Evaluation of handling and storage stability of spray dried protein hydrolysates from sardine (Sardina pilchardus) processing by-products: Effect of enzymatic hydrolysis time, spray drying temperature and maltodextrin concentration

Abstract

The effect of processing conditions on handling and storage stability of spray dried sardine protein hydrolysates (SPH) was determined based on equilibrium moisture content (Xe), glass transition temperature (Tg) and surface morphology. SPH with a degree of hydrolysis (DH) of 38.7% and 76.4%, and 0%, 15% and 30% (w/w dry solids) maltodextrin concentration were spray dried at an inlet air temperature of 180 °C and 220 °C and then stored under controlled atmospheric water activity (aw) ranging from 0.113 to 0.843 for a period of 21 days. The powders had high equilibrium moisture content (0.393 – 0.715 g H2O/g dry powder) at 0.843 aw, with high DH producing powders with high Xe (>0.645 g H2O/g dry powder). DH also had a strong effect on Tg, which ranged from − 27.5–50.3 °C for powders stored at 0.113 and 0.328 aw, while spray drying temperature had the least effect. Addition of maltodextrin only improved storage properties at aw above 0.529 by lowering Xe and particle size (<20 µm). This has implications on powder handling where water activity can be controlled to below 0.529 to avoid the diluting effect of maltodextrin on protein content when it is not required as part of the food formulation. These results show the variable effects that process conditions have on powder properties and the need to consider handling and storage separately.