What question did this study set out to answer?

This study aims to evaluate how drying temperature and storage time affect the quality of soy protein isolates.

May 24, 2026

Impact of Soybean Grain Drying Temperature and Storage Time on the Functional Stability and Isoflavone Profile of Soy Protein Isolates

CFCristiano Dietrich FerreiraUniversidade do Vale do Rio dos Sinos VZValmor ZieglerUniversidade do Vale do Rio dos Sinos NTNewiton da TimmUniversidade Federal de Pelotas

Key Points

This study aims to evaluate how drying temperature and storage time affect the quality of soy protein isolates.
Assess effects of genotype and drying temperatures (70°C and 110°C) on soy protein isolates over 12 months of storage.
Analyze physicochemical properties, functional stability, and isoflavone profiles of the isolates.
Conduct molecular weight analysis and correlate grain soluble protein with isolate functionality.
High-temperature drying (110°C) significantly reduced protein solubility and functional properties compared to moderate drying (70°C).
Isoflavone profiles changed, showing increased malonyl‐glucosides at high temperatures and conversions to β‐glucosides and aglycones during storage.
Grain soluble protein level strongly correlates with the functionality of soy protein isolates, predicting quality reliably.

Abstract

ABSTRACT Soybean is a major source of plant‐based proteins and bioactive compounds. This study assessed the effects of genotype, soybean grain drying temperature, and 12‐month storage on the physicochemical, functional, and bioactive properties of soy protein isolates. High‐temperature drying (110°C) reduced solubility, water‐holding, emulsifying, and foaming properties due to denaturation and disulfide aggregation, whereas moderate drying (70°C) better preserved protein quality. Molecular weight analysis confirmed disulfide‐bonded aggregation, partially reversible with reducing agents. Isoflavone profiles were altered, with malonyl‐glucosides increasing at high temperatures and partially converting to β‐glucosides and aglycones during storage. Importantly, grain soluble protein strongly correlated with isolate functionality, providing a reliable predictor of protein quality. These findings emphasize the need to optimize drying, storage, and genotype selection to maintain functional and bioactive stability, supporting improved nutritional and technological quality of soy products.

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