Enzyme pre-milling treatments improved milling performance of chickpeas by targeting mechanisms of seed coat and cotyledon adhesion with various effects on dhal quality.

Background: Dehulling and splitting are important elements of the milling process to produce dhal from pulses. However, grain that is difficult-to-mill because of tightly adhered seed coats or cotyledons that resist separation makes it difficult to achieve high quality dhal. Milling yields are reduced, energy inputs into the milling process are increased, and the resulting dhal can be of poorer quality, chipped or abraded.

Results: Eight enzyme pre-treatments were chosen based on the hypothesised mechanisms of seed coat and cotyledon adhesion established previously. Using a difficult-to-mill chickpea (Cicer arietinum L.) genotype, we examined the effects of these pre-treatments, over time, on laboratory-scale milling performance and dhal quality. We pioneered a texture analyser method to measure the flex of the cotyledons and the force required to cleave the cotyledons. The enzyme-induced changes ranged from negative (tough seed coat, weight loss, deleterious colour and texture, increased visual damage to cotyledons and increased kibble loss, concave cotyledons, increased flex, and changes in taste) to positive (brittle seed coat, increased seed volume, improved dehulling efficiency and splitting yield, reduced cotyledon cleavage force, and acceptable dhal quality and taste).

Conclusion: All pre-treatments improved milling performance compared to milling the raw seed, although there was considerable variation between them. Two pre-treatments showed no improvement in milling yields compared to the water control, and several pre-treatments resulted in unacceptable qualities. Three pre-treatments, endo-polygalacturonanase, α-galactosidase and cellulase, show potential for commercial milling applications and could assist pulse millers globally to achieve high quality dhal at the same time as minimising milling effort. © 2021 Society of Chemical Industry.