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Nutritional values of raw and cooked ‘calçots’ (Allium cepa L. resprouts), an expanding crop

Sans, Silvia, Bobo, Gloria, Zudaire, Lorena, Lafarga, Tomás, Sabaté, Josep, Casals, Joan, Simó, Joan
Journal of the science of food and agriculture 2019 v.99 no.11 pp. 4985-4992
Allium cepa, antioxidant activity, ash content, bulbs, flavonoids, heat, in vitro digestion, intestines, landraces, markets, minerals, nutritive value, onions, roasting, sweetness
BACKGROUND: ‘Calçot’ is the Catalan name for the immature floral stems of second‐year onion resprouts of the Blanca Tardana de Lleida (BTL) landrace. Highly appreciated for their sensory attributes, these resprouts are typically consumed after roasting on an open fire. Now new preparations are appearing, helping to expand the market for ‘calçots’. This study aimed (i) to compare the nutritional and sensory characteristics of BTL ‘calçots’ versus other onion varieties; (ii) to analyze the effects of cooking and / or in vitro gastrointestinal digestion on the nutritional properties of ‘calçots’; and (iii) to determine the influence of the environment on the antioxidant properties of ‘calçots’. RESULTS: The nutritional and sensory characteristics of both raw and cooked ‘calçots’ differed between varieties, with the exception of some minerals. Flavonoid content decreased by 85% during cooking, and total phenolic content decreased by 30%. By contrast, antioxidant activity increased after cooking. Most traits had a nonlinear response to heating, and differences between varieties generally decreased after cooking. Location also had a strong effect on antioxidant activity. In vitro digestion of cooked ‘calçots’ sharply decreased antioxidant activity after the intestinal phase. The only significant genotypic correlation between sensory and nutritional quality was the correlation between sweetness and ash content (R = −0.97). CONCLUSION: Cooked BTL ‘calçots’ are within the limits of the onion domain for nutritional properties, and the variability reported for onion bulbs is also present in resprouts. The effects of the environment, cooking, and in vitro digestion clearly overlap the genetic effects. © 2019 Society of Chemical Industry