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

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.

Improving the Commercial Value of the 'Calçot' (Allium cepa L.) Landrace: Influence of Genetic and Environmental Factors in Chemical Composition and Sensory Attributes.

Landraces are considered valuable for their close ties to local cultures, adaptation to low inputs, and quality. 'Calçots' are the immature floral stems of second-year sprouts of onions from the 'Blanca Tardana de Lleida' landrace. 'Calçots' grown in their traditional area of cultivation have been awarded Protected Geographic Indication (PGI) 'Calçot de Valls' from the European Union. Despite annual sales of about €15 million, 'calçot' germplasm and cultivation methods are under-researched. This study aimed to estimate the influence of genetic and environmental factors in the chemical and sensory characteristics of 'calçots' to enable strategies to improve their commercial value to be devised. To this end, we tested the landrace and three new, more productive varieties derived from the landrace in experiments conducted over two seasons in six locations (within and outside the PGI zone), using two planting dates and two harvesting times. The results point to a major environmental influence in the quality of 'calçots.' The analysis of variance found all factors related with environmental influence were significant in most chemical traits considered (dry matter content, soluble solids content, pH, titratable acidity, and ash content), while the variety factor was significant only for titratable acidity. In sensory analyses, the variety factor and all the environmental factors had significant effects in all sensory traits recorded (sweetness, fiber perception, and off-flavors). In both chemical and sensory traits, most significant interactions involved the environmental factors. The negative correlation found between sweetness and fiber perception and off-flavors suggests that additional selection can bring 'calçots' closer to the sensory ideotype. Although clearly more productive, the new 'calçot' varieties maintain the chemical composition and sensory value of the landrace. Thus, fine-tuning the cultivation and/or breeding of the landrace for both yield and quality seem viable approaches to obtaining better commercial products.

Determination of chemical properties in 'calçot' (Allium cepa L.) by near infrared spectroscopy and multivariate calibration.

'Calçots', the immature floral stems of second-year onion resprouts, are an economically important traditional crop in Catalonia (Spain). Classical approaches to evaluating the chemical properties of 'calçots' are time consuming and expensive; near-infrared spectroscopy (NIRS) may be faster and cheaper. We used NIRS to develop partial least square (PLS) models to predict dry matter, soluble solid content, titratable acidity, and ash content in cooked 'calçots'. To guarantee the robustness of the models, calibration samples were grown and analyzed in a first season (2014-15) and validation samples in a second season (2015-16). NIRS on puree spectra estimated dry matter and soluble solid content with excellent accuracy (R2pred = 0.953, 0.985 and RPD = 4.571, 8.068, respectively). However, good estimation of titratable acidity and ash content required using ground dried puree spectra (R2pred = 0.852, 0.820 and RPD = 2.590, 1.987, respectively). NIRS can be a helpful tool for 'calçots' breeding and quality control.