Removal of Acid Flocs and Colloidal Particles in Soft Drinks by Microfiltration

Acid flocs are colloidal aggregates formed primarily by the interaction between polysaccharides and other sugar constituents in an acidic medium. Their occurrence in soft drinks based on sucrose syrups can compromise the visual quality of the product, as they lead to precipitate formation, representing a technological challenge for the industry. The aim of this study was to evaluate the reduction of acid flocs and colloidal particles through microfiltration steps. Initially, a commercial soft drink brand, referred to as Brand A, with 10% total sugars, was selected. The applied treatments were: control, filtration through 150 µm, 20 µm, conventional paper filter, 8 µm, and conventional paper filter followed by a 0.7 µm filter. Filtrations were performed under vacuum. Visual evaluation indicated that only the combination of conventional paper filter and 0.7 µm filter completely removed the acid flocs. Subsequently, the same filtration condition was applied to three other fruit juice-based soft drink brands, referred to as Brands B, C, and D, with total sugar contents of 11%, 4.9%, and 3.4%, respectively. In these samples, the treatments were: control and filtration with conventional paper filter followed by 0.7 µm. The physicochemical parameters analyzed were: pH, total solids content, soluble solids, and turbidity. Among these, turbidity was the most impacted parameter. For the control treatments of Brands A, B, C, and D, turbidity values of 537.11 ± 7.10 NTU, 282.56 ± 3.61 NTU, 436.11 ± 3.44 NTU, and 668.44 ± 2.07 NTU were observed, respectively. In the samples subjected to filtration with conventional paper filter followed by 0.7 µm, turbidity values were reduced to 48.56 ± 4.07 NTU, 114.44 ± 3.50 NTU, 239.11 ± 6.83 NTU, and 349.11 ± 35.82 NTU, respectively. These results demonstrate that filtration using the combination of conventional paper filter and 0.7 µm filter removes not only acid flocs but also other colloidal compounds and pigments responsible for turbidity. Therefore, filtration appears promising for industrial-scale application and can be incorporated as an auxiliary step in sugar processing to prevent floc formation and ensure the maintenance of the visual quality of the products.