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Lentils for a sustainable future in food: characterisation of lentil protein isolate and starch, and their application in plant-based dairy alternatives and gluten-free baking
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Date
2025
Authors
Boeck, Theresa
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Publisher
University College Cork
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Abstract
The increasing consumer demand for plant-based dairy alternatives (PBDAs) is driven by lifestyle, health, ethical, and environmental concerns. This thesis explores the potential of lentil protein isolate (LPI) to address the challenges of current PDAs, such as low protein content, imbalanced amino acid profiles, low consumer acceptance and limited plant source variety. Despite their high protein content and environmental benefits, lentils are not commercially used for PBDAs. This thesis explores the potential of LPI as a base ingredient for PBDAs and highlights its techno-functional and nutritional benefits and drawbacks in fermented and non-fermented products.
An LPI emulsion was fermented with a commercial lactic acid bacteria (LAB) yoghurt starter culture and evaluated against dairy and soy products. LAB acidification causes gelation of the LPI emulsion, producing a yoghurt alternative (YA) with high firmness, consistency, water-holding capacity, and low FODMAP content. Confocal laser scanning microscopy confirmed a dense protein matrix, indicating strong gel formation. However, acidification in the lentil emulsion was less pronounced than in the dairy control, indicating that the dairy yoghurt starter culture was less suited for the fermentation of the lentil emulsion.
Therefore, three LAB strains - Leuconostoc citreum TR116, Leuconostoc pseudomesenteroides MP070, and Lacticaseibacillus paracasei FST 6.1—were tested. These strains showed exponential microbial growth, satisfactory textural and rheological properties, and high levels of antifungal phenolic compounds, suggesting potential for shelf-life extension. Leuconostoc spp. produced mannitol from fructose, suitable for sugar-reduced YA. Sensory analysis revealed high acceptance for YA with Lb. paracasei FST 6.1, with flavour comparable to the commercial Streptococcus thermophilus starter culture control.
To address the issue of its incomplete amino acid profile, LPI, was combined with oat, rice, brewer’s spent grain (BSGP), and wheat protein at optimized ratios to improve the nutritional quality of plant-based milk alternatives (PBMA). The complementary amino acid profiles of lentils and cereals resulted in improved indispensable amino acid scores (IAAS), with all combinations except lentil+wheat achieving full IAAS for adults. The in-vitro digestibility assessed by the INFOGEST model showed high PIVDIAAS scores of 0.72 (lentil+wheat), 0.78 (lentil+oat), 0.83 (lentil+BSGP), and 0.98 (lentil+rice). These combinations also exhibited better physical stability, reduced sedimentation and creaming, and higher whiteness index, indicating enhanced protein quality and techno-functionality for PBMAs.
To utilise the starch side-stream of the LPI production, the physicochemical and functional properties of lentil and other underused starches from faba bean, chickpea, and quinoa were compared to maize, pea, waxy rice, potato, and wheat starches, and applied in gluten-free bread applications. Significant variations were found in amylose content, granule size, and gelatinisation behaviour. Lentil, faba bean, and pea starch had high amylose and resistant starch content, while potato, quinoa, and waxy rice starches were highly digestible. Potato starch had the highest peak viscosity and retrogradation properties. In gluten-free bread, potato starch increased loaf volume the most, while lentil, faba bean, and pea starch also improved slice area, colour, and crumb structure. Chickpea and quinoa starches resulted in denser crumbs. These findings highlight the potential of underused starches for innovative and sustainable food applications.
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Controlled Access
Keywords
Plant protein , Dairy alternatives , Protein digestibility , Starch , Fermentation , Rheology , Lactic acid bacteria
Citation
Boeck, T. 2025. Lentils for a sustainable future in food: characterisation of lentil protein isolate and starch, and their application in plant-based dairy alternatives and gluten-free baking. PhD Thesis, University College Cork.