Postharvest Storage Systems Affect Phytochemical Content and Quality of Traditional Portuguese Onion Cultivars

Poscosecha, postcosecha, postharvest, onion, cebolla, pungencia, pungency, antioxidants, antioxidants Onion (Allium cepa) cultivars are generally classified based on color, pungency and use and differ widely in their keeping quality. In addition to sensory characteristics, consumers value the nutritional and health effects, particularly the antioxidants potential of this vegetable. In the traditional onion growing region of P?voa de Varzim, Northwestern Portugal, landrace cultivars are harvest in July and stored in traditional non-refrigerated clamps in the field for up to 5 (white onion) or 7 months (red onion).The aim of this work was to assess the effect of two post-harvest systems, refrigerated storage at 2 ?C and traditional nonrefrigerated clamps, on phytochemicals and physic-chemical quality of two Portuguese landrace cultivars of onions (?Branca da P?voa? and ?Vermelha da P?voa?). Flavonoid composition, dry weight, pH, soluble solids content (SSC), pungency and firmness were measured at harvest and following 3 and 6 months in storage. The red onion was more pungent and had higher dry matter, SSC, and about twice total flavonol levels than the white cultivar. Results from two consecutive years in 2004 and 2005 showed that pH and pungency increased during storage, at a higher rate in the refrigerated system. Flavonols also increased significantly during storage in both cultivars. In contrast, SSC, and firmness tended to decrease. Red onion stored in field clamps reached higher levels of flavonols (64% maximum, at 6-months of storage in 2004) than refrigerated onions (40% maximum). In white onions the flavonol increase was also higher in field storage (60% increase, at 5-months of storage in 2005). These results suggest that storage at fluctuating ambient temperatures can positively affect flavonol metabolism, while maintaining the flavonols profile. Onion storage improved the content on flavonoids and pungent compounds, potentially improving the health benefits of onion consumption. Complete list of authors and source:Postharvest Storage Systems Affect Phytochemical Content and Quality of Traditional Portuguese Onion CultivarsRodrigues, A. S.1; Almeida, D. P. F.2; Garc?a-Falc?n, M. S.3; Simal-G?ndara, J.3; P?rez-Gregorio, M. R.31Escola Superior Agr?ria, Instituto Polit?cnico de Viana do Castelo, Mosteiro de Refoios, Refoios do Lima, 4990-706, Ponte de Lima, Portugal2Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal3Faculty of Food Science and Technology, Ourense Campus, University of Vigo, E-32004 Ourense, Spain International Horticulture Congress, Lisboa 2010, ISHS The picture belongs to the article Armazenamento de cebolas tradicionais da P?voa de Varzim: efeito na qualidade e fitoqu?micos funcionais ?