Soybean germination limits the role of cell wall integrity in controlling protein physicochemical changes during cooking and improves protein digestibility

Mostafa Zahir, Vincenzo Fogliano, Edoardo Capuano*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Previous studies showed that in vitro digestibility of proteins in cooked beans is modulated by heat treatment and that the effect may be different whether proteins are heated in intact cotyledon or in a bean flour. In this study, germinated and non-germinated soybean cotyledons and flour were boiled at 100 °C for varying times (30, 90, or 180 min). After grinding, the level of trypsin inhibitors, protein aggregation, surface hydrophobicity, the secondary structure, and in vitro digestibility were studied. The presence of an intact cell wall during cooking increased protein denaturation temperature by about 10% and reduced the denaturation of trypsin inhibitors, and induced distinct changes in protein surface hydrophobicity and secondary structure. These physicochemical properties translated into an increment in protein degree of hydrolysis (DH, 72%) of protein cooked for 30 min as flour compared to proteins cooked in intact soybean tissues (64%). Increase in cooking times (90 and 180 min) resulted in limited improvement in the protein digestibility and changes in protein physicochemical properties for both boiled cotyledons and flour. Soybean germination resulted in distinct changes in protein physicochemical properties and higher protein DH% of raw soybean (61%) compared to non-germinated raw soybean (36%). An increase in protein digestibility of germinated soybean was also observed after boiling for both cotyledon and flour. However, significant differences in DH% were not observed between proteins boiled in intact cotyledon and in a flour. This work provides extra knowledge of the role of cellular integrity on protein properties in plant foods and suggests that germination or grinding before cooking may increase protein digestibility.

Original languageEnglish
Article number110254
JournalFood Research International
Volume143
DOIs
Publication statusE-pub ahead of print - 26 Feb 2021

Keywords

  • Boiling
  • Cellular integrity
  • Cotyledons
  • Flour
  • Protein digestion
  • Protein physicochemical properties
  • Soybean

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