Impact of lentil flour microstructure on the GC-MS volatile fingerprint and sensory perception of liquid foods: a case study on tomato soup

High-moisture liquid foods, like vegetable soup, are often stabilized using starch-based thickeners to ensure a consistent product. Using lentil flours as thickeners offers a convenient way to increase lentil consumption, although the incorporation of pulse-based ingredients in foods is often associated with off-flavor formation. This study investigated the volatile profile of conventional lentil flour (i.e., open-cell flour), lentil flour containing cotyledon cells (i.e., cellular flour) and blends thereof when incorporated in a model system (flour-in-water dispersion), without and with an additional thermal treatment ( z=10°C PU Tref=90°C = 10 min), and in a food system (tomato soup) as thickeners. Open-cell flour was characterized by a high abundance in lipid oxidation products, which are potentially associated with the typical aroma of pulses. Cellular flour showed a lower abundance of these lipid oxidation products, but a higher level of 3,5-octadiene-2-one and benzoic acid, ethyl ester. A linear relationship was shown between the sum of lipid oxidation markers and the fraction of open-cell flour in the blend. As the incorporation of cellular flour decreased the presence of lipid oxidation volatiles, but also decreases the thickening potential of the flour, blending of open-cell and cellular flour is proposed as an effective strategy to steer the sensory and functional properties of lentil flours. Pasteurization even further decreased the abundance of most compounds in the headspace of flour-in-water dispersions, while some alcohols, terpenes and furans were formed, due to non-enzymatic lipid oxidation and thermal degradation of amino acids. Differences in volatile profiles were small between non-thickened tomato soup and tomato soups thickened to a similar Bostwick consistency index as a commercial tomato soup with starch, open-cell flour and flour blends containing 60% and 80% open-cell flour. However, thickening with lentil flour blends introduced 12 distinct volatiles. S ensory testing showed only a perceptible difference between tomato soup thickened with starch and the 60% open-cell flour blend, as a higher concentration was needed of the latter to thicken the soup to a consistency similar to a commercial tomato soup.