Encapsulation of red sorghum extract rich in proanthocyanidins: Process formulation and mechanistic model of foam-mat drying at various temperature

Foam-mat drying (FD) was applied to encapsulate red sorghum extract (RSE) rich in proanthocyanidins. A sufficient amount of whey protein isolate (WPI) to build the foam that supported the drying acceleration and a mechanistic model for process quantification were required to design FD precisely. This research investigated the WPI percentage necessary for creating the best foam-microstructure to accelerate the drying considering the foam properties profiles during whipping and built a mechanistic model to quantitatively describe the drying phenomena illustrating the moisture distribution in foam. The foam obtained by the best formula (10% of WPI, 15 min of whipping) was then dried at 40, 50, and 60 celcius of temperature. A mechanistic model was developed considering intraparticle diffusion, liquid-gas mass transfer, and liquid-gas equilibrium, involving effectivediffusivities (Deff) and gas-liquid mass transfer coefficient (K) as parameters. The parameters were solved numerically, illustrating drying phenomena at several temperatures. It was observed that the model proposed works well, and the value of Deff and K was temperature-dependent, with the activation energy of 5.904 kJ/mol and 13.857 kJ/mol, respectively. The encapsulation reached the yield (wb) of 16.24 - 18.29%, the encapsulation productivity of 84.17 - 96.01%, and proanthocyanidin content in the product of 9.113-9.227 mg/g.