Optimization of microwave-assisted extration of phenolic compounds from tomao by full factorial design coupled with response surface methodology

Tomato (Lycopersicon esculentum Mill.), apart from being a functional food rich in carotenoids, vitamins and minerals, is also an important source of phenolic compounds [1 ,2]. As antioxidants, these functional molecules play an important role in the prevention of human pathologies and have many applications in nutraceutical, pharmaceutical and cosmeceutical industries. Therefore, the recovery of added-value phenolic compounds from natural sources, such as tomato surplus or industrial by-products, is highly desirable. Herein, the microwave-assisted extraction of the main phenolic acids and flavonoids from tomato was optimized. A S-Ieve! full factorial Box-Behnken design was implemented and response surface methodology used for analysis. The extraction time (0-20 min), temperature (60-180 "C), ethanol percentage (0-100%), solidlliquid ratio (5-45 g/L) and microwave power (0-400 W) were studied as independent variables. The phenolic profile of the studied tomato variety was initially characterized by HPLC-DAD-ESIIMS [2]. Then, the effect of the different extraction conditions, as defined by the used experimental design, on the target compounds was monitored by HPLC-DAD, using their UV spectra and retention time for identification and a series of calibrations based on external standards for quantification. The proposed model was successfully implemented and statistically validated. The microwave power had no effect on the extraction process. Comparing with the optimal extraction conditions for flavonoids, which demanded a short processing time (2 min), a low temperature (60 "C) and solidlliquid ratio (5 g/L), and pure ethanol, phenolic acids required a longer processing time ( 4.38 min), a higher temperature (145.6 •c) and solidlliquid ratio (45 g/L), and water as extraction solvent. Additionally, the studied tomato variety was highlighted as a source of added-value phenolic acids and flavonoids.

Flowers of Gomphrena globosa L. as an alternatve source of betacyanins: optimization of the extraction using response surface methodology

Betacyanins are betalain pigments that display a red-violet colour which have been reported to be three times stronger than the red-violet dye produced by anthocyanins [1]. The applications of betacyanins cover a wide range of matrices, mainly as additives or ingredients in the food industry, cosmetics, pharmaceuticals and livestock feed. Although, being less commonly used than anthocyanins and carotenoids, betacyanins are stable between pH 3 to 7 and suitable for colouring in low acid matrices. In addition, betacyanins have been reported to display interesting medicinal character as powerful antioxidant and chemopreventive compounds either in vitro or in vivo models [2]. Betacyanins are obtained mainly from the red beet of Beta vulgaris plant (between I 0 to 20 mg per I 00 g pulp) but alternative primary sources are needed [3]. In addition, independently of the source used, the effect of the variables that affect the extraction of betacyanins have not been properly described and quantified. Therefore, the aim of this study was to identifY and optimize the conditions that maximize betacyanins extraction using the tepals of Gomphrena globosa L. flowers as an alternative source. Assisted by the statistical technique of response surface methodology, an experimental design was developed for testing the significant explanatory variables of the extraction (time, temperature, solid-liquid ratio and ethanolwater ratio). The identification was performed using high-performance liquid chromatography coupled with a photodiode array detector and mass spectrometry with electron spray ionization (HPLC-PDAMS/ ESI) and the response was measured by the quantification of these compounds using HPLC-PDA. Afterwards, a response surface analysis was performed to evaluate the results. The major betacyanin compounds identified were gomphrenin 11 and Ill and isogomphrenin IJ and Ill. The highest total betacyanins content was obtained by using the following conditions: 45 min of extraction. time, 35•c, 35 g/L of solid-liquid ratio and 25% of ethanol. These values would not be found without optimizing the conditions of the betacyanins extraction, which moreover showed contrary trends to what it has been described in the scientific bibliography. More specifically, concerning the time and temperature variables, an increase of both values (from the common ones used in the bibliography) showed a considerable improvement on the betacyanins extraction yield without displaying any type of degradation patterns.