Rapid, accurate, and direct determination of total lycopene content in tomato paste

Abstract

Lycopene that imparts red color to the tomato fruit is the most potent antioxidant among carotenes, an important nutrient and also used as a color ingredient in many food formulations. Since cooked and processed foods derived from tomatoes were shown to provide optimal lycopene boost, products such as paste, puree, juice, etc. are nowadays gaining popularity as dietary sources. The analysis of lycopene in tomato paste ͑partially dehydrated product prepared by vacuum concentrating tomato juice͒ is carried out using either high pressure liquid chromatography ͑HPLC͒, spectrophotometry, or by evaluating the color. The instability of lycopene during processes of extraction, etc., handling, and disposal of organic solvents makes the preparation of a sample for the analysis a delicate task. Despite a recognized need for accurate and rapid assessment of lycopene in tomato products no such method is available at present. The study described here focuses on a direct determination of a total lycopene content in different tomato pastes by means of the laser optothermal window ͑LOW͒ method at 502 nm. The concentration of lycopene in tomato paste ranged between 25 and 150 mg per 100 g product; the results are in excellent agreement with those obtained by spectrophotometry. The time needed to complete LOW analysis is very short, so that decomposition of pigment and the formation of artifacts are minimized. Preliminary results indicate a good degree of reproducibility making the LOW method suitable for routine assays of lycopene content in tomato paste.

On the photoacoustic, photothermal and colorimetric quantification of carotenoids and other phytonutrients in some foods: a review

“…The first publication on the PT study of carotenoids described the application of an OW sapphire detector for the quantification of lycopene in six tomato pastes [14]; the excitation of the carotenoids was achieved with the c.w. argon-ion laser emitting 20 mW at 502 nm.…”

Optothermistor as a Breakthrough in the Quantification of Lycopene Content of Thermally Processed Tomato-Based Foods: Verification versus Absorption Spectrophotometry and High-Performance Liquid Chromatography

“…The first research study, the outcome of which indicated the intrinsic feasibility of the PT methods for direct detection of lycopene, described the application of the optothermal window (OW) concept to several tomato purée concentrates (7). Optimization of the experimental setup and improved design of the OW sensor enabled the extension of the measuring range of the OW technique to lower concentrations.…”

Solving the Spectroscopy Interference Effects of β-Carotene and Lycopene by Neural Networks

“…For this reason, the necessity for a reliable and rapid analysis method for carotenoid quantification in vegetable products is recognized in the literature (5,6). Carotenoid analysis in food products may be done by different analytical methods such as high-performance liquid chromatography (HPLC), spectrophotometry, or color evaluation (7,8).…”