GRAPE POMACE AS A SUSTAINABLE RESOURCE: EVALUATION OF INORGANIC ELEMENTS IN WINE VARIETIES

Introduction: Brazil produces tons of grapes every year, mainly for wine production. During its processing, around 20% of its weight is discarded as waste. This material consists in grape skin, seeds and pulp and represents an interesting ingredient to be included in the diet, since it retains part of the inorganic elements originally present in the grapes, as well as having a positive impact on economic and environmental factors. Objective: To study the inorganic composition (essential, trace and potentially toxic elements) in 3 grape pomace varieties (Merlot, Cabernet franc and Pinot) using spectrometric techniques (ICP OES and ICP-MS). Methods: The samples were initially dried in an oven at 40°C for 48 hours, ground and sieved (0.60mm). Subsequently, they were mineralized by acid digestion (HNO₃ + H₂O₂) in a digester block at 110°C for 4h and volumized to 20mL. Inorganic elements were determined by ICP OES and ICP-MS. Results: The results indicate that grape waste contain high levels of K (1888-2337 mg/100g), intermediate levels of Ca (217-332 mg/100g), P (267-301 mg/100g) and Mg (91-112 mg/100g); and low levels of Cu, Fe, Mn, Na and Zn (ranging from 1.06 to 8.31 mg/100g). For trace and potentially toxic elements, the levels ranged from ND (<0.006 mg/kg) to 0.26 mg/kg for Co, As, Se, Mo, Sb, Hg and Pb. For Al and Ba, the levels ranged from 32-101 and 34-50.5 mg/kg, respectively. The element Cd was not detected in any of the samples evaluated. Conclusion: The study shows that several inorganic elements were present in the byproducts of Merlot, Cabernet franc and Pinot grapes. Although some elements were found in high concentrations (K, for example), the potentially toxic element levels (As, Cd, Pb, Hg, Sn, Cr and Cu) were within the maximum limits established for fresh fruits (grapes). Thus, grape byproducts represent a promising raw material, with an interesting inorganic composition and high potential to reduce the environmental impact.