Dry fractionation of chickpea flour: balancing protein enrichment, coproduct functionality and environmental...

Dry fractionation is a resource-efficient approach to produce protein-rich fractions from legumes. However, this process has mainly been optimized for protein content and yield of the fine fraction, while the functional properties of the coarse fraction have received less attention. Moreover, its environmental impact has generally been assessed in separate studies. To date, these aspects (fine fraction composition and yield, coarse fraction functionality and environmental impact) have not been considered together to optimize the dry fractionation process. This study evaluated dry fractionation of chickpea flour, performed with industrial scale equipment, under four operating conditions. The main goal was to determine to what extent a higher degree of refinement is justified when fraction composition, coarse fraction functionality and life cycle environmental impact are considered simultaneously. A clear purity-extraction efficiency trade-off was observed across all conditions: the least selective configuration achieved the highest protein extraction efficiency (59%) and fine fraction yield (36.19%) with moderate protein enrichment (36.5 g/100 g DM), while the most selective configuration reached protein content of up to 46.1 g/100 g DM but at a high cost in yield. The limited separation selectivity can be attributed, at least partly, to the overlap in particle size between starch granules and protein-rich particles in chickpea flour. The coarse fractions also differed in composition, which determined their functional properties. The coarse fraction obtained under the least selective conditions exhibited the highest extent of starch granule swelling, disruption and retrogradation during hydrothermal treatment, and formed the stiffest gel network, consistent with its elevated starch content. Life cycle assessment revealed that environmental impacts increased markedly with fractionation intensity when the whole burden was attributed to the fine fraction, decreased under mass allocation, and increased only moderately under economic allocation. This showed that the environmental performance strongly depends on how the coarse fraction is valorised. These findings highlight the three-way trade-off between protein purity, coarse fraction functional properties, and environmental sustainability, and demonstrate that coarse fraction valorisation is central to the overall viability of dry fractionation as a sustainable food ingredient production strategy.