Phenolic Acid Distribution in Wheat Pearling Fractions Using Microwave-Assisted Extraction

Phenolic acids are bioactive compounds in wheat (Triticum aestivum L.) that contribute to its nutritional and functional properties, yet their distribution within the kernel is uneven. This study investigated the effect of progressive pearling on phenolic acid distribution using microwave-assisted extraction (MAE) with water as a solvent. Three commercial Canada Western Red Spring wheat samples were pearled into six fractions (50–450 s), corresponding to 5–45% removal of outer kernel layers. Pearled kernels, pearled kernel flours, and pearled fractions were analyzed for total phenolic content (TPC) and individual phenolic acids using HPLC-DAD. The 10% pearled fraction (PF100) exhibited the highest TPC (9286 ± 168 µg GAE/g), confirming phenolic enrichment in the outer bran and sub-aleurone layers. Outer kernel tissues contained the highest gallic acid (1954 µg/g), whereas the endosperm retained lower levels of gallic (450 µg/g), hydroxycinnamic (122 µg/g), sinapic (87 µg/g), and ferulic (84 µg/g) acids. Both TPC and individual phenolic acids decreased progressively with increased pearling depth, indicating a clear localization gradient. MAE with water enhanced extraction efficiency compared to conventional solvent-based methods, enabling environmentally friendly recovery. These findings demonstrate that controlled pearling can be used to enrich wheat fractions in phenolic acids and optimize functional ingredient development.