L-Proline-Mediated Modulation of Astringency in Black Chokeberry Puree: Molecular Interactions, Process Optimization,...

Aronia melanocarpa puree is rich in anthocyanins and proanthocyanidins, but its pronounced tannin-derived astringency limits product acceptance. This study developed a non-removal astringency-modulation strategy using food-grade L-proline and evaluated its molecular basis, processing window, and quality effects. Ultraviolet-visible (UV-Vis) and Fourier-transform infrared (FT-IR) spectroscopic analyses suggested that L-proline altered the local microenvironment of procyanidin B2 (PC-B2) through hydrogen bonding, hydrophobic association, and molecular packing rearrangement, without evident disruption of the PC-B2 aromatic skeleton. In a PC-B2-bovine serum albumin model, an appropriate L-proline level reduced the protein precipitation rate from 45.3% to 31.2% and increased soluble phenolic retention, suggesting weakened polyphenol-protein precipitation. The strategy was then optimized in puree using machine learning-assisted multi-response analysis and Box-Behnken validation. The recommended condition was 150 mg/100 mL L-proline at 40 °C for 60 min, yielding a deastringency rate of 36.13%, with anthocyanin and vitamin C retention rates of 88.80% and 55.56%, respectively. The optimized treatment maintained red color, colloidal dispersion, and shear-thinning behavior; increased the anthocyanin digestion retention index from 50.0% to 87.4%; and improved overall sensory acceptance from 4.17 to 8.17. These findings support L-proline-mediated microenvironmental modulation as a mild processing approach for high-tannin cloudy berry products.