Characterization and valorization of grape pomace in human nutrition

Details

Supervisors

Dierge, Emeline ; Debisschop, Pauline

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

enThe growing grape pomace production, as well as the current limitations associated with its current valorization pathways have raised major economic and environmental challenge concerns worldwide and, for the past few decades, in Belgium. Characterized as a major source of dietary fibers, phenolic compounds, and antioxidants, grape pomace is attracting increasing interest in the field of scientific research for its potential to be valorized in human nutrition. This master’s thesis aimed to evaluate the potential of Belgian grape pomace for human nutrition through the optimization of stabilization processes, the nutritional characterization of different samples and the development of food products. For this purpose, four samples of grape pomace both fermented and unfermented from Belgian winemaking were subjected to various thermal stabilization processes to produce a powder. The effects of these treatments on water activity, phenolic compounds and antioxidant activity were assessed to identify the most suitable stabilization process. The nutritional composition and microbiological quality, including Ochratoxin A contamination levels, were also evaluated. Incorporation trials were conducted to evaluate grape pomace powder as a partial flour substitute in food formulations, with the aim of maximizing its inclusion level while optimizing the organoleptic and nutritional properties of the resulting products. Finally, a sensory evaluation focusing on appearance, smell, taste and texture was conducted with a consumer panel to assess the products acceptability as well as their potential for inclusion in daily consumption. Among the thermal treatments evaluated, drying at 80 °C for 10 hours provided the best compromise between product stability and preservation of bioactive compounds. The results also highlighted a certain variability among grape pomace samples, reflecting differences related to grape variety and winemaking conditions. In particular, for the unfermented Grenache grape pomace sample, this treatment resulted in a water activity of 0.21, a total phenolic compounds content of 42.12 mg/GAE/g, an antioxidant activity of 858.95 µmol TE/g. Nutritional characterization further revealed a high dietary fiber content, reaching 31.82 g/100g. Based on these results, Grenache grape pomace was incorporated as a partial substitute for wheat flour into various food prototypes. Three products were developed: mini cakes, appetizer crackers and bread, with incorporation rate of 15.66 %, 13.44 % and 13.20 %. All products exhibited favorable nutritional profiles, particularly due their to high fiber content, and achieved Nutri-Scores of B, A, and B, respectively. Sensory evaluation revealed good consumer acceptance of grape pomace enriched products with a marked preference for mini cakes, which received the highest overall appreciation, followed by appetizer crackers and then bread. These findings demonstrate that grape pomace can be successfully valorized as a food ingredient, contributing to the development of sustainable, fiber-rich food products while supporting circular economy strategies in the wine sector.