Powdered Herbal Extracts by Freeze and Spray Drying: Formulation Design, Processing, and Physicochemical and Antiglycation Properties

Drying and carrier effects may differ among botanical materials, but direct comparisons remain limited. This study compared spray drying (SD) and freeze-drying (FD) across four extract formulations from Alchemilla vulgaris, Mentha × piperita, Urtica dioica, and two 1:1 A. vulgaris-based binary mixtures. Each extract was dried without a carrier or with 5% (w/w) maltodextrin, inulin, or a 95:5 inulin-pea-protein isolate blend. Powders were evaluated for process efficiency, moisture content, water activity, total phenolics content (TPC), antioxidant capacity, and apparent inhibition of fluorescent advanced glycation end products (AGE) formation in four in vitro glycation models. SD powders had lower moisture content than FD powders (1.13–4.18% vs. 4.32–10.49%), whereas FD provided higher process efficiency (74.8–98.1% vs. 47.2–82.0%). Carrier-free powders generally had higher water activity, TPC, and antioxidant capacity. TPC ranged from 3.31 to 36.99 g gallic acid equivalents/100 g dry matter, compared with 0.63–3.66 in carrier-containing powders. Mean apparent AGE inhibition of carrier-free powders exceeded that of carrier-containing formulations by 16.9–37.9 percentage points. Botanical rankings were model-dependent: M. piperita was strongest in the BSA–glucose model and A. vulgaris in the BSA–methylglyoxal model. Carrier selection therefore requires balancing process efficiency and water activity against TPC and apparent AGE inhibition.