Foam-mat drying in the encapsulation of red sorghum extract: Effects of xanthan gum addition on foam properties and drying kinetics

Abstract

Red Sorghum Extract (RSE) rich in proanthocyanidins (PA) was encapsulated in Arabic gum (AG), whey protein isolate (WPI), and xanthan gum (XG) to maintain its bioactive stability and dried by foam-mat drying. Xanthan gum was added as a stabilizer to maintain the stability of porous foam to accelerate the foam-mat drying (FD) in the encapsulation. This research investigated the effect of XG addition on the stability or quality of foam, its correlation on the parameter values of the empirical kinetics, and the mass transfer of FD. The research described that the air fraction, foam expansion, and foam overrun increased while the density decreased as a function of the whipping time in each XG addition. The XG addition increased the foam stability by WPI-XG interaction that inhibited their protein interactions. The quality-stability of foam affected the parameters of some empirical drying models and the moisture mass-transfer approach in two drying periods. The optimum foam structure was resulted by the XG addition of 0.5% on the RSE with 10% of WPI, 20% of AG at 15 min of whipping that resulted in 0.0016 /s of drying rate, and 1.617 × 10 −8 m 2 /s of the effective diffusivity. The empirical models and the mass transfer model approach showed high accuracy in predicting the FD. The drying was capable to retain 96.01% proanthocyanidins of the initial RSE, resulted in a powder containing 9.227 mg PA /mg powder with a yield of 16.24% (wet basis) and 99.96% (drybasis). It presented the excellent performance of FD in encapsulating RSE.