Spray drying of an oil-in-water emulsion containing vitamin D3: a synergy between formulation and process conditions to obtain microparticles

Spray drying is a practical solution to convert oil-in-water emulsion into solid microparticles. In this work, a formulation study was conducted to identify the best composition of vitamin D3-loaded oil-in-water emulsion to process via a lab-scale spray dryer. The emulsion was composed of vitamin D3 oily solution (7 % w/w) and maltodextrin (21 % w/w), arabic gum (9 % w/w) and pea protein hydrolysate (1 % w/w) aqueous solution and was characterized by optimal stability (> 24 h). The spray drying process (T_in: 160 °C; T_out: 94 °C; Gas atomization: 1.75 bar; Feeding rate: 8.75 g/min) was successful: the process yield was good, and the obtained powder had an acceptable residual humidity. The average diameter of microparticles was 23 µm with a quite wide particle size distribution. The oil and vitamin D3 recovered from the powder were 85.69 ± 3.91 % and 80.10 ± 9.94 % of the expected, respectively. The accelerated stability and photostability study results showed that the percentage of vitamin D3 present in the powder after storage was twice compared to vitamin D3 in oil solution stored at the same conditions. Moreover, the scale-up of the process from lab- to pilot-scale spray dryer was encouraging. Regardless of the top or bottom spray set-up, the pilot scale treatments increased the production rate and improved drying efficiency. The top spray configuration and a low inlet temperature guaranteed a yield of over 86 %, about 3 % residual humidity in the powder, and preserved the oil quality, maintaining a peroxide value comparable to the initial one.