Functional and thermal properties of yellow pea and red lentil extrudates produced by nitrogen gas injection assisted extrusion cooking.

Background: There are excellent opportunities for greater incorporation into our diets of pulses, which are rich in proteins and dietary fibers, if their functional properties are modified to fit a wide range of applications in the food industry. The objective of this research was to produce high protein and fiber extrudates from yellow pea and red lentil flours using conventional and N₂ gas injection assisted extrusion cooking methods. The effects of process variables on extrudate functional and thermal properties were also investigated.

Results: The cold viscosity of extrudates produced by N₂ gas injection were higher than those produced by conventional extrusion, indicating that gas-assisted extrusion does affect the end-product pasting properties. At higher barrel temperatures (150-175 °C) extrudates did not exhibit any thermal transition in their thermograms, and thus their starches were completely gelatinized and proteins completely denatured during extrusion. In general, water solubility of extrudates produced by N₂ gas injection was significantly (P < 0.05) higher than those produced by conventional extrusion. Emulsion capacity and stability of yellow pea extrudates were in the range of 44-50% and 42-47%, respectively, and the counterpart values of red lentil extrudates were very similar (in the range of 43-47% and 43-46%, respectively).

Conclusion: Nitrogen gas injection assisted extrusion cooking can be used practically in development of pulse extrudates which contain high protein and dietary fiber. This novel and innovative technique is a reliable alternative method to the conventional CO₂ gas injection assisted extrusion cooking methods in the snack food and food ingredient industries. © 2019 Society of Chemical Industry.