Effect of Pulsed Electric Field (PEF) and cryoconcentration (c) in aqueous extracts of maqui (Aristotelia chilensis (Mol.) Stuntz) and calafate (Berberis microphylla G.) on physicochemical properties, microbiological quality, and bioactive compounds

Abstract

The objective of this study was to evaluate the effect of PEF treatment followed by cryoconcentration (c) in aqueous extracts of maqui (Aristotelia chilensis (Mol.) Stuntz) and calafate (Berberis microphylla G.) on their physicochemical properties, microbiological quality, and bioactive compounds. Extracts of maqui and calafate were obtained by aqueous extraction of water-soluble compounds, and then samples were treated by PEF (10 kV/cm, 70 Hz and a pulse width of 10 µs) and pasteurization (90°C/30 s); untreated samples were used as controls. The treated extracts were cryoconcentrated using centrifugation-filtration, and the cryoconcentration parameters included separation efficiency (EFF) and recovered solute (RS). Physicochemical properties were also evaluated, such as soluble solids (SS), titratable acidity (TTA), and viscosity (ƞ), as well as bioactive compound content: total polyphenols (TP), total anthocyanins (TA), total flavonoids (TF) and antioxidant capacity (AOXC). Microbiological quality was evaluated by the counts of the mesophilic aerobic microorganism (MAM) and molds and yeasts (M&Y). The results showed that the EFF of the solutes was higher than 95 % in maqui and 97 % in calafate. As expected, the cryoconcentration process increased TA, ƞ, and SS content. It also significantly increased (p<0.05) in TP, TF, TA, and AOXC content. The microbiological results showed that PEF treatment, together with cryoconcentration and refrigerated storage, maintained the microbiological quality of maqui cryoconcentrates for more than 50 days, whereas in calafate cryoconcentrates, it was maintained for ∼20 days. Moreover, the physicochemical parameters and bioactive compounds of both cryoconcentrates remained stable during the refrigerated storage period. These results demonstrate that the combined use of PEF with cryconcentration seems to be a good option for microbiological and physiochemical stabilization of fruit juices with a high AOXC and for increasing the content of bioactive compounds.