Investigating starch and protein structure alterations of the processed lentil by microwave-assisted infrared thermal treatment and their correlation with the modified properties

Abstract

Microwave-assisted infrared is an emerging green technology that can be used in the thermal processing of lentils to modify their functional and nutritional properties as high-value plant-based protein ingredients. The study employed this technology to heat lentil seeds tempered to three higher moisture contents to produce modified flours. The influence of thermal process conditions on the starch structure was evaluated by reducing the degree of order through gelatinization, and the protein structure was assessed through denaturation, which led to the decline in the ordered structure of protein, β-band and α-helix, and the rise in the aggregated intermolecular structure, β-I, and unordered structure, random coil. Results showed that seeds tempered to the highest moisture content, 50%, and processed in higher thermal intensities, by the rise in microwave power and infrared combinations, experienced a higher degree of starch gelatinization and protein denaturation, improving the water holding capacity while reducing protein solubility. Particle size distributions and scanning electron microscopy analyses illustrated that thermal treatment eased the milling process in breaking down coarse particles. The modification process was also an effective way to improve nutritional properties by increasing in vitro starch and protein digestibility.

Keywords

• Starch structure
• Protein secondary structure
• Microwave
• Infrared
• FT-MIR spectroscopy
• Functional properties