A study of the milling process of Irish-grown peas: NIR spectroscopy, flour pasting properties and dough rheology

Peas contain valuable macronutrients, such as protein and dietary fibre, associated with health benefits. Blending pea flour (PF) with wheat flour (WT) can improve the nutritional profile of bakery products. In addition, the use of locally grown peas for food innovation activities can benefit the environment and the local economy. However, the pea milling process is of paramount importance and can affect the final flour quality. This study aims to evaluate the influence of different milling processes of Irish-grown peas on flour composition, spectral profile (Near Infrared - NIR), pasting properties and dough rheology. Three mills were used: roller (RM), hammer (HM) and cutting (CM) producing RM, HM and CM flours, respectively. A commercial strong wheat flour was used as the base flour. For producing doughs, wheat flour was blended with each pea flour at a 15:85 (pea: wheat). Flour composition, particle size, Scanning Electron Microscopy (SEM), dough mixing properties, viscosity profile, gel texture, dough extensibility and rheology were assessed for the control, all pea flours and flour blends. The hammer mill produced the highest yield of pea flour (93.9 %). Near Infrared Spectroscopy reflected the same results for proximate composition, and the PCA and was able to discriminate the main differences between flour samples. SEM demonstrated that higher particle sizes obtained from the CM tended to have larger starch and protein matrix aggregates. Pea flour from the RM presented the highest viscosity profile and hardness, most likely due to the higher starch and lower total dietary fibre content. The lower pasting viscosity profile of pea flour obtained from CM is most likely due to a high level of damaged starch present in this flour. There were no significant differences found among WT and flour blends for gel hardness. This may imply that the incorporation of 15 % HM and CM flours perhaps will not impact the staling process of the final bread products. Further research is being undertaken to examine the influence of the pea milling process on bread-making performance.