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

Abstract

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 β-cyclodextrin [βCD]), inlet air temperature (130–170 °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 βCD 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.AbbreviationsAIaglycone isoflavones (daidzein and genistein)AGIacetyl β-glucoside isoflavones (6″-O-acetyldaidzin and 6″-O-acetylgenistin)βCDβ-cyclodextrinGAgum arabicGIβ-glucoside isoflavones (daidzin and genistin)MDmaltodextrinMGImalonyl β-glucoside isoflavones (6″-O-malonyldaidzin and 6″-O-malonylgenistin)SEsoybean extractSE-βCDmicroencapsulated soybean extract using β-cyclodextrin as wall materialSE-GAmicroencapsulated soybean extract using gum arabic as wall materialSE-MDmicroencapsulated soybean extract using maltodextrin as wall materialTItotal isoflavones (sum of MGI, AGI, GI and AI)