Thermal damages in spray drying: Particle size-dependent protein denaturation using phycocyanin as model substrate

Abstract Protein denaturation during spray drying is critical for high-quality food powders. This study investigated the influence of particle size on protein denaturation using phycocyanin as a marker. The effect of particle size was investigated at three different air outlet temperatures, with the inlet air temperature held constant. For each temperature combination, different nozzles were utilized to obtain varying particle sizes. Denaturation increased with higher outlet air temperature and larger particle size, up to a size of 40 μm. This increase in denaturation with particle size was attributed to faster drying rates and the absence of denaturation once particles are dry. Particle size had a similar magnitude of effect as outlet air temperature. For larger particles, a plateau in denaturation was observed due to a prolonged constant drying rate regime. It can be assumed that conditions that retain phycocyanin are also suited for the retention for less thermolabile proteins.