Evaluation of total monomeric anthocyanin, total phenolic content and individual anthocyanins of foam-mat freeze-dried and spray-dried blueberry powder

Anthocyanins in blueberries have generated considerable interest in the scientific community owing to their pleiotropic health benefits against cardiovascular diseases, diabetes and cancer. However, anthocyanins are labile in nature due to their sensitivity to temperature, light, pH, and oxidation and final concentrations in blueberry products is influenced by the processing technique employed. This study evaluated the effect of foam-mat freeze-drying (FMFD) and spray-drying (SD) using a feed rate of 180 and 360 mL/h on the total monomeric anthocyanin (TMA), total phenolic content and contents of individual anthocyanins cyanidin-3-glucoside (Cyn3Gl), delphinidin-3-glucoside (Del3Gl) and malvidin-3-glucoside (Mal3Gl) in blueberry powders. The protective effect of mixtures of encapsulating agents namely: maltodextrin (MD), trehalose, whey protein isolate (WPI), bovine serum albumin (BSA) and β-lactoglobulin on anthocyanins and phenolic content was also investigated. Anthocyanin content was measured using the pH differential and HPLC methods, while total phenolic content was evaluated using the Folin’s assay. The outcome of the study revealed that concentrations of TMA and individual anthocyanins were higher with FMFD (7.11–8.09 mg/g: TMA) compared to SD samples (4.34–5.69 mg/g: TMA). Furthermore, Del3Gl, Cyn3Gl and Mal3Gl retentions were greater, in the order: FMFD > SD 180 = SD 360. Retention of total phenolic ranged from 68 to 76% and 48–72% in FMFD and SD samples respectively and the choice of the matrix MD/WPI as encapsulating agent was the most effective in protecting blueberry anthocyanins. FMFD is therefore recommended for developing blueberry powders with good retention of anthocyanins.