Circular economy strategies to reintegrate grape pomace from cv. Lagrein into the food chain

Abstract

The project REALISM (regionality and circular economy in food products to counteract the Metabolic Syndrome (M.S.)) was initiated to develop antioxidant-rich food products with the ability to reduce the risk of developing the M.S. The M.S. summarizes comorbidities like high blood pressure, elevated blood sugar and a large waist circumference, which increase the risk of developing cardiovascular diseases or type 2 diabetes and can probably be prevented by a healthy diet with a high content of bioactive compounds such as antioxidants [1]. In accordance with the principles of the circular economy, grape pomace and apple peels were identified as optimal locally sourced raw materials.

Lagrein, an autochthonous red wine cultivar from South Tyrol, Italy, is a rich source of antioxidants, including polyphenols and anthocyanins [2]. Grape pomace from cv. Lagrein was collected from local organic producers before and after fermentation and processed into a fine flour: the drying and milling processes were optimized to preserve the nutraceutical content of the grape pomace. Antioxidant degradation during the processes was monitored with the following methods: the total polyphenol content was determined by using the Folin-Ciocalteu assay [3], total anthocyanins by using the pH-differential protocol [4] and total antioxidant capacity was measured as ferric reducing antioxidant power [5]. More than 80% of the antioxidants were preserved during the processing of grape pomace, resulting in a flour with a high antioxidant content.

New gluten-free baked goods, namely breadsticks, cookies and focaccia, were developed using grape pomace alongside other functional ingredients like apple peel flour, beta-glucan-rich oats and flaxseeds, which provided omega-3 and omega-6 fatty acids. Backed goods enriched with 5% grape pomace flour and 3-10% apple peel flour showed an increase in bioactive compounds compared to control products: polyphenols increased 3.0 -7.3 fold, anthocyanins 6.0-17 fold and the antioxidant capacity 2.8-12 fold.

Our findings indicate that the antioxidant content of grape pomace remains almost unaffected after processing it into a flour. Adding grape pomace flour and apple peel flour to baked goods has significantly enhanced their nutritional value. Further studies will be needed to validate the effects of these products for the dietary managements of the M.S. This approach provides a sustainable way to utilize industry by-products, supporting the circular economy while also creating new revenue streams for food producers and healthier food options for consumers.

References

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[2] Valls, J.; Agnolet, S.; Haas, F.; Struffi, I.; Ciesa, F.; Robatscher, P.; Oberhuber, (2017). Valorization of Lagrein Grape Pomace as a Source of Phenolic Compounds: Analysis of the Contents of Anthocyanins, Flavanols and Antioxidant Activity. M. Eur. Food Res. Technol. 243, 2211–2224

[3] K.Wolfe, X.Wu, R.H.Liu (2003). Antioxidant Activity of Apple Peels. J. Agric. Food Chem. 51 (3),609-14.

[4] J. Lee, R.W. Durst, R. Wrolstad R. (2005). Determination of Total Monomeric Anthocyanin Pigment Content of Fruit Juices, Beverages, Natural Colorants, and Wines by the PH Differential Method: Collaborative Study. J. AOAC Int. 88 (5), 1269–1278.

[5] I.F. Benzie, J.J. Strain (1996). The Ferric Reducing Ability of Plasma (FRAP) as a Measure of “Antioxidant Power”: The FRAP Assay Anal. Biochem., 239 (1), 70–76.