The growing demand for food, mainly due to the constantly increasing global population, has led to more intensive industrial production in the agricultural sector. Consequently, agro-industrial by-products have become a major concern in terms of waste management and their negative impact on already worsening global environmental conditions. It is well recognised that such discarded materials possess interesting properties, being rich sources of bioactive molecules. Grape pomace (GP), the main discarded solid residue obtained from the winemaking process, is a rich source of polyphenols with proven antioxidant and antimicrobial properties. The application of sustainable methods for the formulation of GP-based supplements is the main aim of this investigation. Preliminary screening of seven Deep Eutectic Solvents (DESs) as green media was performed using Petit Verdot (PV) and Cabernet Sauvignon (CS) grape pomaces. Extracts were characterized by developing and optimizing an HPLC-DAD method and then evaluating their antimicrobial and antioxidant activities. The best Natural DESs (NADESs) were subsequently applied to extract seventeen conventional and organic Apulian grape pomace varieties. All samples were screened using HPLC-DAD, while the richest extracts were further analysed by LC-ESI-QTOF-MS metabolomics, semi-quantitative antimicrobial activity, scavenging power, and total polyphenol content analyses. Finally, in vitro digestion experiments were conducted to evaluate biostability. The screening of PV and CS grape pomaces using HPLC-DAD, alongside antioxidant and quantitative antibacterial assays, identified the three most effective solvents among the seven initial ones. The use of these selected NADESs on a wider range of GP varieties allowed a more complete and clear characterization of this by-product. HPLC-DAD analyses evidenced significant differences in the phenolic compound profiles among the seventeen red and white GPs considered. Conventional Sangiovese and organic Merlot cultivars, both dried and extracted with Betaine/Lactic acid 1:4 (mol/mol + 40% H₂O; Bet/LA) and Choline Chloride/Ascorbic acid 2:1 (mol/mol + 40% H₂O; ChCl/AA) NADESs, emerged as the most promising extracts. The comprehensive semi-quantitative metabolomics analysis showed better recoveries for Bet/LA than for ChCl/AA, with yields around three times higher for both cultivars. The evaluation of antimicrobial activity by agar diffusion test showed stronger effectiveness against pathogenic bacteria than against fungi. Moreover, among pathogenic fungi, freeze-dried Bet/LA samples from Merlot exhibited the largest inhibition halos against Botrytis alii compared to any other extract and microorganism. On the other hand, interesting results were obtained for the ChCl/AA sample from Sangiovese against Escherichia coli; in this case, both the control and the extract from Merlot displayed smaller halos. The evaluation of antioxidant activity showed similar scavenging power for betaine-based extracts. On the other hand, extremely high values were found for ChCl/AA extracts and controls. [3] In the latter case, it was difficult to discriminate the contribution of the numerous identified phenolic compounds, since ascorbic acid, the main component of the solvent, exhibited strong antioxidant capacity. However, the intrinsic activity of the solvent, although predominant in some cases, should not be considered a drawback, considering the potential relevance that the solvent itself may have in the formulation of ready-to-use supplements. The determination of total polyphenol content evidenced a slightly higher content for Bet/LA extracts from both varieties compared to the hydroalcoholic extracts, although still significantly lower than that of ChCl/AA-based samples. Finally, metabolomic characterization during the in vitro digestion experiments performed on Bet/LA extracts revealed an increase in glycoside content from the initial to the duodenal phase, whereas the addition of lactic acid bacteria during the colon phase led to higher levels of free polyphenols. To obtain more insights into the combination of such GP-derived polyphenols with probiotics, a strain of Lactobacillus plantarum was added to Bet/LA extracts (from both cultivars) from the beginning of the experiments. The results showed a drastic reduction in the amount of GP-derived bioactive molecules originally present, as a result of the metabolism exerted by this microorganism. Moreover, the detection of high scavenging activity and total polyphenol content in each phase revealed the presence of other lactic acid bacteria-derived bioactive compounds. These findings suggest a potential prebiotic effect and support the possibility of developing, in the near future, a dietary product with symbiotic characteristics combining both prebiotic and probiotic components. Bet/LA- and ChCl/AA-based NADES extracts from the GPs under study provided the richest samples in terms of polyphenol content, yielding edible extracts with antimicrobial and antioxidant properties. While cultivar differences showed no noticeable impact, certain NADES components, such as ascorbic acid, strongly influenced the extracts’ characteristics. Furthermore, since the solvent itself represents a valuable constituent, it may offer advantages for supplement formulation. Ongoing studies using these extracts as feed supplements in quails will provide deeper insights into their applications.
Sustainable valorization of grape pomace for potential ready-to-use extracts-based supplements
Roselli Vincenzo
2026-01-01
Abstract
The growing demand for food, mainly due to the constantly increasing global population, has led to more intensive industrial production in the agricultural sector. Consequently, agro-industrial by-products have become a major concern in terms of waste management and their negative impact on already worsening global environmental conditions. It is well recognised that such discarded materials possess interesting properties, being rich sources of bioactive molecules. Grape pomace (GP), the main discarded solid residue obtained from the winemaking process, is a rich source of polyphenols with proven antioxidant and antimicrobial properties. The application of sustainable methods for the formulation of GP-based supplements is the main aim of this investigation. Preliminary screening of seven Deep Eutectic Solvents (DESs) as green media was performed using Petit Verdot (PV) and Cabernet Sauvignon (CS) grape pomaces. Extracts were characterized by developing and optimizing an HPLC-DAD method and then evaluating their antimicrobial and antioxidant activities. The best Natural DESs (NADESs) were subsequently applied to extract seventeen conventional and organic Apulian grape pomace varieties. All samples were screened using HPLC-DAD, while the richest extracts were further analysed by LC-ESI-QTOF-MS metabolomics, semi-quantitative antimicrobial activity, scavenging power, and total polyphenol content analyses. Finally, in vitro digestion experiments were conducted to evaluate biostability. The screening of PV and CS grape pomaces using HPLC-DAD, alongside antioxidant and quantitative antibacterial assays, identified the three most effective solvents among the seven initial ones. The use of these selected NADESs on a wider range of GP varieties allowed a more complete and clear characterization of this by-product. HPLC-DAD analyses evidenced significant differences in the phenolic compound profiles among the seventeen red and white GPs considered. Conventional Sangiovese and organic Merlot cultivars, both dried and extracted with Betaine/Lactic acid 1:4 (mol/mol + 40% H₂O; Bet/LA) and Choline Chloride/Ascorbic acid 2:1 (mol/mol + 40% H₂O; ChCl/AA) NADESs, emerged as the most promising extracts. The comprehensive semi-quantitative metabolomics analysis showed better recoveries for Bet/LA than for ChCl/AA, with yields around three times higher for both cultivars. The evaluation of antimicrobial activity by agar diffusion test showed stronger effectiveness against pathogenic bacteria than against fungi. Moreover, among pathogenic fungi, freeze-dried Bet/LA samples from Merlot exhibited the largest inhibition halos against Botrytis alii compared to any other extract and microorganism. On the other hand, interesting results were obtained for the ChCl/AA sample from Sangiovese against Escherichia coli; in this case, both the control and the extract from Merlot displayed smaller halos. The evaluation of antioxidant activity showed similar scavenging power for betaine-based extracts. On the other hand, extremely high values were found for ChCl/AA extracts and controls. [3] In the latter case, it was difficult to discriminate the contribution of the numerous identified phenolic compounds, since ascorbic acid, the main component of the solvent, exhibited strong antioxidant capacity. However, the intrinsic activity of the solvent, although predominant in some cases, should not be considered a drawback, considering the potential relevance that the solvent itself may have in the formulation of ready-to-use supplements. The determination of total polyphenol content evidenced a slightly higher content for Bet/LA extracts from both varieties compared to the hydroalcoholic extracts, although still significantly lower than that of ChCl/AA-based samples. Finally, metabolomic characterization during the in vitro digestion experiments performed on Bet/LA extracts revealed an increase in glycoside content from the initial to the duodenal phase, whereas the addition of lactic acid bacteria during the colon phase led to higher levels of free polyphenols. To obtain more insights into the combination of such GP-derived polyphenols with probiotics, a strain of Lactobacillus plantarum was added to Bet/LA extracts (from both cultivars) from the beginning of the experiments. The results showed a drastic reduction in the amount of GP-derived bioactive molecules originally present, as a result of the metabolism exerted by this microorganism. Moreover, the detection of high scavenging activity and total polyphenol content in each phase revealed the presence of other lactic acid bacteria-derived bioactive compounds. These findings suggest a potential prebiotic effect and support the possibility of developing, in the near future, a dietary product with symbiotic characteristics combining both prebiotic and probiotic components. Bet/LA- and ChCl/AA-based NADES extracts from the GPs under study provided the richest samples in terms of polyphenol content, yielding edible extracts with antimicrobial and antioxidant properties. While cultivar differences showed no noticeable impact, certain NADES components, such as ascorbic acid, strongly influenced the extracts’ characteristics. Furthermore, since the solvent itself represents a valuable constituent, it may offer advantages for supplement formulation. Ongoing studies using these extracts as feed supplements in quails will provide deeper insights into their applications.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
