Abstract
Saffron is a well-known spice, produced for a long time, mainly in the Mediterranean area. In the last few years, saffron has been seen as an alternative crop for the diversification of agricultural production and a new source of income, due to its high price, including in Alpine areas. Apart from the spice, constituted by the stigmas, saffron production provides a high amount of fresh tepals, which have so far been considered agricultural waste. Recently, studies on the composition of saffron tepals have been revealing their potential as a rich source of bioactive compounds. In this study, we evaluated the productive traits and the quality of the spice of saffron cultivated in open fields in the north western Italian Alps, for 2 years. In addition, in order to valorize the crop residues, we evaluated the bioactive compound content in tepals by using maceration and ultrasound assisted extraction with different rates of water and methanol as solvents. Higher yields in spice were obtained in the second year of cultivation. However, in both years, the spice had a high quality (ISO 3632), and a very high total phenolic content and antioxidant activity. Thirteen bioactive compounds were identified, including flavonols, cinnamic acids, benzoic acids, catechins, and vitamin C, with few differences between sites and year of cultivation. In tepals, the extraction method and the solvent used influenced the evaluated parameters, i.e., total phenolics and total anthocyanins content, antioxidant activity, and the amount of the four phenolic compounds found (hyperoside, rutin, ellagic acid, and epicatechin). Overall, this study revealed that both saffron spice and its by-product, the fresh tepals, produced in the north western Italian Alps can be considered a source of bioactive compounds with nutraceutical properties, having an antioxidant capacity that is often similar or higher than those of some vegetables and fruits.
Highlights
Saffron spice consists of dried red stigmas coming from the flowers of Crocus sativus L., an autumn-flowering geophyte
Results were expressed as mg 100 g−1 of dry weight (DW) for stigmas and mg 100 g−1 of fresh weight (FW) for tepals
Dastranj et al [48], on the base of a dataset from an eight-year open field saffron experiment conducted in Iran, showed that saffron yield cannot be predicted with adequate accuracy by using the annual rainfall
Summary
Saffron spice consists of dried red stigmas coming from the flowers of Crocus sativus L., an autumn-flowering geophyte. Spain, Morocco, India, Greece, and Italy are the major saffron producing countries in the world. Annual production exceeds 220,000 kg and circa 110,000–165,000 flowers are needed to produce 1 kg of dried stigmas [1,2]. The intensive hand labour required for flower picking and stigma separation make the saffron the world’s highest-priced spice, and for this reason named as “red gold” [3]. Saffron flower induction is a complicated mechanism directly related to pedoclimatic conditions and field management [3]. As in most geophyte plants, both seasonal and daily thermoperiodism are Agronomy 2020, 10, 1473; doi:10.3390/agronomy10101473 www.mdpi.com/journal/agronomy
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