engleski

Quantification of lycopene in processed tomato-based products using light-emitting device and the optothermal detector

Several epidemiological studies conducted on humans indicate the benefits of lycopene (antioxidant) intake. The evidence was found that teh intake of this carotenoid lowers the risk of contracting the cardiovascular and chronic diseases as well as of some cancers. The presence of lycopene in the tomato gives this product a specific, vibrant, deep red colour. Other nutritional sources of lycopene are watermelon, guava, papaya, rosehip, red grapefruit etc. It has been established that products derived from the thermally processed tomatoes are particularly rich in lycopene. In addition, the bioavailability of this beneficila antioxidant from the processed tomato-based foods is higher than that from raw tomatoes. The generally recognized importance of lycopene requires the need for its accurate quantitation. The most widely used approach to determine lycopene is that of the wet chemistry-the HPLC and spectrophotometry are both slow, cumbersome and costly due to a need for extraction of the pigment prior to the actual analysis. To shorten the analysis time and to reduce the investment costs, different attempts have been made to explore the correlation between the lycopene content of tomatoes tomato-based products determined by the wet chemical methods and the colorimetric indices such as L*, a*, b*, hue and chroma. This paper describes the experimental study the main objective of which was to investigate the prospects for the construction of a simple, practical, compact and inexpensive instrument to quantify lycopene in a variety of tomato-based foods. The selection of test samples include tomato ketchup, tomato juice, tomato purees and paste. The performance of the newly proposed technique that makes the use of the low-cost LED source, mechanical chopper, the pair of lenses and the optothermal window (OW) as detector was evaluated at 502 nm. At this analytical wavelenght, the absorption of lycopene is high while at the same time the interference of beta-carotene is minimized. The HPLC method served as a golden standard reference. The outcome of the study indicates the proportionality between the magnitude of the OW signal and the lycopene content of different tomato-based foods. The new approach is very fast, obviates the extraction and requires only a single, initial calibration step against the HPLC values. The reproducibility of OW measurements is very good. As such, the new approach to the detection of lycopene may prove a practical tool to tomato processors and for the quality control purposes.

lycopene; tomato products; HPLC; optothermal window

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