Characterisation of bioactive compounds in berry juices by traditional photometric and modern microplate methods

Berries and berry production are an important economic factor. Berries contain nutritive components but also pertinent non-nutritive bioactives like phenolic-type phytochemicals. It is well accepted that consumption of bioactives from berries prevent or delay chronic and degenerative diseases. Therefore, a thorough evaluation of bioactive compounds is of utmost interest to assess berry quality. The most accepted photometric methods for the determination of bioactive compounds are presented for conventional cuvette and modern microplate applications. All methods are precisely described and advantages of the microplate methods are discussed. Cuvette and microplate methods show slightly different sensitivity and limits of detection depending on concentrations used for reagents and standard compounds. In general, with microplate methods reagents can be saved up to 12-fold and less time to perform the analyses is needed (up to factor 33). Applicability of all the methods has been shown with selected berry juices. Among all analysed commercial juices, blueberry juice had the highest content of total polyphenols, flavonoids, proanthocyanidins, while the lowest content was observed in pomegranate juice. Blueberry juice had also the highest antioxidant capacity measured by TEAC by ABTS, FRAP and ORAC method when compared to the cranberry, açai, goji and pomegranate juice.