Milling and differential sieving to diversify flour functionality: A comparison between pulses and cereals.

In this study, pulse (pea, lentil) and cereal (barley, oats) seeds were firstly milled into whole flours, which were then sieved into coarse and fine flours. The particle sizes of the three generated flour streams followed a descending order of coarse > whole > fine, consistent with the observation under scanning electron microscopy (SEM). Among the four crops, the three flour streams showed the same rank order of fine > whole > coarse in starch and damaged-starch contents but the opposite order in ash and total dietary fiber contents. Thus, those functional properties closely related to starch occurring in flour, such as L* (brightness), starch gelatinization enthalpy change (ΔH), and gel hardness, followed the same order of fine > whole > coarse. By contrast, protein contents of the three flour streams did not vary in pea and lentil but showed a trend of coarse > whole > fine in barley and oats, which could partially explain generally comparable foaming and emulsifying properties of the three streams of pulse flours as well as an order of coarse > whole > fine in oil-binding capacity (OBC) of cereal flours, respectively. The different particle sizes and chemical compositions of the three flour streams only resulted in a descending order of fine > whole > coarse in the pasting viscosities of the pulse flours but did not lead to such a clear trend in the cereal flours, which could be partly attributable to the different microscopic structures of the pulse and cereal seeds and their corresponding flours. This research clearly demonstrated that particle size, chemical composition, and microscopic structure were important variables determining the specific techno-functional properties of pulse and cereal flours.

Improvement of the nutritional quality of lentil flours by infrared heating of seeds varying in size.

The present study aimed to tackle research gaps regarding how infrared heating affected macro- and micronutrients of lentil flours from seeds varying in size. Infrared treatments reduced resistant starch contents of lentil flours from 26.1-33.6% to 6.0-17.8%, increased protein digestibility from 73.6-75.0% to 78.2-82.2%, and enhanced soluble dietary fiber contents from 6.1-7.8% to 7.4-10.3%. Infrared treatments did not alter the primary limiting amino acid of Greenstar and Imvincible lentil flours (tryptophan) but changed that of Maxim to methionine + cysteine at 150 °C heating. Regarding micronutrients, the thermal modifications decreased the levels of heat-labile B vitamins, including B1 (thiamine), B3 (niacin), and B9 (mainly 5-methylterahydrofolate), consistent with reducing α-amylase activity to an undetectable level in all the three lentil flours. The novel findings from this research will be meaningful for the agri-food industry to utilize infrared processing as an effective and clean-label approach to improving the nutritional profiles of lentil and other flours.

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

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.