Evaluation of freeze-dried milk-blackberry pulp mixture: Influence of adjuvants over the physical properties of the powder, anthocyanin content and antioxidant activity

The blackberry fruit (Rubus spp.) presents an attractive color ranging from purple red to blue, due to the high content of bioactive compounds, such as anthocyanins. Bioactive compounds have antioxidant properties, acting as free radical scavengers and are also frequently linked to the prevention of cardiovascular and other chronic diseases. Due to native-form anthocyanins instability against environmental stress, bioactive compounds are not always as effective in improving human health as they could be. Therefore, the production of powders using adjuvants is a promising approach for encapsulating anthocyanins-rich pastes, in order to improve their stability and application. Thus, the aim of the present study was to evaluate the influence of adjuvants on the physical properties of the powder, and on anthocyanin content and antioxidant activity of the pastes and freeze-dried milk-blackberry pulp mixtures. The pastes formulated were of milk-blackberry pulp (25%:75%, (weight/weight (w/w)) and of milk-blackberry pulp-adjuvant (25%:70%:5%, (w/w/w)), and the adjuvants employed were maltodextrins 10DE and 20DE and Capsul®. The addition of maltodextrin 20DE and Capsul® resulted in pastes with high anthocyanins content (451.6 ± 80.0 μg/g and 453.1 ± 26.0 μg/g, respectively), similar to the paste without adjuvants (568.6 ± 3.4 μg/g). Also, maltodextrin 20DE and Capsul® showed a high protection capacity of the anthocyanins present on the powders (around 96% of anthocyanins retention). When no adjuvants were used, the anthocyanins retention was very low (40.1%). The freeze-drying process maintained the antioxidant capacity of the bioactive compounds and the powders obtained showed good quality with low moisture content and hygroscopicity.