ENVIRONMENTAL EFFECTS IN TROPEA RED ONION FLAVONOIDS COMPOSITION

INTRODUCTION This study discusses some of the environmental parameters (including temperature and rainfall patter influence the content of flavonoid content in red onion (Allium cepaL.). Onion bulbs are good sou phenolic compounds which are highly variable, depending on the cultivar, production technique, environ conditions. Some authors (Patil et al. 1995; Hertog et al. 1992, A.S. Rodrigues et al. 2011) shown t temperature and rainfall have a stronger influence on flavonoid concentration and above all on qu (3,3’,4’,5,7-pentahydroxyflavone), the major flavonoid of onion, than soil factors or plant maturity and a sig differences in quercetin content between harvest of different years. In this study quercetin variability in different local ecotypes of Tropea red onion PGI, from two different years of production (2011 and 201 been evalutated. MATERIALS AND METHODS Samples were collected from the local cultivar member of the PGI Consortium. Environmental data all experimental years were obtained from the National Agrometeorological Database. Flavonoids ha determined according Gennaro et al. (2002). RESULTS AND DISCUSSION Total and individual flavonoids were determinated. Seven flavonols were identified: quercetin 7,4’-diglu quercetin 3,4’-diglucoside, isorhamnetin 3,4’-diglucoside, quercetin 3-rutinoside (rutin), quercetin 4’-glu isorhamnetin 4’-glucoside and quercetin. Both total and individual flavonoids levels varied significantly the years, with higher levels of total flavonols in 2012, probably related to the very hot and global radiation the growing season. CONCLUSION The results, in good accordance with Robrigues et al. (2011), showed that the environmental conditio enhance secondary metabolism, influencing flavonoids profiles of red onion. This aspect play an importan in defining of quality and authenticity parameters of a product protected by a Community trade mark.