Effect of pH on the extraction and stability of anthocyanins from jaboticaba berries

Anthocyanins are water-soluble plant pigments whose stability is strongly influenced by pH. The effects of pH on the extraction of anthocyanins from jaboticaba berries were investigated using an ultrasound-assisted method. A strong acidic condition (pH 1.5) was found to produce a higher yield and monomeric anthocyanin content, particularly at longer ultrasonication time (30 min). The small pH increment of 0.3 over 2 weeks following a zero-order kinetic model. The monomeric anthocyanins increased more rapidly in refrigerated samples, with a kinetic constant of 0.017 mg/g per day, following a first-order kinetic model. Anthocyanins underwent a two-step mechanism in which colour intensity was reduced significantly in the first week, followed by lightness reduction in the second week. The decline of browning index suggested enzymatic reactions contributed to colour darkening. Negative activation energy reflected the complexity of biochemical reactions, possibly involving a balance of reversible and irreversible processes where the reaction equilibrium was influenced by temperature.