Microwave-assisted extraction, encapsulation and bioaccesibility study of carotenoids from a by-product of the organic tomato industry

Abstract

Tomato (Solanum lycopersicum) is a widely consumed fruit in the world. In 2021, the annual production was 186 million tons of which 5% of discarded biomass was produced. This agro-residue has a huge potential, as tomato peel is rich in carotenoid content. This study focuses on the recovery of carotenoids from tomato industry agro-wastes, specifically peel and seeds. Firstly, a characterization was conducted, where the following parameters were quantified: total dietary fiber (49.95 ± 0.72 g/100g sample dried basis (DB)), mineral content (1255.6 mg K/100g sample DB, 205.6 mg Mg/100g sample DB, among others), total phenolic content (1.21 ± 0.15 mg GA/g sample DB), EC50 (1784.47 ± 30.49 µg/mL), Trolox equivalent antioxidant capacity (25.84 ± 1.20 µmol TE/g sample), and beta-carotene concentration (3.19 ± 0.23 mg beta-carotene/g sample DB) were quantified. A carotenoid profiling of the sample revealed high concentration of 5-cis-lycopene (1340.1 ± 15.6 µg all-trans-beta-carotene eq/g sample), 9-cis lycopene (1062.7 ± 12.8 µg all-trans-beta-carotene eq/g sample) and all-trans-beta-carotene (1246.4 ± 1.7 µg all-trans-beta-carotene eq/g sample). Microwave-assisted extraction (MAE) was employed as a green extraction method to optimize biomass-solvent ratio (BSR), extraction time (ET), and microwave power (MP) for achieving maximum recovery of carotenoids. A surface response methodology based on a Box-Behnken Design was used. The optimized extract (BSR 1:10 g:mL, ET 60s, and MP 283.84W) was microencapsulated using maltodextrin (MD) combined with either gum arabic (GA) or whey protein isolate (WP) as wall materials. Freeze-drying was utilized for capsule sealing. The properties of the encapsulates were characterized, including moisture content (0.99 ± 0.04% for MD:GA and 0.80 ± 0.07% for MD:WP), water activity (0.087±0.01 for MD:GA and 0.084 ± 0.01 for MD:WP), dissolution rate (140.4 1± 6.41 s for MD:GA and 86.49 ± 1.68 s for MD:WP), tapped density (0.48 ± 0.01 g/mL for MD:GA and 0.44 ± 0.01g/mL for MD:WP), drying yield (90.73 ± 3.34% for MD:GA and 89.73 ± 3.47% for MD:WP), and encapsulation efficiency (68.12 ± 1.42% for MD:GA and 74.55 ± 1.62% for MD:WP). Bioaccessibility studies for encapsulated extract revealed values of 27.68% ± 0.72 and 25.10% ± 0.04 for MD:GA and MD:WP, respectively. This research highlights the potential of tomato agro-wastes as a valuable source of bioactive compounds. The implementation of MAE and microencapsulation techniques demonstrates effective strategies for their recovery and preservation. These findings contribute to the valorization of tomato industry by-products and their potential application in functional food products.