Tomato Solanum lycopersicum

Summary

Sample preparation

Tomato pomace was ground on a Robot Coupe rotary cutter, with blade speeds up to 28,000 rpm, to a particle size of 1 mm or below. Two tomato pulps — one home-grown, one shop-bought — were freeze-dried as thin slices and then milled the same way. Sea buckthorn pomace was prepared alongside as a comparison carotenoid source and extracted at 450 bar and 65 °C with 100 mL min⁻¹ CO₂ for 240 minutes (solvent-to-material ratio 69). Moisture content was determined gravimetrically for each material.

Extraction

Extraction ran on a lab-scale SuperEx SC-1000 SFE system with a single extraction vessel rated to 500 bar and 200 °C. Material was loaded in a steel basket fitted with 10 µm filters; the vessel was then sealed, heated to setpoint and pressurised. Once at temperature and pressure, extraction proceeded in dynamic flow-through mode at constant CO₂ flow, with the outlet held by an automatic back-pressure regulator.

All tomato runs used 450 bar and 65 °C. Pomace was extracted at 80 mL min⁻¹ CO₂ for 300 minutes, to a solvent-to-material ratio of 78; the freeze-dried pulps at 100 mL min⁻¹ for 300 minutes, to a ratio of 98. Extract was collected through an internal needle valve. Residue left on the separator walls was washed out with food-grade ethanol, which was then removed on a rotary evaporator.

To build the overall extraction curve, fractions were taken from the separator every 30 minutes during the pomace run.

Comparison method

A conventional Soxhlet extraction with chloroform was run in parallel at a solvent-to-material ratio of 25, for 8 hours or until the solvent ran colourless. The flask was covered with foil to prevent photodegradation of the carotenoids.

Analysis

Carotenoids were quantified by HPLC-DAD. A 10.0 ± 0.1 mg portion of extract was diluted to 1.0 ± 0.1 mg mL⁻¹ in 40:60 chloroform:acetone in an amber vial, shaken by hand for one minute and vortexed; 1 mL was then filtered through a 0.22 µm PTFE membrane into the analysis vial. Injection volume was 10 µL.

Separation used a Shimadzu i-Series LC-2050 3D with diode-array detection on a C18 column (250 × 4.6 mm, 5 µm) at 30 °C, eluted isocratically with isopropanol : acetonitrile : methanol : water at 52 : 39 : 5 : 4 (v/v) and 1.2 mL min⁻¹ over a 25-minute run. Lycopene was followed at 472 nm and β-carotene at 450 nm, each against external standards — 20–120 ppm for lycopene, 20–500 ppm for β-carotene.

Measured yields, compositions and chromatograms are reported in the full application note (PDF above).

At a glance

Plant material

Tomato — Solanum lycopersicum

Target compounds

Lycopene, β-carotene

Compound class

Pigments

Published

September 2024

Document

PDF, free download