Dane Bicanic,1,2 Ruud Cuypers,1 Svjetlana Luterotti,3 Maja Šporec,1 Angela Zoppi4 and Jasminka Vugec3
1Laboratory of Biophysics, Agrotechnology and Food Sciences, Wageningen
University, Dreijenlaan 3,
6703 HA Wageningen, The Netherlands
2Faculty of Food Technology and Biotechnology, University of Zagreb, Pierotijeva
6, Zagreb, Croatia
3Faculty of Pharmacy and Biochemistry, University of Zagreb, Ante Kovačića 1,
Zagreb, Croatia
4European Laboratory for Non-linear Spectroscopy, LENS, University of Florence,
via Nello Carrara 1, Sesto Fiorentino, Italy
* Corresponding author: E-mail: dane.bicanic@wur.ml
Abstract
Light emitting diode (LED) combined with the concept of optothermal window (OW)
is proposed as a new approach
(LED-OW) to detect lycopene in a wide range of tomato-based products (tomato
juice, tomato ketchup, tomato passata
and tomato puree). Phytonutrient lycopene is a dominant antioxidant in these
products while beta-carotene is present in
significantly lower quantities. Therefore for all practical reasons the
interfering effect of beta-carotene at 502 nm analytical
wavelength can be neglected. The LED-OW method is low-cost and simple, yet
accurate and precise. The major attributes
of the new method are its rapid speed of response and the fact that no
preparation whatsoever of the sample is
needed before the analysis. The lycopene found in tomato products studied here
varies from 8 mg/100 g to 60 mg/100 g
fresh product. Results obtained by LED-OW method were compared to the outcome of
conventional, time consuming
spectrophotometric methods and the correlation was very good (R ≥ 0.98).
Precision of the LED-OW instrumental setup
ranged from 0.5 to 7.4%; the RSD achieved for lycopene-richest samples (≥ 40
mg/100 g) did not exceed 1.7%. Repeatability
of analysis by LED-OW was found to vary between 0.7 and 7.1%.
Keywords: Lycopene, LED, optothermal window, tomato products