Quality and safety of fresh Spirulina (Arthrospira platensis) maintained by bubbling plasma-activated air

Spirulina ( Arthrospira platensis ) is a blue-green alga valued for its protein, phycocyanin, and other bioactive compounds. However, its commercial outdoor cultivation makes it susceptible to microbial contamination, affecting both biomass productivity and quality. Additionally, most commercial Spirulina is sold in dried forms such as powder, flakes, and tablets, which can degrade these bioactive components. To address these issues, non-thermal techniques, such as cold plasma, offer a promising solution by effectively reducing microbial contamination while preserving product quality without the need for drying. This study investigated the potential of bubbling cold plasma-activated (BCPA) air through freshly grown Spirulina to reduce microbial contamination and maintain quality during storage. Spirulina grown in an outdoor paddle-wheel driven pond was harvested in paste form, resuspended in deionized water, treated with plasma-activated air and stored at 4 °C for 28 days. The treatment significantly reduced microbial contamination and maintained Spirulina biomass and pigment contents compared to untreated control. The cellular structure remained intact, and colour changes were minimal in the treated samples when compared to the controls. Moreover, the Spirulina suspension pH became acidic (pH = 4), and oxidation-reduction potential was significantly higher (>150 mV) in treated samples compared to controls throughout the storage period. The results demonstrate the potential for BCPA air to maintain the quality of fresh Spirulina. This finding may have significant applications in the Spirulina industry for offering customers fresh products rather than dried Spirulina. • Bubbling cold plasma-activated (BCPA) air significantly reduces microbial contaminants. • Biomass contents did not change significantly for 28 days post-treatment. • Cellular structure including phycocyanin remains stable with minimal colour changes. • Increased acidity and oxidation-reduction potential were observed. • BCPA air application can extend shelf life of fresh Spirulina suspension.