Influence of infrared heating on the functional properties of processed lentil flours: A study focusing on tempering period and seed size

Abstract Lentils are an important member of the nutritious Leguminous crops, and the functional properties of lentil flours can be effectively improved by infrared heating, an efficient and short-time thermal processing method. This research primarily focused on the effects of tempering time (24–96 h) and seed size on the modification of lentils using infrared heating. Lentil seeds of three varieties, including CDC Greenstar (large green), CDC Imvincible (small green), and CDC Maxim (small red), were tempered at 25% moisture for 24, 48 and 96 h and then infrared heated to a surface temperature of 130 and 150 °C. Overall, under the same infrared heating treatment, a longer tempering period and a smaller seed size led to greater degrees of starch gelatinization and protein denaturation. In addition, a smaller seed size and a higher surface temperature tended to cause a higher level of photodegradation of amylose (possibly amylopectin too). Due to these physicochemical changes, the combined treatment of tempering and infrared heating noticeably reduced the average particle sizes, enhanced the water-holding capacity, diminished the peak and final viscosities, and decreased the gel hardness of the processed lentil flours. Generally, more obvious effects were found with higher levels of starch gelatinization, protein denaturation, and breakdown of amylose. The present study advanced our understanding of how extended tempering and seed size influenced the techno-functional properties of lentil flours modified using infrared heating. The new findings from the research are meaningful for the utilization of infrared heating to process lentil seeds for the development of novel food ingredients.