Polyphenols and volatiles in fruits of two sour cherry cultivars, some berry fruits and their jams

This paper reports about the content of polyphenols and volatiles in fresh fruits of two sour cherry cultivars (Marasca and Oblačinska), some berry fruits (strawberry Maya, raspberry Willamette and wild blueberry) and the corresponding low sugar jams. Phenolic compounds (hydroxybenzoic and hydroxycinnamic acids, flavan-3-ols and flavonols) were determined by high-performance liquid chromatography (HPLC). Those found in the fruits were also found in the jams. Jams contained lower amounts of polyphenols than fresh fruits, but their overall retention in jams was relatively high. Among fruits, sour cherry Marasca had the highest level of polyphenols, while sour cherry Marasca jam and raspberry Willamette jam had the highest level of polyphenols among jams. The major flavonoid in all investigated fruits, except in sour cherry Oblačinska, was (–)-epicatechin. Sour cherry Marasca had the highest level of (–)-epicatechin (95.75 mg/kg), and it also contained very high amounts of flavonols, derivatives of quercetin and kaempferol. Hydroxybenzoic acids (HBAs) were not found in sour cherries Marasca and Oblačinska but were found in berry fruits and jams. Phenolic compound (+)-gallocatechin was found only in Marasca fruit and jam. Ellagic acid was found in the highest concentration in raspberry Willamette fruit and jam. Hydroxycinnamic acids (HCAs) were found in all the investigated fruits, with the exception of a derivative of ferulic acid, which was not found in strawberry. Derivatives of caffeic, p-coumaric and chlorogenic acids were found in all the investigated fruits, with chlorogenic acid being the most abundant, especially in sour cherry Marasca. Volatiles were determined by gas chromatography (GC) and expressed as the peak area of the identified compounds. All investigated volatiles of fresh fruit were also determined in the related jams with relatively high retention. Sour cherries Marasca and Oblačinska contained the same volatile compounds, but Marasca had higher level of total volatiles. The main volatile compound in both sour cherry cultivars was benzaldehyde (characteristic cherry aroma compound), which was followed by hexanal, 2-hexenal, 2-heptanone, linalool, nerol, and a-terpineol. Our results show that g-decalactone and linalool were the most abundant volatile compounds in strawberry Maya and raspberry Willamette, respectively. The most abundant group of volatiles in wild blueberry was esters, and they were followed by terpenes, ethyl butanoate and linalool