[Natural pigments in fruit and vegetable juices: the content of anthocyanins, carotenoids and betalaines]

The color of the juice is determined by the color of the corresponding fruit or vegetable from which the juice is made. The color of a fruit or vegetable, in turn, is determined by the presence of natural coloring pigments - secondary plant metabolites, which include mainly anthocyanins, carotenoids and betalains. These substances, in addition to bright colors, give the juices properties that largely provide a positive effect on health. The quantitative content of these pigments in juices (especially in commercially produced juices, the most commonly consumed by the population at present) is important for understanding of the contribution of that juices in real intake of these bioactive compounds with diet. The purpose of the work was to study the content of anthocyanins, carotenoids and betalaines in juices a nd nectars (cherry, pomegranate, red grapes, tomato, carrot, peach and vegetable juices containing red beetroot) widely represented on the Russian market. Material and methods. The content of natural coloring pigments was determined by HPLC: anthocyanins - according to GOST 32709-2014 "Juice products. Methods for the determination of anthocyanins», carotenoids - in accordance with R 4.1.1672-03 "Guidelines for methods of quality control and safety of biologically active food supplements", betalains by revised IFU method of analysis No 71 (rev. 2023) "Anthocyanins and Betalains by HPLC". The results of measurements in 66 samples selected from Russian retail chains were analyzed. Results. The highest content of anthocyanins (in terms of cyanidin-3-O-glucoside) was found in cherry nectars - an average of 11.4 mg/100 cm3, lower values were obtained for red grape juices (an average of 2.5 mg/100 cm3) and pomegranate juices (0.9 mg/100 cm3). In tomato juices, in addition to lycopene (7.0-14.1 mg/100 cm3), β-carotene was found in an amount of 0.3- 1.2 mg/100 cm3. In carrot juices, the content of β-carotene was at the level of 5.7-12.5 mg/100 cm3, in peach nectars - 0.14- 0.38 mg/100 cm3. The highest concentrations of betalains were found in directly pressed red beet juice at a level of 156.2 mg/100 cm3, with a predominance of betacyanins (99.4 mg/100 cm3) over betaxanthins (56.8 mg/100 cm3). The content of betacyanins decreased to 51.5 mg/100 cm3 in directly pressed lacto-fermented juice and to 2-3 mg/100 cm3 in multi-vegetable juices; betaxanthins were not detected in these samples. Conclusion. The study showed high levels of natural coloring substances - anthocyanins, carotenoids and in some extent betalains in juice products. A serving (200 cm3) of cherry nectar can provide up to 100% of an adequate daily intake of anthocyanins, a serving of red grape juice and a serving of pomegranate juice can provide up to 20% and up to 10%, respectively. The content of β-carotene in a serving of carrot juice is several times higher than the daily requirement for adults; a serving of peach nectar contains up to 10% of the daily requirement for β-carotene. Tomato juice is rich in lycopene, this carotenoid content in a serving is several times higher than the adequate daily intake, while the content of β-carotene is also at a high level - up to 50% of the daily requirement for this substance. Despite the fact that direct data on the adequate daily intake of betalains have not yet been established, relatively high concentrations of betalains, especially in directly pressed red beet juices, determine their significant potential in increasing the nutritive value of the diet through beet-based juices intake.

Protection of Erwinia amylovora bacteriophage Y2 from UV-induced damage by natural compounds

Bacteriophages have regained much attention as biocontrol agents against bacterial pathogens. However, with respect to stability, phages are biomolecules and are therefore sensitive to a number of environmental influences. UV-irradiation can readily inactivate phage infectivity, which impedes their potential application in the plant phyllosphere. Therefore, phages for control of Erwinia amylovora, the causative agent of fire blight, need to be protected from UV-damage by adequate measures. We investigated the protective effect of different light-absorbing substances on phage particles exposed to UV-light. For this, natural extracts from carrot, red pepper, and beetroot, casein and soy peptone in solution, and purified substances such as astaxanthin, aromatic amino acids, and Tween 80 were prepared and tested as natural sunscreens for phage. All compounds were found to significantly increase half-life of UV-irradiated phage particles and they did not negatively affect phage viability or infectivity. Altogether, a range of readily available, natural substances are suitable as UV-protectants to prevent phage particles from UV-light damage.