Abstract
The potential of saffron flowers as a source of polyphenols, and in particular anthocyanins, for the extraction of bioactive compounds and the production of a cyanic colorant was analyzed. A microwave pretreatment, prior to the conventional solid–liquid extraction process, was proposed as a feasible intensification step. The effectiveness of microwave pretreatment was assessed in terms of increased yield and improved quality of the final product. The operational variables studied were the pretreatment temperature (60–120 °C) and the solid–liquid ratio (0.30–0.50 g/mL). It was found that the addition of the microwave pretreatment to the conventional process allowed one to reduce extraction time by up to 12 times and to greatly improve the characteristics of the final product, using microwave energy densities as low as 0.16–0.54 kJ/mL. The extract quality was evaluated in terms of polyphenol richness (25% increase), product composition (80% of the anthocyanins was delphinidin), antioxidant capacity (boosted by the pretreatment) and color (variations in red and blue hue depending on conditions). To conclude, a microwave pretreatment in which the material is heated to a temperature of 65 °C with a solvent ratio of 0.30 g/mL was selected as the optimum to maximize process efficiency and product quality.
Highlights
Extracts from natural products have drawn the attention of food industry as an alternative to synthetic complements due to the antioxidant properties and health benefits of their main components: polyphenols [1,2]
The experimental conditions used to carry out the conventional solid–liquid extractions, both in the control experiments and to complete the extraction in the experiments with microwave pre-treatment, were selected based on the analysis of three inputs: (1) the optimal conditions reported in the literature and listed in Table 2 for conventional extraction processes; (2) industrial and scaleup aspects, such as solvent consumption, extract concentration or the use of saffron flowers without any conditioning; and (3) some preliminary experimental work, presented below in Figure 1, to evaluate the influence of the solid–liquid ratio on extraction efficiency
The use of a microwave pretreatment, consisting of a short but intense heating step followed by rapid cooling before conventional solid–liquid extraction, has been shown to accelerate the extraction of polyphenols while minimizing their degradation
Summary
Extracts from natural products have drawn the attention of food industry as an alternative to synthetic complements due to the antioxidant properties and health benefits of their main components: polyphenols [1,2]. Saffron biofloral residues have recently been nominated as an outstanding source of polyphenols, especially anthocyanins, due to their great potential and availability [3,4]. A rich polyphenolic extract stemming from saffron flowers would be highly valued in the food industry as a natural colorant. In the case of saffron flowers, it is their high content of antioxidant compounds that makes them a convenient food ingredient [9], and their composition in minerals, dietary fiber, sugars, anions and organic acids [10,11]. Blue colorants are rare in nature [7]
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