Yellow lentils pasta: how extrusion conditions impact on cooking quality

Thanks to their high fibre and protein content, food products from pulses can successfully satisfy the growing interest in healthy and sustainable diets. Furthermore, pulses are more sustainable than cereals, and the lack of gluten makes them suitable for gluten-free (GF) diets. Regarding pasta, the way starch goes to reorganization upon processing strongly affects the cooking quality of pasta from GF cereals. GF pasta is generally produced by applying an extrusion cooking process to native flours or by using flours that have already undergone a gelatinization step (i.e., pre-gelatinized flours). On the other hand, the combination of native flour and conventional extrusion leads to an unacceptable product. In pulses, it is still not clear if the pre-gelatinization process is required to obtain 100% pulse pasta. To address this knowledge gap, this work focused on understanding the relationships between raw materials and processing conditions and their effect on starch structure and pasta quality. Pasta from native flour (100% yellow lentils) was produced using both conventional extrusion (A) and extrusion-cooking (B). The effect of the process on starch properties was evaluated by measuring the starch susceptibility to amylolytic enzymes, thermal and pasting properties. Regarding the dried pasta, colour and homogeneity indices were evaluated. Cooking behaviour was assessed at optimal cooking time and in overcooking, considering the water absorption, cooking loss and texture. As for starch properties, process B - that combines thermal and mechanical stress- promoted a high degree of gelatinization, 75.5 g/100g of total starch compared to 57.6 g/100g of total starch in process A. Process B is more effective in gelatinizing the starch, but at the same time, the un-gelatinizable fraction seems to be organized in a more compact structure that requires higher temperature for melting (66.5°C and 64.2°C in process B and A respectively). A better starch modification also affects the improvement of the cooking behaviour, especially in the case of overcooking. Indeed, pasta from process B exhibited higher stability during cooking and resistance to overcooking. Therefore, contrary to what has been shown for GF cereals, yellow lentils can be processed into dry pasta even without a pre-gelatinization step. However, samples obtained through process B resulted in the best product, presenting less heterogeneity before cooking and the absence of white spots.