Microwave-assisted extraction of lycopene in tomato peels: Effect of extraction conditions on all-trans and cis-isomer yields

Abstract

Lycopene is the primary carotenoid in tomato peels, a processing byproduct, and can be used as a natural color or bioactive ingredient. Unfortunately, extractions are inefficient as lycopene is extremely nonpolar and susceptible to degradation. As a rapid technique, microwave-assisted extraction (MAE) potentially offers efficient lycopene recovery. Thus, the objectives of this research were to: 1) optimize MAE of lycopene from tomato peels and 2) evaluate the effect of treatment on all-trans and isomer yields. Response surface methodology (RSM) was employed to optimize lycopene extraction with solvent ratio solid-liquid ratios, microwave power, and delivered energy equivalents as factors. High performance liquid chromatography with a diode array detector (HPLC-DAD) was used for isomer separation and quantification. Optimum MAE conditions were determined as: 0:10 solvent ratio at 400 W with a yield of 13.592 mg/100 g of extracted all-trans-lycopene. RSM suggested that ethyl acetate was a better MAE solvent for lycopene recovery as compared to hexane, which overall extracted less lycopene. HPLC-DAD indicated that MAE significantly improved all-trans and total lycopene yields, while conventional extraction demonstrated higher proportions of cis-isomer yields. Additionally, electron micrographs showed that significant structural disruption occurred in MAE-treated samples, possibly allowing for the improved lycopene extraction.

Green extraction methods and environmental applications of carotenoids-a review

“…b-carotene and other carotenoids have been extracted via MAE in which hexane was chosen as a solvent due to its lower dielectric constant so that microwave energy is absorbed at a lower level 66. Lycopene was extracted quickly from tomato peels through MAE as the carotenoids are highly sensitive to heat and light so short duration of its extraction is advantageous for their extraction 67. A variety of 30 solvent mixtures have been used to extract carotenoids from powder of paprika (Capsicum annuum) by means of MAE.68a …”

Trends and Challenges in the Industrialization of Natural Colorants

“…In MAE, the moisture inside the cell is heated and its evaporation increases the porosity of the biological matrix, which in turn allows for better penetration of a solvent [58,59]. The elevated temperature also generally increases solubility and improves yield.…”

Processing, Valorization and Application of Bio-Waste Derived Compounds from Potato, Tomato, Olive and Cereals: A Review

“…In particular, the migration of lycopene into the extraction solvent is enhanced by superheating of the polar cellular components. Whereas the heat impact on non-polar components is limited by short treatment periods [230,231]. The extraction arises due to modifications in the cell structure, caused by electromagnetic waves [232].…”

“…On the other hand, some disadvantages have been reported e.g., additional filtration or centrifugation is required to remove solid residues. Moreover, the efficiency of microwaves might be influenced by applying non-polar or volatile target compounds [214,231,234].…”