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.

Abbreviations
AI	=	aglycone isoflavones (daidzein and genistein)
AGI	=	acetyl β-glucoside isoflavones (6″-O-acetyldaidzin and 6″-O-acetylgenistin)
βCD	=	β-cyclodextrin
GA	=	gum arabic
GI	=	β-glucoside isoflavones (daidzin and genistin)
MD	=	maltodextrin
MGI	=	malonyl β-glucoside isoflavones (6″-O-malonyldaidzin and 6″-O-malonylgenistin)
SE	=	soybean extract
SE-βCD	=	microencapsulated soybean extract using β-cyclodextrin as wall material
SE-GA	=	microencapsulated soybean extract using gum arabic as wall material
SE-MD	=	microencapsulated soybean extract using maltodextrin as wall material
TI	=	total isoflavones (sum of MGI, AGI, GI and AI)

Keywords:

• Cyclodextrin
• gum Arabic
• isoflavones
• maltodextrin
• microencapsulation

Additional information

Funding

Author Niamnuy expresses her sincere appreciation to the Thailand Research Fund (TRF), the Commission on Higher Education (CHE) and Kasetsart University for the study financial support through the Research Grant for New Scholar (Grant No. MRG5580172), to the Agricultural Research Development Agency (ARDA) (Grant No. CRP5605010340) and to the National Nanotechnology Center (NANOTEC), NSTDA, Ministry of Science and Technology, Thailand, through its program of Research Network NANOTEC (RNN). All authors express their sincere appreciation to the Thailand Research Fund (TRF) for supporting the study financially through the Senior Research Scholar Grant (Grant No. RTA6180008) to author Devahastin.