Evaluation of the performance of ultrasouns-assisted membrane processes in the recovery of anthocyanins from blueberry pomace

This thesis evaluates the performance of ultrasound-assisted membrane processes for the recovery of anthocyanins from blueberry pomace. The study aimed to enhance membrane performance and the recovery of bioactive compounds by applying ultrasound as a pretreatment and integrating it into the ultrafiltration (UF) system. Both untreated and ultrasound-pretreated samples were subjected to microfiltration and UF processes. During the microfiltration of untreated blueberry pomace extract (BPE), the permeate flux decreased by 85%, while the decrease was reduced to 79.4% in ultrasound-pretreated samples. With ultrasound pretreatment, the initial permeate flux in the UF and ultrasound-assisted UF (UA-UF) systems increased by 8.83% and 35%, respectively. Additionally, in the UF and UA-UF systems, the hydraulic permeability loss of the ultrasound-pretreated BPE decreased, and recovery rates improved. The highest total resistance was observed in the UF process of untreated BPE, while the lowest total resistance was recorded in the UA-UF process of ultrasound-pretreated BPE. Ultrasound integration reduced the cake layer formation in the UF process of untreated and ultrasound-pretreated BPE by 37% and 34%, respectively. Quality control analyses were conducted to determine the physicochemical quality characteristics of feed, permeate, and retentate samples in the UF process applied for anthocyanin recovery from BPE. Ultrasound pretreatment increased the total phenolic content, total flavonoid content, total monomeric anthocyanin content, and total antioxidant activity (ABTS) of the BPE. Ultrasound pretreatment resulted in statistically significant increases (p < 0.05) in the total phenolic content, flavonoid content, monomeric anthocyanin, and antioxidant activity (ABTS and DPPH) of UF and UA-UF permeates, except for the antioxidant activity (DPPH) of the UF permeate, which did not show a statistically significant increase (p > 0.05). In the pretreated samples, the total phenolic content and antioxidant activity (DPPH) of UA-UF permeates increased by 12.70% and 8.96%, respectively, compared to UF permeates. In conclusion, this study demonstrates that ultrasound-assisted membrane processes are an effective method for recovering anthocyanins from blueberry pomace and improving membrane performance during long-term ultrafiltration operations. The anthocyanin-rich extract obtained is considered a potential natural source of colorants and antioxidants.