Effects of Infrared and Microwave Radiation on the Bioactive Compounds of Microalga Spirulina platensis after Continuous and Intermittent Drying

Abstract

Pharmaceutical, nutritional and food industries have recently become interested in the potential of Spirulina platensis, a kind of cyanobacterium with high levels of proteins, vitamins and bioactive compounds. Because of its high moisture, this microalga needs to be submitted to a preservation technique such as drying to be properly used. The aim of this work is to investigate the use of infrared and microwave radiation in the Spirulina platensis drying process. The experiments were performed in continuous and intermittent modes, evaluating different operating conditions for infrared and microwave drying, as well as their effects on the quality of the final product, expressed by the content of bioactive compounds (i.e., total phenolic, total flavonoid, citric acid and phycocyanin contents). The results proved that the use of electromagnetic radiation in the drying of spirulina is an interesting alternative for processing this material if performed under adequate operating conditions. The experiments carried out continuously at lower temperatures and powers and the combination between different temperatures and powers in the intermittent mode resulted in a final product with satisfactory levels of bioactive compounds and low operation times in comparison with conventional methodologies.

The Impact of Different Drying Methods on the Metabolomic and Lipidomic Profiles of Arthrospira platensis

“…This signal is a characteristic of carotenoids containing a keto group (as the only substituent on the β-ring) conjugated to the polyene chain. The fragment ion at m/z 135.1 was a characteristic of hydroxylated carotenoids, such as myxoxanthophyll (15), adonixanthin (20), antheraxanthin (18,21,26,30), diadinoxanthin (23) and zeaxanthin (24). The fragment ion at m/z 147.1 was observed in ketocarotenoids containing a hydroxyl group in carbon 3, (3 ′ ) and a keto group in carbon 4, (4 ′ ) in the β-ring such as adonirubin (10) and adonixanthin (20).…”

“…Despite the undeniable importance of drying in the industrial production of spirulina, this process strongly affects the quality of the final product; therefore, the technique and conditions should be carefully selected [18]. Freeze drying is considered to be the best method for preserving heat-sensitive products such as spirulina, but due to its high energy consumption it seems to be too expensive and less accessible for industrial purposes [19].…”