## 4 Discussion  
Functional food production is becoming more and more popular. This food is dedicated to various social problems related to nutrition, e.g., people exposed to stress. Enriching food with plant extracts is very common, but adding green tea ingredients, especially matcha powder used in tea ceremonies, is very popular in Japan [63; 64]. The truth is that  
Figure 6: Activity of designed chocolates with yellow tea extract as an acetylcholinesteraseinesterase (**A**) and butylrylcholinesteraseterase (**B**) inhibitors during storage (1—not stored; 2—3 rd month, 3—6 th month). it was Japan that inspired many to use powdered tea as an addition to numerous food products, including chocolate [65; 66; 67; 68; 69]. Today's consumer is looking for additives that are natural, perceived as safe and, moreover, introduce pro-health compounds into the product, increasing its functionality [70]. One of best-studied plants are tea leaves (_Camelia sinensis_ L.), known for their sensory and outstanding pro-health value, but also for their strong antioxidant properties. The value of tea results from the compounds present, among which are polyphenols, commonly known as flavonoids or catechins [71]. Antioxidant properties of tea preparations are due to the presence of catechins: (-)-epigallocatechin (EGC), (-)-epicatechin (EC), (-)-catechin (C), (-)-epicatechin gallate (ECG), (-)-epigallocatechin gallate (EGCG) [64]. The individual composition of tea leaves differs with production technique and fermentation process conditions [21]. Yellow tea next to green and black starts to be appreciated by the science. Tea leaves manufacturing processes differ within the region and type of tea. The main division is based on the degree of leaves fermentation, which recognizes white and green (non-fermented), yellow (partly fermented), oolong (semi-fermented), and black tea (fully fermented) [72]. The processing of tea leaves consists of several steps including withering, rolling, fermentation, postfermentation and drying [21; 73]. The main active components of tea leaves are flavan-3-ols, phenolic acids, tannins (condensed and hydrolysable), and purine alkaloids, which after processing go through several steps leading to the formation of theflavins, thearbibigins, and flavan-3-ols derivatives with a corresponding decrease in catechins concentrations [74]. Results indicate that yellowing time, a key factor in yellow tea processing, improves quality and biological activity of the final product [75; 76]. Yellow tea has numerous health-promoting values, which mainly come from the presence of flavonoids and offer antioxidant, antihyperglycemic, antihyperlipidemic, and anticancer activity [75; 76; 77; 78; 79; 80]. Yellow tea exhibits strong antioxidant activity in in vitro systems, e.g., fats, emulsions, foods and other systems [81; 80; 82; 39]. Although epigallocatechin-3-gallate (EGCG) is the most studied catechin in the group of secondary metabolites of tea, the results showed however that its bioavailability was reduced since most of EGCG was not absorbed in intestinal and blood environment [83; 84]. Despite the fact that EGCG is a very powerful antioxidant, research has indicated that it is pure compounds that can exhibit toxic effects, which was not found in water extracts from tea leaves [85; 86]. Therefore, it was found that the appropriate addition of aqueous extract, which is a concentrated infusion, is safe. Previous studies have focused on phenolic content and antioxidant activity of yellow tea and chocolate either separately or mixed with other ingredients, but no research has been found combining these two products. The functional properties of tea and chocolate have encouraged the development of products and their combination as confectionery shown to be a promising market [87]. New formulations need the quantitative characterization of the sensory features of the product with the participation of trained panel and proper principles of the study.