In vitro starch digestion and technological properties of spaghetti fortified with lupin protein isolate

Spaghetti commonly made with durum wheat, typically lacks essential amino acids and with low fibre. Legumes offer potential to improve these properties and lupin is a good choice because it is cheaper with fewer antinutritional compounds than other legumes. Spaghetti was prepared with 0%, 5%, 17% and 30% lupin protein isolate (LPI) using both single-screw (SSEP) and twin-screw extrusion (TSEP). LPI increased protein up to 129%, reduced cooking time, water absorption and cooked firmness while stickiness and cooking loss were increased, especially using TSEP. LPI made the dried pasta more red and yellow and decreased brightness. The percentage of starch digested under in vitro conditions was reduced using 17%LPI with TSEP and 30%LPI with SSEP compared vs. control. Microscopy revealed changes in structure by LPI which may explain impacts on technological properties and digestion. Inclusion of LPI in pasta represents a potential approach for a low-cost improvement of nutritional value of spaghetti and potentially reducing its starch digestibility.