Particle size reduction influences starch and protein functionality, and nutritional quality of stone milled whole wheat flour from hard red spring wheat

Authors: ISALM, MD AHMADUL - North Dakota State University; KULATHUNGA, JAYANI - North Dakota State University; RAY, AMRITA - North Dakota State University; Ohm, Jae-Bom; ISLAM, SHAHIDUL - North Dakota State University

Submitted to: Food Bioscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2024
Publication Date: 6/26/2024
Citation: Isalm, M., Kulathunga, J., Ray, A., Ohm, J., Islam, S. 2024. Particle size reduction influences starch and protein functionality, and nutritional quality of stone milled whole wheat flour from hard red spring wheat. Food Bioscience. 61. https://doi.org/10.1016/j.fbio.2024.104612.
DOI: https://doi.org/10.1016/j.fbio.2024.104612

Interpretive Summary: The whole wheat flour (WWF), which is particularly obtained from hard red spring wheat using a stone mill, is recently surging in demand for craft baking of hearth bread and sourdough bread. The flour particle size is considered one of the most important parameters of WWF since it notably influences the processing and end-product quality characteristics. However, limited scientific data still hinders a comprehensive understanding of the impact of particle size on the functional properties of stone-milled WWF. Therefore, this research investigated how particle size reduction influences the starch and protein functionality, as well as the nutritional components in hard red spring wheat flour obtained by a stone mill. Overall, the results indicated that the flour particle size reduction resulted in positive changes to several functional properties of protein and starch. Additionally, it also improved dough handling and end-product quality. The information obtained from this research will be a valuable reference for wheat millers and bakers to produce or screen WWF that has better quality for processing end-products.

Technical Abstract: Flour particle size (PS) influences the functional properties of starch, protein, and other nutritional components, which ultimately impact the quality of the end-products. Regarding stone-milled whole wheat flour (WWF), bakers often prefer a finer flour PS for enhanced color and texture in the end-products based on experience. However, limited scientific data still hinders a comprehensive understanding of the impact of PS on the functional properties of stone-milled WWF. Therefore, this research compared hard red spring (HRS) WWFs with different mean PS values: 151 and 117 µm, which were obtained using a Kombi mill type A 500 MSM stone mill. PS reduction increased starch damage from 6.58% to 6.71%, and the amylose content decreased from 31.7% to 29.4%. Increases in syneresis, solubility, oil-holding capacity, and peak viscosity were also observed. Glutopeak and wet gluten analyses showed increase of gluten strength by PS reduction. Glutenin/gliadin, polymeric/monomeric protein ratios, and percentage of unextractable polymeric protein were increased by 2.10%, 4.11%, and 4.55%, respectively, indicating increased availability of proteins with relatively larger molecular sizes by PS reduction. Significant differences were also observed in the relative proportions of glutenin and gliadin individual subgroups. Dietary fiber and resistant starch contents were found to be lower for the lower PS WWF. The reduction in phytic acid and FODMAPs was also observed. PS reduction finally improved bread loaf volume and crumb structure. Overall, the reduction in PS of HRS-WWF by stone milling resulted in positive changes to several functional properties of protein and starch and improved dough rheology and end-product quality.