## 4 Discussion  
The many components in the plants used in this study contribute to their antibacterial properties. The most important compounds of fennel are trans-anethole and \(\alpha\)-pinene [62]. Trans-anethole has strong antifungal activity by inhibiting the mycelial growth of a wide range of fungi and could be used as a preservative in food preparation and processing [63; 64]. The tested antimicrobial potential of \(\alpha\)-pinene is moderate [65]. The antimicrobial capacity of volatile fennel oil is also given by compounds such as \(\beta\)-myrrene, eucalypt [66], \(\gamma\)-Terpinene [67; 68], camphor [69], terpinen-4-ol [70], and linalool [71]. \(\gamma\)-Terpinene is a very potent antimicrobial agent against Gram-positive and Gram-negative bacteria [67], especially _Escherichia coli_ and _Staphylococcus aureus_ bacteria [68]. Lavender volatile oil compounds with antimicrobial character are \(\alpha\)-pinene [65], eucalypt [66], nerolidol [72], p-Cymene [73], \(\beta\)-caryophylle, camphor [69], terpinen-4-ol [70], linalool [71], and linalyal acetate [74]. Studies have shown that nerolidol has potent antibacterial activity against _Staphylococcus aureus_[72]. The antimicrobial character of volatile mint oil is provided by compounds such as \(\alpha\)-pinene [65], \(\beta\)-myrrene, eucalypt [66], eugenol [75; 76], p-Cymene [73], \(\gamma\)-Terpinene [67; 68], \(\beta\)-caryophylle [69], pulegone [77], menthone [78], sabinene [79], and linalool [71]. Eugenol has been reported to have high antibacterial activity [75], inhibiting the growth of several test microorganisms such as _Escherichia coli_, _Aeromonas hydrophila_, and _Salmonella typhi_[76]. The study aimed to produce a functional dairy product that brings nutritional benefits to the consumer's health. The use of volatile oils with antimicrobial capacity aims to increase the finished product's shelf life. The antimicrobial capacity of the volatile oils used was initially tested on several types of microorganisms affecting food products, especially dairy products. Following the antimicrobial determination, volatile mint oil has the highest antibacterial activity against the chosen microorganisms, with _Aspergillus niger_ being the only microorganism that showed resistance to it. The most sensitive bacteria to this kind of oil include _Escherichia coli_, _Penicillium expansum_, and _Geotrichum candidum_. _Escherichia coli_ is quite susceptible to the antibacterial effects of lavender and fennel volatile oils. The antibacterial activity  
Figure 9: Comparative variation of L-lactic acid content determined by the enzymatic method in keffer samples with encapsulated volatile oils and the control sample. of volatile lavender oil is low to moderate against _Aspergillus niger_ and intermediate against _Geotrichum candidium_ and _Penicillium expansum_. The remaining chosen microorganisms are only weakly inhibited by the fennel volatile oil's antimicrobial properties. Using encapsulated volatile oils and cow's milk, we created three different forms of kefir. We analyzed different chemical compounds in kefir using enzymatic methods. Enzyme kits from the R-Biopharm company were used. The analyzed compounds were lactose, D-glucose, D-galactose, acetic acid, ethanol, L-lactic acid, and L-glutamic acid. The kefir with lavender oil has the highest lactose concentration, while the control sample has the lowest amount. The lactose level, as assessed by the enzymatic method, gradually declines during storage in the case of kefir samples enhanced with volatile oils, especially between days 10 and 20. The lactose concentration of the control sample is lower than that of the kefir samples with oils, and it decreases more quickly throughout storage. The D-galactose content of the four kefir samples reduces throughout storage. The kefir sample with volatile lavender oil has the highest concentration of D-galactose, while the control sample has the lowest concentration.