Flavonols and Phenolic Acids in Berries and Berry Products

The purpose of this thesis was to identify and quantify the non-anthocyanin phenolic compounds in Finnish berries. The compounds of interest were kaempferol, quercetin and myricetin (flavonols); p-coumaric, caffeic and ferulic acids (hydroxycinnamic acids); p-hydroxybenzoic, gallic and ellagic acids (hydroxybenzoic acids). These compounds were selected because of their proposed healthpromoting effects as antioxidants and anticarcinogens. High-performance liquid chromatographic methods for the screening of these phenolic compounds and for the quantification of flavonols and ellagic acid in berries were optimised and validated. Phenolic profiles were determined in 19, flavonols in 25 and ellagic acid in eight berries. Marked differences were observed in the phenolic profiles among the berries, with certain similarities within families and genera. Total contents of flavonols (100–263 mg/kg) in cranberry (Vaccinium oxycoccos), bog whortleberry (Vaccinium uliginosum), lingonberry (Vaccinium vitis-idaea), black currant (Ribes nigrum) and crowberry (Empetrum nigrum and Empetrum hermaphroditum) were higher than those reported for the commonly consumed fruits or vegetables, except for onion, kale and some lettuces. Ellagic acid content varied from 350 to 700 mg/kg, being highest in arctic bramble (Rubus arcticus). Varietal differences were observed in the contents of flavonols and phenolic acids among the six strawberry and four blueberry cultivars studied. Some regional differences were detected in strawberries grown in Finland or in Poland. No consistent differences between conventional and organic cultivation of strawberries were detected. The effects of juicing, cooking or crushing on flavonols were studied in five berries commonly consumed in Finland. Juicing or crushing of the berries by common domestic methods resulted in marked losses of flavonols (40–85%), whereas jam-cooking caused only a small loss (<20%) of flavonols and ellagic acid. Compared to steam-extraction, cold-pressing was a superior juicing method in extracting flavonols from black currants. The contents of flavonols and ellagic acid in the frozen berries and berry products were analysed after 3, 6 and 9 months of storage in a domestic refrigerator or freezer. Effects of freezing on quercetin varied in different berries. Myricetin and kaempferol were more susceptible than quercetin to losses during processing and long-term storage of berries. Ellagic acid content decreased during jam-making and storage of berries. In 1998, the average daily intakes of flavonols and ellagic acid from berries by the Finnish population were 3.4 and 8.7 mg, respectively. Berries accounted for 30% of the total dietary intake of flavonols, and they probably represented the most important source of ellagic acid. In conclusion, the present results demonstrate that Finnish berries are excellent sources of flavonols and ellagic acid. They also show that consumption of berries plays a significant role in the dietary intake of these phenolics by the Finnish population. National Library of Medicine Classification: QU 220, QU 145.5, WB 430 Medical Subject Headings: anticarcinogenic agents; antioxidants; bioflavonoids; chromatography, high pressure, liquid; coumaric acids; eating; ellagic acid; Finland; food/analysis; food handling; fruit; hydroxybenzoic acids; quercetin