## 4 Discussion  
Stress is one of the factors that can affect people's mental health. Long-term stress leads to various cellular and neuronal disorders, playing a significant role in the onset of depression and Alzheimer's disease [1; 2; 3]. Oxidative stress influences physiological and pathological conditions leading to the appearance of various cardiovascular and neuronal diseases. To avoid and reduce the effects of stress on the human body, studies recommend the external intake of antioxidants. Medicinal and aromatic plants have been excellent sources of antioxidants. Creating food products that meet certain food needs, but also contribute to health [78] is a growing interest for many processors in the food industry. The antioxidant character of the three plants used in this study is given by their different compounds. The main compound in fennel volatile oil is \(\alpha\)-pinene [31]. \(\alpha\)-pinene is a natural and active monoterpene that is very often used as a flavoring or pharmaceutical agent [79]. This compound is known to have notable antioxidant activity [80]. The antioxidant character of the volatile mint oil is given by menthone, caryophyllene and linalool [20]. Menthone is generally used in the flavoring industry. It is very often found in combination with menthol in various types of volatile oil. This compound has antimicrobial and antioxidant properties, its insecticidal potential has been proven in rice control [81]. Caryophyllene is a sesquiterpene found in reasonable amounts in the volatile oils of many plants [82]. Following studies, it has been shown that caryophyllene gives volatile oil antioxidant and antimicrobial properties [83]. Linalool is a linear monoterpene alcohol [81] that has been shown to have antimicrobial and antioxidant activity [84]. The compounds present in lavernder volatile oil that give it antioxidant properties are linalool [43] and terpineol [41]. Terpineol is a monoterpene that has a wide range of properties: antimicrobial [85], antioxidant, anti-inflammatory, anticancer, and insecticidal [81]. The mechanism of action may be due to cytoplasmic membrane compromise or organic membrane penetration that induces deformation, damage and ultimately death of microbial cells [86]. In 2019 we started the study of the antioxidant activity of various yoghurt samples enriched with encapsulated volatile oils, and due to the positive results obtained we decided to test these effects on other dairy products. We chose kefir because of its notoriety and the benefits it brings to consumers' health. Before the antioxidant analysis, we analyzed consumer acceptance of the new kefir assortments through sensory and textural analysis. The purpose of this study was to produce a dairy product with high nutritional properties. Thus, three types of kefir with volatile oils were made: lavernder, mint and  
Figure 6: The decline in antioxidant activity on day 10 and day 20 of storage compared to day 1 of storage for kefir samples. fennel. The volatile oils are sensitive to various external factors, and they were encapsulated and introduced as spherical capsules into the dairy product. According to studies, these volatile oils have a high antimicrobial and antioxidant capacity. Initially, we tested the antioxidant activity of the volatile oils obtained from their extraction from plants harvested from authorized crops in Sibiu, Romania. The highest value of the antioxidant activity of pure volatile oils belongs to the volatile oil of fennel, followed by the volatile oil of mint, and the lowest value belongs to the volatile oil of lavender. Three spectrophotometer readings were taken for each volatile oil. The antioxidant activity of kefir samples decreased during the twenty days of storage. The highest values of antioxidant activity were obtained on the first day of storage, and the lowest values were obtained on the 20 th day of storage. The largest decrease was recorded between day 10 and day 20 of storage for all kefir samples.