Todor Vulić

Biochemical Properties of the Fresh and Frozen Black Currants and Juices

Thirteen black currant varieties (Ribes nigrum L.) cultured in Serbia were characterized for their pomological properties and chemical composition (total phenolics, total anthocyanins, anthocyanin aglycones, sugars, and vitamin C). The average amount of vitamin C varied from 122.4 to 193.2 mg/100 g fresh weight (FW), while concentration of invert sugars ranged from 6.3% to 11.1%. The highest amounts of total phenolics and anthocyanins were detected in variety Ometa (278.9 mg of gallic acid equivalents per 100 g of FW [mg GAE/100 g FW] and 135.4 mg/100 g, respectively). Quantitative analyses of anthocyanin aglycones in berries were performed using high-performance liquid chromatography, and delphinidin was found to be dominant compound in 11 varieties. Total phenolics and anthocyanins contents decreased during the processing of berry fruits to juices, and the reduction of anthocyanins was more pronounced, 12%-80%. The radical scavenging activity of black currant juices was investigated by 1,1-diphenyl-2-picrylhydrazyl, and the IC(50) value ranged from 1.9 to 4.0 mg/mL. Our results also showed that freezing as a way of preservation and storage could save important phytochemicals and health benefits of berries and berry juices. The amount of total phenolics in berries increased during 1 year of storage by 46.09%-171.76% and in juices by even 107.58%, while the amount of total anthocyanins in berries and juices decrease by 5.63%-52.76% and 13.04%-36.82%, respectively.

Polyphenolic Profile of Pear Leaves with Different Resistance to Pear Psylla (Cacopsylla pyri)

The European pear psylla, Cacopsylla pyri L. (Hemiptera: Psyllidae), is one of the most serious arthropod pests of pear. Since proper control of this pest is essential, better understanding of the complex plant-pest relationship is mandatory. This research deals with constitutive polyphenolic profiles in leaves of 22 pear cultivars of diverse origin (P. communis, P. pyrifolia, and P. pyrifolia × P. communis) and different resistance to psylla. The study was designed to show which differences in the polyphenolic profile of leaves from resistant and susceptible pear cultivars could be utilized as information in subsequent breeding programs. The results demonstrated that the leaves of Oriental pear cultivars contained much higher amounts of p-hydroxybenzoic acid, ferulic acid, aesculin, and naringin, that, together with detected 3-O-(6″-O-p-coumaroyl)-hexoside, apigenin, apigenin 7-O-rutinoside, and hispidulin, indicated a clear difference between the species and might represent phenolics responsible for psylla resistance.

Variation in the Fatty-Acid Content in Seeds of Various Black, Red, and White Currant Varieties

Currant seeds, a by‐product of juice production, are recognized as a valuable source of oil rich in polyunsaturated fatty acids. We have evaluated 28 currant varieties for their oil content and fatty‐acid composition. The oil content in the seeds ranged from 18.2–27.7%, and no statistical difference between varieties of different fruit color were recorded. Furthermore, the estimated oil yields in the field production ranged from 26.4–212.4 kg/ha. The GC and GC/MS chemical profiles of the seed oils extracted from all examined varieties were common for currants. Linoleic acid (LA) was the major component, with contents ranging from 32.7–46.9% of total fatty acids, followed by α‐linolenic acid (ALA; 2.9–32.0 %), oleic acid (OA; 9.8–19.9%), γ‐linolenic acid (GLA; 3.3–18.5%), palmitic acid (PA; 4.4–8.1%), stearidonic acid (SDA; 2.2–4.7%), and stearic acid (SA; 1.2–2.4%). Quantitative differences in the fatty‐acid profiles between varieties of different fruit color were observed. Blackcurrant varieties showed significantly higher contents of LA, GLA, and PA than red and white currant varieties, whereas significantly higher amounts of ALA and OL were detected in the red and white varieties. Cluster analysis based on the chemical oil profiles joined the blackcurrants in one group, while most of the red and white cultivars joined in a second group at the same linkage distance.