Abstract
Blackcurrant juices prepared with or without enzyme treatment at industrial scale were stored at room temperature or + 4 °C for 1 year, and their sensory profiles, chemical composition and rheological properties were investigated. The juice without enzyme treatment had less intense colour and it was perceived and measured as more viscose than the juice produced with enzyme assistance. Content of monomeric anthocyanins decreased significantly during storage in both juice types under both storing conditions. However, changes in colour intensity were observed only in the non-enzymatic juices. In the discrimination tests based on the appearance, the stored samples were detected as significantly different. Storage resulted in significant changes in contents of hydroxycinnamic acids and flavonols, but this did not have an impact on the bitterness or astringency of the juices. Moreover, sugar and acid contents were mainly unchanged during storage. Storage resulted in a decrease in dynamic viscosity and greater differences in viscoelastic properties for the juice with enzymatic assistance. This study provides important information about the stability of juices typically stored at room temperature for a long time.
Highlights
Berries and fruits are typically processed to juices, jams, jellies, purées, concentrates, alcoholic drinks or eaten whole
Enzyme treatment is typically used to break down polymeric structures, such as pectins, cellulose and hemicellulose in the berry pulp and skins to reduce increase the juice yield and reduce its viscosity
Processing typically involves the application of high temperatures, e.g., pasteurisation, to deactivate spoiling micro-organisms and endogenous enzymes, which in turn result in losses of various phenolic compounds, of anthocyanins [17,18,19,20,21]
Summary
Berries and fruits are typically processed to juices, jams, jellies, purées, concentrates, alcoholic drinks or eaten whole. Juice samples from both processes (Enz- and NEnz-juices), both storage conditions (+ 4 °C, RT) and all the time-points i.e., 0, 3 and 12 months were included in the test. The samples for the descriptive analysis were selected based on the results of our previous study with laboratory made juices [20] in which we found relatively small changes in the sensory quality of juices stored for 1 year.
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