Changes in bioactive components, biological activities and starch digestibility of soymilk residues as affected by far-infrared radiation combined with hot-air and hot-air drying

Abstract

We investigated the bioactive components and their biological activities of soymilk residue (SI) collected from the industry. Two drying methods, namely combined far-infrared radiation and hot-air drying (FIR-HA) and hot air drying (HA), were employed for reducing the moisture content of the residue. After drying, the contents of total phenolic, flavonoid isoflavone, daidzein and genistein of dried SI increased significantly when compared to untreated whole soybean and soy residue. The extracts were the most efficient in inhibiting α-amylase (85–96%), being involved in lowering starch digestion. The correlations between different phenolic fractions of soy residue extract and biological activities as well as starch digestibility were reported. We suggest that SI could be used as an ingredient in functional foods, thus providing added health-promoting properties.

Graphical Abstract

Keywords:

• Soymilk residue
• isoflavones
• daidzein
• genistein
• α-amylase inhibition
• α-glucosidase inhibition

Acknowledgments

The authors thankfully acknowledge the Thai research funds (TRF) for supporting via a scholarship under the Royal Golden Jubilee (RGJ) Ph.D. program under. We also grateful to Dr. Colin Wrigley, Honorary Professor at the University of Queensland, Australia, for his critical reading of the manuscript as well as English proofreading.

CRediT author statement

Ekkarat Tangkhawanit: Conceptualization, Methodology, Validation, Writing - Original Draft. Naret Meeso: Conceptualization, Methodology, Formal analysis, Investigation, Writing - Review & Editing. Sirithon Siriamornpun: Conceptualization, Methodology, Formal analysis, Investigation, Writing - Review & Editing.

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Please check the following as appropriate:

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• The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript

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Declaration of competing interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.