The storage stability of spray-dried Nannochloropsis oculata protein (NP) powder was evaluated over six months at -30, 4, 25, and 45°C under sealed conditions that prevented moisture exchange and minimised gas transfer. Physicochemical and functional properties, including moisture content, water activity, colour, particle size distribution, solubility, water and oil absorption capacities, foaming behaviour, emulsifying properties, and gelation characteristics, were systematically assessed. Storage at -30 and 4°C preserved all evaluated properties throughout the study, with solubility maintained at 81.8–82.3%, emulsifying activity index at 125–128 m 2 /g, emulsion stability index at 105–107 days, and particle size remaining close to 13.5 µm. At 25°C, the powder remained relatively stable for the first four months, after which measurable declines in solubility, emulsifying properties, and gelation performance were observed, indicating a practical shelf life of approximately 4–5 months. In contrast, storage at 45°C caused substantial deterioration across all measured properties. Solubility decreased to 50.2%, particle size increased to 1,580 µm because of extensive aggregation, emulsifying activity index declined to 52 m 2 /g, and emulsion stability index dropped from 107 to 4 days. These findings indicate that refrigerated or frozen storage is optimal for preserving NP powder for at least six months, whereas ambient storage should be limited to approximately four months. These results provide a basis for storage temperature recommendations and shelf-life management of microalgal protein powders intended for food applications.
Le et al. (Fri,) studied this question.