Effect of enzyme-assisted extraction on the chilled storage stability of bilberry (Vaccinium myrtillus L.) anthocyanins in skin extracts and freshly pressed juices

• Enzymatic treatment enhances extractability of bilberry skin anthocyanins.
• Improved pigment stability of bilberry skin extracts obtained by enzymatic treatment.
• Enzymatic mash maceration has potential for extending the shelf-life of bilberry juices.

Three different commercial enzyme preparations were evaluated with respect to the extractability and chilled storage (10 °C, 9 days) stability of bilberry skin anthocyanins in model systems. Using ultra high-performance liquid chromatography–diode array detection, 15 individual anthocyanins were characterized, with delphinidin and cyanidin glycosides being the predominant compounds. Except for the galactosides of cyanidin and peonidin, 1.2–4.7 times higher concentrations of individual anthocyanins were observed for the extracts from enzymatically treated bilberry skin suspensions. Anthocyanin degradation followed well (R2 = 0.89–0.98) a first-order reaction kinetics and the half-life values increased (12–64%) due to enzyme-assisted extraction. The results obtained demonstrate an improved storage stability of anthocyanins, enzymatically released from the bilberry skin matrix. On the basis of the enzyme screening assay, a novel process, composed of partial dejuicing (pressing, ~ 40% juice yield) of the bilberry mash followed by enzymatic maceration (EMPD), was developed. Interestingly, enzymatic treatment resulted in a decrease among counts of mesophilic and psychrotrophic microorganisms and moulds and yeasts in the bilberry juice upon chilled storage (10 °C, 9 days), implying an inhibition of the microbial growth. Therefore, applying the EMPD process, this two-step juice extraction technology may be very helpful, allowing both enhanced contents of bioactive compounds and extended microbiological shelf-life of “fresh-like” berry juices.