# Compositional and microstructural changes in faba bean (Vicia faba L.) during soaking and boiling

## TL;DR

This paper studies how soaking and boiling faba beans changes their composition and properties, showing that these treatments reduce harmful compounds and improve functionality for plant-based beverages.

## Contribution

The study introduces a novel soaking and boiling strategy using Lactiplantibacillus plantarum to reduce anti-nutritional factors and enhance functional properties in faba beans.

## Key findings

- Soaking with L. plantarum and boiling reduced vicine, convicine, and phytic acid by up to 71.3%.
- LAB-treated beans produced beverages with higher viscosity and stability.
- Resistant starch decreased significantly after processing, increasing digestible starch.

## Abstract

Faba bean is increasingly cultivated in Nordic regions due to its nutritional value and agronomic adaptability, but its use is limited by anti-nutritional factor (ANF) content and functional properties. This study evaluated soaking and boiling as treatments to modulate composition and functional properties. Beans were soaked in water, sodium bicarbonate, Lactiplantibacillus plantarum (LAB), or a combination of both, followed by heat treatment as boiling. Microbiology analysis showed that LAB inoculation during soaking lowered pH and maintained microbial safety, potentially influencing the breakdown of ANFs. Protein content ranged from 28 to 37% dry matter (DM). Resistant starch decreased from 12.8% in raw beans to 3.7–6.0% DM after processing, with a corresponding increase in digestible starch. The highest reduction of vicine, convicine, and phytic acid occurred in samples soaked only with L. plantarum and boiled, with decreases of 45.7%, 47.1%, and 71.3%, respectively. Free amino acids in treated samples ranged from 2.9 to 3.6 mg/g DM, and total phenolic content ranged from 1.0 to 1.7 mg GAE/g. Microscopy confirmed that sodium bicarbonate loosened the plant matrix, while LAB softened the cell wall structure. To evaluate functional implications, an unfiltered plant-based beverage model (12% w/v solids) was prepared. LAB-treated beverages exhibited improved low-shear viscosity, higher water-holding capacity, reduced phase separation, and lighter colour compared with other samples. These findings demonstrate that soaking strategy influences not only compositional and structural properties but also techno-functional performance relevant for plant-based beverage applications.

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•Soaking changes pH and bacterial counts, lactic acid bacteria strongest acidifier, yeast negligible.•L. plantarum soaking + boiling reduces vicine and convicine by ∼45%.•Phytic acid shows the largest reduction after L. plantarum soaking and boiling.•Free amino acids decrease after soaking and boiling in all treatments.•LAB-treated beverages showed increased viscosity and stability.

Soaking changes pH and bacterial counts, lactic acid bacteria strongest acidifier, yeast negligible.

L. plantarum soaking + boiling reduces vicine and convicine by ∼45%.

Phytic acid shows the largest reduction after L. plantarum soaking and boiling.

Free amino acids decrease after soaking and boiling in all treatments.

LAB-treated beverages showed increased viscosity and stability.