## 1 Introduction  
The currant belongs to the genus _Ribes_ of the higher dicotyledonous plants, family _Grossulariaceae_, including about 150 species and hybrids of currants and gooseberries. The commercially cultivated species include black currants (_Ribes rigrum L._), red currants (_Ribes rubrum_ L._), and white currants (colour forms of _R. rubrum_ L._), which are a white variety of the red currant. The world's most grown cultivars of black currants are Roodknop, Ojebyn, Tiben, Mortti, Ola, Ben Lomond, [PERSON], [PERSON], [PERSON], Bona, Magnus, Boskoop Giant, and Titania; those of red currants are Jonkheer van Tets, Red Dutch, Heinemann's R.S., Rondom, Stanza, Red Lake, Rovada, Rolan, Hron, Rosetta, and Redpoll [1; 2; 3; 4]. The total world currant production in 2022 was almost 764.5 thousand tonnes. According to FAOSTAT, the Czech Republic ranked among the top 10 currant producers in the world in 1993-2022, along with Russia, Poland, Germany, Ukraine, Great Britain, Austria, France, Hungary, and Denmark. On average over this period, the Czech Republic produced 8 118 tonnes of currants [5]. Currants are primarily grown to produce fruit juices, nectars, non-alcoholic beverages (fruit drinks, teas, flavoured mineral waters), alcoholic beverages (like the French 'Creme de cassis'), fruit drink concentrates, jams, purees, fillings, toppings, ice creams, candies, jelly, functional foods, nutraceutical ingredients, or to be eaten fresh [1; 2; 3; 4; 6]. The industrial production of currant juices involves several steps, such as thawing and crushing the berries (to obtain the homogenate of the fruit), heating them to a certain temperature, enzymatic maceration, pressing, filtering, clarification, pasteurisation, and filling. The production of concentrates is like the production of currant juice, but the final product is concentrated by the evaporation of water. In general, the reasons for the different steps in berry processing are to maximise juice yield, inactivate microorganisms, deactivate enzymes, and maintain the sensory characteristics of the final product The use of pectorolytic enzymes in juice production is quite common, because these treatments improve juicing, prevent the gelatinisation of the juice, increase juice yield, reduce viscosity, and significantly increase the extraction of bioactive compounds such as polyphenols. Commonly used enzymes usually contain mixtures of endo-polygalacturonase, pectin lyase, and pectinsterase, as well as other enzymes with cellulolytic and hemicellulose effects, mostly originating from fungal sources (notably from _A. niger_ spp.). The purpose is to break up polymeric structures such as pectin, cellulose, and hemicellulose in the flesh of berries. The degradation of pectin changes physico-chemical properties such as the total soluble solids, pH, turbidity, aroma, and increased bitterness (astringency) due to a significant increase in polyphenol content [4; 6; 7; 8; 9; 10]. The quality of black currant and red currant juices depends on many aspects. The correct choice of variety (the suitability of the raw material for industrial processing, adaptation to climatic conditions, and resistance to diseases and microorganisms) is essential. The processing technology itself is also crucial, as each step affects the chemical composition of the final product and therefore its nutritional and sensory properties [4; 11; 12]. [PERSON] et al. (2020) investigated the effects of enzymatic and non-enzymatic treatments on the chemical composition of juices. For the black currant cultivar Mott, the total anthocyanin concentration was 152 \(\pm\) 12 mg/100 g without enzymatic assistance and 229 \(\pm\) 1 mg/100 g with enzymatic assistance [6]. It also depends on the harvest year, as confirmed in a paper by [PERSON] et al. (2021). For the black currant variety Ben Lomond, the total anthocyanin content was 217 mg/100 g, 131 mg/100 g, and 283 mg/100 g in a three-year period [13]. In study by [PERSON] et al.