Recovery of bioactive compounds from agri-food industry waste using eco-efficient technologies

Abstract

The growing global demand for natural, clean-label ingredients has significantly promoted the pectin market, especially due to its use in food, pharmaceuticals and cosmetics. Traditional pectin production focuses on homogalacturonan pectin extraction from citrus peels and apple pomace through acidic extraction and alcohol precipitation. However, rhamnogalacturonan-I (RG-I) pectin is being studied to be a source of pectic derived oligosaccharides (POS) which are being evaluated for their potential as prebiotics. The growing demand for pectin and new applications have led to exploring alternative sources and more efficient production methods. The agri-food industry generates significant organic waste, which can cause environmental issues if not managed properly. Valorizing these residues into valuable compounds like pectin and POS can mitigate negative impacts and align with the United Nations Sustainable Development Goals (SDGs), particularly SDG 9 and SDG 12. Integrating waste valorization into circular economy frameworks can reduce waste, optimize resource use, and create new economic opportunities. In this context, this thesis delves into the valorization of such agri-food residues as sugar beet pulp (SBP) and discarded red beetroot (DRB) through the recovery of RG-I pectin and POS rich in neutral sugars with potential prebiotic properties using more sustainable processes. For this purpose, emerging extraction technologies including hydrothermal extraction (HE), hydrothermal and surfactant aided microwave-assisted extraction (MAE), and hybrid extraction using sequential ultrasound-assisted extraction (UAE) and MAE (UMAE) were evaluated. A novel downstream process which involved membrane diafiltration (DF) and ultrafiltration (UF) was proposed to minimize solvent use in the downstream process and increase the recovery yield and purity of the final product. The results concluded that SBP and DRB are raw materials suitable for the production of RG-I pectin and POS with potential prebiotic properties and antioxidant capacity similar or higher than commercial prebiotics such as inulin and fructooligosaccharides. The emerging extraction technologies evaluated led to higher POS yield compared to acid-based methods, since neutral sugar side chains were not degraded. Moreover, the membrane downstream processes were found to be more effective for the recovery of POS. By last, the LCA and TEA concluded not only that emerging processes are more environmentally friendly but also that they are more economically feasible for the production of RG-I pectin.