Phenolic compounds contribute to quality factors, such as color (anthocyanins) and taste (flavonols and phenolic acids), which characterize commercial products based on fruits and berries (1). The storage conditions, such as temperature, determine the stability of easily degradable phenolic compounds. In this study, blackcurrant juices were stored for 12 months in refrigerator (+4 °C) or in room temperature. The stability of the phenolic compounds was examined in the juice, and analyzed with HPLC coupled with DAD, MS(/MS) and QTOF. The structures of several previously unknown phenolic acid sugar derivatives were determined with NMR after separation with preparative HPLC.



The content of anthocyanins dropped drastically during 12 months of storage when stored in room temperature, most being degraded already after 6 months of storage. The anthocyanins remained more stable in the refrigerator, as well as the flavonolglycosides and hydroxycinnamic acid derivatives. The content of protocatechuic acid and 4-hydroxybenzoic acid, as degradation products derived from anthocyanins, clearly increased when stored in room temperature. Unlike anthocyanins, the flavonolglycosides and hydroxycinnamic acid derivatives degraded to their corresponding aglycones. The content of flavonol aglycones myricetin, quercetin, kaempferol and isorhamnetin increased 0.4–5-fold in room temperature. The content of caffeic acid, ferulic acid and p-coumaric acid, as aglycones derived from hydroxycinnamic acid derivatives, increased 1–7-fold after storage for 12 months in room temperature. The concentration of the nitrogen containing phenolic acid sugar derivatives decreased remarkably during storage in room temperature.



To minimize the degradation of phenolic and polyphenolic compounds, it is necessary to choose storage conditions at low temperatures. Understanding degradation mechanisms is a prerequisite in order to maintain the original nutritional and sensory quality of consumer products.