Effect of conventional milling on the nutritional value and antioxidant capacity of wheat types common in Ethiopia and a recovery attempt with bran supplementation in bread.
Level 5 - mechanism / opinion, no new human data
Laboratory bench food composition and chemistry study without human clinical trial design (CEBM Level 5).
PubMed 27386103 · doi:10.1002/fsn3.315
What was done
Hard and soft wheat grown in Ethiopia were milled to produce whole wheat flour (100% extraction) and refined white wheat flour (68% extraction). Both flours were evaluated for proximates, minerals (iron, zinc, phosphorus), total phenolic content (TPC), and DPPH antioxidant scavenging capacity. Breads were subsequently formulated by supplementing white wheat flour with 0%, 10%, 20%, and 25% wheat bran and evaluated for nutrient content and sensory acceptability using a 7-point hedonic scale.
What was found
Refined milling at 68% extraction significantly (P < 0.05) decreased protein, fat, fiber, ash, iron, zinc, phosphorus, and antioxidant contents. TPC in white wheat flours (3.34 to 3.49 mg GAE/g) was significantly lower than in whole wheat flours (7.66 to 8.20 mg GAE/g; P < 0.005). At 50 mg/mL, DPPH radical scavenging declined from 90.39% (soft whole) and 89.89% (hard whole) to 75.80% (soft white) and 57.57% (hard white). Bran supplementation significantly increased bread nutrient levels (P < 0.05), with 25% bran yielding 12.0 g/100 g protein, 2.6 g/100 g fat, 2.5 g/100 g fiber, 3.3 g/100 g ash, 4.8 mg/100 g iron, and 2.33 mg/100 g zinc. All bran supplementation levels achieved mean sensory preference scores above 4 on the 7-point scale.
Why it matters
Refining wheat markedly depletes essential minerals and phenolic antioxidants, but reintroducing 10% to 25% wheat bran into bread formulations can recover nutritional density while maintaining acceptable sensory qualities.
Limits
The abstract does not state the number of wheat samples tested, experimental replicates, or the number and characteristics of sensory panel participants. Human digestion, nutrient bioavailability, and health outcomes were not assessed.
Cited by
- supports Refining flour by removing the outer layers and germ removes substantial amounts of the grain's protein and fiber.