Obtaining powders of winemaking by-products: Effect of drying methods and particle size on functional properties

In the Norpatagonia region of Argentina, the wine industry has consolidated in recent years, generating large amounts of agro-industrial waste. Grape pomace and stalks are valuable sources of dietary fiber and phenolic compounds. This study aimed to valorize white wine production waste (pomace, WP, and stalks, WSs) by processing and characterizing it from physicochemical and techno-functional perspectives to assess its potential for use as food ingredients. The waste underwent air-drying (AD) and freeze-drying (F) followed by milling and sieving to obtain particle sizes of 210 µm and 590 µm. Eight particulate products were obtained (aw: 0.209–0.256). The powders were evaluated for their total polyphenol content (TPC), antioxidant capacity (DPPH), superficial color (CIELAB), and techno-functional properties, such as their water holding capacity (WHC), water retention capacity (WRC), and oil holding capacity (OHC). Both the particle size and drying method significantly affected all the parameters studied. The stalk powders had the highest polyphenol content and antioxidant capacity, with freeze-dried 210 µm samples showing the greatest TPC (WS-F210: 3339.4±128.7 mg gallic acid equivalents (GAE)/100 g dry basis (db)) and DPPH value (WS-F210: 1870.4±8.7 mg GAE/100 g db). All the powders presented a yellowish hue (a = 5.14±0.76; b = 12.9±0.6; L* = 48.5±2.2). Generally, the WS powders absorbed more water (WHC: 8.5–10.04 g/g; WRC: 7.3–10.7 g/g). Freeze-dried samples with larger particle sizes exhibited the highest OHC values, particularly WP-F590 (2.93 g/g), suggesting a higher content of insoluble fiber. These results demonstrate the feasibility of obtaining products from winemaking waste with potential as ingredients rich in bioactive compounds for use in various food applications. WP waste could enrich solid foods such as breakfast cereals or dairy products like yogurts, providing fiber, polyphenols, and color. Grape stalks could be used in premixes for developing gluten-free or diabetes-friendly products due to their superior hydration properties and high polyphenol content.