Abstract
Highland barley (HB) is commonly milled into flour for direct consumption or further processed with other food formulations. Nevertheless, the association between milling and HB flour properties remains lacking. This work studied the effect of particle sizes (coarse, 250–500 μm; medium, 150–250 μm; fine, <150 μm) on physicochemical and nutritional properties of raw and sand-roasted HB flour. Gelatinization enthalpy decreased with increasing particle sizes of raw HB flour, while no endothermic transitions were observed in sand-roasted flour. Sand roasting destroyed starch granules and decreased short-range molecular order. Starch digestibility increased while total short-chain fatty acids (SCFAs) production decreased with decreasing particle sizes in all samples. The relative crystallinity of sand-roasted HB flour decreased by 80–88% compared with raw samples. Sand roasting raised in vitro starch digestibility, while total SCFAs during in vitro fecal fermentation decreased. Sand-roasted HB flour with particle sizes <150 μm had the highest starch digestibility (94.0%) but the lowest production of total SCFAs (1.89–2.24 mM). Pearson’s correlation analysis confirmed the relationship between the nutritional qualities of HB flour and milling.
Highlights
The effects of food processing on the sensory and nutritional qualities of whole grain flours and their finished products have attracted increasing interest
Noodles made from wet-milled flour had a harder texture and lower cooking loss than those made from dry-milled flour [11]
Total glucose oxidase/peroxidase (GOPOD) kit, β-glucan kit, total dietary fiber kit, and total starch kit were obtained via Megazyme International Ireland, Ltd. (Bray Co., Wicklow, Ireland). α-amylase from porcine pancreas type VI-B (A3176, 11 units/mg) and pepsin from porcine gastric mucosa (P7125, ≥400 units/mg) were obtained via Sigma Chemical Co
Summary
The effects of food processing on the sensory and nutritional qualities of whole grain flours and their finished products have attracted increasing interest. Hard cell walls and microstructures of grains can be destructed differently by milling, leading to different colors, physicochemical properties, and starch digestibility in flours and their finished products [1,4]. A common method to produce flours with a wide range of particle sizes, causes varied distributions of components, bioavailability of nutrients, and baking properties of grain flours. Until now, milling affects textural and pasting qualities of starch, which are detrimental for finished product properties, such as stability, flow, functionality, texture, mouth feel, and structure [1,5,6]. Noodles made from wet-milled flour had a harder texture and lower cooking loss than those made from dry-milled flour [11]
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