Structural, Culinary, Nutritional and Anti-Nutritional Properties of High Protein, Gluten Free, 100% Legume Pasta

Abstract

Wheat pasta has a compact structure built by a gluten network entrapping starch granules resulting in a low glycemic index, but is nevertheless unsuitable for gluten-intolerant people. High protein gluten-free legume flours, rich in fibers, resistant starch and minerals are thus a good alternative for gluten-free pasta production. In this study, gluten-free pasta was produced exclusively from faba, lentil or black-gram flours. The relationship between their structure, their cooking and Rheological properties and their in-vitro starch digestion was analyzed and compared to cereal gluten-free commercial pasta. Trypsin inhibitory activity, phytic acid and α-galactosides were determined in flours and in cooked pasta. All legume pasta were rich in protein, resistant starch and fibers. They had a thick but weak protein network, which is built during the pasta cooking step. This particular structure altered pasta springiness and increased cooking losses. Black-gram pasta, which is especially rich in soluble fibers, differed from faba and lentil pasta, with high springiness (0.85 vs. 0.75) and less loss during cooking. In comparison to a commercial cereal gluten-free pasta, all the legume pasta lost less material during cooking but was less cohesive and springy. Interestingly, due to their particular composition and structure, lentil and faba pasta released their starch more slowly than the commercial gluten-free pasta during the in-vitro digestion process. Anti-nutritional factors in legumes, such as trypsin inhibitory activity and α-galactosides were reduced by up to 82% and 73%, respectively, by pasta processing and cooking. However, these processing steps had a minor effect on phytic acid. This study demonstrates the advantages of using legumes for the production of gluten-free pasta with a low glycemic index and high nutritional quality.

Fig 1. General appearance and color scores of dried pasta.

F: faba, L: lentil, BG: black-gram and C: commercial pasta. Arrows denote bumps on the surface of C pasta. L* values measure black to white (0–100); a* values measure redness when positive, and greenness when negative; b* values measure yellowness when positive, and blueness when negative.

Fig 2. Changes in protein solubility in sodium dodecyl sulfate (SDS) and dithioerythritol (DTE).

(1) Legume flours, (2) dry and (3) cooked pasta. F: faba, L: lentil and BG: black-gram flours. C: gluten-free commercial pasta. Results are means of three replicates, standard errors shown as vertical bars. Raw material and pasta were subjected to two sequential protein extractions first in SDS to disrupt the weak interactions, and then in SDS/DTE + sonication to disrupt disulfide bonds. All protein extracts were analyzed by SE-HPLC [32]. Areas of SDS-soluble and DTE-soluble proteins were expressed as the percentage of the total area corresponding to the total extractable proteins.

Fig 3. Light microscopy image of 100% legume cooked pasta.

F: faba bean, L: lentil and BG: black-gram. The internal regions of the pasta are in the left panels and external regions in the right, panels. S, starch; P, protein and Cs, cell structure.