Fresh Spirulina Biomass: Quality Deterioration, Microbiological Stability, and Shelf-Life Assessment

The stability of fresh Spirulina biomass was investigated performing microbiological and quality analyses for refrigerated and ambiently stored (4°C, 10°C, and 20°C) samples. During a period of 36 days, Spirulina samples were evaluated at different time intervals, in terms of color, pH, total solids, microbial load, moisture content, total and autolysis-induced released C-phycocyanin, lipid oxidation, and sensory characteristics (color, odor, and viscosity). According to the obtained results, a temperature-dependent autolysis of Spirulina cells was observed during storage, leading to a corresponding gradual increase in the concentration of total dissolved solids (by 48.7%-67.9%) in the growing medium. This phenomenon led to a consequent release of C-phycocyanin, causing significant biomass color changes (lightness decrease, redness, and blueness increase) (p < 0.05). The concentration in C-phycocyanin, chlorophyll, and carotenoids remained unaffected during the studied period (p > 0.05). Secondary lipid oxidation products were increased by 83.7%-91.1% with the maximum value of 2.104 ±  0.010 mg malondialdehyde (MDA)/kg of wet biomass to be observed after 36 days of storage at 20°C. Higher storage times and temperatures led to increased values in the total viable count (TVC) (p < 0.05). The sensory acceptability limit of fresh Spirulina (non-characteristic off-odor detected) corresponded to a TVC of approximately 6.0 log CFU/g. At this point, thiobarbituric acid reactive substances (TBARs) values were observed to remain within ∼1.0 mg MDA/kg, indicating limited lipid oxidation during storage. On the basis of the TVC data and Baranyi model, the shelf life was estimated as 8, 20, and 36 days for storage at 20°C, 10°C, and 4°C, respectively. PRACTICAL APPLICATIONS: Fresh Spirulina biomass represents a promising ingredient for the development of high-value functional foods, beverages, and nutraceuticals. Unlike the dried form, fresh Spirulina retains its native pigments, proteins, and bioactive compounds with minimal structural degradation, offering superior nutritional and sensory properties. However, its high moisture content makes it highly perishable, posing challenges for handling, storage, and formulation in industrial applications. Understanding its shelf life and quality stability is therefore essential for the food industry to ensure safety, optimize preservation methods, and fully exploit its potential as a sustainable, natural, and nutrient-dense raw material for innovative product development.