Germination time shapes digestibility, functionality, and structure of lupin-corn extrudates

Area of Science:

• Food Science
• Nutritional Biochemistry
• Extrusion Technology

Background:

• Lupin (Lupinus angustifolius L.) flour is a valuable source of protein.
• Germination is a traditional method to improve the nutritional quality of grains and legumes.
• Extruded formulations offer a versatile matrix for incorporating functional ingredients.

Purpose of the Study:

• To investigate the effect of lupin flour germination duration on the nutritional and antidiabetic properties of corn starch-based extruded products.
• To assess changes in protein content, amino acid profile, and structural characteristics.
• To evaluate the impact on starch digestibility, glycaemic index, and enzyme inhibitory activities (α-amylase and DPP-IV).

Main Methods:

• Corn starch-based formulations were prepared using lupin flour germinated for 3, 5, and 7 days.
• Nutritional composition, including protein content and amino acid profile, was analyzed.
• Microstructural analysis was performed using microscopy.
• In vitro simulated intestinal digestion was employed to assess peptide release and bioaccessibility.
• Starch hydrolysis, glycaemic index, α-amylase, and DPP-IV inhibitory activities were determined.

Main Results:

• Germination significantly increased protein content, with 7-day germinated flour reaching 15.23%.
• Microscopy showed structural modifications indicating improved digestibility and bioactivity.
• Germinated lupin flour (GLE5, GLE7) enhanced peptide release (<10 kDa) and bioaccessibility (<0.2 kDa).
• The GLE5 formulation exhibited the lowest starch hydrolysis (12.66) and a medium glycaemic index (46.66).
• DPP-IV inhibitory activity improved with germination (IC50: 8.35-8.51 mg/mL), while α-amylase inhibition remained comparable.
• Seven digestion-resistant peptides demonstrated high predicted DPP-IV inhibition.

Conclusions:

• Germination of lupin flour positively impacts the nutritional profile and antidiabetic potential of extruded foods.
• The study demonstrates the feasibility of using germinated lupin flour to develop functional foods with improved health benefits.
• Optimized germination periods can enhance peptide bioaccessibility and enzyme inhibitory activities, contributing to better glycaemic control.