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Article

Evaluation of the Impact of Whey Edible Coatings with Bioprotective Cultures and Thyme Essential Oil Applied to Cheese

by
Carlos Dias Pereira
1,2,*,
Klaudia Hodowaniec
3,
Karolina Kucz
3,
Katarzyna Szkolnicka
3,
David Gomes
1 and
Arona Pires
1,2
1
School of Agriculture, Polytechnic University of Coimbra, Bencanta, 3045-601 Coimbra, Portugal
2
Centro de Estudos dos Recursos Naturais, Ambiente e Sociedade—CERNAS, 3045-601 Coimbra, Portugal
3
Department of Toxicology, Dairy Technology and Food Storage, West Pomeranian University of Technology, Al. Piastów 17, 70-310 Szczecin, Poland
*
Author to whom correspondence should be addressed.
Dairy 2025, 6(5), 56; https://doi.org/10.3390/dairy6050056
Submission received: 12 June 2025 / Revised: 31 August 2025 / Accepted: 4 September 2025 / Published: 26 September 2025
(This article belongs to the Section Milk Processing)
Browse Figures
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Abstract

This research work evaluated the application of whey-based edible coatings to cheeses. Coatings were prepared with a bioprotective culture (BC) containing Lacticaseibacillus paracasei and Lacticaseibacillus rhamnosus alone, or in conjunction with thyme essential oil (TEO). The samples containing the BC or the BC plus TEO were compared with cheeses without coating, with cheeses with whey-based coatings without BC or TEO, and with cheeses treated with natamycin. The cheeses were evaluated regarding their physicochemical, microbiological, and sensory properties. All cheeses produced were classified as full-fat (≥45–60% fat in dry matter—FDM) and semihard (>54–<63% moisture in the defatted cheese—MDC), with an exception made for the control cheese, which presented lower levels of MDC, graded as hard (>49–<56% MDC). Most of the parameters evaluated presented significant differences between samples and as a result of ripening time. Regarding color parameters, it was observed that, after ripening, the external color of the samples with the whey coating presented higher lightness values (L*), higher a* values, and lower b* values. These differences clearly resulted from the white color imparted by the coating. Significant differences were also observed with respect to the texture parameters of the cheeses. The samples containing the BC or the BC plus TEO presented higher values for hardness and chewiness. In what concerns the microbiological evaluation, in all cases, lactic acid bacteria counts increased from log 7.5–8 CFU/g on the first day to ca. log 10 CFU/g at the end of the ripening period. Yeast and mold counts were significantly lower in samples containing the BC or the BC plus TEO, with values of ca. log 3 CFU/g and log 2.5 CFU/g, respectively. These values are like those obtained in samples with natamycin, with 1–2 log cycles below those of cheeses without treatment. However, the use of BC and BC plus TEO had a negative impact on the sensory properties of cheeses. Future work should evaluate the synergistic effect of different BCs and EOs.

1. Introduction

Whey edible coatings used in cheese are based on whey proteins and designed to maintain product shelf life and provide barrier properties and microbiological stability, while maintaining the sensory characteristics of the product. In addition, edible coatings must not be toxic and should have low production costs [1,2,3]. These coatings are flexible and offer high water vapor permeability and excellent oxygen permeability [3]. They can also allow for the maintenance of moisture and of the textural properties of cheese [4,5,6,7,8,9,10]. Whey protein-based coatings can also include active ingredients such as antimicrobials, antioxidants, and probiotics. The mentioned features are dependent on the formulations, namely regarding the properties imparted by the additives used [11]. The incorporation of antimicrobials in whey coatings reduces microbial contamination and prevents the growth of pathogens in cheeses [5,6]. It is reported that the addition of antimicrobials to coatings has a low impact on cheeses’ sensory acceptability [4,6,12]. However, the use of essential oils (EOs) may modify the flavor of cheeses with an effect on consumer’s choices.
Consumers worldwide increasingly demand food without chemical additives. The “Clean Label” trend has boosted the search for new bioprotective cultures (BCs). Lactic acid bacteria (LAB) have been extensively evaluated as BC. These bacteria have been used for a long time, and their activity against spoilage and pathogenic microorganisms is widely documented [13]. Biopreservation is nowadays defined as the use of antagonistic microorganisms, or their metabolites, with the aim of inhibiting undesirable microorganisms and increasing the shelf life of food, with minimal modifications of its sensory properties [14]. Bioprotective cultures are known to inhibit the growth of pathogenic bacteria and fungi in cheese [15,16,17]. Other studies report that the addition of BC to cheese can improve its safety by inhibiting specific pathogens such as Listeria monocytogenes [18,19]. However, the efficacy of BC can vary with the fungi strains, application method, and type of cheese [20,21,22,23,24,25]. The availability of commercial BCs with proven efficacy on the control of spoilage and pathogenic microorganisms in foods allows producers to reduce the use of chemical additives without compromising safety. BC can become a very useful aid to increase the safety of food products with geographical indication (GI) or with protected designation of origin (PDO). These products are often produced without the use of food preservatives, which may raise some health concerns. Particularly concerning PDO and GI cheeses, the use of refrigerated raw milk may cause quality problems due to the presence of psychrotrophic bacteria, namely Pseudomonas spp., which predominate over LAB in this milk. The lack of LAB yields cheeses with sensory defects and facilitates the growth of pathogenic bacteria such as L. monocytogenes, Staphylococcus aureus, or pathogenic fungi, as a result of the low acidification of the cheese paste. Thus, research efforts should continue in order to produce specific indigenous starter and bioprotective cultures that do not modify the sensory properties of the products and increase their safety. GI and PDO regulators should evaluate this matter, considering the already available information.
Essential oils (EOs) have antimicrobial, antiviral, and antifungal properties. The antimicrobial efficacy of EOs is attributed to different chemical constituents, such as carvacrols, thymols, and eugenols [26]. The antimicrobial action of EOs involves disrupting microbial cell membranes, causing the leakage of cellular contents and inhibition of essential cellular processes [27,28]. Several authors have reported on the action of EOs as antimicrobial agents in whey films or as coatings in cheese. Clove essential oil, added at different levels, inhibited the growth of Escherichia coli, Salmonella sp., S. aureus, and molds in whey-based films [29]. However, high levels of EO incorporation (5–15%) may affect the sensory properties of the food products. Other authors have tested the addition of lemon and bergamot EO in whey-based films. Bergamot oil showed high antimicrobial activity against E. coli and S. aureus, but lemon oil showed lower efficacy against S. aureus. Both EOs impaired the development of Aspergillus niger [30]. Whey protein isolate-based films containing oregano and garlic EOs have also been tested in cheeses. Oregano EO was effective against E. coli O157:H7 [30]. Other authors state that the direct addition of EOs may change the sensory characteristics of food products [31]. Oregano EO was also efficient in the control of S. aureus, psychrophilic bacteria, and molds and yeasts in cheese [32]. The antimicrobial activity of coatings with EOs depends on EO concentration and on the active compounds present. In oregano, carvacrol is the most abundant, while in sage, camphor, α-thujone and 1,8-cineole predominate [33,34]. TEO is also rich in carvacrol, with antimicrobial and antioxidant activities [35]. The efficacy of EOs also depends on other factors (e.g., microorganism strains and the chemical composition of the food to which they are added).
The present work aimed to evaluate the use of whey-based edible coatings with the addition of BC and BC plus TEO.

2. Materials and Methods

The methods used for coating production, for cheese manufacture, and for the evaluation of the physicochemical, microbiological, and sensory parameters of cheese samples are similar to those reported in a previous work by Pereira et al., in which we evaluated the use of sheep’s whey edible coatings with a bioprotective culture, kombucha tea, and oregano essential oil on cheese [36].

2.1. Coating Production

Five different types of cheese samples were produced: without coating (CON); coated with an aqueous solution of natamycin (NAT); coated with whey-based coating without additives (WCO); coated with whey-based coating plus BC (WFQ); coated with whey-based coating with BC and TEO (WFQT).
The production process of the coatings is reported elsewhere [36]. Whey powder (WP 80% w/w protein) was hydrated in distilled water (7% w/w protein basis). For the coatings containing the bioprotective culture, only half of the amount of water was used, obtaining a 14% solution. The remaining volume of water was replaced with the BC, which was added after the heat treatment of the prepared coating solution. Glycerol, used as plasticizer, was added (1:1 WP protein content–plasticizer ratio). The coating solution was heated to 65 °C, homogenized at 15 MPa, heated again to 95 °C, and recirculated trough the homogenizer valve.
BC FreshQ4™ (Chr. Hansen, Hoersholm, Denmark) was added (0.01% w/v) to skimmed U.H.T. milk and maintained at 30 °C for 15 h. Then, it was added to the WP/glycerol solution and the mixture homogenized using Ultra-Turrax.
To produce the coating with BC and TEO, the EO (0.1% v/v) was directly added to a previously prepared coating containing BC, and the mixture was homogenized using Ultra-Turrax.
Natamycin (Nataseen™-L, Siveele, Breda, The Netherlands) was previously diluted in distilled water (at 0.32% w/v) and the samples were immersed in it for one minute.

2.2. Cheese Production

Milk used for cheese production was pasteurized at 74 °C (± 1 °C) for 30 s. The method of cheese production is identical to the one described in a previous work [36]. After stabilizing the temperature of the milk at 30 ± 0.5 °C, CaCl2 solution, a starter culture containing lactic acid bacteria, and lysozyme were added to the vat. Rennet, diluted in water, was added afterwards. After curdling, the curd was washed with salted water. Curd pieces were pressed in plastic molds for 4 h before being immersed in a brine solution. The coatings were applied after the salting step, and the cheeses (ca. 250 g; 8 cm diameter; 4 cm height) were maintained at 4 °C. The application of coatings was repeated the following day. Finally, the samples were transferred to the ripening room and maintained at 10 ± 2 °C for 28 days.

2.3. Physicochemical Analysis

Methods for physicochemical analysis were similar to those used in a previous work [36]. Dry matter (DM) was determined by oven drying, according to NP 3544 [37]. Ashes were evaluated through the incineration of dry cheese samples. Fat was determined according to NP 2105 [38]. The cheese samples were classified in accordance with NP 1598 [39]. Titratable acidity (TA) (as % lactic acid) was determined based on AOAC 920.124 [40].
Color coordinates were evaluated in the CIEL*a*b* system. Color difference (ΔEab*) between samples, and for the same sample over time, was calculated according to Equation (1) [41]:
ΔEab* = (ΔL*2 + Δa*2 + Δb*2)0.5
A TA.XT Express Enhanced system (Stable Micro Systems™, Godalming, UK) was used for texture evaluation. Whole cheeses were used for texture determinations. A texture profile analysis (TPA-type) test was applied, with a penetration distance of 20 mm (50% compression) at 2 mm/s, using a cylindrical probe with a diameter of 6 mm.

2.4. Microbiological Evaluation

The counts of LAB (presumptive lactobacilli and lactococci) were performed on the 1st, 14th, and 28th days of ripening. Lactobacilli were cultured on MRS agar at 37 °C for 48 h (in anaerobiosis) and lactococci were cultured at 37 °C for 48 h on M17 agar (in aerobiosis) (both culture media from Biokar Diagnostics, Oise, France) (ISO 7889, IDF 117, 2003) [42]. Yeasts and molds were counted according to ISO 6611 IDF 94 (2004) [43]. Analyses were carried out in triplicate, with two controls for each medium. Results were expressed as log CFU/g of cheese.

2.5. Sensory Analysis

Cheese samples were evaluated for aroma, taste, texture, and overall impression by a non-trained panel with 30 members. A nine-point hedonic scale, where 1 = dislike extremely and 9 = like extremely, was used [44].

2.6. Statistical Analysis

Differences among cheese samples were evaluated by two-way ANOVA. Means were compared using Tukey’s post hoc test. A significance level of p < 0.05 was used. Pearsons’ correlations and principal components analysis (PCA) were also applied to data. The Statistica Software, version 12, was used to treat results (Stasoft Europe, Hamburg, Germany).

3. Results

Table 1 depicts the physicochemical characteristics of cheese samples at the end of ripening (28th day). Significative differences were observed between samples, particularly regarding moisture in defatted cheese (MDC). The NAT sample presented a significantly higher value of MDC, while the samples containing the coating presented intermediate values, although not statistically different from the CON sample. With regard to fat in dry matter, the CON sample presented a significantly lower value, and the WFQ and WFQT samples presented significantly higher values.
Figure 1 presents the evolution of dry matter and of the water activity of cheeses. Cheeses with natamycin presented the lowest value of dry matter, although not significantly different from all others. However, the difference was significant regarding MDC, as observed in Table 1. The cheeses containing the whey-based coating presented intermediate MDC values. Higher values of MDC indicate increased water retention. Unexpectedly, cheeses coated with natamicin presented a lower aw compared to WCO, WFQ, and WFQT. The slightly higher ash content of these cheeses may indicate that this product absorbed more salt, which induced the reduction in aw.
Figure 2 depicts the evolution of the compositional parameters used for the classification cheeses, according to the Portuguese standard [39]. After ripening, all cheeses were graded as full-fat (≥45 <60% fat in DM) and semihard (>54 <63% MDC), with an exception made for the control cheese, which presented lower levels of MDC (>49 <56%), classified as hard.
The evolution of TA (Figure 3B) results from the activity of starter LAB that metabolize lactose to lactic acid. The production of lactic acid originates from the increase in TA and the decrease in pH values (Figure 3A). It can be observed that the control cheese presented a tendency to show lower values of TA from the 7th day until the end of ripening. The lower MDC content of this sample might have been responsible for this occurrence, although it did not affect LAB counts.
Table S1 of the Supplementary Materials presents the results of the two-way anova of the physicochemical characteristics of the samples over the ripening period. The parameters of dry matter, MDC, FDM pH, TA, and aw presented significant differences (p < 0.05), both between samples and as a result of the ripening time.
Figure 4 displays the textural parameters of the different samples. Compared to the control sample, samples WFQ and WFQT presented higher values for hardness and chewiness, despite showing higher values of MDC. Most probably, the increase in hardness and chewiness of those samples resulted from the coating. Table S2 of the Supplementary Materials presents the results of the two-way anova of the textural parameters of the samples over the ripening period. In all cases, significant differences (p < 0.05) were observed, except for the interaction product x time, in the case of cohesiveness.
As expected, color parameters changed over ripening (Figure 5). It can be observed that, after ripening, the external color of the samples containing the whey coating (WCO, WFQ, and WFQT) presented higher lightness (>L*), higher a* values (green-red axis) and lower b* values (blue-yellow axis), indicating lower yellowness of these samples. These differences clearly resulted from the white color imparted by the whey-based edible coating.
Table 2 presents ΔEab* values of each sample at different days of ripening. Values higher than 1 indicate that differences can be detected by a common observer [41]. In all samples, differences were observed, with an exception made for the color of NAT and WCO cheeses, between the 1st and the 7th day, and for sample WCO, between the 21st and the 28th days of ripening. Color differences are more evident in the rind than in the paste, which were undetectable in several cases.
Table 3 presents ΔEab* values of the rind and of the paste between samples, at the end of ripening. In all cases, clear differences could be observed in the color of the rind of the different cheeses. Again, differences were less pronounced in the paste of cheeses, being undetectable in some cases (CON vs. NAT; WCO vs. WFQ; WCO vs. WFQT; WFQ vs. WFQT).
Table S3 of the Supplementary Materials shows the results of the two-way anova of the color parameters over the ripening period.
The microbiological characteristics of the samples are displayed in Figure 6. LAB counts increased from ca. log 7.5–8 CFU/g, on the first day, to ca. log 10 CFU/g, by the end of ripening. By the end of ripening, yeast and mold counts were significantly higher in the WCO (ca. log 4.5 CFU/g) and CON samples (ca. log 3.5 CFU/g) compared to the WFQ and WFQT samples, which presented counts of ca. log 3 CFU/g and ca. log 2.5 CFU/g, respectively.
Despite showing higher values of yeast and mold counts, at the beginning and at the 14th day of ripening, compared to the sample containing natamycin, the WFQT sample presented values of ca. log 2.5 CFU/g at the end of ripening, similar to those of the NAT sample. It can be considered that BCs or BCs plus TEO restricted the development of yeasts and molds.
Table S4 of the Supplementary Materials presents the results of the two-way anova of the microbiological counts of the samples over the ripening period. Significant differences (p < 0.05), both between samples and as a result of the ripening time, were observed regarding yeast and mold counts, whereas in the case of presumptive lactobacilli and lactococci, significant differences were only observed as a result of the ripening time.
Figure 7A depicts a projection of the physicochemical and microbiological attributes on principal components 1 and 2, representing 61.62% of the variance. Figure 7B presents a projection of the samples on factor planes 1 and 2 of PCA. The physicochemical parameters of pH, TA, chewiness, FDM, and MDC are correlated with the positive side of PC1 and with the negative side of PC2, whereas the parameters of hardness, cohesiveness, L*, a*, and aw correlated with the positive side of both PC1 and PC2. The microbiological counts appear isolated on the negative side of PC1 and on the positive side of PC2, whereas the parameters of adhesiveness and b* appear on the negative side of both PC1 and PC2. Figure 7B indicates that PCA allowed for the discrimination of cheese samples.
Concerning the results of the sensory evaluation (Figure 8), it can be considered that all samples were well accepted. However, samples WFQ and WFQT received lower scores regarding all parameters evaluated. Taking into consideration that sample WCO received scores similar to those of samples CON and NAT, it can be postulated that the lower scores obtained by the samples containing the bioprotective culture and the BC plus TEO result from these additions. Hence, this aspect must be considered in future work.

4. Discussion

Significant correlations were observed between ripening time and dry matter (0.91), pH (−0.78), TA (0.83), and aw (−0.55). These correlations were expected, since during ripening, cheeses loose moisture, increasing DM and decreasing aw. Ripening time also correlated with the counts of presumptive lactobacilli (0.81) and lactococci (0.83). In addition, the increasing LAB counts cause the production of lactic acid, with the correspondent increase in TA and decrease in pH. As expected, TA correlated positively with the counts of lactobacilli (0.68) and lactococci (0.74). Conversely, pH correlated negatively with those counts (−0.68 and −0.66, respectively). Ripening time also correlated significantly with hardness (0.96), adhesiveness (−0.87), chewiness (0.92), and cohesiveness (−0.60). The changes in the texture parameters result from the loss of moisture. Ripening time also showed a significant negative correlation with the lightness of the rind (−0.76). The water activity correlated negatively with LAB counts (−0.49 and −0.52, respectively).
The application of edible whey coating is expected to protect cheese from excessive loss of moisture. This finding has been reported by other authors [5,9]. Due to the slightly higher MDC, coated cheeses are also expected to have higher aw than the control. Higher aw translates into a better environment for LAB and higher metabolic activity. The higher lactic acid concentration of coated cheeses reflects this observation (Figure 3). It should be mentioned that the changes in aw during cheese ripening not only result from the decrease in moisture content but can also be influenced by protein degradation and the release of carboxyl and amino groups, which are able to bind water [6].
Hardness and chewiness values increased from ca. 7 N on the 1st day to ca. 38 N, in the NAT sample, and to more than 50 N for samples WFQ and WFQT. On the 28th day, chewiness values were of the order of 12 J in the control sample, while samples WFQ and WFQT presented values higher than 20 J. The WFQ and WFQT samples presented higher values for hardness and chewiness, despite showing higher values of MDC, in comparison to the control. We consider this increase to have resulted from the addition of the coating containing the bioprotective culture. At the end of ripening, the distribution of the edible coating presented irregularities as a result of the external drying of samples. A higher proportion of the plasticizer in the formulation is advisable, in order to prevent this undesirable feature. Higher values of hardness in cheeses with coating containing BC (WFQ and WFQT) also indicate higher thickness of these coatings. Thick coatings influence the consistency of cheese rind, which translates into a harder texture [45]. A harder texture of cheeses with a coating made of acid whey protein concentrate with a Lactobacillus helveticus strain, compared with the same coating without LAB, was also reported by Vasiliauskaite et al. [46]. Comparing the hardness and adhesiveness of WFQ and WFQT, it can be noticed that TEO addition decreased the former and increased the latter. Lipids added to coatings connect with the protein network and modify the textural properties of coated cheese [46]. Reduction in hardness through the addition of EOs to edible coatings was also reported by other authors [47,48]. In a previous work [36], with the same type of experimental cheeses, we obtained slightly higher values for the hardness and chewiness of the control sample and of samples with whey-based coating. The samples with natamycin and with oregano essential oil presented significantly lower values for hardness (ca. 40 N), similar to those observed for the sample treated with natamycin, produced in the present work.
Regarding the evolution of color parameters, it can be considered that the whey-based edible coating imparted a white color on the rind. In analyzing the difference in color (ΔEab*) of the ripened products, the cheese with natamycin was closer to the control sample than to the coated samples. Among cheeses with coatings, those with BC and those with BC and TEO (WFQ; WFQT) showed smaller differences than the one without additives (WCO). Taking into account the time of ripening, changes in color were the most distinct in the control cheese, and the smallest in the WCO cheese, which is in line with the findings of other authors [5,9].
The counts of presumptive lactocacilli and lactococci exceeded log 9 CFU/g by the end of ripening. So, it can be considered that none of the treatments inhibited LAB growth.
Considering the reduction in the counts of yeasts and molds by 1–2 log cycles, one can conclude that BC can reduce those counts, while its use in combination with TEO further increased the protective effect. Although the focus of the present work was not on testing the efficacy of the BC or of TEO against pathogenic microorganisms, it can be expected that such additives have an effect on not only on molds but also on pathogenic bacteria.
Mold spoilage of dairy products yielda food waste and high economic losses. In addition, it raises health concerns due to the production of mycotoxins. Penicillium, Mucor, Cladosporium, Aspergillus, Fusarium, and Geotrichum genera are the main ones responsible for dairy product spoilage. Most of these molds can grow under low temperatures, low water activity, low pH, and low-oxygen-tension atmospheres [13]. The main antifungal compounds produced by LAB include organic acids (lactic, acetic, benzoic, formic, succinic, and propionic, among others), fatty acids (e.g., dodecanoic and decanoic acids), hydrogen peroxide, diacetyl, acetoin, ethanol, and bacteriocins (e.g., nisin, pediocin, lacticin, enterocin), among others [13,49]. Bacteriocins are peptides produced by bacteria that have activity against other bacteria. Although nisin is allowed for commercialization, it is important to note that it may not be claimed as a clean label because it is a food additive approved for use in foods (E234) [13]. Besides the mentioned inhibition mechanisms, competition for glucose and glucosamine, amino acids, peptides, and ions (particularly manganese) also plays a significant role in the antimicrobial activity of BC [13,34]. The use of edible coatings with added antimicrobials is therefore an adequate method for reducing yeast and mold growth [23,50]. The improvement in edible coating function may be achieved with the aid of BC [50] or essential oil addition [48,49,51,52]. Bioprotective cultures, such as Lactiplantibacillus plantarum and Lactobacillus delbruekii subsp. sunkii, have been studied for their inhibitory action against pathogens like L. monocytogenes in Pecorino Sardo PDO cheese. These cultures have shown inhibitory action against pathogens, resulting in reduced levels of pathogen growth in cheese [15]. BC has also been found to inhibit the growth of spoilage microorganisms in sheep’s milk Ricotta Fresca cheese, with Carnobacterium spp. being effective in controlling Pseudomonas spp. and Enterobacteriaceae [18]. The use of BC, such as Lactococcus lactis KJ660075, has also been shown to enhance the microbial quality and safety of fresh goat cheeses, leading to a significant reduction in the growth of S. aureus [21]. Ye et al. [45] also report that the bioprotective strain Lactococcus lactis ATCC11454 may be successfully incorporated into edible films. In the study of Vasiliauskaite et al. [46], a strain of Lactobacillus helveticus was immobilized in edible coating made of acid whey protein concentrate, applied on acid-curd cheese. In cheese coated with the LAB strain, a significant decrease in the counts of yeast (1 log cycle) and suppression of mold growth were observed. Guimarães et al. tested whey protein edible coatings with Lactobacillus buchneri to control the growth of Penicillium nordicum, inoculated on the surface of the coating. Coatings with L. buchneri prevented mold contamination of cheese over a 1 month storage period. Edible coatings may also be used as carriers for probiotic bacteria, but the concentration of such microorganisms tends to decrease during the storage time [53,54].
TEO could improve the microbial quality of cheese, not only through the active substances but also by improving the coating cohesiveness. Lipids added to protein coating connect with the protein network, improving the performance of the coating [46]. Considering the results obtained in the present study, the combination of BC with TEO used as hurdles for the development of fungi proved to be effective.
When applying new edible coatings to cheeses, an important issue is the sensory evaluation of the products. In the present work, the use of a WCO edible coating did not negatively influence the sensory aspects of cheese. However, the addition of BC or BC and TEO (samples WFQ and WFQT) led to lower sensory scores. This resulted from the modified textural properties of cheeses WFQ and WFQT, as well as from alterations in cheese taste, especially in the case of the sample with TEO. On the other hand, LAB produce different metabolites, which may influence the flavor and structure of food products. In a study on cheese with edible coating based on acid whey [45], the incorporation of L. helveticus increased the score for the sensory assessment of cheese, due to the sour taste of the coating, positively affecting the mild flavor of the tested cheese. In another study, the addition of Bifidobacterium animalis subsp. lactis BB-12 to the edible coating did not influence the sensory properties of the coated cheese [54]. However, it is reported that despite showing great potential as natural antimicrobial agents, EOs added to edible coatings are restricted due to their intense flavor affecting the sensory characteristics of cheeses [31,54].
Since in our previous work the cheeses containing oregano EO were graded better by the members of the sensory panel when compared to all the other EOs, it becomes evident that the type of EO must be chosen regarding not only its antimicrobial properties but also its impact on the sensory properties of the products. Thus, future work should aim at evaluating the use of BC with different EOs added, in order to evaluate their impact on the sensory properties of cheeses.

5. Conclusions

This study demonstrated that edible coatings based on whey with the addition of a bioprotective culture alone, or in combination with thyme essential oil, has a positive influence on the reduction in the mold and yeast contamination of cheese. Neither whey-based edible coatings nor natamycin influenced the growth of LAB responsible for the cheese ripening process. The coatings with BC and TEO showed a reduction in yeasts and molds by 1–2 log cycles. Coating without antimicrobial additives, as well as coatings with BC and TEO, increased MDC, FDM, and water activity and decreased dry matter content in cheese after a 28-day ripening period. Concerning the color parameters, cheeses with edible coatings were characterized with higher lightness and lower yellowness than the control cheese. These differences clearly resulted from the white color imparted by the whey-based edible coating. Coatings also increased the chewiness of the cheese. In addition, coatings with BC and TEO increased hardness, and in the case of a coating with both additives (WFQT), the adhesiveness of cheese also increased. These findings indicate that the active components of the coating have an impact on the textural properties of cheese. Regarding sensory quality, it was observed that all samples were well accepted. However, samples WFQ and WFQT were less appreciated than the control sample and sample WCO. It can be postulated that the lower sensory scores of those samples result from the addition of BC and TEO. Further studies on the modification of coating properties by increasing the plasticizer proportion are recommended. Moreover, the evaluation of the use of BC with other EOs should be considered.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/dairy6050056/s1. Table S1. Two-way Anova of the physicochemical characteristics of the samples. MDC=moisture in defatted cheese; FDM=fat in dry matter. Table S2. Two-way Anova of the textural parameters of the samples. Table S3. Two-way Anova of the color parameters of the rind and of the paste of cheese samples. Table S4. Two-way anova of the microbial counts of the samples.

Author Contributions

Conceptualization, C.D.P. and D.G.; methodology, C.D.P., D.G., and A.P.; formal analysis, C.D.P., D.G., K.H., K.K., and A.P.; investigation, D.G., K.H., K.K., and A.P.; resources, C.D.P.; data curation, C.D.P.; writing—original draft preparation, C.D.P.; writing—review and editing, C.D.P. and K.S.; supervision, C.D.P.; project administration, C.D.P.; funding acquisition, C.D.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Foundation for Science and Technology (FCT, Portugal) through national funds provided to the research unit Research Centre for Natural Resources, Environment, and Society—CERNAS (https://doi.org/10.54499/UIDP/00681/2020, accessed on 26 May 2025).

Institutional Review Board Statement

Sensory analysis is not a procedure that requires submission to the ethics commission (EC) of the Polytechnic of Coimbra. Most of the panelists are members of the staff of the institution and frequently perform such types of tests. However, when consumer sensory tests were carried out, the panelists were informed about the objectives of the work and signed the informed consent form provided by the EC (CIEIPC_CILE_02). Hence, this research did not necessitate formal ethical approval per the situation at that time. Over the course of the implementation of this study, no experiments violating human or animal laws were performed. This research followed Law No. 58/2019 of 8 August, the GDPR, the Declaration of Helsinki, and the Oviedo Convention.

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Evolution of dry matter (A) and water activity (B) of cheese samples over ripening (n = 3) (point-mean; whisker-standard deviation). (CON) = control cheese, without coating; (NAT) = cheese without coating, treated with natamycin; (WCO) = cheese with WP coating without additives; (WFQ) = cheese with WP coating with bioprotective culture; (WFQT) = cheese with WP coating with bioprotective culture and with thyme essential oil (Same notation in all figures).
Figure 1. Evolution of dry matter (A) and water activity (B) of cheese samples over ripening (n = 3) (point-mean; whisker-standard deviation). (CON) = control cheese, without coating; (NAT) = cheese without coating, treated with natamycin; (WCO) = cheese with WP coating without additives; (WFQ) = cheese with WP coating with bioprotective culture; (WFQT) = cheese with WP coating with bioprotective culture and with thyme essential oil (Same notation in all figures).
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Figure 2. Evolution of fat in dry matter (A) and moisture in defatted cheese (B) of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation).
Figure 2. Evolution of fat in dry matter (A) and moisture in defatted cheese (B) of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation).
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Figure 3. Evolution of pH (A) and titratable acidity (B) of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation).
Figure 3. Evolution of pH (A) and titratable acidity (B) of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation).
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Figure 4. Evolution of texture parameters of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation). (A) Hardness; (B) adhesiveness; (C) chewiness; (D) cohesiveness.
Figure 4. Evolution of texture parameters of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation). (A) Hardness; (B) adhesiveness; (C) chewiness; (D) cohesiveness.
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Figure 5. Evolution of color parameters of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation). (A) L*-Rind; (B) L*-Paste; (C) a*-Rind; (D) a*-Paste; (E) b*-Rind; (F) b*-Paste.
Figure 5. Evolution of color parameters of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation). (A) L*-Rind; (B) L*-Paste; (C) a*-Rind; (D) a*-Paste; (E) b*-Rind; (F) b*-Paste.
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Figure 6. Evolution of microbial counts of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation). (A) Lactobacilli; (B) lactococci; (C) yeasts and molds.
Figure 6. Evolution of microbial counts of cheese samples over ripening (n = 3) (point—mean; whisker—standard deviation). (A) Lactobacilli; (B) lactococci; (C) yeasts and molds.
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Figure 7. Principal component analysis (PCA). (A) Projection of the variables on factor planes 1 and 2; (B) projection of samples on factor planes 1 and 2 (FDM = fat in dry matter; MDC = moisture in defatted cheese; Y&M = yeasts and molds).
Figure 7. Principal component analysis (PCA). (A) Projection of the variables on factor planes 1 and 2; (B) projection of samples on factor planes 1 and 2 (FDM = fat in dry matter; MDC = moisture in defatted cheese; Y&M = yeasts and molds).
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Figure 8. Sensory scores of cheese samples (point—mean; box—standard error; whisker—standard deviation).
Figure 8. Sensory scores of cheese samples (point—mean; box—standard error; whisker—standard deviation).
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Table 1. Physicochemical parameters of cheese samples at the end of ripening. DM = dry matter; MDC = moisture in defatted cheese; FDM = fat in dry matter (mean ± standard deviation).
Table 1. Physicochemical parameters of cheese samples at the end of ripening. DM = dry matter; MDC = moisture in defatted cheese; FDM = fat in dry matter (mean ± standard deviation).
SAMPLEDM %MDC %FAT %FDM %ASH %
CON65.39 ± 2.89 a49.44 ± 4.13 a30.00 ± 0.00 a45.97 ± 2.02 a3.49 ± 0.53 a
NAT59.91 ± 0.34 a57.82 ± 0.57 b30.67 ± 0.50 a51.19 ± 0.79 b3.70 ± 0.14 a
WCO61.72 ± 0.81 a54.96 ± 1.52 ab30.33 ± 0.47 a49.16 ± 1.39 b3.05 ± 0.10 a
WFQ62.50 ± 1.32 a56.23 ± 1.59 ab33.33 ± 0.40 b53.34 ± 0.37 c3.10 ± 0.08 a
WFQT63.57 ± 2.22 a54.90 ± 3.02 ab33.67 ± 0.45 b53.00 ± 1.27 c3.33 ± 0.09 a
(CON) = control cheese, without coating; (NAT) = cheese without coating, treated with natamycin; (WCO) = cheese with WP coating without additives; (WFQ) = cheese with WP coating with bioprotective culture; (WFQT) = cheese with WP coating with bioprotective culture and with thyme essential oil. Different letters in the same column indicate significant differences (p < 0.05) between samples.
Table 2. ΔEab* values of the rind and of the paste of samples at different days of ripening.
Table 2. ΔEab* values of the rind and of the paste of samples at different days of ripening.
RINDCONNATWCOWFQWFQT
1st vs. 7th14.11.31.910.43.9
7th vs. 14th20.110.22.03.414.7
14th vs. 21th9.016.32.52.410.7
21st vs. 28th2.99.21.84.15.4
PASTECONNATWCOWFQWFQT
1st vs. 7th1.63.22.56.21.1
7th vs. 14th3.60.77.02.23.8
14th vs. 21th3.30.82.22.03.9
21st vs. 28th1.74.72.32.40.8
(CON) = control cheese, without coating; (NAT) = cheese without coating, treated with natamycin; (WCO) = cheese with WP coating without additives; (WFQ) = cheese with WP coating with bioprotective culture; (WFQT) = cheese with WP coating with bioprotective culture and with thyme essential oil.
Table 3. ΔEab* values of the rind and of the paste for between samples, at the end of ripening.
Table 3. ΔEab* values of the rind and of the paste for between samples, at the end of ripening.
CHEESESRINDPASTE
CON vs. NAT81.51.8
CON vs. WCO124.73.1
CON vs. WFQ96.82.8
CON vs. WFQT101.12.4
NAT vs. WCO114.24.8
NAT vs. WFQ102.94.5
NAT vs. WFQT94.14.0
WCO vs. WFQ34.50.4
WCO vs. WFQT24.01.2
WFQ vs. WFQT21.11.2
(CON) = control cheese, without coating; (NAT) = cheese without coating, treated with natamycin; (WCO) = cheese with WP coating without additives; (WFQ) = cheese with WP coating with bioprotective culture; (WFQT) = cheese with WP coating with bioprotective culture and with thyme essential oil.
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Pereira, C.D.; Hodowaniec, K.; Kucz, K.; Szkolnicka, K.; Gomes, D.; Pires, A. Evaluation of the Impact of Whey Edible Coatings with Bioprotective Cultures and Thyme Essential Oil Applied to Cheese. Dairy 2025, 6, 56. https://doi.org/10.3390/dairy6050056

AMA Style

Pereira CD, Hodowaniec K, Kucz K, Szkolnicka K, Gomes D, Pires A. Evaluation of the Impact of Whey Edible Coatings with Bioprotective Cultures and Thyme Essential Oil Applied to Cheese. Dairy. 2025; 6(5):56. https://doi.org/10.3390/dairy6050056

Chicago/Turabian Style

Pereira, Carlos Dias, Klaudia Hodowaniec, Karolina Kucz, Katarzyna Szkolnicka, David Gomes, and Arona Pires. 2025. "Evaluation of the Impact of Whey Edible Coatings with Bioprotective Cultures and Thyme Essential Oil Applied to Cheese" Dairy 6, no. 5: 56. https://doi.org/10.3390/dairy6050056

APA Style

Pereira, C. D., Hodowaniec, K., Kucz, K., Szkolnicka, K., Gomes, D., & Pires, A. (2025). Evaluation of the Impact of Whey Edible Coatings with Bioprotective Cultures and Thyme Essential Oil Applied to Cheese. Dairy, 6(5), 56. https://doi.org/10.3390/dairy6050056

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