## 4 Discussion
In present study, the addition of 0.2% yellow tea extracts into white chocolate showed that aroma, color, texture, and overall acceptability were highly scored in comparison to other concentrations. Therefore, this concentration was decided for subsequent testing, which was applied in white, milk and bitter chocolate samples. Today's market strategy for the development of innovative food products is primarily focused on a positive perception by the consumer, especially in terms of sensory values. Therefore, in our research we used different chocolates in order to reflect the possible ability to mask the sensory properties, mostly bitterness of yellow tea extract. The consumer analysis covering quality related properties including visual, and sensory attributes, as well as overall acceptability of enriched chocolates showed satisfactory rating of all the products, however milk chocolate was the highest rated. Results of our studies showed that functional additive of yellow tea extract accounting for 0.2% of dry mass of chocolates did not influence the basic chemical composition, however it significantly influenced total polyphenols content (TPC) in all the samples (\(p<0.05\)). Therefore, it was noticed that the amount of phenolic compounds significantly shaped the antioxidant activity of enriched chocolates (\(p<0.05\)). Other studies have confirmed that the antioxidant capacity of tea and chocolate could be a result of favorable composition of polyphenic compounds such as flavonoids [14; 25]. Therefore, it is promising to enrich the product with ingredients derived from yellow tea leaves, which may increase the supply of these compounds in the diet. Polyphenols are plant origin antioxidants which control or prevent the oxidation process by scavenging of radicals [88]. General classification of antioxidants include primary and secondary natural antioxidants, differing within the mechanism of action [89]. Primary antioxidants, including phytochemicals as flavonoids present in coca and tea, are the chain breaking antioxidants donating the electrons and reacting with lipid radicals, and therefore converting them into more stable products. Secondary antioxidants include phenolic compounds performing the function of capturing free radicals, chain reaction catalysts, and therefore stopping the chain reactions. Antioxidants such as polyphenols may be present in foods as endogenous agents or may be added in order to preserve their lipid components from deterioration. BHA (butylated hydroxyapatite), BHT (butylated hydroxytoluene) or PG (propyl gallate) are synthetic antioxidants commonly used in food products, however, due to safety concerns, the attention of today's consumer is focused on natural antioxidants perceived as safe, but nevertheless requiring further safety research [90]. To meet the consumer's needs, herbal extracts such as tea extracts have been widely commercialized for applications in food and nutraceuticali [91]. However, it should not also be forgotten that plant extracts are the mixture of different properties constituents, which is why its antioxidant activity could vary according to the reaction environment [92]. All of tea polyphenols, particularly catechins, possess antioxidant activity; however, it particularly depends on its proportions [93]. Partially fermented yellow tea consists of, e.g., catechins, gallic acid and theaflavins, which are more effective in bulk oils [94]. However, studies show that many phenolic antioxidants can also exhibit pro-oxidant behavior under certain conditions dependent on solubility characteristics, chelating behavior or pH [95; 96]. Present research found that all the tested samples showed higher activity in DPPH radical scavenging compared to ABTS assay. The highest activity toward radical, measured in Trolox equivalents, was found in samples of dark chocolates, which differed significantly from other samples (\(p<0.05\)).