Impacts of spray drying conditions on stability of isoflavones in microencapsulated soybean extract

Soybean extract rich in isoflavones has attracted widespread attention for dietary supplement and pharmaceutical purposes. However, it has poor solubility and low stability. Encapsulation using spray drying is a good alternative for overcoming these problems in soybean extract. Isoflavones profiles in soybean extract are altered during encapsulation and storage. The objective of this work was to investigate the effect of spray drying conditions on the isoflavones profiles and the various properties of microencapsulated soybean extract. The studied parameters comprised the type of wall material (maltodextrin [MD], gum arabic [GA], and beta-cyclodextrin [beta CD]), inlet air temperature (130-170 degrees C) and storage time (0-6 months), while the investigated properties included moisture content, particle size, hygroscopicity, morphology, isoflavones content, encapsulation properties, and Fourier transform infrared analysis. Type of wall material had a more significant impact on the properties of microencapsulated soybean extract than inlet air temperature. The degradation of total isoflavones during storage mainly depended on the inter-conversion level of isoflavones during encapsulation, hygroscopicity and heating history of microencapsulated soybean extract. The use of beta CD as wall material could preserve total isoflavones after encapsulation and storage at 0.1-1.3 and 2.4-3.1 times that in the case of MD and 1.1-1.3 and 1.5-1.8 times that in the case of GA, respectively.