates the viability of the degradable solvent SDS for the extraction of liposoluble bioactive compounds, like carotenoids and mainly lycopene. The lycopene extract could be used for the technological and nutritional enrichment of new foods and/or the design of nutraceuticals.