Detection of key factors in the extraction and quantification of lycopene from tomato and tomato products

The analytical process of lycopene extraction and photometrical determination was critically examined for raw tomato and processed tomato products by means of a 2 IV (15-10) Plackett-Burman experimental design in order to identify the key factors (KFs) involved. Fifteen apparent key factors (AKFs) reported in the literature were selected: sample weight (X1); volume of extraction solution (X2); antioxidant concentration (BHT, X3); neutralizing agent concentration (MgCO 3, X4); light presence during lycopene extraction (X5), homogenization velocity (X6) and time (X7), agitation time (X8), and temperature (X9) during the extraction process; water volume for separation of polar/nonpolar phases (X11); presence of inert atmosphere throughout the process (X12); time (X13), temperature (X14), and light presence (X10) during separation of phases and time delay for reading (X15). In general, higher lycopene concentrations in samples led to a higher number of key factors (KF). Thus, for raw tomato (lycopene range 1.22-2.29 mg/100 g) no KF were found, whereas for tomato sauce (lycopene range from 5.80 to 8.60 mg/100 g) one KF (X4) and for tomato paste (lycopene range from 35.80 to 51.27 mg/100 g) five KFs (X1, X2, X4, X11, and X12) were detected. For lycopene paste, X1 and X2 were identified as the KFs with the greatest impact on results, although in fact the X1/X2 ratio was the real cause. The results suggest that, with increased processing, the physical and chemical structure of lycopene becomes less important since the identified KFs explain almost 90% of variability in tomato paste but only 32% in raw tomato.