Food Science and Agriculture: Research Highlights Vol. 5

Grape pomace is one of the most abundant solid by-products generated during winemaking. It holds significant relevance in terms of use in animal nutrition, as many of the bioactive substances present in grapes, which have beneficial functional properties and positive technical applications. This study aimed to characterise the preservation of white grape pomace (WGP) through baled silage under commercial-scale conditions over six months, with emphasis on its potential application in ruminant feeding. Fermentation parameters, microbial dynamics, nutrient composition, and antioxidant activity were monitored and compared with untreated grape pomace. It was hypothesised that baled silage would allow this winery by-product to retain its nutritional and sensory attributes for at least six months, offering practical advantages over other ensiling systems due to its lack of infrastructure requirements, strong compaction, airtight sealing, and ease of handling. WGP from wineries under the PDO “Vino de Alicante” was sampled at days 0, 7, 14, 35, 60, and 180, collecting representative subsamples from both silage bales and untreated grape pomace. Silage was produced using an Agronic MR 820 rotary baler, wrapped with netting and layers of plastic film, while untreated pomace was stored in bulk under Mediterranean environmental conditions. Results showed a marked increase in lactic acid bacteria in silage (6.57 → 8.22 log₁₀ cfu/g FM, P < .05) and the disappearance of Enterobacteriaceae and moulds after day 35, whereas untreated grape pomace reached 8.07 and 8.50 log₁₀³ cfu/g FM, respectively (P < .001). Lactic acid accumulation (26.02 g/kg DM) and stable pH (~4.0) confirmed successful fermentation, contrasting with the pH rise to 8.42 in untreated grape pomace (P < .05). Nutritional composition in silage remained stable (DM ~441 g/kg; OM ~887 g/kg DM; CP ~109 g/kg DM; EE ~681 g/kg DM; NDF ~491 g/kg DM), while untreated pomace deteriorated markedly. Bioactive properties were preserved in silage, with total phenolics (~8–9 mg GAE/g DM) and antioxidant activity (423–596 mg Trolox eq/g DM) remaining stable, whereas untreated pomace declined to near-zero values by day 180 (P < .05). Overall, WGP silage achieved fermentation stability by day 35 and remained stable for six months, maintaining nutritional and bioactive quality. Baled silage proved to be an effective and economically advantageous preservation strategy, supporting the sustainable valorisation of winery by-products in ruminant feeding systems.