# Possibility of Using Fermented Curly Kale Juice to Manufacture Feta-Type Cheese
###### Abstract  
This paper reports the potential use of fermented curly kale juice in Feta-type cheese production. The rheological study and Turbiscan assay demonstrated that fermented curly kale juice coupled with rennet accelerated curd formation resulted in a stronger curd compared to the sample containing rennet alone. Laboratory-scale cheese was manufactured from cow's milk with the use of fermented curly kale juice. Several parameters that affect the quality of cheese were investigated, including physicochemical, textural and microstructure characteristics. The content of amino acids and fatty acids was determined, surface properties were assessed and microbial enumeration of the experimental cheese was carried out before and after ripening. The values of pH and the content of lactose and protein significantly decreased as a result of maturation. In turn, an increase in LAB growth as well as saturated and unsaturated fatty acids was observed. The use of the fermented curly kale juice improved the textural characteristics and changed the microstructure of the obtained cheese. Finally, the ripening process enhanced the amino acid profile of the Feta-type cheese. These findings indicate that the fermented curly kale juice can be used for manufacture of cheese with improved characteristics and functional properties. Feta-type cheese; curly kale; plant coagulants 202020  
in recent years. Consumption of curly kale, considering its superfood nature, can provide a variety of biological substances (starting from glucosinolates, polyphenols and phenolic acids ending with carotenoids) with well-documented health benefits [3; 4; 5; 6; 7]. Furthermore, fermentation of curly kale with autochthonous lactic acid bacteria (LAB) was found to contribute to many favorable food features, for example, improved nutritional quality, safety and organoleptic characteristics [8]. Moreover, due to the presence of LAB, consumption of such foods can provide beneficial effects on the human organism by enhancing mucosal barriers, inhibiting intestinal inflammatory processes, decreasing cholesterol content, inhibiting the growth of pathogenic bacteria and mitigating the course of diarrhea [9; 10]. Currently, fermented foods account for almost 25-30% of diets worldwide. Especially in the western diet, fermented milk products (in which cheese occupies an important place) represent 60% of fermented foods [11]. In the cheese production process, enzymatic coagulation of milk is a key step, since it defines the final features of the product. After the addition of rennet, this step begins with the enzymatic cleavage of the Met \({}_{105}\)- Phe \({}_{106}\) bond of \(\kappa\)-casein present on the surface of casein micelles [12]. In general, coagulation of milk with calf rennet is the most commonly used procedure [13]. Recently, proteases from various plants have been investigated and used in cheesemaking. Most of them are classified as aspartic proteases; however, cysteine and serine proteases have also been reported to exhibit the ability to clot milk in appropriate conditions [13]. These include a novel thrombol protease discovered in _Aster yomena_[14], a cysteine protease from the latex of _Ficus microcarpa_[15], a glycosylated protease from _Euphoria_ cf. _lactea_ latex [16] or a serine/threonine-endopeptidase from _Moringa oleifera_ Lam leaves [17]. Moreover, [PERSON] et al. [18] have shown protease activity in _Brassica_ vegetables, such as broccoli having a probable serine protease as one of the most promising activities among 90 plant resources. Based on this, other vegetables belonging to the _Brassicaceae_ family, such as curly kale could be another potential source of these enzymes. _Lactobacillus plantarum_ 332, _Lb. paraplantarum_ G2114 and _Pediococcus pentosacus_ 2211, previously isolated from spontaneously fermented curly kale, were used in the present study as a starter culture for making Feta-type cheese.