The pasta filata cheese is a diverse group of cheeses, which originated mainly in the northern Mediterranean, in countries such as Italy, Greece, the Balkans, Turkey and Eastern Europe (Zimanová et al., 2016).

Parenica is a steamed, lightly smoked or unsmoked cheese wounded into a roll made from pasteurized cow’s milk. It is known for the characteristic pronounced fibrous structure of curd. The roll is ussualy bounded with cheese string.

In the last years, there has been a growing attention towards food quality and food safety, as well as an increasing demand for “natural” products, especially those enjoying a ‘recognition of quality’ status and recognition of ‘geographical indications and traditional specialties’ (PDO, PGI and TSG) conferred by the European Community to promote and protect the names of quality agricultural products and foodstuffs (Todaro et al., 2017).

Steamed cheese production has a long tradition in Slovakia, although originally made from sheep's milk (Čuboň et al., 2015). However, similar dairy product “Slovenská parenica” cheese obtained the “Protected Geographic Indication” designation (PGI) in 2008, but according the “Methods of Production” described in application for registration of “Slovenské parenica”, it could be made from fresh raw, unprocessed sheep's milk or a mixture with fresh raw, unprocessed cow's milk, containing at least 50% sheep's milk (Council Regulation (EC) No. 510/2006).

In comparison to Cheddar and Dutch-type cheeses, pastafilata cheeses represent a special case, in terms of proteolytic pattern (Salek et al., 2017). The pasta filata cheeses varied in sensory quality, which depends on the quality of milk and processing technology (including the process of pasteurisaztion). These cheeses could be made according the following methods: 1. traditional process of making steamed cheese, 2. a method of making steamed cheese using direct acidification of the milk and continuous processing (Zimanová et al., 2016).

Recent studies aimed to the traditional pasta filata, stretched or steamed cheese making technology have been published (Di Grigoli et al., 2015; Scatassa et al., 2015; Sulejmani and Hayaloglu, 2016; Cuffia et al., 2017; Paz et al., 2017; Salek et al., 2017; Todaro et al., 2017). However, many of them deal with the physicochemical and microbial quality of the pasta filata cheeses.

Cheese is an irreplaceable dairy product in human nutrition and it could be consumed fresh or ripened (Ozcan et al., 2011). Parenica cheese could be lightly smoked during the processing of curd. Smoking is technique of food preservation, but it is also used to enhance sensory properties, taste, color and texture (Esposito et al., 2015). The special taste and textural parameters of traditional cheese specialties could make them popular (Farahani, Ezzatpanah and Abbasi, 2014).

Generally, smoking of high protein foods enrich the food with aromatic components that provide organoleptic properties as color and flavour to meals and have bacteriostatic and antioxidant effect (Amran and Abbas, 2011). Because of that it is very important to study the qualitative sensory parameters that define the product in order to determine its acceptability to consumers (Semjon et al., 2018). The sensory quality of a product like parenica cheese can be also evaluated using quantitative descriptive analysis.

The aim of this study was to describe sensory profile of smoked and unsmoked parenica cheese manufactured according to the traditional method of production during storage period.

Description terminology for the sensory attributes of both varieties of parenica cheese (PU and PS) was introduced during the training sessions of panellist. Descriptors for appearance (white, polished, fibrous, smoked), aroma (lactit, buthyric, yoghurt, nutty), consistency (firm, elastic, cohesive, gummy, juicy, sticky, formable, fibrous, supple greasy) and taste (sour, bitter, sweet, salty, lactic, creamy, spicy, smoked), were selected.

The results of overall sensory characteristics in PU experimental cheese samples during storage period are shown in Figure 2. We observed decreased trend in overall sensory characteristics after storage in PU samples at a statistical significance level p <0.05 (Figure 2). Descriptive sensory analysis performed on unsmoked experimental parenica cheese samples demonstrated statistically significant influence of storage on the intensities of sensory descriptors of white appearance; descriptors of aroma: buthyric, yoghurt, nutty; descriptors of consistency: firm, cohesive, juicy, sticky, formable, fibrous, greasy; descriptors of taste: sweet, lactic, spicy and smoked (p <0.001). In comparison to Cheddar and Dutch-type cheeses, pasta-filata cheeses represent a special case (in terms of proteolytic pattern). Particularly, the casein molecules (“fibres” or “strings”) are arranged distinctly after the stretching process (Costabel, Pauletti and Hynes, 2007).The cheese stretching temperature can dramatically influence the behavior of aroma compounds, colour and texture attributes (Sulejmani and Hayaloglu, 2016). The immersion of the cheese-curd in the hot liquid is a specific process enhancing its plasticization and stretching properties (Salek et al., 2017).

At the initial stage of storage were found statistically significant differences between experimental cheese varieties in each sensory descriptor except fibrous appearance, nutty aroma, firm, elastic, cohesive, gummy, sticky, fibrous consistency, and sour and spicy taste.

Figure 3 shown that overall sensory paramters in PS samples significantly changed after storage period only in consistency, taste and acceptability (p <0.05).

Descriptive sensory analysis performed on smoked experimental parenica cheese samples demonstrated statistically significant influence of storage on the intensities of sensory descriptors of white and smoked appearance; descriptors of aroma: buthyric and nutty; descriptors of consistency: elastic, cohesive, gummy, juicy, sticky, formable and greasy; descriptors of taste: sweet, lactic and smoked (p <0.001). Consistency is an important viscoelastic property of the product (Amiri et al., 2018). Cais-Sokolińska, Pikul and Lasik (2012), found that changes in texture parameters of cheeses as a result of smoking depended on their storage time. We agree with the autors that smoked cheese not subjected to storage was harder than unsmoked cheese. It could be caused by increased dry matter of smoked cheese, or by loss of water content, respectively.

We observed statistical significant efect of storage on salty taste only in PU samples. Assessors evaluated salty taste in PU samples after storage with higher intensity. On the other hand, intensity of salty taste in PS samples was at the same level before and after storage period of 14 days. We agree with the authors Todaro et al. (2017) and Gaucheron et al. (1999) who found a slightly increase of salt during 14 days of storage of stretched cheese, and moreover, these authors established a migration of sodium, potassium and chloride ions from the outer layer versus the core of cheese which ended after 5 days.

In our study, multiple factorial analysis (MFA) method was applied to the sensory data, whereas were analysed results of overall sensory characteristics and sensory profile of two varieties of parenica cheese samples during storage period of 14 days. The analysis extracted the most significant variables with a minimum loss of information. Kaiser’s criterion (eigenvalue >1) was applied to determine the number of final factors from the initial ones (Chapman, Lawless and Boor, 2001).

The results of MFA showed in parenica cheese samples three selected components that explain more than 69% of the total variation in the dataset. The first dimension (Dim1) explains 34.79% of variation, second dimension (Dim2) 25.64% and third dimension (Dim3) 8.39%.

The highest contribution of the analysed data in Dim1 was related to the effect of storage period (21.93%, r = 0.95) and overall sensory parameters (18.19%, r = 0.89). The highest contribution in Dim 1 included following overall sensory parameters: acceptability (r = 0.91), consistency (r = 0.89), taste (r = 0.86), appearance (r = 0.46) and aroma (r = 0.28), which correlated at statistically significant level (p <0.05).

The first two dimensions explained a total of 60.43% of variance (Figure 4). The highest effect of variety on parenica cheese characteristics was in Dim2 (30.33%, r = 0.84), followed by the descriptors of taste (30.48%, r = 0.52) and descriptors of appearance (21.59%, r = 0.89). In Dim 2 were significantly correlated following descriptors of taste smoked (r = 0.96), lactic (r = -0.25), creamy (r = -0.59) ans spicy (r = -0.66) and following descriptors of appearance: smoked (r = 0.96), fibrous (r = 0.45) and polished (r = 0.26), at statistically significant level (p <0.05) (Figure 5).

Descriptors of consistency contribute mainly to Dim3 with 25.07% (r = 0.67), followed by the descriptor of aroma 24.64% (r = 0.57). In Dim3 were correlated following descriptors of consistency: supple (r = 0.65), firm (r = 0.54), greasy (r = 0.34), formable (r = 0.32), fibrous (r = 0.28) and juicy (r = 0.24).

MFA analysis showed that each sample group was different in observed sensory characteristics, according to measured attributes data (p <0.05). Figure 4 shown that experimental cheese samples groups were not plotted closely to each other. We agree with the authors Smit et al. (2005) that flavor of cheese improved with storage days because during ripening the metabolic processes are responsible for the basic flavor and texture changes. However, further study of individual sensory dexriptors, particularly their intensities, could provide methods such as measurement of intensity in time (Pavelková, Flimelová and Vietoris, 2012).

In this experiment we set up the sensory profile of smoked and unsmoked parenica cheese varieties made from pasteurized cow’s milk. Panelist evaluate each sensory descriptor of two parenica cheese varieties before and after 14 days of storage period. Sensory profile of parenica cheese varieties changed during storage (p <0.05). We observed decreased trend in overall sensory characteristics after storage in unsmoked parenica cheese samples, but in smoked variety only in consistency taste and overall acceptability (p <0.05).