Valorization on the Antioxidant Potential of Volatile Oils of _Lavandula angustifolia_ Mill., _Mentha piperita_ L. and _Foeniculum vulgare_ L. in the Production of Kefir  
[PERSON]  
1 Department of Agricultural Sciences and Food Engineering, Lucian Blaga University of Sibiu, Doctor [PERSON] No. 7, 550012 Sibiu, Romania 1  
[PERSON]  
2 Faculty of Food Engineering, Stefan and Mare University of Suceva, 720229 Suceva, Romania 2  
[PERSON]  
1 Correspondence: [EMAIL_ADDRESS] (T.J.); [EMAIL_ADDRESS] (C.G. ); Tel. : +40-745-292-031 (O.T. ); +40-745-292-031 (O.T. ); +40-745-292-031 (O.T. include polyphenols, stilbene, flavonoids, chalcone, capsaicinoids and casinoids, lignans and curcuminoids, carotenoids, isothi cyanates and catechins. Thus, natural antioxidants have therapeutic potential for many diseases caused by stress [12]. The antioxidant activity of plants is the result of their phenolic compounds. Phenolic compounds are functional compounds synthesized by plants. They play an important role in human nutrition for a healthy life, and mint is an important source [13]. Mint (_Mentha piperita_ L) is a medicinal and aromatic plant used in traditional medicine and drugs for its antimicrobial and antioxidant properties [14]. The antioxidant activity of mint prevents oxidative stress at the cellular level by its chemical composition [15]. Mint-derived secondary metabolites are antioxidants that have immunostimulatory, cardio-tonic and antiviral properties [16]. Mint contains volatile components, flavonoids, organic acids, and quinones, necessary for the digestive system, central nervous system, and respiratory system. It has antioxidant, antimicrobial, anti-inflammatory and anesthetic properties [14; 17; 18; 19]. The most important components of volatile oil are menthol, menthone, menthofuran, isomenthone, cyanophyllene, eucalypt, linalool, limonene, carvone, pulegone and \(\alpha\)-terpinol [20]. In the study conducted by [PERSON] et al., in 2017, it was observed that mint and sage oil are the freest amino acids (\(>\)4 mg\(\cdot\)g\({}^{-1}\)) [21]. In 2013, [PERSON] et al., demonstrated that the most important compound of mint essential oil is menthol and it has a high antimicrobial activity against _Pseudomonas aeruginosa_, _Staphylococcus aureus_ and _Escherichia coli_. Antioxidant activity has been demonstrated using the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) method and the \(\beta\)-Carovtene-linoleic acid test [14]. [PERSON] et al., in 2018 demonstrated that mint essential oil is a good source of compounds with antioxidant, cytoprotective and immunomododulatory properties [22]. In 2019, [PERSON] et al., using high-performance liquid chromatography (HPLC) analysis demonstrated that the mint flower has a higher level of phenolic compounds, flavonoids and anthocyanins that offer antimicrobial and antioxidant effects compared to the stem and leaves [23]. Two other studies conducted in 2019 and 2021 by [PERSON] et al., and [PERSON] et al., respectively, demonstrated the antioxidant activity using the Trolox equivalent antioxidant capacity test and the DPPH method [24; 25]. Fennel (_Foeniculum vulgare_ L) is part of the family _Apiacene_ Lindl. [26]. It is a medicinal plant used as an analgesic, diuretic, anti-inflammatory and antispasmodic [27; 28; 29]. The essential oil is used as a component in cosmetics, pharmaceuticals and flavoring agents in different food products. Fennel essential oils have hepatocyte and antispasmodic effects. It is also known for its diuretic, analgesic, anti-inflammatory and antioxidant properties [26; 27; 30]. The most important components of the essential oil are \(\alpha\)-pinene [31], estragol, trans-anethole, a-phellandrene and fenchore [27]. Numerous studies have shown its antioxidant, anti-inflammatory and antimicrobial action [28; 30; 32; 33; 34; 35; 36]. In 2021, [PERSON] et al., showed that volatile fennel oil had a positive effect on human neutrophils [37] and [PERSON] et al., in 2015 studied the antioxidant and antimicrobial effects during the storage of silver carp filler [38].