Evaluating the Effect of Adding Selected Herbs, Spices, and Fruits to Fermented Olympus Mountain Tea (Sideritis scardica) Kombucha Sweetened with Thyme Honey: Assessment of Physicochemical and Functional Properties

This study examined the effects of adding herbs, spices, and fruits into fermented Olympus Mountain tea (Sideritis scardica) kombucha using thyme honey as a sweetener. This study evaluated how these additions affected the tea's physical, chemical, and functional characteristics. Two different enrichments were proposed: a "Golden Mountain tea and honey Kombucha" (KG) with fresh ginger, turmeric powder, and lemon zest and juice and a "Red Mountain tea and honey Kombucha" (KR) with dried hibiscus calyces, rose petals, and lavender blossoms. In KR, the levels of vitamin C increased from 33.2 +/- 2.7 to 48.4 +/- 4.5. Additionally, the levels of calcium increased from 31.0 +/- 1.2 to 55.7 +/- 1.2, while the levels of potassium practically doubled from 64.7 +/- 0.6 to 115.7 +/- 2.5. An increased potassium concentration was observed in KG, and ionic iron was found for the first time after both enrichments. The total phenolic and flavonoid contents, along with antioxidant capacity, as assessed by the ABTS and DPPH methods, were found to be substantially enhanced in KR. In KG, the total phenolic content increased, together with antioxidant activity, as assessed by ABTS. Enrichment with hibiscus calyces, rose petals, and lavender blossoms significantly increased inhibitory effects against alpha-amylase, alpha-glucosidase, acetylcholinesterase, and butyrylcholinesterase. On the other hand, enrichment with ginger, turmeric, and lemon zest and juice decreased inhibitory effects against alpha-glucosidase and increased those against alpha-amylase, acetylcholinesterase, and butyrylcholinesterase. KR had the strongest enzyme-inhibiting activity, with its alpha-glucosidase-inhibiting activity increased by approximately 18 times. Therefore, enrichment with selected herbs, spices, and fruits can transform fermented Olympus Mountain tea kombucha sweetened with honey into a novel beverage with enhanced functional properties.